LT8631: 100V, 1A Synchronous - analog.com

1 LT863118631fbFor more information TO 100 VVOUT 5V, F22 = 400kHz8631 TA01aEN/UVPGINTVCCRTSYNC/MODEBSTSWINDGND VOUTFBTR/SS47 APPLICATION FEATURESDESCRIPTION100V, 1A SynchronousMicropower Step-Down RegulatorThe LT 8631 is a current mode PWM step-down DC/DC converter with internal Synchronous switches that provide current for output loads up to 1A. The wide input range of 3V to 100V makes the LT8631 suitable for regulating power from a wide variety of sources, including automotive and industrial systems and 36V to 72V telecom supplies. Low ripple Burst Mode operation enables high efficiency operation down to very low output currents while keeping the output ripple below 10mVP-P. Resistor programmable 100kHz to 1 MHz frequency range and synchronization ca-pability enable optimization between efficiency and external component size.

2 The soft-start feature controls the ramp rate of the output voltage, eliminating input current surge during start-up, while also providing output tracking. A power good flag signals when the output voltage is within of the regulated output. Undervoltage lockout can be programmed using the EN/UV pin. Shutdown mode reduces the total quiescent current to < 5 A. The LT8631 is available in a 20-lead TSSOP package with exposed pad for low thermal resistance and high voltage lead , LT , LT C, LT M, Linear Technology, Burst Mode and the Linear logo are registered trademarks of analog Devices, Inc. All other trademarks are the property of their respective owners. n Ultrawide Input Voltage Range: 3V to 100Vn Output Voltage Range: to 60Vn Internal Synchronous Switchesn Low Ripple Burst Mode Operation: 16 A IQ at 12 VIN to 5 VOUT Output Ripple <10mVP-P 7 A IQ at 48 VIN to 5 VOUT Output Ripple <10mVP-Pn Low Dropout: 99% Maximum Duty Cyclen Peak Current Mode Controln Fixed Frequency Operation: 100kHz to 1 MHzn Synchronization Inputn Programmable Undervoltage Lockout n Power Good Flagn Flexible Output Voltage Trackingn Short-Circuit Protection n Low Shutdown Current.

3 5 An Tolerates Pin Open/Short Faultsn Thermally Enhanced 20-Lead TSSOP with High Voltage Lead Spacingn Automotive Supplies n Telecom Suppliesn Distributed Supply Regulation5V, 1A Step-Down ConverterEfficiency vs Load CurrentLOAD CURRENT (A)0 EFFICIENCY (%) = 400kHzVIN = 12 VVIN = 24 VVIN = 48 VLT863128631fbFor more information CONFIGURATIONABSOLUTE MAXIMUM RATINGS(Note 1)FE PACKAGEVARIATION FE20(16)20-LEAD PLASTIC TSSOP135678910 TOP VIEW2018161514131211 VINEN/UVPGNCSYNC/MODERTNCTR/SSSWBSTINTVC CNCINDNCVOUTFB21 GND JA = 40 C/W, JC(PAD) = 10 C/W EXPOSED PAD (PIN 21) IS GND, MUST BE SOLDERED TO PCBORDER INFORMATIONLEAD FREE FINISHTAPE AND REELPART MARKING*PACKAGE DESCRIPTIONTEMPERATURE RANGELT8631 EFE#PBFLT8631 EFE#TRPBFLT8631FE20-Lead Plastic TSSOP 40 C to 125 CLT8631 IFE#PBFLT8631 IFE#TRPBFLT8631FE20-Lead Plastic TSSOP 40 C to 125 CLT8631 HFE#PBFLT8631 HFE#TRPBFLT8631FE20-Lead Plastic TSSOP 40 C to 150 CConsult LT C Marketing for parts specified with wider operating temperature ranges.

4 *The temperature grade is identified by a label on the shipping container. Consult LT C Marketing for information on nonstandard lead based finish more information on lead free part marking, go to: For more information on tape and reel specifications, go to: Some packages are available in 500 unit reels through designated sales channels with #TRMPBF , EN/UV, PG ..100 VIND, VOUT, ..60V/ ..6 VFB, TR/SS ..4 VOperating Junction Temper atur e Range LT8631 EFE (Note 2) .. 40 C to 125 C LT8631 IFE (Note 2) .. 40 C to 125 CLT8631 HFE (Note 2) .. 40 C to 150 CStorage Temper atur e Range .. 65 C to 150 C #orderinfoLT863138631fbFor more information CHARACTERISTICSPARAMETERCONDITIONSMINTYP MAXUNITSEN/UV Voltage ThresholdVEN/UV Voltage Hysterisis91725mVEN/UV Input Current5100nAVIN Undervoltage Lockout VFB = Current from VINVEN/UV = 0V VFB = , VVOUT = 0V VFB = , VVOUT = 5V5 16 30 A A AQuiescent Current from VINVEN/UV = 0V VFB = , VVOUT = 0V VFB = , VVOUT = 5Vl l l5 16 64 22 A A AQuiescent Current from VOUTVFB = , VVOUT = 5Vl1045 AVIN Current in RegulationVVOUT = 5V, ILOAD = 100 A VVOUT = 5V, VSYNC/MODE = 2V, ILOAD = 100 A VVOUT = 5V, ILOAD = 1mA90 180 475160 350 650 A A AFeedback Bias CurrentVFB = 25 15nAFeedback Voltage (VFBREF)

5 VVOUT = 5V, ILOAD = 100mAl796808820mVFeedback Voltage Line Regulation Feedback Voltage Load RegulationVIN = 7V to 100V, VOUT = 5V, ILOAD = 500mA VIN = 15V, VOUT = 5V, ILOAD = 100mA to 1A %/V %/ATrack/Soft-Start Source CurrentVFB = , VTR/SS = 0V ATrack/Soft-Start VOHVFB = Sink CurrentVFB = , VTR/SS = 1V153045 ATrack/Soft-Start VOLVFB = 0V5075mVTrack/Soft-Start to Feedback OffsetVTR/SS = , VVOUT = 5V, ILOAD = 100mA 25525mVTrack/Soft-Start Sink Current POR (Note 4) VFB = , VTR/SS = APG Leakage CurrentVFB = 0V, VPG = 100V 2000200nAPG Lower Threshold % of VFBREF (Note 5)VFB Risingl Upper Threshold % of VFBREF (Note 5)VFB Hysterisis (Note 5) Sink CurrentVFB = , VPG = ASwitching FrequencyRRT =187k , VVOUT = 5V, ILOAD = 100mA RRT = , VVOUT = 5V, ILOAD = 100mA RRT = , VVOUT = 5V, ILOAD = 100mA l75 460 925100 500 1000125 540 1075kHz kHz kHzMinimum Switch ON TimeVIN = 15V to 25V, RRT = , VVOUT = , ILOAD = 500mA100120nsMinimum Switch OFF TimeVIN = 5V, RRT = , VVOUT = 5V, ILOAD = 500mA190nsIND to VOUT Burst Current (Note 6)280mAIND to VOUT Peak Current (Note 7)

6 VOUT Current in RegulationVIN = , RRT = , VVOUT = 5V, L = 15 H VIN = 50V, RRT = , VVOUT = 5V, L = 15 ASwitch Pin Leakage CurrentVSW = 0V, VEN/UV = 0V VSW = 100V, VIN =100V, VEN/UV = 0V50 ATop Switch On-Resistance775m Bottom Switch On-Resistance550m BST Pin CurrentVBST = 18V180 A The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TJ = 25 C. VIN = 15V, VEN/UV = 2V, unless otherwise specified. (Note 2)LT863148631fbFor more information CHARACTERISTICS The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TJ = 25 C. VIN = 15V, VEN/UV = 2V, unless otherwise specified. (Note 2)PARAMETERCONDITIONSMINTYPMAXUNITSBST Pin Threshold (Note 8) Pin CurrentVSYNC/MODE = ASYNC/MODE Range1001000kHzNote 1: Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device.

7 Exposure to any Absolute Maximum Rating condition for extended periods may affect device reliability and 2: The LT8631 EFE is guaranteed to meet performance specifications from 0 C to 125 C junction temperature. Specifications over the 40 C to 125 C operating junction temperature range are assured by design, characterization and correlation with statistical process controls. The LT8631 IFE is guaranteed over the full 40 C to 125 C operating junction temperature range. The LT8631 HFE is guaranteed over the full 40 C to 150 C operating junction temperature range. High junction temperatures degrade operating lifetimes. Operating lifetime is derated at junction temperatures greater than 125 C. Note 3: The LT8631 includes overtemperature protection that is intended to protect the device during thermal overload conditions. Internal junction temperature will exceed 150 C when the overtemperature circuitry is active.

8 Note 4: An internal power on reset (POR) latch is set on the positive transition of the EN/UV pin through its threshold or thermal shutdown. The output of the latch activates a current source on the TR/SS pin which typically sinks 230 A while discharging the TR/SS capacitor. The latch is reset when the TR/SS pin is driven below the soft-start POR threshold or the EN/UV pin is taken below its 5: The threshold is expressed as a percentage of the feedback reference 6: The IND to VOUT burst current is defined as the maximum value of current flowing from the IND pin to the VOUT during a switch cycle when operating in Burst 7: The IND to VOUT peak current is defined as the maximum value of current flowing from the IND pin to the VOUT during a switch 8: The BST pin threshold is defined as the minimum voltage between the BST and SW pins to keep the top switch on.

9 If the the voltage falls below the threshold when the top switch is on, a minimum switch off pulse will be generated. LT863158631fbFor more information PERFORMANCE CHARACTERISTICSE fficiency at VOUT = Supply CurrentEN/UV ThresholdsVIN Undervoltage LockoutReference VoltageEfficiency at VOUT = 5 VEfficiency at VOUT = at VOUT = 5 VLOAD CURRENT (A)0 EFFICIENCY (%) = 400kHzVIN = 12 VVIN = 24 VVIN = 48 VLOAD CURRENT (A)0 EFFICIENCY (%) = 400kHzVIN = 12 VVIN = 24 VVIN = 48 VLOAD CURRENT (A)EFFICIENCY (%)8631 = 12 VVIN = 24 VVIN = 48 VFSW = 400kHzLOAD CURRENT (A)EFFICIENCY (%)8631 = 12 VVIN = 24 VVIN = 48 VFSW = 400kHzTEMPERATURE ( C) 50 VOLTAGE (V) 1258631 G081500 2550 TEMPERATURE ( C) 50 VOLTAGE (mV)8128108088068048027988002575100 1258631 G091500 2550 LOAD = 0mALOAD = 100mALOAD = 1 ASWITCHING FREQUENCY (kHz)EFFICIENCY (%)

10 100909580708575400200600 700 800 9008631 G051000300100500 VIN = 12 VVOUT = 5 VLOAD = = ( C) 50 CURRENT ( A) 1258631 G061500 2550 TEMPERATURE ( C) 50 VOLTAGE (V) 1258631 G071500 2550EN/UV FALLINGEN/UV RISINGLT863168631fbFor more information PERFORMANCE CHARACTERISTICSB urst FrequencyNo Load Supply CurrentNo Load Supply CurrentSleep Quiescent CurrentsPeak Switch CurrentPeak Switch CurrentSwitching FrequencyMinimum On-TimeSwitch ResistanceTEMPERATURE ( C) 50 FREQUENCY (kHz)52552051551050550049547549048548025 75100 1258631 G101500 2550 RRT = VOLTAGE (V)0 CURRENT ( A)25201501053050 60 70 80 908631 G13100201040 VOUT = = 5 VOUTPUT VOLTAGE (V) ( A) ( C) 50 CURRENT (A) 1258631 G151500 2550 DUTY CYCLE = 20%DUTY CYCLE = 80%DUTY CYCLE (%)0 CURRENT (A) G1610020 TEMPERATURE ( C) 50 CURRENT ( A)60504030020102575100 1258631 G121500 2550 VIN = 12 VVOUT = = 5 VTEMPERATURE ( C) 50 RESISTANCE ( ) 1258631 G181500 2550 TOP SWITCHBOTTOM SWITCHLOAD CURRENT (mA)0 BURST FREQUENCY (kHz)4504003503002502000150100501525 30 35 45 458631 G115010520 VIN = 12 VVOUT = 5VL = 22 HFREQUENCY = 400kHzTEMPERATURE ( C) 50 TIME (ns)2001801601401201000806040202575100 1258631 G171500 2550 LOAD = 500mAON-TIMELT863178631fbFor more information PERFORMANCE CHARACTERISTICSLine RegulationLoad RegulationFB to TR/SS Offset VoltageSoft-Start TrackingPG High ThresholdsINPUT VOLTAGE (V)0 CHANGE IN VOUT (%) G191002550 VOUT = 5 VLOAD = CURRENT (A)0 CHANGE IN VOUT (%) = 12 VVOUT = 5 VTEMPERATURE ( C) 50 VFB VTR/SS (mV)10987625432575100 1258631 G211500 2550 VTR/SS = = VOLTAGE (V)0FB VOLTAGE (V) = ( C)