SINGLE-CHIP PROGRAMMABLE CONTROLLERS WITH 5-BIT DESCRIPTION speci

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LX1662 62A, LX1663 /63A
SINGLE-CHIP PROGRAMMABLE CONTROLLERS WITH 5-BIT
DESCRIPTION specification. device drive dual LX1662/62A LX1663/63A MOSFET's resulting typical efficiencies Monolithic Switching Regulator Controller IC's designed provide cost, high even with loads excess amperes. performance adjustable power supply cost sensitive applications, bottom advanced microprocessors other applications MOSFET replaced with Schottky diode requiring very fast transient response high (non-synchronous operation). degree accuracy. Smallest Package Size. LX1662 available narrow body 14-pin surface mount Short-Circuit Current Limiting without Expensive Current Sense Resistors. Currentpackage space sensitive applications. sensing mechanism trace resistance LX1663 provides additional functions parasitic resistance main inductor. Over Voltage Protection (OVP) Power Good LX1662A LX1663A have reduced current (PWRGD) output drives applications sense comparator threshold optimum requiring output voltage monitoring performance using trace. applications protection functions. requiring high degree accuracy, Ultra-Fast Transient Response Reduces conventional sense resistor used sense System Cost. modulated offtime architecture current. results fastest transient response given inductor, reducing output capacitor requirements, Programmable Synchronous Rectifier Driver Core. main output adjustable reducing total regulator system cost. from 1.3V 3.5V using 5-bit code. Over-Voltage Protection Power Good read signal switch Flag. output LX1663 motherboard, hardwired into processor's LX1663A used drive crowbar package case Pentium® circuit protect load event shortPentium processors). 5-bit code adjusts circuit main MOSFET. LX1663 output voltage between 1.30 2.05V 50mV LX1663A also have logiclevel Power Good increments between 3.5V 100mV Flag signal when output voltage increments, conforming Intel Corporation specified limits.
IMPORTANT: most current data, consult MICROSEMI's website: http://www.microsemi.com
FEATURES
5-bit Programmable Output Core Supply Sense Resistor Required Short-Circuit Current Limiting Designed Drive Either Synchronous NonSynchronous Output Stages Lowest System Cost Possible Price- Sensitive Pentium Pentium Class Applications Soft-Start Capability Modulated, Constant Off-Time Architecture Fast Transient Response Simple System Design Available Over-Voltage Protection (OVP) Crowbar Driver Power Good Flag (LX1663 only) Small, Surface-Mount Packages
FEATURES
Socket Microprocessor Supplies (including Intel Pentium Processor, AMDK6And Cyrix® 6x86TM, Gx86and M2Processors) Pentium Deschutes Processor L2-Cache Supplies Voltage Regulator Modules General Purpose DC:DC Converter Applications
PRODUCT HIGHLIGH12V
0.1µF
6.3V 1500µF
LX1662
TDRV BDRV VID4
VCC_CORE VID0 VID1 VID2 VID3
IRL3102
2.5µH
IRL3303
2.5m
Supply Voltage Core
VID0
VID1
VID2
VID3
VID4
680pF
6.3V, 1500µF
Three capacitors Pentium Four capacitors Pentium
14-pin, Narrow Body SOIC
(°C)
Plastic 14-Pin
PACKAGE ORDER INFO Plastic Plastic SOIC 16-Pin 14-Pin LX1663CN LX1663ACN LX1662CD LX1662ACD
Plastic SOIC 16-Pin LX1663CD LX1663ACD
RoHS Compliant Pb-free Transition DC:0503
RoHS Compliant Pb-free Transition DC:0440
LX1662CN LX1662ACN
Note: Available Tape Reel. Append letters `TR' part number. (i.e. LX1663CD-TR)
Copyright 1999 Rev. 1.2a,2005-03-09
LINFINITY MICROELECTRONICS INC.
11861 WESTERN AVENUE, GARDEN GROVE, 92841, 714-898-8121, FAX: 714-893-2570
PRODUCT DATABOOK 1996/1997
LX1662/62A, LX1663/63A
SINGLE-CHIP PROGRAMMABLE CONTROLLERS WITH 5-BIT
Power Good
PACKAGE OUTS
DEVICE SELECTION GUIDE DEVICE LX1662 LX1662A LX1663 LX1663A Packages 14-pin SOIC 16-pin SOIC Current-Sense Comp. Thresh. (mV) Optimal Load Pentium-class (<10A) Pentium 10A) Pentium-class (<10A) Pentium 10A)
VCC_CORE VID0 VID1 VID2 VID3
TDRV BDRV VID4
PACKAGE 14-Pin LX1662/1662A (Top View)
(Note
VCC_CORE VID0 VID1 VID2 VID3 VID4
Supply Voltage (VC1) Supply Voltage (VCC) Output Drive Peak Current Source (500ns) 1.5A Output Drive Peak Current Sink (500ns) 1.5A Input Voltage (SS, INV, VCC_CORE, VID0-VID4) -0.3V Operating Junction Temperature Plastic Packages) 150°C Storage Temperature Range -65°C +150°C Lead Temperature (Soldering, Seconds) 300°C
Peak Package Solder Reflow Temp. second max. exposure).260°C (+0, Note Exceeding these ratings could cause damage device. voltages with respect Ground. Currents positive into, negative specified terminal. numbers refer packages only.
TDRV BDRV PWRGD
PACKAGE 16-Pin LX1663/1663A (Top View)
VCC_CORE VID0 VID1 VID2 VID3
PACKAGE: THERMAL RESISTANCE-JUNCTION AMBIENT, PACKAGE: THERMAL RESISTANCE-JUNCTION AMBIENT, 120°C/W 65°C/W
TDRV BDRV VID4
PACKAGE 14-Pin LX1662/1662A (Top View)
VCC_CORE VID0 VID1 VID2 VID3 VID4
Junction Temperature Calculation: JA). numbers guidelines thermal performance device/pc-board system. above assume ambient airflow
TDRV BDRV PWRGD
PACKAGE 16-Pin LX1663/1663A (Top View)
RoHS Pb-free 100% Matte Lead Finish
Copyright 1999 Rev. 1.2a, 11/04
PRODUCT DATABOOK 1996/1997
LX1662/62A, LX1663/63A
SINGLE-CHIP PROGRAMMABLE CONTROLLERS WITH 5-BIT
ELECTRICAL CHARACTERISTICS
(Unless otherwise specified, 10.8 13.2, 70°C. Test conditions: 12V, 25°C. Application Circuit.)
Parameter Reference Section
Regulation Accuracy (See Table Regulation Accuracy
Symbol
Test Conditions
LX1662/1663 Min. Typ. Max.
0.42 0.06 10.1 0.31 0.15
Units
(See Table Next Page) (Less 40mV output adaptive positioning), 12V, ILOAD
1.8V VOUT 2.8V VCC_CORE 1.3V, 390pF VCC_CORE 3.5V, 390pF VCC_CORE 1.3V 3.5V VCC_CORE 1.3V, 1.5V VCC_CORE 1.3V VCC_CORE 3.5V Overdrive 1.3V VINV 3.5V
Timing Section
Time Initial Time Temp Stability Discharging Current Ramp Peak Ramp Peak-Valley Ramp Valley Delay Output
IDIS VRPP
0.37
0.47
Error Comparator Section
Input Bias Current Input Offset Voltage Delay Output Overdrive VCLP 1.3V VINV VCC_CORE 3.5V Initial Accuracy Initial Accuracy Overdrive 12V, 3000pF 12V, 3000pF 12V, ISOURCE 20mA 12V, ISINK 200mA 12V, ISOURCE 20mA 12V, ISINK 200mA IPULL
Current Sense Section
Input Bias Current (VCC_CORE Pin) Pulse Pulse LX1662/1663 LX1662A/1663A Delay Output
Output Drivers Section
Drive Rise Time Drive Fall Time Drive High Drive Output Pull Down VHYST
10.4
UVLO S.S. Section
Start-Up Threshold Hysteresis Sink Current Voltage
10.1V 200µA 12V, Freq 200kHz, (VCC_CORE DACOUT) IPWRGD (VCC_CORE VDAC)
Supply Current Section
Dynamic Operating Current Lower Threshold Hysteresis Power Good Voltage Over-Voltage Threshold Sourcing Current
Power Good Over-Voltage Protection Section (LX1663 Only)
Copyright 1999 Rev. 1.2a, 11/04
PRODUCT DATABOOK 1996/1997
LX1662/62A, LX1663/63A
SINGLE-CHIP PROGRAMMABLE CONTROLLERS WITH 5-BIT
ELECTRICAL CHARACTERISTICS
Table Adaptive Transient Voltage Output Processor Pins
Ground, Open (Floating)
(Output Voltage Setpoint Typical)
Output Voltage (VCC_CORE) VID0 0.0A
Nominal Output*
VID4
VID3
VID2
VID1
Nominal
setpoint voltage
1.34V 1.30V 1.39V 1.35V 1.44V 1.40V 1.49V 1.45V 1.54V 1.50V 1.59V 1.55V 1.64V 1.60V 1.69V 1.65V 1.74V 1.70V 1.79V 1.75V 1.84V 1.80V 1.89V 1.85V 1.94V 1.90V 1.99V 1.95V 2.04V 2.00V 2.09V 2.05V 2.04V 2.00V 2.14V 2.10V 2.24V 2.20V 2.34V 2.30V 2.44V 2.40V 2.54V 2.50V 2.64V 2.60V 2.74V 2.70V 2.84V 2.80V 2.94V 2.90V 3.04V 3.00V 3.14V 3.10V 3.24V 3.20V 3.34V 3.30V 3.44V 3.40V 3.54V 3.50V with adaptive output voltage positioning.
Note: Adaptive Transient Voltage Output order improve transient response 40mV offset built into Current Sense comparator. high currents, peak output voltage will lower than nominal point shown Figure actual output voltage will function sense resistor, output current output ripple.
Output Load
5A/Div.
Time 100µs/Div.
FIGURE Output Transient Response (Using sense resistor output inductor)
Copyright 1999 Rev. 1.2a, 11/04
Output Voltage
2.8V 100mV/Div.
PRODUCT DATABOOK 1996/1997
LX1662/62A, LX1663/63A
SINGLE-CHIP PROGRAMMABLE CONTROLLERS WITH 5-BIT
CHARACTERISTICS CURVES
EFFICIENCY
EFFICIENCY
Output Point
Output Point
EFFICIENCY 3.1V EFFICIENCY 2.8V EFFICIENCY 1.8V
EFFICIENCY 3.1V EFFICIENCY 2.8V EFFICIENCY 1.8V
IOUT
IOUT
FIGURE Efficiency Test Results: Non-Synchronous Operation,
FIGURE Efficiency Test Results: Synchronous Operation,
Output Point
1.8V EFFICIENCY
2.8V EFFICIENCY 3.3V EFFICIENCY
IOUT
FIGURE Efficiency Test Results: Synchronous Operation, 12V. Note: Non-synchronous operation recommended operation, power loss Schottky diode.
Copyright 1999 Rev. 1.2a, 11/04
PRODUCT DATABOOK 1996/1997
LX1662/62A, LX1663/63A
SINGLE-CHIP PROGRAMMABLE CONTROLLERS WITH 5-BIT
BLOCK DIAGRAM
UVLO 10.6/10.1 Trimmed Internal VREG Break Before Make 0.7V SYNC Comp Latch
TDRV
40mV
BDRV
Error Comp
Off-Time Controller
100mV VCC_CORE
Comp Comp
Comp
PWRGD*
LX1663/1663A ONLY
VID0
VID1
VID2
VID3
VID4
Note: numbers correct LX1663/1663A, 16-pin package. connected LX1662/1662A. 60mV LX1662A LX1663A
FIGURE Block Diagram
Copyright 1999 Rev. 1.2a, 11/04
PRODUCT DATABOOK 1996/1997
LX1662/62A, LX1663/63A
SINGLE-CHIP PROGRAMMABLE CONTROLLERS WITH 5-BIT
Name
VCC_CORE VID0 VID1 VID2 VID3 VID4
FUNCTIONAL DESCRIPTION
LX1662
LX1663
Description
Soft-Start pin, internally connected non-inverting input error comparator. Inverting input error comparator. Output voltage. Connected non-inverting input current-sense comparator. Voltage Identification (LSB) input used output voltage. Voltage Identification (2nd input. Voltage Identification (3rd input. Voltage Identification (4th input. Voltage Identification (MSB) input. This also range select when (CLOSED), output voltage between 1.30 2.05V 0.05V increments. When high (OPEN), output adjusted from 3.5V 0.1V increments. Open collector output pulls when output voltage limits. driver goes high when processor's supply over specified voltage limits. off-time programmed connecting timing capacitor this pin. This (12V) supply well gate drive bottom FET. This gate drive bottom FET. Leave open non-synchronous operation (when bottom replaced Schottky diode). Both power signal ground device. Gate drive MOSFET. This separate power supply input drive. connected charge pump when only available.
PWRGD BDRV TDRV
N.C. N.C.
Copyright 1999 Rev. 1.2a, 11/04
PRODUCT DATABOOK 1996/1997
LX1662/62A, LX1663/63A
SINGLE-CHIP PROGRAMMABLE CONTROLLERS WITH 5-BIT
OPERATION Referring block diagram typical application circuit, output turns MOSFET, allowing inductor current increase. error comparator threshold, latch reset, MOSFET turns synchronous MOSFET turns OFF-time capacitor allowed discharge. valley voltage, synchronous MOSFET turns MOSFET turns special break-before-make circuit prevents simultaneous conduction MOSFETs. VCC_CORE offset +40mV enhance transient response. connected positive side current sense resistor, controller regulates positive side sense resistor. light loads, output voltage will regulated above nominal setpoint voltage. heavy loads, output voltage will drop below nominal setpoint voltage. minimize frequency variation with varying output voltage, OFF-time modulated function voltage VCC_CORE pin. ERROR VOLTAGE COMPARATOR error voltage comparator compares voltage positive side sense resistor voltage plus 40mV. external filter recommended high-frequency noise. CURRENT LIMIT Current limiting done sensing inductor current. Exceeding current sense threshold turns output drive latches until latch input goes high again. Current Limit Section "Using LX1662/63 Devices" later this data sheet. OFF-TIME CONTROL TIMING SECTION timing capacitor allows programming OFF-time. timing capacitor quickly charged during time MOSFET allowed discharge when MOSFET OFF. order minimize frequency variations while providing different supply voltages, discharge current modulated voltage VCC_CORE pin. OFF-time inversely proportional VCC_CORE voltage. UNDER VOLTAGE LOCKOUT SECTION purpose UVLO keep output drive until input voltage reaches start-up threshold. voltages below start-up voltage, UVLO comparator disables internal biasing, turns output drives, (Soft-Start) pulled low. SYNCHRONOUS CONTROL SECTION synchronous control section incorporates unique breakbefore-make function ensure that primary switch synchronous switch turned same time. Approximately nanoseconds deadtime provided breakbefore-make circuitry protect MOSFET switches. PROGRAMMING OUTPUT VOLTAGE output voltage means 5-bit digital Voltage Identification (VID) word (See Table code incorporated into package processor output voltage means switch jumpers. signal, connect ground (DIP switch CLOSED); high signal, leave open (DIP switch OFF/OPEN). five pins LX166x series designed interface directly with Pentium Pentium processor. Therefore, inputs expected either ground floating. floating input will pulled high internal connections. using Socket processor, other load, code directly connecting jumpers switches VID[0:4] pins. pins designed take inputs, should connected high. Unpredictable output voltages result. LX166x devices connected logic circuit, such BIOS, programming output voltage, they should buffered using CMOS gate with open-drain, such 74HC125 74C906. POWER GOOD SIGNAL (LX1663 only) open collector output provided which presents high impedance when output voltage between 117% programmed voltage, measured pin. Outside this window output presents impedance path ground. Power Good function also toggles during operation. OVER-VOLTAGE PROTECTION controller inherently protected from over-voltage condition constant OFF-time architecture. However, should failure occur power switch, over-voltage drive provided LX1663 only) which drive external crowbar (Q3), blow fuse (F1). fault condition must removed power recycled LX1663 resume normal operation (See Figure
Copyright 1999 Rev. 1.2a, 11/04
PRODUCT DATABOOK 1996/1997
LX1662/62A, LX1663/63A
SINGLE-CHIP PROGRAMMABLE CONTROLLERS WITH 5-BIT
0.1µF
LX1662
6.3V 1500µF
VCC_CORE VID0 VID1 VID2 VID3
TDRV BDRV VID4
IRL3102 IRL3303
6.3V, 1500µF Three capacitors Pentium Four capacitors Pentium
2.5µH
Supply Voltage Core
VID0 VID1 VID2 VID3 VID4
680pF
14-pin, Narrow Body SOIC
FIGURE LX1662 Pentium Pentium Processor Single Chip Power Supply Controller Solution With Loss-Less Current Sensing (Synchronous)
0.1µF
6.3V 1500µF IRL3102 MBR2535 680pF
LX1662
VCC_CORE VID0 VID1 VID2 VID3
TDRV BDRV VID4
VID0 VID1 VID2 VID3 VID4
0.005
VOUSupply Voltage Core
6.3V, 1500µF
Three capacitors Pentium Four capacitors Pentium
14-pin, Narrow Body SOIC
FIGURE LX1662 Non-Synchronous Pentium Socket Power Supply Application
Copyright 1999 Rev. 1.2a, 11/04
PRODUCT DATABOOK 1996/1997
LX1662/62A, LX1663/63A
SINGLE-CHIP PROGRAMMABLE CONTROLLERS WITH 5-BIT
6.3V 1500µF IRL3102 2.5µH IRL3303
6.3V, 1500µF
Three capacitors Pentium Four capacitors Pentium
0.1µF
LX1663
TDRV BDRV
VCC_CORE VID0 VID1 VID2 VID3 VID4
VID0 VID1 VID2 VID3 VID4
Supply Voltage Core
PWRGD
680pF
16-pin Narrow Body SOIC
PWRGD
FIGURE Pentium Processor Application With OVP, Power Good Loss-Less Current Sensing (Synchronous)
1N4148
1N4148 0.1µF IRL3102
0.1µF
1500µF
LX1663
VCC_CORE VID0 VID1 VID2 VID3 VID4
TDRV BDRV PWRGD
2.5µH IRL3303
1N5817
2.5m9
Supply Voltage Core
VID0 VID1 VID2 VID3 VID4
1200pF C10,
16-pin Narrow Body SOIC
6.3V, 1500µF Three capacitors Pentium 2N6504 Four capacitors Pentium
PWRGD
FIGURE Full-Featured Pentium Processor Supply With Power Input
Copyright 1999 Rev. 1.2a, 11/04
PRODUCT DATABOOK 1996/1997
LX1662/62A, LX1663/63A
SINGLE-CHIP PROGRAMMABLE CONTROLLERS WITH 5-BIT
LX1662 Bill Materials (Refer Product Highlight)
Total
Description
1500µF, 6.3V capacitor 1500µF, 6.3V capacitor 680pF 0.1µF 1µF, Inductor Inductor MOSFET MOSFET 2.5m Sense Resistor (PCB trace) Controller
Part Number Manufacturer
MV-GX Sanyo MV-GX Sanyo Ceramic HM0096832 IRL3102 International Rectifier equivalent IRL3303 International Rectifier equivalent LX1662CD Linfinity
Qty.
USING LX1662/63 LX1662/63 devices very easy design with, requiring only simple calculations implement given design. following procedures considerations should provide effective operation virtually applications. Refer Application Information section component reference designators. TIMING CAPACITOR SELECTION frequency operation LX166x function duty cycle OFF-time. OFF-time proportional timing capacitor (which shown application schematics this data sheet), modulated minimize frequency variations with duty cycle. frequency constant, during steady-state operation, modulation OFF-time. timing capacitor (CT) should selected using following equation:
DEVICES
When using input voltage, switching frequency (fS) approximated follows: 0.621
IDIS
Choosing 680pF capacitor will result operating frequency 183kHz VOUT 2.8V. When power input used, capacitor value must changed (the optimal timing capacitor input will range 1000-1500pF). OUTPUT INDUCTOR SELECTION inductance value chosen determines ripple current present output power supply. Size inductance allow nominal ±10% swing above below nominal load current, using equation T/I, where OFF-time, voltage across inductor during OFFtime, peak-to-peak ripple current inductor. sure select high-frequency core material which handle current, such 3C8, which sized correct power level. Typical inductance values range from 10µH. Note that ripple current will increase with smaller inductor. Exceeding ripple current rating capacitors could cause reliability problems.
VOUT /VIN IDIS (1.52 0.29* VOUT
Where IDIS fixed 200µA switching frequency (recommended around 200kHz optimal operation component selection).
Copyright 1999 Rev. 1.2a, 11/04
PRODUCT DATABOOK 1996/1997
LX1662/62A, LX1663/63A
SINGLE-CHIP PROGRAMMABLE CONTROLLERS WITH 5-BIT
USING LX1662/63 DEVICES INPUT INDUCTOR SELECTION order cope with faster transient load changes, smaller output inductor needed. However, reducing size output inductor will result higher ripple voltage input supply. This noise rail affect other loads, such graphics cards. recommended that smaller input inductor, 1.5µH), used rail filter ripple. Ensure that this inductor same current rating output inductor. FILTER CAPACITOR SELECTION capacitors output section used filter output current ripple, well help during transient load conditions, capacitor bank should sized meet ripple transient performance specifications. When transient (step) load current change occurs, output voltage will have step which equals product Effective Series Resistance (ESR) capacitor current step (I). when current increases from sleep mode) high, output voltage will drop below steady state value. advanced microprocessor power supply, capacitor should usually selected basis value, rather than capacitance current capability. Capacitors that satisfy requirement usually have larger capacitance current capability than needed application. allowable found (IRIPPLE Where allowable output voltage excursion transient IRIPPLE inductor ripple current. Regulators such LX166x series, have adaptive output voltage positioning, which adds 40mV set-point voltage therefore difference between load voltage minimum dynamic voltage allowed microprocessor. Ripple current function output inductor value (LOUT), approximated follows: IRIPPLE FILTER CAPACITOR SELECTION (continued) aluminum electrolytic, have demonstrated reliability. Oscon series from Sanyo generally provides very best performance terms long term stability general reliability, substantial cost penalty. MV-GX series provides excellent performance, meeting Intel transient specifications, reasonable cost. Beware off-brand, very-low cost filter capacitors, which have been shown degrade both general electrolyte characteristics over time. CURRENT LIMIT Current limiting occurs when sensed voltage, proportional load current, exceeds current-sense comparator threshold value. current sensed either using fixed sense resistor series with inductor cause voltage drop proportional current, using resistor capacitor parallel with inductor sense voltage drop across parasitic resistance inductor. LX166x family offers different comparator thresholds. LX1662 1663 have threshold 100mV, while LX1662A LX1663A have threshold 60mV. 60mV threshold better suited higher current loads, such Pentium Deschutes processor.
Sense Resistor current sense resistor, selected according formula:
VTRIP ITRIP Where VTRIP current sense comparator threshold (100mV LX1662/63 60mV LX1662A/63A) ITRIP desired current limit. Typical choices shown below. TABLE Current Sense Resistor Selection Guide
Load
Pentium-Class Processor (<10A) Pentium Class (>10A)
Sense Resistor Value
2.5m
Recommended Controller
LX1662 LX1663 LX1662A LX1663A
VOUT VOUT LOUT
Where switching frequency. Electrolytic capacitors used output filter capacitor bank, less stable with than tantalum capacitors. they age, their degrades, reducing system performance increasing risk failure. recommended that multiple parallel capacitors used that, increases with age, overall performance will still meet processor's requirements. There frequently strong pressure least expensive components possible, however, this could lead degraded longterm reliability, especially case filter capacitors. Linfinity's demo boards Sanyo MV-GX filter capacitors, which
smaller sense resistor will result lower heat dissipation also smaller output voltage droop higher currents. There several alternative types sense resistor. surface-mount metal "staple" form resistor advantage exposure free dissipate heat value controlled very tightly. main drawback, however, cost. alternative construct sense resistor using copper trace. Although resistance cannot controlled tightly, trace very cost.
Copyright 1999 Rev. 1.2a, 11/04
PRODUCT DATABOOK 1996/1997
LX1662/62A, LX1663/63A
SINGLE-CHIP PROGRAMMABLE CONTROLLERS WITH 5-BIT
USING LX1662/63 DEVICES CURRENT LIMIT (continued) CURRENT LIMIT (continued) current flowing through inductor triangle wave. sensor components selected such that: L/RL voltage across capacitor will equal current flowing through resistor, i.e. ILRL Since reflects inductor current, selecting appropriate made reach comparator voltage (60mV LX166xA 100mV LX166x) desired trip current.
Sense Resistor sense resistor should constructed shown Figure attaching directly large pads capacitor inductor, heat dissipated efficiently larger copper masses. Connect current sense lines shown avoid errors.
2.5m9 Inductor
Sense Resistor
100mil Wide, 850mil Long 2.5mm 22mm oz/ft2 copper)
Output Capacitor Sense Lines
FIGURE Sense Resistor Construction Diagram Recommended sense resistor sizes given following table: TABLE Sense Resistor Selection Guide
Copper Weight
oz/ft2
Design Example (Pentium circuit, with maximum static current 14.2A) gain sensor characterized
|T(j
L/RSCS
Copper Desired Resistor Thickness Value
68µm 2.5m
Dimensions inches
0.85
1/RSCS
RL/L
FIGURE Sensor Gain dc/static tripping current Itrip,S satisfies: Vtrip Itrip,S Select L/RSCS have higher dynamic tripping current than static one. dynamic tripping current Itrip,d satisfies: Vtrip Itrip,d L/(RSCS)
Loss-Less Current Sensing Using Resistance Inductor inductor parasitic resistance, which causes voltage drop when current flows through inductor. Figure shows sensor circuit comprising surface mount resistor, capacitor, parallel with inductor, eliminating current sense resistor.
Load
Current Sense Comparator
General Guidelines Selecting Vtrip Select: trip,S according
above equation taken into account current-dependency inductance. test circuit (Figure used following parameters: 0.1µF, 2.5µH current.
FIGURE Current Sense Circuit
Copyright 1999 Rev. 1.2a, 11/04
PRODUCT DATABOOK 1996/1997
LX1662/62A, LX1663/63A
SINGLE-CHIP PROGRAMMABLE CONTROLLERS WITH 5-BIT
USING LX1662/63 DEVICES CURRENT LIMIT (continued) cases where large that trip point current would lower than desired short-circuit current limit, resistor (RS2) parallel with shown Figure selection components follows: SELECTION (continued) IRL3102 (13m RDS(ON)), converting 2.8V will result typical heat dissipation 1.48W.
(Required) (Actual)
(Actual) (RS2 (Actual)
Synchronous Rectification Lower MOSFET lower pass element either MOSFET Schottky diode. MOSFET (synchronous rectification) will result higher efficiency, higher cost than using Schottky diode (non-synchronous). Power dissipated bottom MOSFET will
RDS(ON) Duty Cycle] 2.24W
Again, select (RS2//RS) 10k. SELECTION insure reliable operation, operating junction temperature switches must kept below certain limits. Intel specification states that 115°C maximum junction temperature should maintained with ambient 50°C. This achieved properly derating part, adequate heat sinking. most critical parameters selection resistance. This parameter directly contributes power dissipation devices, thus impacts heat sink design, mechanical layout, reliability. general, larger current handling capability FET, lower will since more area available. TABLE Selection Guide
This table gives selection suitable FETs from International Rectifier.
[IRL3303 1.12W IRL3102]
Catch Diode Lower MOSFET low-power Schottky diode, such 1N5817, recommended connected between gate source lower MOSFET when operating from 12V-power supply (see Figure This will help protect controller against latch-up inductor voltage going negative. Although latch-up unlikely, such catch diode will improve reliability highly recommended. Non-Synchronous Operation Schottky Diode typical Schottky diode, with forward drop 0.6V will dissipate 2.8/5] 3.7W (compared 2.2W dissipated MOSFET under same conditions). This power loss becomes much more significant lower duty cycles synchronous rectification recommended especially when 12V-power input used. dual Schottky diode single TO-220 package (e.g. MBR2535) helps improve thermal dissipation.
MOSFET GATE BIAS power MOSFETs biased methods: charge pump supply connected VC1. Charge Pump (Bootstrap) When supplied drain MOSFET, Figure gate drive needs higher than order turn MOSFET Capacitor diodes used charge pump voltage doubling circuit raise voltage that TDRV always provides high enough voltage turn supply must always connected provide power itself, well gate drive bottom MOSFET. Supply When supplied drain supply should connected both VC1.
Device
IRL3803 IRL22203N IRL3103 IRL3102 IRL3303 IRL2703
RDS(ON)
100°C
Max. Breakdown Voltage
devices TO-220 package. surface mount devices (TO-263 D2-Pak), part number, e.g. IRL3103S.
recommended solution IRL3102 high side IRL3303 side FET, best combination cost performance. Alternative FET's from manufacturer could used, provided they meet same criteria RDS(ON).
Heat Dissipated Upper MOSFET heat dissipated MOSFET will
RDS(ON) Duty Cycle) (0.51 Where switching transition line body diode (~100ns) switching frequency.
Copyright 1999 Rev. 1.2a, 11/04
PRODUCT DATABOOK 1996/1997
LX1662/62A, LX1663/63A
SINGLE-CHIP PROGRAMMABLE CONTROLLERS WITH 5-BIT
USING LX1662/63 DEVICES LAYOUT GUIDELINES THERMAL DESIGN great deal time effort were spent optimizing thermal design demo boards. user intends implement embedded motherboard would well advised carefully read follow these guidelines. switches have been carefully selected, external heatsinking generally required. However, this means that copper trace board must used. This potential trouble spot; much copper area possible must dedicated heatsinking switches, diode well non-synchronous solution used. module, heatsink area taken from internal ground planes which were actually split connected with VIAS power device tabs. TO-220 TO-263 cases well suited this application, preferred packages. Remember remove conformal coating from exposed traces which involved heatsinking.
Input
LX166x
Output
FIGURE Power Traces these traces should made wide thick possible, order minimize resistance hence power losses. also recommended that, whenever possible, ground, input output power signals should separate planes (PCB layers). Figure bold traces power traces.
General Notes always, sure provide local capacitive decoupling close chip. sure ground plane construction highfrequency work. capacitors where justified, alert damping ringing problems. High-frequency designs demand careful routing layout, require several iterations achieve desired performance levels. Power Traces reduce power losses ohmic resistance, careful consideration should given layout traces that carry high currents. main paths consider are:
Input power from supply drain MOSFET. Trace between MOSFET lower MOSFET Schottky diode. Trace between lower MOSFET Schottky diode ground. Trace between source MOSFET inductor, sense resistor load.
Input Decoupling (VCC) Capacitor Ensure that this capacitor placed close possible minimize effects noise device. Layout Assistance Please contact Linfinity's Applications Engineers assistance with layout component selection issues. Gerber file with layout most popular devices available upon request. Evaluation boards also available upon request. Please check Linfinity's site further application notes.
LX1664/1665 Dual Output µProcessor Applications LX1668 Triple Output µProcessor Applications LX1553 3.3V Conversion
Pentium registered trademark Intel Corporation. Cyrix registered trademark 6x86, Gx86 trademarks Cyrix Corporation. trademark AMD. Power trademark International Business Machines Corporation. Alpha trademark Digital Equipment Corporation. PRODUCTION DATA Information contained this document proprietary LinFinity, current publication date. This document modified without express written consent LinFinity. Product processing does necessarily include testing parameters. Linfinity reserves right change configuration performance product discontinue product time.
Copyright 1999 Rev. 1.2a, 11/04

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