SLVS569D JANUARY 2005 REVISED JULY 2005 Fixed 3.3-V, 5-V, 12-V, 1
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LM2575 SIMPLE STEP-DOWN SWITCHING VOLTAGE REGULATOR
SLVS569D JANUARY 2005 REVISED JULY 2005
Fixed 3.3-V, 5-V, 12-V, 15-V Options With Regulation (Max) Over Line, Load, Temperature Conditions Adjustable Option With Range 1.23 Regulation (Max) Over Line, Load, Temperature Conditions Specified Output Current Wide Input Voltage Range.4.75 Requires Only Four External Components (Fixed Versions) Uses Readily Available Standard Inductors 52-kHz (Typ) Fixed-Frequency Internal Oscillator Shutdown Capability With 50-µA (Typ) Standby Current High Efficiency.as High (Typ) Thermal Shutdown Current-Limit Protection With Cycle-by-Cycle Current Limiting
(TO-263) PACKAGE (TOP VIEW)
ON/OFF FEEDBACK OUTPUT
(PDIP) PACKAGE (TOP VIEW)
OUTPUT
ON/OFF
APPLICATIONS
Simple High-Efficiency Step-Down (Buck) Regulator Pre-Regulator Linear Regulators On-Card Switching Regulators Positive-to-Negative Converter (Buck-Boost)
DESCRIPTION/ORDERING INFORMATION
LM2575 greatly simplifies design switching power supplies conveniently providing active functions needed step-down (buck) switching regulator integrated circuit. Accepting wide input voltage range available fixed output voltages adjustable output version, LM2575 integrated switch capable delivering load current, with excellent line load regulation. device also offers internal frequency compensation, fixed-frequency oscillator, cycle-by-cycle current limiting, thermal shutdown. addition, manual shutdown available external ON/OFF pin. LM2575 represents superior alternative popular three-terminal linear regulators. high efficiency, significantly reduces size heat sink and, many cases, heat sink required. Optimized with standard series inductors available from several different manufacturers, LM2575 greatly simplifies design switch-mode power supplies requiring minimal addition only four external components operation. LM2575 characterized operation over virtual junction temperature range -40°C 125°C.
Please aware that important notice concerning availability, standard warranty, critical applications Texas Instruments semiconductor products disclaimers thereto appears this data sheet.
PRODUCTION DATA information current publication date. Products conform specifications terms Texas Instruments standard warranty. Production processing does necessarily include testing parameters.
Copyright 2005, Texas Instruments Incorporated
LM2575 SIMPLE STEP-DOWN SWITCHING VOLTAGE REGULATOR
SLVS569D JANUARY 2005 REVISED JULY 2005
ORDERING INFORMATION
(NOM) -40°C 125°C TO-263 Tube Reel 2000 Tube Reel 2000 Tube Reel 2000 Tube Reel 2000 Tube Reel 2000 PDIP Tube PACKAGE ORDERABLE PART NUMBER LM2575-33IN LM2575-05IN LM2575-12IN LM2575-15IN LM2575IN LM2575-33IKTT LM2575-33IKTTR LM2575-05IKTT LM2575-05IKTTR LM2575-12IKTT LM2575-12IKTTR LM2575-15IKTT LM2575-15IKTTR LM2575IKTT LM2575IKTTR TOP-SIDE MARKING PREVIEW PREVIEW PREVIEW PREVIEW LM2575IN PREVIEW PREVIEW PREVIEW PREVIEW PREVIEW
Package drawings, standard packing quantities, thermal data, symbolization, design guidelines available www.ti.com/sc/package.
LM2575 SIMPLE STEP-DOWN SWITCHING VOLTAGE REGULATOR
SLVS569D JANUARY 2005 REVISED JULY 2005
FUNCTIONAL BLOCK DIAGRAM
Unregulated Input
Internal Regulator
On/Off
ON/OFF
FEEDBACK Fixed-Gain Error
Comparator
Driver
Switch OUTPUT COUT VOUT
1.23-V Band-Gap Reference
52-kHz Oscillator Reset Thermal Shutdown Current Limit
8.84 11.3 ADJ: Open,
numbers (TO-263) package.
FEEDBACK 40-V Unregulated Input +VIN LM2575-05 OUTPUT ON/OFF 1N5819 COUT Regulated Output Load
Optional Output Ripple Filter
numbers (TO-263) package.
Figure Typical Application Circuit (Fixed Version)
LM2575 SIMPLE STEP-DOWN SWITCHING VOLTAGE REGULATOR
SLVS569D JANUARY 2005 REVISED JULY 2005
Absolute Maximum Ratings
over operating free-air temperature range (unless otherwise noted)
Supply voltage ON/OFF input voltage Output voltage (steady state) Tstg Maximum junction temperature Storage temperature range -0.3 UNIT
Stresses beyond those listed under "absolute maximum ratings" cause permanent damage device. These stress ratings only, functional operation device these other conditions beyond those indicated under "recommended operating conditions" implied. Exposure absolute-maximum-rated conditions extended periods affect device reliability.
Package Thermal Data
PACKAGE PDIP TO-263 (KTT) BOARD High JESD 51-7 High JESD 51-5 51°C/W 67°C/W
Maximum power dissipation function TJ(max), maximum allowable power dissipation allowable ambient temperature (TJ(max) TA)/JA. Operating absolute maximum 150°C affect reliability.
Recommended Operating Conditions
over operating free-air temperature range (unless otherwise noted)
Supply voltage Operating virtual junction temperature 4.75 UNIT
LM2575 SIMPLE STEP-DOWN SWITCHING VOLTAGE REGULATOR
SLVS569D JANUARY 2005 REVISED JULY 2005
Electrical Characteristics
ILOAD 3.3-V, 5-V, adjustable versions, 12-V version, 15-V version (unless otherwise noted) (see Figure
PARAMETER LM2575-33 TEST CONDITIONS ILOAD 4.75 ILOAD ILOAD LM2575-05 VOUT Output voltage LM2575-12 ILOAD ILOAD ILOAD ILOAD LM2575-15 ILOAD VOUT ILOAD VOUT ILOAD ILOAD ILOAD ILOAD ILOAD VOUT ILOAD VOUT (ADJ version only)
25°C 25°C Full range 25°C 25°C Full range 25°C 25°C Full range 25°C 25°C Full range 25°C 25°C Full range
3.234 3.168 3.135 4.75 11.76 11.52 11.4 14.7 14.4 14.25 1.217 1.193 1.18
1.23 1.23
3.366 3.432 3.465 5.25 12.24 12.48 12.6 15.3 15.6 15.75 1.243 1.267 1.28
UNIT
Feedback voltage
LM2575-ADJ
LM2575-33 LM2575-05 Efficiency LM2575-12 LM2575-15 LM2575-ADJ VSAT Feedback bias current Oscillator frequency Saturation voltage Maximum duty cycle ISTBY ON/OFF logic input level ON/OFF input current Peak current Output leakage current Quiescent current Standby quiescent current
25°C
25°C Full range 25°C Full range 25°C Full range 25°C 25°C Full range
IOUT
(4), Output (4), Output
25°C 25°C 25°C 25°C Full range 25°C Full range 25°C
(ON/OFF (VOUT (VOUT nominal voltage) (ON/OFF (ON/OFF
event output short overload condition, self-protection features lower oscillator frequency minimum duty cycle from resulting output voltage drops nominal value, causing average power dissipated lower. Output connected diode, inductor, capacitor. Output sourcing current. Feedback disconnected from output connected force output transistor off, FEEDBACK disconnected from output connected adjustable, 3.3-V, versions; 12-V 15-V versions.
LM2575 SIMPLE STEP-DOWN SWITCHING VOLTAGE REGULATOR
SLVS569D JANUARY 2005 REVISED JULY 2005
TYPICAL OPERATING CHARACTERISTICS
25°C (unless otherwise noted)
GRAPH PREVIEWS Figure Normalized Output Voltage Figure Line Regulation Figure Dropout Voltage Figure Current Limit Figure Quiescent Current Figure Standby Quiescent Current Figure Quiescent Current Duty Cycle Figure Oscillator Frequency Figure Switch Saturation Voltage Figure Efficiency Figure Minimum Operating Voltage (Adjustable Version) Figure Feedback Voltage Duty Cycle Figure Feedback Current (Adjustable Version) Figure Switching Waveforms Figure Load Transient Response
LM2575 SIMPLE STEP-DOWN SWITCHING VOLTAGE REGULATOR
SLVS569D JANUARY 2005 REVISED JULY 2005
APPLICATION INFORMATION Layout Guidelines
With switching regulator, circuit layout plays important role circuit performance. Wiring parasitic inductances, well stray capacitances, subjected rapidly switching currents, which result unwanted voltage transients. minimize inductance ground loops, length leads indicated heavy lines should minimized. Optimal results achieved single-point grounding (see Figure ground-plane construction. same reasons, programming resistors used adjustable version should located close possible regulator keep sensitive feedback wiring short.
Fixed Output Voltage Versions FEEDBACK LM2575-xx Fixed Output OUTPUT Unregulated Input ON/OFF COUT VOUT
+VIN
Aluminum Electrolytic COUT Aluminum Electrolytic Schottky
Adjustable Output Voltage Versions FEEDBACK LM2575 (ADJ) OUTPUT 60-V Unregulated Input ON/OFF 11DQ06 COUT VOUT
+VIN
VOUT VREF(1 R2/R1) Where, VREF 1.23 6.12
numbers (TO-263) package.
Figure Test Circuit Layout Guidelines
LM2575 SIMPLE STEP-DOWN SWITCHING VOLTAGE REGULATOR
SLVS569D JANUARY 2005 REVISED JULY 2005
APPLICATION INFORMATION (continued) Input Capacitor (CIN)
stability concerns, input bypass capacitor (electrolytic, needs located close possible regulator. operating temperatures below -25°C, need larger value. addition, since most electrolytic capacitors have decreasing capacitances increasing temperature drops, adding ceramic solid tantalum capacitor parallel increases stability cold temperatures. extend capacitor operating lifetime, capacitor ripple current rating should
C,RMS 1.2(
where: LOAD
{buck regulator}, |VOUT| {buck-boost regulator} OUT|
Output Capacitor (COUT)
both loop stability filtering ripple voltage, output capacitor also required, again close proximity regulator. best performance, low-ESR aluminum electrolytics recommended, although standard aluminum electrolytics adequate some applications. Based following equation: Output Ripple Voltage (ESR COUT) (inductor ripple current) Output ripple typically achieved with capacitor values Larger COUT reduce ripple peak-to-peak. improve further output ripple, paralleling standard electrolytic capacitors used. Alternatively, higher-grade capacitors such "high frequency", "low inductance", "low ESR" used. following should taken into account when selecting COUT: cold temperatures, electrolytic capacitors rise dramatically (typically nominal value -25°C). Because solid tantalum capacitors have significantly better specifications cold temperatures, they should used operating temperature lower than -25°C. alternative, tantalums also paralleled aluminum electrolytics should contribute total capacitance. COUT desirable output ripple. However, should greater than 0.05 avoid possibility regulator instability. Hence, sole tantalum capacitor used COUT most susceptible this occurrence. capacitor's ripple current rating should least higher than peak-to-peak inductor ripple current.
Catch Diode
with other external components, catch diode should placed close output minimize unwanted noise. Schottky diodes have fast switching speeds forward voltage drops and, thus, offer best performance, especially switching regulators with output voltages (VOUT high-efficiency, fast-recovery, ultra-fast-recovery diode used place Schottky, should have soft recovery (versus abrupt turn-off characteristics) avoid chance causing instability EMI. Standard 50-/60-Hz diodes, such 1N4001 1N5400 series, suitable.
Inductor
Proper inductor selection performance-switching power-supply designs. important factor consider whether regulator will used continuous (inductor current flows continuously never drops zero) discontinuous mode (inductor current goes zero during normal switching cycle). Each mode distinctively different operating characteristics and, therefore, affect regulator performance requirements. many applications, continuous mode preferred mode operation, since offers greater output power with lower peak currents, also result lower output ripple voltage. advantages continuous mode operation come expense larger inductor required keep inductor current continuous, especially output currents and/or high input voltages.
LM2575 SIMPLE STEP-DOWN SWITCHING VOLTAGE REGULATOR
SLVS569D JANUARY 2005 REVISED JULY 2005
APPLICATION INFORMATION (continued)
LM2575 operate either continuous discontinuous mode. With heavy load currents, inductor current flows continuously regulator operates continuous mode. Under light load, inductor fully discharges regulator forced into discontinuous mode operation. light loads (approximately less), this discontinuous mode operation perfectly acceptable desirable solely keep inductor value size small. buck regulator eventually will operate discontinuous mode when load current light enough. type inductor chosen have advantages disadvantages. high performance/quality concern, then more-expensive toroid core inductors best choice, magnetic flux contained completely within core, resulting less noise nearby sensitive circuits. Inexpensive bobbin core inductors, however, generate more open core will confine flux within core. Multiple switching regulators located proximity each other particularly susceptible mutual coupling magnetic fluxes from each other's open cores. these situations, closed magnetic structures (such toroid, core, E-core) more appropriate. Regardless type value inductor used, inductor never should carry more than rated current. Doing cause inductor saturate, which case inductance quickly drops, inductor looks like low-value resistor (from resistance windings). result, switching current rises dramatically (until limited current-by-current limiting feature LM2575) result overheating inductor itself. Note that different types inductors have different saturation characteristics.
Output Voltage Ripple Transients
with switching power supply, output LM2575 will have sawtooth ripple voltage switching frequency. Typically about output voltage, this ripple mainly inductor sawtooth ripple current output capacitor (see note COUT). Furthermore, output also contain small voltage spikes peaks sawtooth waveform. This fast switching output switch parasitic inductance COUT. These voltage spikes minimized through low-inductance capacitors. There several ways reduce output ripple voltage: larger inductor, larger COUT, both. Another method small filter output. This filter reduce output ripple voltage factor (see Figure
Feedback Connection
fixed voltage options, FEEDBACK must wired VOUT. adjustable version, FEEDBACK must connected between programming resistors. Again, both these resistors should close proximity regulator, each should less than minimize noise pickup.
ON/OFF Input
ON/OFF should grounded low-level voltage (typically <1.6 normal operation. shut down LM2575 standby mode, high-level CMOS voltage should supplied this pin. ON/OFF should left open safely pulled with without pullup resistor.
Grounding
power ground connections LM2575 must impedance help maintain output stability. 5-pin packages, both ground, either connection used they both part same lead frame. With 16-pin 24-pin packages, ground pins (including signal power grounds) should soldered directly wide copper traces ensure low-inductance connections good thermal dissipation.
PACKAGE OPTION ADDENDUM
17-Oct-2005
PACKAGING INFORMATION
Orderable Device LM2575-33IN LM2575IN LM2575INE4
Status PREVIEW ACTIVE ACTIVE
Package Type PDIP PDIP PDIP
Package Drawing
Pins Package Plan Pb-Free (RoHS) Pb-Free (RoHS)
Lead/Ball Finish Call NIPD NIPD
Peak Temp Call Level-NC-NC-NC Level-NC-NC-NC
marketing status values defined follows: ACTIVE: Product device recommended designs. LIFEBUY: announced that device will discontinued, lifetime-buy period effect. NRND: recommended designs. Device production support existing customers, does recommend using this part design. PREVIEW: Device been announced production. Samples available. OBSOLETE: discontinued production device.
Plan planned eco-friendly classification: Pb-Free (RoHS) Green (RoHS Sb/Br) please check latest availability information additional product content details. TBD: Pb-Free/Green conversion plan been defined. Pb-Free (RoHS): TI's terms "Lead-Free" "Pb-Free" mean semiconductor products that compatible with current RoHS requirements substances, including requirement that lead exceed 0.1% weight homogeneous materials. Where designed soldered high temperatures, Pb-Free products suitable specified lead-free processes. Green (RoHS Sb/Br): defines "Green" mean Pb-Free (RoHS compatible), free Bromine (Br) Antimony (Sb) based flame retardants exceed 0.1% weight homogeneous material)
MSL, Peak Temp. Moisture Sensitivity Level rating according JEDEC industry standard classifications, peak solder temperature. Important Information Disclaimer:The information provided this page represents TI's knowledge belief date that provided. bases knowledge belief information provided third parties, makes representation warranty accuracy such information. Efforts underway better integrate information from third parties. taken continues take reasonable steps provide representative accurate information have conducted destructive testing chemical analysis incoming materials chemicals. suppliers consider certain information proprietary, thus numbers other limited information available release. event shall TI's liability arising such information exceed total purchase price part(s) issue this document sold Customer annual basis.
Addendum-Page
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