LM2599 SIMPLE SWITCHER Power Converter Step-Down Voltage Regulator, wi

The Datasheet Archive - 100 Million Datasheets from 7500 Manufacturers.

LM2599 SIMPLE SWITCHER Power Converter Step-Down Voltage Regulator, wi

Datasheet Thumbnail

Top Searches for this datasheet

LM2599 SIMPLE SWITCHER Power Converter Step-Down Voltage Regulator, with Features
LM2599 SIMPLE SWITCHER Power Converter Step-Down Voltage Regulator, with Features
LM2599 series regulators monolithic integrated circuits that provide active functions step-down (buck) switching regulator, capable driving load with excellent line load regulation. These devices available fixed output voltages 3.3V, 12V, adjustable output version. This series switching regulators similar LM2596 series, with additional supervisory performance features added. Requiring minimum number external components, these regulators simple include internal frequency compensation, improved line load specifications, fixed-frequency oscillator, Shutdown/Soft-start, error flag delay error flag output. LM2599 series operates switching frequency thus allowing smaller sized filter components than what would needed with lower frequency switching regulators. Available standard 7-lead TO-220 package with several different lead bend options, 7-lead TO-263 Surface mount package. standard series inductors (both through hole surface mount types) available from several different manufacturers optimized with LM2599 series. This feature greatly simplifies design switch-mode power supplies. Other features include guaranteed tolerance output voltage under conditions input voltage output load conditions, oscillator frequency. External shutdown included, featuring typically standby current. Self protection features include stage current limit output switch over temperature shutdown complete protection under fault conditions.
Features
3.3V, 12V, adjustable output versions Adjustable version output voltage range, 1.2V over line load conditions Guaranteed output current Available 7-pin TO-220 TO-263 (surface mount) Package Input voltage range fixed frequency internal oscillator Shutdown/Soft-start regulation error flag Error output delay power standby mode, typically High Efficiency Uses readily available standard inductors Thermal shutdown current limit protection
Applications
Simple high-efficiency step-down (buck) regulator Efficient pre-regulator linear regulators On-card switching regulators Positive Negative converter
Note: Patent Number 5,382,918.
Typical Application
(Fixed Output Voltage Versions)
DS012582-1
SIMPLE SWITCHER Switchers Made Simple registered trademarks National Semiconductor Corporation.
2001 National Semiconductor Corporation
DS012582
www.national.com
LM2599
Absolute Maximum Ratings (Note
Military/Aerospace specified devices required, please contact National Semiconductor Sales Office/ Distributors availability specifications. Maximum Supply Voltage (VIN) Input Voltage (Note Delay Voltage (Note Flag Voltage Feedback Voltage Output Voltage Ground (Steady State) Power Dissipation Storage Temperature Range 1.5V -0.3 -0.3 +25V Internally limited -65°C +150°C
Susceptibility Human Body Model (Note Lead Temperature Package Vapor Phase sec.) Infrared sec.) Package (Soldering, sec.) Maximum Junction Temperature
+215°C +245°C +260°C +150°C
Operating Conditions
Temperature Range Supply Voltage -40°C +125°C 4.5V
LM2599-3.3 Electrical Characteristics
Specifications with standard type face 25°C, those with boldface type apply over full Operating Temperature Range. Symbol Parameter Conditions (Note SYSTEM PARAMETERS (Note Test Circuit Figure VOUT Output Voltage 4.75V 40V, 0.2A ILOAD 3.168/3.135 3.432/3.465 Efficiency 12V, ILOAD V(min) V(max) LM2599-3.3 Limit (Note Units (Limits)
LM2599-5.0 Electrical Characteristics
Specifications with standard type face 25°C, those with boldface type apply over full Operating Temperature Range. Symbol Parameter Conditions (Note SYSTEM PARAMETERS (Note Test Circuit Figure VOUT Output Voltage 40V, 0.2A ILOAD 4.800/4.750 5.200/5.250 Efficiency 12V, ILOAD V(min) V(max) LM2599-5.0 Limit (Note Units (Limits)
www.national.com
LM2599
LM2599-12 Electrical Characteristics
Specifications with standard type face 25°C, those with boldface type apply over full Operating Temperature Range. Symbol Parameter Conditions (Note SYSTEM PARAMETERS (Note Test Circuit Figure VOUT Output Voltage 40V, 0.2A ILOAD 11.52/11.40 12.48/12.60 Efficiency 25V, ILOAD V(min) V(max) LM2599-12 Limit (Note Units (Limits)
LM2599-ADJ Electrical Characteristics
Specifications with standard type face 25°C, those with boldface type apply over full Operating Temperature Range. Symbol Parameter Conditions (Note SYSTEM PARAMETERS (Note Test Circuit Figure Feedback Voltage 4.5V 40V, 0.2A ILOAD VOUT programmed Circuit Figure Efficiency 12V, VOUT ILOAD 1.230 1.193/1.180 1.267/1.280 V(min) V(max) LM2599-ADJ Limit (Note Units (Limits)
Output Voltage Versions Electrical Characteristics
Specifications with standard type face 25°C, those with boldface type apply over full Operating Temperature Range. Unless otherwise specified, 3.3V, Adjustable version version. ILOAD Symbol Parameter Conditions LM2599-XX (Note DEVICE PARAMETERS Feedback Bias Current Oscillator Frequency Adjustable Version Only, 1.3V (Note 50/100 127/110 173/173 VSAT Saturation Voltage Duty Cycle (ON) Duty Cycle (OFF) Current Limit IOUT (Note (Note (Note (Note Peak Current, (Note (Note 1.16 1.4/1.5 3.6/3.4 6.9/7.5 Output Leakage Current (Note (Note (Note Output Output A(min) A(max) µA(max) mA(max) (max) kHz(min) kHz(max) V(max) Limit (Note Units (Limits)
www.national.com
LM2599
Output Voltage Versions Electrical Characteristics (Continued)
Specifications with standard type face 25°C, those with boldface type apply over full Operating Temperature Range. Unless otherwise specified, 3.3V, Adjustable version version. ILOAD Symbol Parameter Conditions LM2599-XX (Note DEVICE PARAMETERS ISTBY Shutdown Threshold Voltage Soft-start Voltage Shutdown Current Soft-start Current Low, (Shutdown Mode) High, (Soft-start Mode) VOUT Nominal Output Voltage VOUT 100% Nominal Output Voltage VSHUTDOWN 0.5V VSoft-start 2.5V FLAG/DELAY CONTROL Test Circuit Figure Regulator Dropout Detector Threshold Voltage VFSAT Flag Output Saturation Voltage Flag Output Leakage Current Delay Threshold Voltage Delay Source Current Delay Saturation (Flag High (Flag OFF) VOUT Regulated VDELAY 0.5V (Flag 350/400 ISINK VDELAY 0.5V VFLAG 1.25 1.21 1.29 0.7/1.0 (Flag %(min) %(max) V(max) V(min) V(max) µA(max) mV(max) µA(max) µA(max) Operating Quiescent Current Standby Quiescent Current Thermal Resistance TO220 TO263 Package, Junction Case TO220 Package, Juncton Ambient (Note TO263 Package, Juncton Ambient (Note TO263 Package, Juncton Ambient (Note TO263 Package, Juncton Ambient (Note (Note 200/250 Open (Note mA(max) µA(max) °C/W °C/W °C/W °C/W °C/W V(max) V(min) Limit (Note Units (Limits)
SHUTDOWN/SOFT-START CONTROL Test Circuit Figure
Note Absolute Maximum Ratings indicate limits beyond which damage device occur. Operating Ratings indicate conditions which device intended functional, guarantee specific performance limits. guaranteed specifications test conditions, Electrical Characteristics. Note Voltage internally clamped. clamp voltage exceeded, limit current maximum Note human body model capacitor discharged through 1.5k resistor into each pin. Note Typical numbers 25°C represent most likely norm. Note limits guaranteed room temperature (standard type face) temperature extremes (bold type face). room temperature limits 100% production tested. limits temperature extremes guaranteed correlation using standard Statistical Quality Control (SQC) methods. limits used calculate Average Outgoing Quality Level (AOQL). Note External components such catch diode, inductor, input output capacitors affect switching regulator system performance. When LM2599 used shown Figure test circuit, system performance will shown system parameters section Electrical Characteristics. Note switching frequency reduced when second stage current limit activated. amount reduction determined severity current overload.
www.national.com
LM2599
Output Voltage Versions Electrical Characteristics (Continued)
Note diode, inductor capacitor connected output pin. Note Feedback removed from output connected force output transistor switch Note Feedback removed from output connected 3.3V, ADJ. version, version, force output transistor switch OFF. Note 40V. Note Junction ambient thermal resistance external heat sink) package mounted TO-220 package mounted vertically, with leads soldered printed circuit board with oz.) copper area approximately in2. Note Junction ambient thermal resistance with TO-263 package soldered single sided printed circuit board with oz.) copper area. Note Junction ambient thermal resistance with TO-263 package soldered single sided printed circuit board with oz.) copper area. Note Junction ambient thermal resistance with TO-263 package soldered double sided printed circuit board with oz.) copper area LM2599S side board, approximately copper other side board. application hints this data sheet thermal model Switchers Made Simple version 4.2.1 later) software.
Typical Performance Characteristics
Normalized Output Voltage Line Regulation
(Circuit Figure Efficiency
DS012582-3 DS012582-2
DS012582-4
Switch Saturation Voltage
Switch Current Limit
Dropout Voltage
DS012582-6 DS012582-5
DS012582-7
Operating Quiescent Current
Shutdown Quiescent Current
Minimum Operating Supply Voltage
DS012582-8
DS012582-9
DS012582-10
www.national.com
LM2599
Typical Performance Characteristics
Feedback Bias Current Flag Saturation Voltage
(Circuit Figure (Continued)
Switching Frequency
DS012582-13 DS012582-11 DS012582-12
Soft-start
Shutdown /Soft-start Current
Daisy Current
DS012582-14 DS012582-15
DS012582-16
Soft-start Response
Shutdown/Soft-start Threshold Voltage
DS012582-18 DS012582-53
www.national.com
LM2599
Typical Performance Characteristics
Continuous Mode Switching Waveforms 20V, VOUT ILOAD COUT COUT
(Circuit Figure (Continued)
Discontinuous Mode Switching Waveforms 20V, VOUT ILOAD COUT COUT
DS012582-20
Output Voltage, 10V/div. Inductor Current 1A/div. Output Ripple Voltage, mV/div.
DS012582-19
Horizontal Time Base: µs/div.
Output Voltage, 10V/div. Inductor Current 0.5A/div. Output Ripple Voltage, mV/div.
Horizontal Time Base: µs/div. Load Transient Response Continuous Mode 20V, VOUT ILOAD COUT COUT
Load Transient Response Discontinuous Mode 20V, VOUT ILOAD COUT COUT
DS012582-22 DS012582-21
Output Voltage, mV/div. (AC) Load Pulse
Output Voltage, mV/div. (AC) Load Pulse
Horizontal Time Base: µs/div.
Horizontal Time Base: µs/div.
Connection Diagrams Order Information
Bent Staggered Leads, Through Hole Package 7-Lead TO-220 Surface Mount Package 7-Lead TO-263
DS012582-50
Order Number LM2599T-3.3, LM2599T-5.0, LM2599T-12 LM2599T-ADJ Package Number TA07B
DS012582-23
Order Number LM2599S-3.3, LM2599S-5.0, LM2599S-12 LM2599S-ADJ Package Number TS7B
www.national.com
LM2599
Test Circuit Layout Guidelines
Fixed Output Voltage Versions
DS012582-24
Component Values shown 15V, VOUT ILOAD 50V, Aluminum Electrolytic Nichicon Series" COUT Aluminum Electrolytic, Nichicon Series" Schottky Rectifier, 1N5825 Typical Values CDELAY RPull 4.7k
www.national.com
LM2599
Test Circuit Layout Guidelines
(Continued)
Adjustable Output Voltage Versions
DS012582-25
where VREF 1.23V
Select approximately resistor best stability. Component Values shown 20V, VOUT 10V, ILOAD CIN: 35V, Aluminum Electrolytic Nichicon Series" COUT: Aluminum Electrolytic, Nichicon Series" Schottky Rectifier, 1N5824 7.15k, Application Information Section Application Information Section Typical Values CDELAY RPULL 4.7k
FIGURE Standard Test Circuits Layout Guides switching regulator, layout very important. Rapidly switching currents associated with wiring inductance generate voltage transients which cause problems. minimal inductance ground loops, wires indicated heavy lines should wide printed circuit traces should kept short possible. best results, external components should located close switcher possible using ground plane construction single point grounding. open core inductors used, special care must taken location positioning this type inductor. Allowing inductor flux intersect sensitive feedback, groundpath COUT wiring cause problems. When using adjustable version, special care must taken location feedback resistors associated wiring. Physically locate both resistors near route wiring away from inductor, especially open core type inductor. (See application section more information.)
www.national.com
LM2599
LM2599 Series Buck Regulator Design Procedure (Fixed Output)
PROCEDURE (Fixed Output Voltage Version) Given: VOUT Regulated Output Voltage (3.3V, 12V) VIN(max) Maximum Input Voltage ILOAD(max) Maximum Load Current Inductor Selection (L1) Select correct inductor value selection guide from Figure Figure (Output voltages 3.3V, respectively.) other voltages, design procedure adjustable version. From inductor value selection guide, identify inductance region intersected Maximum Input Voltage line Maximum Load Current line. Each region identified inductance value inductor code (LXX). Select appropriate inductor from four manufacturer's part numbers listed Figure Output Capacitor Selection (COUT) majority applications, (Equivalent Series Resistance) electrolytic capacitors between solid tantalum capacitors between provide best results. This capacitor should located close using short capacitor leads short copper traces. capacitors larger than additional information, section output capacitors application information section. simplify capacitor selection procedure, refer quick design component selection table shown Figure This table contains different input voltages, output voltages, load currents, lists various inductors output capacitors that will provide best design solutions. capacitor voltage rating electrolytic capacitors should least times greater than output voltage, often much higher voltage ratings needed satisfy requirements output ripple voltage. computer aided design software, Switchers Made Simple (version 4.2.1 later). EXAMPLE (Fixed Output Voltage Version) Given: VOUT VIN(max) ILOAD(max) Inductor Selection (L1) inductor selection guide version shown Figure From inductor value selection guide shown Figure inductance region intersected horizontal line vertical line inductor code L40. inductance value required From table Figure line choose inductor part number from four manufacturers shown. most instance, both through hole surface mount inductors available.) Output Capacitor Selection (COUT) section output capacitors application information section. From quick design component selection table shown Figure locate output voltage section. load current column, choose load current line that closest current needed your application, this example, line. maximum input voltage column, select line that covers input voltage needed your application, this example, line. Continuing this line recommended inductors capacitors that will provide best overall performance. capacitor list contains both through hole electrolytic surface mount tantalum capacitors from four different capacitor manufacturers. recommended that both manufacturers manufacturer's series that listed table used. this example aluminum electrolytic capacitors from several different manufacturers available with range numbers needed. Panasonic Series Nichicon Series output, capacitor voltage rating least 7.5V more needed. even ESR, switching grade, aluminum electrolytic capacitor would exhibit approximately (see curve Figure voltage rating). This amount would result relatively high output ripple voltage. reduce ripple output voltage, less, capacitor with higher value with higher voltage rating (lower ESR) should selected. capacitor will reduce ripple voltage approximately half.
www.national.com
LM2599
LM2599 Series Buck Regulator Design Procedure (Fixed Output)
PROCEDURE (Fixed Output Voltage Version) Catch Diode Selection (D1) catch diode current rating must least times greater than maximum load current. Also, power supply design must withstand continuous output short, diode should have current rating equal maximum current limit LM2599. most stressful condition this diode overload shorted output condition. reverse voltage rating diode should least 1.25 times maximum input voltage. This diode must fast (short reverse recovery time) must located close LM2599 using short leads short printed circuit traces. Because their fast switching speed forward voltage drop, Schottky diodes provide best performance efficiency, should first choice, especially output voltage applications. Ultra-fast recovery, High-Efficiency rectifiers also provide good results. Ultra-fast recovery diodes typically have reverse recovery times less. Rectifiers such IN5400 series much slow should used. Input Capacitor (CIN) aluminum tantalum bypass capacitor needed between input ground prevent large voltage transients from appearing input. addition, current rating input capacitor should selected least load current. capacitor manufacturers data sheet must checked assure that this current rating exceeded. curve shown Figure shows typical current ratings several different aluminum electrolytic capacitor values. This capacitor should located close using short leads voltage rating should approximately times maximum input voltage. solid tantalum input capacitors used, recomended that they surge current tested manufacturer. caution when using ceramic capacitors input bypassing, because cause severe ringing pin. additional information, section input capacitors Application Information section. Catch Diode Selection (D1)
(Continued)
EXAMPLE (Fixed Output Voltage Version) Refer table shown Figure this example, 20V, 1N5823 Schottky diode will provide best performance, will overstressed even shorted output.
Input Capacitor (CIN) important parameters Input capacitor input voltage rating current rating. With nominal input voltage 12V, aluminum electrolytic capacitor with voltage rating greater than (1.5 VIN) would needed. next higher capacitor voltage rating 25V. current rating requirement input capacitor buck regulator approximately load current. this example, with load, capacitor with current rating least 1.5A needed. curves shown Figure used select appropriate input capacitor. From curves, locate line note which capacitor values have current ratings greater than 1.5A. capacitor could used. through hole design, µF/35V electrolytic capacitor (Panasonic series Nichicon series equivalent) would adequate. other types other manufacturers capacitors used provided ripple current ratings adequate. surface mount designs, solid tantalum capacitors recommended. series available from AVX, 593D series from Sprague both surge current tested.
www.national.com
LM2599
LM2599 Series Buck Regulator Design Procedure (Fixed Output)
Conditions Output Voltage Load Current Input Voltage Inductor Inductance (µH) Inductor Panasonic Series (µF/V) 470/25 560/35 680/35 560/35 470/25 330/35 330/35 470/25 560/25 330/35 330/35 470/25 180/35 180/35 470/25 330/25 180/25 180/35 330/25 180/25 82/25 Output Capacitor Through Hole Electrolytic Nichicon Series (µF/V) 560/16 560/35 680/35 470/35 470/35 330/35 270/50 560/16 560/25 330/35 270/35 560/16 180/35 180/35 470/25 330/25 180/25 180/35 330/25 180/25 82/25
(Continued)
Surface Mount Tantalum Series (µF/V) 330/6.3 330/6.3 330/6.3 330/6.3 330/6.3 330/6.3 220/10 220/10 220/10 220/10 220/10 220/10 100/10 100/10 100/16 100/16 100/16 100/16 100/16 100/16 68/20 Sprague 595D Series (µF/V) 390/6.3 390/6.3 390/6.3 390/6.3 390/6.3 390/6.3 330/10 330/10 330/10 330/10 330/10 330/10 270/10 270/10 180/16 180/16 120/20 120/20 180/16 120/20 68/25
FIGURE LM2599 Fixed Voltage Quick Design Component Selection Table
LM2599 Series Buck Regulator Design Procedure (Adjustable Output)
PROCEDURE (Adjustable Output Voltage Version) Given: VOUT Regulated Output Voltage VIN(max) Maximum Input Voltage ILOAD(max) Maximum Load Current Switching Frequency (Fixed nominal kHz). Programming Output Voltage (Selecting shown Figure following formula select appropriate resistor values. EXAMPLE (Adjustable Output Voltage Version) Given: VOUT VIN(max) ILOAD(max) Switching Frequency (Fixed nominal kHz). Programming Output Voltage (Selecting shown Figure Select Solve
Select value between lower resistor values minimize noise pickup sensitive feedback pin. (For lowest temperature coefficient best stability with time, metal film resistors.)
(16.26 15.26k, closest value 15.4 15.4
www.national.com
LM2599
LM2599 Series Buck Regulator Design Procedure (Adjustable Output)
(Continued) PROCEDURE (Adjustable Output Voltage Version) Inductor Selection (L1) Calculate inductor Volt microsecond constant µs), from following formula: EXAMPLE (Adjustable Output Voltage Version) Inductor Selection (L1) Calculate inductor Volt microsecond constant
where VSAT internal switch saturation voltage 1.16V diode forward voltage drop 0.5V value from previous formula match with number vertical axis Inductor Value Selection Guide shown Figure horizontal axis, select maximum load current. Identify inductance region intersected value Maximum Load Current value. Each region identified inductance value inductor code (LXX). Select appropriate inductor from four manufacturer's part numbers listed Figure Output Capacitor Selection (COUT) majority applications, electrolytic solid tantalum capacitors between provide best results. This capacitor should located close using short capacitor leads short copper traces. capacitors larger than additional information, section output capacitors application information section. simplify capacitor selection procedure, refer quick design table shown Figure This table contains different output voltages, lists various output capacitors that will provide best design solutions. capacitor voltage rating should least times greater than output voltage, often much higher voltage ratings needed satisfy requirements needed output ripple voltage.
34.2 ILOAD(max) From inductor value selection guide shown Figure inductance region intersected horizontal line vertical line inductor code L39. From table Figure locate line L39, select inductor part number from list manufacturers part numbers. Output Capacitor SeIection (COUT) section COUT Application Information section. From quick design table shown Figure locate output voltage column. From that column, locate output voltage closest output voltage your application. this example, select line. Under output capacitor section, select capacitor from list through hole electrolytic surface mount tantalum types from four different capacitor manufacturers. recommended that both manufacturers manufacturers series that listed table used. this example, through hole aluminum electrolytic capacitors from several different manufacturers available. 220/35 Panasonic Series 150/35 Nichicon Series output, capacitor rating least more needed. this example, either capacitor would work. rating chosen because lower which provides lower output ripple voltage. Other manufacturers other types capacitors also used, provided capacitor specifications (especially ESR) closely match types listed table. Refer capacitor manufacturers data sheet this information. Feedforward Capacitor (CFF) table shown Figure contains feed forward capacitor values various output voltages. this example, capacitor needed.
Feedforward Capacitor (CFF) (See Figure output voltages greater than approximately 10V, additional capacitor required. compensation capacitor typically between wired parallel with output voltage setting resistor, provides additional stability high output voltages, input-output voltages, and/or very output capacitors, such solid tantalum capacitors.
This capacitor type ceramic, plastic, silver mica, etc. (Because unstable characteristics ceramic capacitors made with material, they recommended.)
www.national.com
LM2599
LM2599 Series Buck Regulator Design Procedure (Adjustable Output)
(Continued) PROCEDURE (Adjustable Output Voltage Version) Catch Diode Selection (D1) catch diode current rating must least times greater than maximum load current. Also, power supply design must withstand continuous output short, diode should have current rating equal maximum current limit LM2599. most stressful condition this diode overload shorted output condition. reverse voltage rating diode should least 1.25 times maximum input voltage. This diode must fast (short reverse recovery time) must located close LM2599 using short leads short printed circuit traces. Because their fast switching speed forward voltage drop, Schottky diodes provide best performance efficiency, should first choice, especially output voltage applications. Ultra-fast recovery, High-Efficiency rectifiers also good choice, some types with abrupt turn-off characteristic cause instability problems. Ultra-fast recovery diodes typically have reverse recovery times less. Rectifiers such 1N4001 series much slow should used. Input Capacitor (CIN) aluminum tantalum bypass capacitor needed between input ground prevent large voltage transients from appearing input. addition, current rating input capacitor should selected least load current. capacitor manufacturers data sheet must checked assure that this current rating exceeded. curve shown Figure shows typical current ratings several different aluminum electrolytic capacitor values. This capacitor should located close using short leads voltage rating should approximately times maximum input voltage. solid tantalum input capacitors used, recomended that they surge current tested manufacturer. caution when using high dielectric constant ceramic capacitor input bypassing, because cause severe ringing pin. additional information, section input capacitor application information section. EXAMPLE (Adjustable Output Voltage Version) Catch Diode Selection (D1) Refer table shown Figure Schottky diodes provide best performance, this example 40V, 1N5825 Schottky diode would good choice. diode rating more than adequate will overstressed even shorted output.
Input Capacitor (CIN) important parameters Input capacitor input voltage rating current rating. With nominal input voltage 28V, aluminum electrolytic aluminum electrolytic capacitor with voltage rating greater than (1.5 VIN) would needed. Since next higher capacitor voltage rating 50V, capacitor should used. capacitor voltage rating (1.5 VIN) conservative guideline, modified somewhat desired. current rating requirement input capacitor buck regulator approximately load current. this example, with load, capacitor with current rating least 1.5A needed. curves shown Figure used select appropriate input capacitor. From curves, locate line note which capacitor values have current ratings greater than 1.5A. Either capacitor could used. through hole design, µF/50V electrolytic capacitor (Panasonic series Nichicon series equivalent) would adequate. Other types other manufacturers capacitors used provided ripple current ratings adequate. surface mount designs, solid tantalum capacitors used, caution must exercised with regard capacitor sure current rating (see Application Information input capacitors this data sheet). series available from AVX, 593D series from Sprague both surge current tested.
further simplify buck regulator design procedure, National Semiconductor making available computer design software used with Simple Switcher line switching regulators. Switchers Made Simple (version 4.2.1 later) available 31/2" diskette compatible computers.
www.national.com
LM2599
LM2599 Series Buck Regulator Design Procedure (Adjustable Output)
(Continued)
Output Voltage
Through Hole Output Capacitor Panasonic Series (µF/V) 820/35 560/35 470/25 330/25 330/25 220/35 220/35 100/50 Nichicon Series (µF/V) 820/35 470/35 470/25 330/25 330/25 220/35 150/35 100/50 Feedforward Capacitor
Surface Mount Output Capacitor Series (µF/V) 330/6.3 330/6.3 220/10 100/16 100/16 68/20 33/25 10/35 Sprague 595D Series (µF/V) 470/4 390/6.3 330/10 180/16 180/16 120/20 33/25 15/50 Feedforward Capacitor
FIGURE Output Capacitor Feedforward Capacitor Selection Table
LM2599 Series Buck Regulator Design Procedure
INDUCTOR VALUE SELECTION GUIDES (For Continuous Mode Operation)
DS012582-26
DS012582-28
FIGURE LM2599-3.3
FIGURE LM2599-12
DS012582-27
DS012582-29
FIGURE LM2599-5.0
FIGURE LM2599-ADJ
www.national.com
LM2599
LM2599 Series Buck Regulator Design Procedure
Inductance (µH) Current Schott Through Hole 0.99 0.99 1.17 1.40 1.70 0.80 1.00 1.20 1.47 1.78 1.70 67148350 67144070 67144080 67144090 67148370 67148380 67144100 67144110 67144120 67144130 67144140 67144150 67144160 67148390 67148400 67144170 67144180 67144190 67144200 67144210 67144220 67144230 67148410 67144240 67144250 Surface Mount 67148460 67144450 67144460 67144470 67148480 67148490 67144480 67144490 67144500 67144510 67144520 67144530 67144540 67148500 67148790 67148290 67148300 Hole RL-1284-22-43 RL-5471-5 RL-5471-6 RL-5471-7 RL-1283-22-43 RL-1283-15-43 RL-5471-1 RL-5471-2 RL-5471-3 RL-5471-4 RL-5471-5 RL-5471-6 RL-5471-7 RL-1283-22-43 RL-1283-15-43 RL-5473-1 RL-5473-4 RL-5472-1 RL-5472-2 RL-5472-3 RL-5472-4 RL-5472-5 RL-5473-4 RL-5473-2 RL-5473-3 Renco Through
(Continued)
Pulse Engineering Surface Mount RL1500-22 RL1500-68 Through Hole PE-53815 PE-53821 PE-53822 PE-53823 PE-53824 PE-53825 PE-53826 PE-53827 PE-53828 PE-53829 PE-53830 PE-53831 PE-53932 PE-53933 PE-53934 PE-53935 PE-54036 PE-54037 PE-54038 PE-54039 PE-54040 PE-54041 PE-54042 PE-54043 PE-54044 Surface Mount PE-53815-S PE-53821-S PE-53822-S PE-53823-S PE-53825-S PE-53824-S PE-53826-S PE-53827-S PE-53828-S PE-53829-S PE-53830-S PE-53831-S PE-53932-S PE-53933-S PE-53934-S PE-53935-S PE-54036-S PE-54037-S PE-54038-S PE-54039-S PE-54040-S PE-54041-S PE-54042-S
Coilcraft Surface Mount DO3308-223 DO3316-683 DO3316-473 DO3316-333 DO3316-223 DO3316-153 DOS022P-334 DOS022P-224 DOS022P-154 DOS022P-104 DOS022P-683 DOS022P-473 DOS022P-333 DOS022P-223 DOS022P-153
FIGURE Inductor Manufacturers Part Numbers
Coilcraft Inc. Coilcraft Inc., Europe Pulse Engineering Inc. Pulse Engineering Inc., Europe Renco Electronics Inc. Schott Corp.
Phone Phone Phone Phone Phone Phone
(800) 322-2645 (708) 639-1469 1236 1236 (619) 674-8100 (619) 674-8262 +353 +353 (800) 645-5828 (516) 586-5562 (612) 475-1173 (612) 475-1786
FIGURE Inductor Manufacturers Phone Numbers
www.national.com
LM2599
LM2599 Series Buck Regulator Design Procedure
Nichicon Corp. Panasonic Corp. Sprague/Vishay Phone Phone Phone Phone
(Continued)
(708) 843-7500 (708) 843-2798 (714) 373-7857 (714) 373-7102 (803) 448-9411 (803) 448-1943 (207) 324-4140 (207) 324-7223
FIGURE Capacitor Manufacturers Phone Numbers
Diodes Surface Mount Schottky Ultra Fast Recovery SK32 30WQ03 SK33 these diodes rated least 50V. SK34 MBRS340 30WQ04 more SK35 MBRS360 30WQ05 MURS320 30WF10 1N5820 SR302 MBR320 1N5821 MBR330 31DQ03 1N5822 SR304 MBR340 31DQ04 SR305 MBR350 31DQ05 FIGURE Diode Selection Table 50WQ05 MUR320 Through Hole Schottky Ultra Fast Recovery these diodes rated least 50V. 50WQ04 50WQ03 Schottky
Diodes Surface Mount Ultra Fast Recovery these diodes rated least 50V. SR503 1N5824 SB530 SR504 1N5825 MURS620 50WF10 SB550 50SQ080 SB540 MUR620 HER601 SR502 1N5823 SB520 Through Hole Schottky Ultra Fast Recovery these diodes rated least 50V.
www.national.com
LM2599
Block Diagram
DS012582-30
FIGURE
Application Information
FUNCTIONS +VIN (Pin This positive input supply switching regulator. suitable input bypass capacitor must present this minimize voltage transients supply switching currents needed regulator. Ground (Pin Circuit ground. Output (Pin Internal switch. voltage this switches between approximately (+VIN VSAT) approximately -0.5V, with duty cycle VOUT/VIN. minimize coupling sensitive circuitry, board copper area connected this should kept minimum. Feedback (Pin Senses regulated output voltage complete feedback loop. Shutdown /Soft-start (Pin This dual function provides following features: Allows switching regulator circuit shut down using logic level signals thus dropping total input supply current approximately Adding capacitor this provides soft-start feature which minimizes startup current provides controlled ramp output voltage. Error Flag (Pin Open collector output that provides signal (flag transistor when regulated output voltage drops more than from nominal output voltage. start Error Flag until VOUT reaches nominal output voltage delay time determined Delay capacitor. This signal used reset microprocessor power-up. Delay (Pin power-up, this used provide time delay between time regulated output voltage reaches nominal output voltage, time error flag output goes high.
www.national.com
Special Note above three features (Shutdown /Soft-start, Error Flag, Delay) used, respective pins should left open. EXTERNAL COMPONENTS SOFT-START CAPACITOR capacitor this provides regulator with Soft-start feature (slow start-up). When input voltage first applied regulator, when Shutdown /Soft-start allowed high, constant current (approximately begins charging this capacitor). capacitor voltage rises, regulator goes through four operating regions (See bottom curve Figure 13).
Regulator Shutdown. When voltage between 1.3V, regulator shutdown, output voltage zero, quiescent current approximately Regulator output voltage zero. With voltage between approximately 1.3V 1.8V, internal regulator circuitry operating, quiescent current rises approximately output voltage still zero. Also, 1.3V threshold exceeded, Soft-start capacitor charging current decreases from down approximately This decreases slope capacitor voltage ramp. Soft-start Region. When voltage between 1.8V 2.8V 25°C), regulator Soft-start condition. switch (Pin duty cycle initially starts very low, with narrow pulses gradually wider capacitor ramps towards 2.8V. duty cycle increases, output voltage also increases controlled ramp center curve Figure input supply current requirement also starts level
LM2599
Application Information
(Continued)
narrow pulses ramp controlled manner. This very useful feature some switcher topologies that require large startup currents (such inverting configuration) which load down input power supply.
Note: lower curve shown Figure shows Soft-start region from 100%. This duty cycle percentage, output voltage percentage. Also, Soft-start voltage range negative temperature coefficient associated with Soft-start curve electrical characteristics section.
Normal operation. Above 2.8V, circuit operates standard Pulse Width Modulated switching regulator. capacitor will continue charge until reaches internal clamp voltage approximately this driven from voltage source, current must limited about part operated with input voltage below internal soft-start clamp voltage approximately voltage SD/SS tracks input voltage disturbed step voltage. maintain proper function under these conditions, strongly recommended that SD/SS clamped externally between maximum soft-start threshold 4.5V minimum input voltage. Figure example external 3.7V (approx.) clamp that prevents line-step related glitch does interfere with soft-start behavior device.
DS012582-31
FIGURE Soft-start, Delay, Error, Output
DS012582-32
FIGURE Timing Diagram Output
www.national.com
LM2599
Application Information
(Continued)
DS012582-65
FIGURE External 3.7V Soft-Start Clamp DELAY CAPACITOR CDELAY Provides delay error flag output. upper curve Figure also refer timing diagrams Figure capacitor this provides time delay between time regulated output voltage (when increasing value) reaches nominal output voltage, time error flag output goes high. constant current from delay charges delay capacitor resulting voltage ramp. When this voltage reaches threshold approximately 1.3V, open collector error flag output power goes high. This signal used indicate that regulated output reached correct voltage stabilized. reason, regulated output voltage drops more, error output flag (Pin immediately goes (internal transistor turns on). delay capacitor provides very little delay regulated output dropping regulation. delay time output that decreasing approximately 1000 times less than delay rising output. delay capacitor, delay time would approximately when output rising passes through threshold, delay output dropping would only approximately RPull error flag output, power collector transistor, with emitter internally grounded. error flag, pullup resistor positive voltage needed. error flag transistor rated maximum sink approximately error flag used, left open. FEEDFORWARD CAPACITOR (Adjustable Output Voltage Version) Feedforward Capacitor CFF, shown across Figure used when output voltage greater than when COUT very ESR. This capacitor adds lead compensation feedback loop increases phase margin better loop stability. selection, design procedure section. output ripple large nominal output voltage), this ripple coupled feedback through feedforward capacitor cause error comparator trigger error flag. this situation, adding resistor, RFF, series with feedforward capacitor, approximately times will attenuate ripple voltage feedback pin. INPUT CAPACITOR aluminum tantalum bypass capacitor needed between input ground pin. must located near regulator using short leads. This capacitor prevents large voltage transients from appearing input, provides instantaneous current needed each time switch turns important parameters Input capacitor voltage rating current rating. Because relatively high currents flowing buck regulator's input capacitor, this capacitor should chosen current rating rather than capacitance voltage ratings, although capacitance value voltage rating directly related current rating. current rating capacitor could viewed capacitor's power rating. current flowing through capacitors internal produces power which causes internal temperature capacitor rise. current rating capacitor determined amount current required raise internal temperature approximately 10°C above ambient temperature 105°C. ability capacitor dissipate this heat surrounding will determine amount current capacitor safely sustain. Capacitors that physically large have large surface area will typically have higher current ratings. given capacitor value, higher voltage electrolytic capacitor will physically larger than lower voltage capacitor, thus able dissipate more heat surrounding air, therefore will have higher current rating.
www.national.com
LM2599
Application Information
(Continued)
bypassing, several precautions must observed. small percentage solid tantalum capacitors short inrush current rating exceeded. This happen turn when input voltage suddenly applied, course, higher input voltages produce higher inrush currents. Several capacitor manufacturers 100% surge current testing their products minimize this potential problem. high turn currents expected, necessary limit this current adding either some resistance inductance before tantalum capacitor, select higher voltage capacitor. with aluminum electrolytic capacitors, ripple current rating must sized load current. OUTPUT CAPACITOR COUT output capacitor required filter output provide regulator loop stability. impedance Electrolytic solid tantalum capacitors designed switching regulator applications must used. When selecting output capacitor, important capacitor parameters are; Equivalent Series Resistance (ESR), ripple current rating, voltage rating, capacitance value. output capacitor, value most important parameter. output capacitor requires value that upper lower limit. output ripple voltage, value needed. This value determined maximum allowable output ripple voltage, typically output voltage. selected capacitor's extremely low, there possibility unstable feedback loop, resulting oscillation output. Using capacitors listed tables, similar types, will provide design solutions under conditions. very output ripple voltage (less than required, refer section Output Voltage Ripple Transients post ripple filter. aluminum electrolytic capacitor's value related capacitance value voltage rating. most cases, higher voltage electrolytic capacitors have lower values (see Figure 17). Often, capacitors with much higher voltage ratings needed provide values required output ripple voltage. output capacitor many different switcher designs often satisfied with only three four different capacitor values several different voltage ratings. quick design component selection tables Figure typical capacitor values, voltage ratings, manufacturers capacitor types. Electrolytic capacitors recommended temperatures below -25°C. rises dramatically cold temperatures typically rises -25°C much -40°C. curve shown Figure Solid tantalum capacitors have much better spec cold temperatures recommended temperatures below -25°C. CATCH DIODE Buck regulators require diode provide return path inductor current when switch turns off. This must fast diode must located close LM2599 using short leads short printed circuit traces. Because their very fast switching speed forward voltage drop, Schottky diodes provide best performance, especially output voltage applications lower). Ultra-fast recovery, High-Efficiency rectifiers also good choice, some types with abrupt turnoff charac21 www.national.com
DS012582-33
FIGURE Current Ratings Electrolytic Capacitors (Typical)
DS012582-34
FIGURE Capacitor Capacitor Voltage Rating (Typical Electrolytic Capacitor) consequences operating electrolytic capacitor above current rating shortened operating life. higher temperature speeds evaporation capacitor's electrolyte, resulting eventual failure. Selecting input capacitor requires consulting manufacturers data sheet maximum allowable ripple current. maximum ambient temperature 40°C, general guideline would select capacitor with ripple current rating approximately load current. ambient temperatures 70°C, current rating load current would good choice conservative design. capacitor voltage rating must least 1.25 times greater than maximum input voltage, often much higher voltage capacitor needed satisfy current requirements. graph shown Figure shows relationship between electrolytic capacitor value, voltage rating, current rated for. These curves were obtained from Nichicon "PL" series ESR, high reliability electrolytic capacitors designed switching regulator applications. Other capacitor manufacturers offer similar types capacitors, always check capacitor data sheet. "Standard" electrolytic capacitors typically have much higher numbers, lower current ratings typically have shorter operating lifetime. Because their small size excellent performance, surface mount solid tantalum capacitors often used input
LM2599
Application Information
(Continued)
teristic cause instability problems. Ultra-fast recovery diodes typically have reverse recovery times less. Rectifiers such IN5400 series much slow should used.
DS012582-36
FIGURE (IIND) Peak-to-Peak Inductor Ripple Current Percentage Load Current) Load Current
DS012582-35
FIGURE Capacitor Change Temperature INDUCTOR SELECTION switching regulators have basic modes operation; continuous discontinuous. difference between types relates inductor current, whether flowing continuously, drops zero period time normal switching cycle. Each mode distinctively different operating characteristics, which affect regulators performance requirements. Most switcher designs will operate discontinuous mode when load current low. LM2599 Simple Switcher family) used both continuous discontinuous modes operation. many cases preferred mode operation continuous mode. offers greater output power, lower peak switch, inductor diode currents, have lower output ripple voltage. does require larger inductor values keep inductor current flowing continuously, especially output load currents and/or high input voltages. simplify inductor selection process, inductor selection guide (nomograph) designed (see Figure through This guide assumes that regulator operating continuous mode, selects inductor that will allow peak-to-peak inductor ripple current certain percentage maximum design load current. This peak-to-peak inductor ripple current percentage fixed, allowed change different design load currents selected. (See Figure 19).
allowing percentage inductor ripple current increase load currents, inductor value size kept relatively low. When operating continuous mode, inductor current waveform ranges from triangular sawtooth type waveform (depending input voltage), with average value this current waveform equal output load current. Inductors available different styles such core, toroid, E-core, bobbin core, etc., well different core materials, such ferrites powdered iron. least expensive, bobbin, stick core, consists wire wound ferrite bobbin. This type construction makes inexpensive inductor, since magnetic flux completely contained within core, generates more Electro-Magnetic Interference (EMl). This magnetic flux induce voltages into nearby printed circuit traces, thus causing problems with both switching regulator operation nearby sensitive circuitry, give incorrect scope readings because induced voltages scope probe. Also section Open Core Inductors. When multiple switching regulators located same board, open core magnetics cause interference between more regulator circuits, especially high currents. torroid E-core inductor (closed magnetic structure) should used these situations. inductors listed selection chart include ferrite E-core construction Schott, ferrite bobbin core Renco Coilcraft, powdered iron toroid Pulse Engineering. Exceeding inductor's maximum current rating cause inductor overheat because copper wire losses, core saturate. inductor begins saturate, inductance decreases rapidly inductor begins look mainly resistive (the resistance winding). This cause switch current rise very rapidly force switch into cycle-by-cycle current limit, thus reducing output load current. This also result overheating inductor and/or LM2599. Different inductor types have different saturation characteristics, this should kept mind when selecting inductor. inductor manufacturer's data sheets include current energy limits avoid inductor saturation.
www.national.com
LM2599
Application Information
DISCONTINUOUS MODE OPERATION
(Continued)
selection guide chooses inductor values suitable continuous mode operation, current applications and/or high input voltages, discontinuous mode design better choice. would inductor that would physically smaller, would need only half third inductance value needed continuous mode design. peak switch inductor currents will higher discontinuous design, these load currents below), maximum switch current will still less than switch current limit. Discontinuous operation have voltage waveforms that considerable different than continuous design. output (switch) waveform have some damped sinusoidal ringing present. (See Typical Performance Characteristics photo titled Discontinuous Mode Switching Waveforms) This ringing normal discontinuous operation, caused feedback loop instabilities. discontinuous operation, there period time where neither switch diode conducting, inductor current dropped zero. During this time, small amount energy circulate between inductor switch/ diode parasitic capacitance causing this characteristic ringing. Normally this ringing problem, unless amplitude becomes great enough exceed input voltage, even then, there very little energy present cause damage. Different inductor types and/or core materials produce different amounts this characteristic ringing. Ferrite core inductors have very little core loss therefore produce most ringing. higher core loss powdered iron inductors produce less ringing. desired, series could placed parallel with inductor dampen ringing. computer aided design software Switchers Made Simple (version 4.3) will provide component values continuous discontinuous modes operation.
capacitors because they affect loop stability, resulting oscillation problems. very output ripple voltage needed (less than mV), post ripple filter recommended (See Figure inductance required typically between with resistance, maintain good load regulation. output filter capacitor also required assure good dynamic load response ripple reduction. this capacitor desired, because regulator feedback loop. photo shown Figure shows typical output ripple voltage, with without post ripple filter. When observing output ripple with scope, essential that short, inductance scope probe ground connection used. Most scope probe manufacturers provide special probe terminator which soldered onto regulator board, preferable output capacitor. This provides very short scope ground thus eliminating problems associated with inch ground lead normally provided with probe, provides much cleaner more accurate picture ripple voltage waveform. voltage spikes caused fast switching action output switch, diode, parasitic inductance output filter capacitor, associated wiring. minimize these voltage spikes, output capacitor should designed switching regulator applications, lead lengths must kept very short. Wiring inductance, stray capacitance, well scope probe used evaluate these transients, contribute amplitude these spikes.
DS012582-49
FIGURE Peak-to-Peak Inductor Ripple Current Load Current When switching regulator operating continuous mode, inductor current waveform ranges from triangular sawtooth type waveform (depending input voltage). given input output voltage, peak-to-peak amplitude this inductor current waveform remains constant. load current increases decreases, entire sawtooth current waveform also rises falls. average value center) this current waveform equal load current. load current drops enough level, bottom sawtooth current waveform will reach zero, switcher will smoothly change from continuous discontinuous mode operation. Most switcher designs (irregardless large inductor value will forced discontinuous output lightly loaded. This perfectly acceptable mode operation. switching regulator design, knowing value peak-to-peak inductor ripple current (IIND) useful
www.national.com
DS012582-37
FIGURE Post Ripple Filter Waveform OUTPUT VOLTAGE RIPPLE TRANSIENTS output voltage switching power supply operating continuous mode will contain sawtooth ripple voltage switcher frequency, also contain short voltage spikes peaks sawtooth waveform. output ripple voltage function inductor sawtooth ripple current output capacitor. typical output ripple voltage range from approximately 0.5% output voltage. obtain ripple voltage, output capacitor must low, however, caution must exercised when using extremely
LM2599
Application Information
(Continued)
OPEN CORE INDUCTORS Another possible source increased output ripple voltage unstable operation from open core inductor. Ferrite bobbin stick inductors have magnetic lines flux flowing through from bobbin other end. These magnetic lines flux will induce voltage into wire board copper trace that comes within inductor's magnetic field. strength magnetic field, orientation location copper trace magnetic field, distance between copper trace inductor, determine amount voltage generated copper trace. Another looking this inductive coupling consider board copper trace turn transformer (secondary) with inductor winding primary. Many millivolts generated copper trace located near open core inductor which cause stability problems high output ripple voltage problems. unstable operation seen, open core inductor used, it's possible that location inductor with respect other traces problem. determine this problem, temporarily raise inductor away from board several inches then check circuit operation. circuit operates correctly, then magnetic flux from open core inductor causing problem. Substituting closed core inductor such torroid E-core will correct problem, re-arranging layout necessary. Magnetic flux cutting device ground trace, feedback trace, positive negative traces output capacitor should minimized. Sometimes, locating trace directly beneath bobbin inductor will provide good results, provided exactly center inductor (because induced voltages cancel themselves out), center direction other, then problems could arise. flux problems present, even direction inductor winding make difference some circuits. This discussion open core inductors frighten user, alert user what kind problems watch when using them. Open core bobbin "stick" inductors inexpensive, simple making compact efficient inductor, they used millions many different applications. THERMAL CONSIDERATIONS LM2599 available packages, 7-pin TO-220 7-pin surface mount TO-263 (S). TO-220 package needs heat sink under most conditions. size heat sink depends input voltage, output voltage, load current ambient temperature. curves Figure show LM2599T junction temperature rises above ambient temperature load different input output voltages. data these curves taken with LM2599T (TO-220 package) operating buck switching regulator ambient temperature 25°C (still air). These temperature rise numbers approximate there many factors that affect these temperatures. Higher ambient temperatures require more heat sinking. TO-263 surface mount package designed soldered copper printed circuit board. copper board heat sink this package other heat producing components, such catch diode inductor. board copper area that package soldered should least in2, ideally should have more square inches (0.0028 copper. Additional copper area improves thermal characteristics,
determining number other circuit parameters. Parameters such peak inductor peak switch current, minimum load current before circuit becomes discontinuous, output ripple voltage output capacitor calculated from peak-to-peak IIND. When inductor nomographs shown Figure through used select inductor value, peak-to-peak inductor ripple current immediately determined. curve shown Figure shows range (IIND) that expected different load currents. curve also shows peak-to-peak inductor ripple current (IIND) changes from lower border upper border (for given load current) within inductance region. upper border represents higher input voltage, while lower border represents lower input voltage (see Inductor Selection Guides). These curves only correct continuous mode operation, only inductor selection guides used select inductor value Consider following example: VOUT maximum load current 2.5A 12V, nominal, varying between 16V. selection guide Figure shows that vertical line 2.5A load current, horizontal line input voltage intersect approximately midway between upper lower borders inductance region. inductor will allow peak-to-peak inductor current (IIND) flow that will percentage maximum load current. Referring Figure follow 2.5A line approximately midway into inductance region, read peak-to-peak inductor ripple current (IIND) left hand axis (approximately p-p). input voltage increases 16V, approaches upper border inductance region, inductor ripple current increases. Referring curve Figure seen that load current 2.5A, peak-to-peak inductor ripple current (IIND) with range from upper border (16V lower border (10V in). Once IIND value known, following formulas used calculate additional information about switching regulator circuit. Peak Inductor peak switch current
Minimum load current before circuit becomes discontinuous
Output Ripple Voltage (IIND)x(ESR COUT) 0.62Ax0.1=62
www.national.com
LM2599
Application Information
(Continued)
with copper areas greater than approximately in2, only small improvements heat dissipation realized. further thermal improvements needed, double sided, multilayer pc-board with large copper areas and/or airflow recommended. curves shown Figure show LM2599S (TO-263 package) junction temperature rise above ambient temperature with load various input output voltages. This data taken with circuit operating buck switching regulator with components mounted board simulate junction temperature under actual operating conditions. This curve used quick check approximate junction temperature various conditions, aware that there many factors that affect junction temperature. When load currents higher than used, double sided multilayer pc-boards with large copper areas and/or airflow might needed, especially high ambient temperatures high output voltages.
DS012582-39
Circuit Data Temperature Rise Curve TO-263 Package Capacitors Inductor Diode board Surface mount tantalum, molded size Surface mount, Pulse engineering, Surface mount, 40V, Schottky square inches single sided copper (0.0028")
FIGURE Junction Temperature Rise, TO-263 best thermal performance, wide copper traces generous amounts printed circuit board copper should used board layout. (One exception this output (switch) pin, which should have large areas copper.) Large areas copper provide best transfer heat (lower thermal resistance) surrounding air, moving lowers thermal resistance even further. Package thermal resistance junction temperature rise numbers approximate, there many factors that will affect these numbers. Some these factors include board size, shape, thickness, position, location, even board temperature. Other factors are, trace width, total printed circuit copper area, copper thickness, single- double-sided, multilayer board amount solder board. effectiveness board dissipate heat also depends size, quantity spacing other components board, well whether surrounding still moving. Furthermore, some these components such catch diode will heat board heat vary input voltage changes. inductor, depending physical size, type core material resistance, could either heat sink taking heat away from board, could heat board. SHUTDOWN /SOFT-START circuit shown Figure standard buck regulator with out, load, using 0.068 Soft-start capacitor. photo Figure Figure show effects Soft-start output voltage, input current, with, without Soft-start capacitor. reduced input current required startup very evident when comparing photos. Soft-start feature reduces startup current from 2.6A down delays slows down output voltage rise time.
www.national.com
DS012582-38
Circuit Data Temperature Rise Curve TO-220 Package Capacitors Inductor Diode board Through hole electrolytic Through hole Renco Through hole, 40V, Schottky square inches single sided copper (0.0028")
FIGURE Junction Temperature Rise, TO-220
LM2599
Application Information
(Continued)
DS012582-41
DS012582-40
FIGURE Output Voltage, Input Current, Start-Up, WITHOUT Soft-start This reduction start current useful situations where input power source limited amount current deliver. some applications Soft-start used replace undervoltage lockout delayed startup functions. very slow output voltage ramp desired, Soft-start capacitor made much larger. Many seconds even minutes possible. only shutdown feature needed, Soft-start capacitor eliminated.
FIGURE Output Voltage, Input Current, Start-Up, WITH Soft-start
DS012582-42
FIGURE Typical Circuit Using Shutdown /Soft-start Error Flag Features
www.national.com
LM2599
Application Information
(Continued)
DS012582-43
FIGURE Inverting Regulator With Shutdown Soft-start lNVERTING REGULATOR circuit Figure converts positive input voltage negative output voltage with common ground. circuit operates bootstrapping regulator's ground negative output voltage, then grounding feedback pin, regulator senses inverted output voltage regulates This example uses LM2599-5 generate output, other output voltages possible selecting other output voltage versions, including adjustable version. Since this regulator topology produce output voltage that either greater than less than input voltage, maximum output current greatly depends both input output voltage. curve shown Figure provides guide amount output load current possible different input output voltage conditions. maximum voltage appearing across regulator absolute input output voltage, this must limited maximum 40V. this example, when converting +20V -5V, regulator would between input ground pin. LM2599 maximum input voltage rating 40V. Inverting Regulator additional diode required this regulator configuration. Diode used isolate input voltage ripple noise from coupling through capacitor output, under light load conditions. Also, this diode isolation changes topology closely resemble buck configuration thus providing good closed loop stability. Schottky diode recommended input voltages, (because lower voltage drop) higher input voltages, IN5400 diode could used. Because differences operation inverting regulator, standard design procedure used select inductor value. majority designs, 3.5A inductor best choice. Capacitor selection also narrowed down just values. Using values shown Figure will provide good results majority inverting designs. This type inverting regulator require relatively large amounts input current when starting even with light loads. Input currents high LM2599 current limit (approximately 4.5A) needed more, until output reaches nominal output voltage. actual time depends output voltage size output capacitor. Input power sources that current limited sources that deliver these currents without getting loaded down, work correctly. Because relatively high startup currents required inverting topology, Soft-start feature shown Figure recommended. Also shown Figure several shutdown methods inverting configuration. With inverting configuration, some level shifting required, because ground regulator longer ground, negative output voltage. shutdown methods shown accept ground referenced shutdown signals. UNDERVOLTAGE LOCKOUT Some applications require regulator remain until input voltage reaches predetermined voltage. Figure contains undervoltage lockout circuit buck configuration, while Figure inverting types (only circuitry pertaining undervoltage lockout
www.national.com
DS012582-44
FIGURE Maximum Load Current Inverting Regulator Circuit
LM2599
Application Information
(Continued)
shown). Figure uses zener diode establish threshold voltage when switcher begins operating. When input voltage less than zener voltage, resistors hold Shutdown /Soft-start low, keeping regulator shutdown mode. input voltage exceeds zener voltage, zener conducts, pulling Shutdown /Soft-start high, allowing regulator begin switching. threshold voltage undervoltage lockout feature approximately 1.5V greater than zener voltage.
DS012582-47
FIGURE Undervoltage Lockout Without Hysteresis Inverting Regulator
DS012582-45
FIGURE Undervoltage Lockout Buck Regulator
Figure apply same feature inverting circuit. Figure features constant threshold voltage turn turn (zener voltage plus approximately volt). hysteresis needed, circuit Figure turn voltage which different than turn voltage. amount hysteresis approximately equal value output voltage. Since internal zener clamp, needed limit current into this approximately when
DS012582-46
FIGURE Undervoltage Lockout With Hysteresis Inverting Regulator NEGATIVE VOLTAGE CHARGE PUMP Occasionally current negative voltage needed biasing parts circuit. simple method generating negative voltage using charge pump technique switching waveform present pin, shown Figure This unregulated negative voltage approximately equal positive input voltage (minus volts), supply output current. There requirement however, that there minimum load 1.2A regulated positive output charge pump work correctly. Also, resistor required limit charging current some value less than LM2599 current limit (typically 4.5A). This method generating negative output voltage without additional inductor used with other members Simple Switcher Family, using either buck boost topology.
DS012582-48
FIGURE Charge Pump Generating Current, Negative Output Voltage
www.national.com
LM2599
Application Information
(Continued)
TYPICAL THROUGH HOLE BOARD LAYOUT, FIXED OUTPUT SIZE), DOUBLE SIDED
DS012582-51
CIN: 50V, Aluminum Electrolytic Panasonic, "HFQ Series" COUT: 35V, Aluminum Electrolytic Panasonic, "HFQ Series" Schottky Rectifier, 1N5825 L39, Renco, Through Hole RPULL CDELAY: CSD/SS: Thermalloy Heat Sink #7020
www.national.com
LM2599
Application Information
(Continued)
TYPICAL THROUGH HOLE BOARD LAYOUT, ADJUSTABLE OUTPUT SIZE), DOUBLE SIDED
DS012582-52
CIN: 50V, Aluminum Electrolytic Panasonic, "HFQ Series" COUT: Aluminum Electrolytic Panasonic, "HFQ Series" Schottky Rectifier, 1N5825 L39, Renco, Through Hole formula Design Procedure CFF: Figure RFF: Application Information Section (CFF Section) RPULL CDELAY: CSD/SS: Thermalloy Heat Sink #7020
FIGURE Board Layout
www.national.com
LM2599
Physical Dimensions
inches (millimeters) unless otherwise noted
7-Lead TO-220 Bent Staggered Package Order Number LM2599T-3.3, LM2599T-5.0, LM2599T-12 LM2599T-ADJ Package Number TA07B
www.national.com
LM2599 SIMPLE SWITCHER Power Converter Step-Down Voltage Regulator, with Features
Physical Dimensions
inches (millimeters) unless otherwise noted (Continued)
7-Lead TO-263 Bent Formed Package Order Number LM2599S-3.3, LM2599S-5.0, LM2599S-12 LM2599S-ADJ Package Number TS7B
LIFE SUPPORT POLICY NATIONAL'S PRODUCTS AUTHORIZED CRITICAL COMPONENTS LIFE SUPPORT DEVICES SYSTEMS WITHOUT EXPRESS WRITTEN APPROVAL PRESIDENT GENERAL COUNSEL NATIONAL SEMICONDUCTOR CORPORATION. used herein: Life support devices systems devices systems which, intended surgical implant into body, support sustain life, whose failure perform when properly used accordance with instructions provided labeling, reasonably expected result significant injury user.
National Semiconductor Corporation Americas Tel: 1-800-272-9959 Fax: 1-800-737-7018 Email: support@nsc.com www.national.com National Semiconductor Europe Fax: 180-530 Email: europe.support@nsc.com Deutsch Tel: 9508 6208 English Tel: 2171 Tel: 8790
critical component component life support device system whose failure perform reasonably expected cause failure life support device system, affect safety effectiveness.
National Semiconductor Asia Pacific Customer Response Group Tel: 65-2544466 Fax: 65-2504466 Email: ap.support@nsc.com
National Semiconductor Japan Ltd. Tel: 81-3-5639-7560 Fax: 81-3-5639-7507
National does assume responsibility circuitry described, circuit patent licenses implied National reserves right time without notice change said circuitry specifications.

LM2599 SIMPLE SWITCHER Power Converter Step-Down Voltage Regulator, wi

Top Searches for this datasheet

Other recent searches