LM2638 Motherboard Power Supply Solution with 5-Bit Programmable Switc

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LM2638 Motherboard Power Supply Solution with 5-Bit Programmable Switc

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LM2638 Motherboard Power Supply Solution with 5-Bit Programmable Switching Controller Linear Regulator Controllers
LM2638 Motherboard Power Supply Solution with 5-Bit Programmable Switching Controller Linear Regulator Controllers
LM2638 provides comprehensive embedded power supply solution motherboards hosting high performance MPUs such PentiumII, IITM, K6TM-2 other similar high performance MPUs. LM2638 incorporates 5-bit programmable, synchronous buck switching controller high-speed linear regulator controllers 24-pin package. typical application, switching controller supplies core, linear regulator controllers supply GTL+ clock graphics chip core. charge pump helps provide necessary voltage power linear sections when shut during system standby such mode. Both linear controllers have under voltage latch-off.
Features
Provides regulated voltages Power Good flag output enable Charge pump Switching Section Synchronous rectification 5-bit programmable down 1.3V Typical tolerance Switching frequency: Over-voltage protection methods over-current protection Adaptive non-overlapping gate drives Soft start without external capacitor Linear Section N-FET drive capability Ultra fast response speed Under voltage latch-off 0.63V Output voltages default 1.5V 2.5V adjustable
Switching Section switching regulator controller features Intel-compatible, 5-bit programmable output voltage, over-current over-voltage protection, power good signal, logic-controlled output enable. There user-selectable over-current protection methods. provides accurate over-current protection with external sense resistor. other saves cost taking advantage rDS_ON high-side FET. When there over voltage, controller turns high side turns side. Linear Section linear regulator controllers feature wide control bandwidth, N-FET transistor driving capability adjustable output. wide control bandwidth makes meeting GTL+ transient response requirement easy job. minimum configuration, controllers default 1.5V 1.25V respectively.
Applications
Embedded power supplies motherboards Triple DC/DC power supplies Programmable high current DC/DC power supply
Configuration
24-Lead SOIC
DS101034-1
View Order Number LM2638M Package Number M24B
IIis trademark Cyrix Corporation wholly owned subsidiary National Semiconductor Corporation. Pentiumis trademark Intel Corporation. K6is trademark Advanced Micro Devices, Inc.
1999 National Semiconductor Corporation
DS101034
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Absolute Maximum Ratings (Note
Military/Aerospace specified devices required, please contact National Semiconductor Sales Office/ Distributors availability specifications. Junction Temperature Power Dissipation (Note 150°C 1.6W
Storage Temperature Susceptibility Soldering Time, Temperature sec.)
-65°C +150°C 300°C
Operating Ratings (Note
Junction Temperature Range 4.75V 5.25V +125°C
Electrical Characteristics unless otherwise specified. Typicals limits appearing plain type apply +25°C. Limits appearing boldface type apply over +70°C range.
Symbol IQ_VCC IQ_VDD RDS_CP Parameter Internal Pull-up Current Operating Current Shutdown Current Shutdown Current Resistance 10111 Pins Floating Pins Floating High Side Side SWITCHING SECTION VDACOUT IVID fOSC DMAX DMIN RSNS1 RDS_SRC RDS_SINK VCC_TH1 VCC_TH2 VDAC_IH VDAC_IL BWEA VRAMP_L VRAMP_H DSTEP_SS tPWGD tPWBAD 5-Bit Output Voltage Pins Internal Pull-up Current Oscillator Frequency Maximum Duty Cycle Minimum Duty Cycle SNS1 Resistance Ground Gate Driver Resistance When Sourcing Current Gate Driver Resistance When Sinking Current Power-On-Reset Threshold Shutdown Threshold Input High Voltage Input Voltage Error Amplifier Gain Error Amplifier Unity Gain Bandwidth Ramp Signal Valley Voltage Ramp Signal Peak Voltage Soft Start Time Duty Cycle Step Change during Soft Start PWGD Response Time PWGD Response Time SNS1 Rises from Rated Output Voltage SNS1 Falls from Rated Output Voltage 1.25 3.25 4096 12.5 (Note Conditions Units
N-1.5%
1000
N+1.5%
Clock Cycles
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Electrical Characteristics unless otherwise specified. Typicals limits appearing plain type apply +25°C. Limits appearing boldface type apply over +70°C range. (Continued)
Symbol SWITCHING SECTION VPWGD_HI PWGD High Trip Point Above Rated Output Voltage When Output Voltage Above Rated Output Voltage When Output Voltage (Note VPWGD_LO PWGD Trip Point Below Rated Output Voltage When Output Voltage Below Rated Output Voltage When Output Voltage (Note VOVP_TRP ICS+ VOCP Over-Voltage Trip Point Sink Current Over-Current Trip Point (CS+ Differential Voltage) SNS2 Voltage Output Resistance SNS2 Bias Current PWGD High Trip Point PWGD Trip Point SNS3 Voltage Output Resistance SNS3 Bias Current PWGD High Trip Point PWGD Trip Point When Regulating (Note (Note When Regulating (Note (Note 12V, 4.75V 5.25V, SNS1 Above Rated Output 4.8V Drops from 11.5 Parameter Conditions Units
1.5V CONTROLLER SECTION VSNS2 ROUT2 ISNS2 VPWGD_HI VPWGD_LO VSNS3 ROUT3 ISNS3 VPWGD_HI VPWGD_LO 12V, 4.75V 5.25V, 1.463 0.63 0.44 1.538
1.25V CONTROLLER SECTION 1.219 1.25 0.63 0.44 1.281
Note Absolute Maximum Ratings limits beyond which damage device occur. Operating ratings conditions under which device operates correctly. Operating Ratings imply guaranteed performance limits. Note Maximum allowable power dissipation function maximum junction temperature, TJMAX, junction-to-ambient thermal resistance, ambient temperature, maximum allowable power dissipation ambient temperature calculated using: PMAX (TJMAX TA)/JA. junction-to-ambient thermal resistance, LM2638 78°C/W. TJMAX 150°C 25°C, maximum allowable power dissipation 1.6W. Note letter stands typical output voltages appearing italic boldface type Table Note output level PWGD logic power good function switching section, 1.5V section 1.25V section. switching section, power good window. linear sections, power good threshold with some hysteresis.
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Electrical Characteristics unless otherwise specified. Typicals limits appearing plain type apply +25°C. Limits appearing boldface type apply over +70°C range. (Continued)
TABLE 5-Bit Output Voltage Table (VCC 25°C, Test Mode) Symbol VDACOUT Parameter 5-Bit Output Voltages Different Codes Conditions VID4:0 01111 VID4:0 01110 VID4:0 01101 VID4:0 01100 VID4:0 01011 VID4:0 01010 VID4:0 01001 VID4:0 01000 VID4:0 00111 VID4:0 00110 VID4:0 00101 VID4:0 00100 VID4:0 00011 VID4:0 00010 VID4:0 00001 VID4:0 00000 VID4:0 11111 VID4:0 11110 VID4:0 11101 VID4:0 11100 VID4:0 11011 VID4:0 11010 VID4:0 11001 VID4:0 11000 VID4:0 10111 VID4:0 10110 VID4:0 10101 VID4:0 10100 VID4:0 10011 VID4:0 10010 VID4:0 10001 VID4:0 10000 Typical Units
1.30
1.35
1.40
1.45
1.50 1.55 1.60
1.65
1.70
1.75
1.80
1.85
1.90
1.95
2.00
2.05 (shutdown)
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Description
PGND SNS2 SGND SNS1 FREQ PWGD VID4 VID3 VID2 VID1 VID0 SNS3 Name side N-FET gate driver output. Ground drivers switching section. Supply gate drivers. Usually tied +12V. Feedback 1.5V linear regulator. Gate drive output external N-MOS fast 1.5V linear regulator. Ground internal signal circuitry system ground reference. Supply voltage. Usually +5V. Output voltage monitor input switching regulator. Switching regulator current sense input, positive node. Switching regulator current sense input, negative node. Charge pump. Output square wave with duty cycle. Amplitude close voltage. Switching frequency adjustment pin. external resistor needed desired frequency. Output error amplifier. Used compensating switching regulator. Inverting input error amplifier. Used compensating switching regulator. Open collector Power Good signal. 5-Bit input, MSB. 5-Bit input. 5-Bit input. 5-Bit input. 5-Bit input, LSB. Gate drive external N-MOS 1.25V linear regulator. Feedback 1.25V linear regulator. Output Enable. logic shuts whole chip down. High side N-FET gate driver output. Function
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Block Diagram
DS101034-3
Test Circuit
DS101034-4
FIGURE Controller Test Circuit
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Typical Application
DS101034-2
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FIGURE Using LM2638 Supply GTL+ (VTT, 1.5V, 5.6A), 2.5V Standby (VCC2_5SBY, Full Power Suspend) 3.3V Standby (VCC3_3SBY, 1.5A Full Power, 0.5A Suspend)
LM2638 Motherboard Power Supply Solution with 5-Bit Programmable Switching Controller Linear Regulator Controllers
Physical Dimensions
inches (millimeters) unless otherwise noted
24-Lead Small Outline Package Order Number LM2638M Package Number M24B
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: 80-530 Email: europe.support@nsc.com Deutsch Tel: 80-530 English Tel: 80-532 Tel: 80-532 Italiano Tel: 80-534
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: sea.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.

LM2638 Motherboard Power Supply Solution with 5-Bit Programmable Switc

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