LTC3787 - PolyPhase Synchronous Boost Controller

1 LTC3787 . PolyPhase Synchronous Boost Controller FEATURES DESCRIPTION. n 2-Phase Operation Reduces Required Input and The LTC 3787 is a high performance PolyPhase single Output Capacitance and Power Supply Induced Noise output Synchronous Boost converter Controller that drives n Synchronous Operation for Highest Efficiency and two N-channel power MOSFET stages out-of-phase. Reduced Heat Dissipation Multiphase operation reduces input and output capacitor n Wide VIN Range: to 38V (40V Abs Max) and requirements and allows the use of smaller inductors than Operates Down to After Start-Up the single-phase equivalent. Synchronous rectification in- n Output Voltage Up to 60V creases efficiency, reduces power losses and eases thermal n 1% Reference Voltage requirements, enabling high power Boost applications. n RSENSE or Inductor DCR Current Sensing n A to 38V input supply range encompasses a wide 100% Duty Cycle Capability for Synchronous MOSFET.

2 N range of system architectures and battery chemistries. Low Quiescent Current: 135 A. n When biased from the output of the Boost converter or Phase-Lockable Frequency (75kHz to 850kHz). n another auxiliary supply, the LTC3787 can operate from Programmable Fixed Frequency (50kHz to 900kHz). n an input supply as low as after start-up. The operat- Power Good Output Voltage Monitor n ing frequency can be set for a 50kHz to 900kHz range or Low Shutdown Current, IQ < 8 A. n synchronized to an external clock using the internal PLL. Internal LDO Powers Gate Drive from VBIAS or EXTVCC. n PolyPhase operation allows the LTC3787 to be configured Thermally Enhanced Low Profile 28-Pin 4mm 5mm for 2-, 3-, 4-, 6- and 12-phase operation. QFN Package and Narrow SSOP Package The SS pin ramps the output voltage during start-up. The APPLICATIONS PLLIN/MODE pin selects Burst Mode operation, pulse- skipping mode or forced continuous mode at light loads.

3 N Industrial L, LT, LTC, LTM, Linear Technology, the Linear logo, Burst Mode, OPTI-LOOP and PolyPhase n Automotive are registered trademarks and No RSENSE and ThinSOT are trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. Protected by n Medical U. S. Patents, including 5408150, 5481178, 5705919, 5929620, 6144194, 6177787, 6580258. n Military TYPICAL APPLICATION Efficiency and Power Loss 12V to 24V/10A 2-Phase Synchronous Boost Converter vs Output Current VIN TO 24V START-UP VOLTAGE VIN 100 10000. OPERATES THROUGH TRANSIENTS DOWN TO 90. 80 1000. 4m F F 4m 47 F. POWER LOSS (mW). 70. EFFICIENCY (%). TG1 VBIAS INTVCC TG2 60 100. H BOOST1 BOOST2 H 50. F F. SW1 SW2 VOUT 40 10. 24V AT 10A. BG1 LTC3787 30. BG2. SENSE1+ VIN = 12V. 20 1. VOUT = 24V. 232k SENSE1 SENSE2+. VFB 10 Burst Mode OPERATION. FREQ SENSE2 FIGURE 10 CIRCUIT.

4 0 PLLIN/MODE PGND. 1 10. ITH SS SGND OUTPUT CURRENT (A). 15nF 220 F 3787 TA01b 100pF BURST EFFICIENCY. BURST LOSS. F. 3787 TA01a 3787fc 1. LTC3787 . ABSOLUTE MAXIMUM RATINGS (Notes 1, 3). VBIAS .. to 40V EXTVCC .. to 6V. BOOST1 and BOOST2 .. to 76V SENSE1+, SENSE1 , SENSE2+, SENSE2 .. to 40V. SW1 and to 70V (SENSE1+ - SENSE1 ), (SENSE2+ - SENSE2 ) .. to RUN .. to 8V ILIM, SS, ITH, FREQ, PHASMD, VFB .. to INTVCC. Maximum Current Sourced into Pin Operating Junction Temperature From Source >8V ..100 A Range (Note 2).. 55 C to 150 C. PGOOD, PLLIN/MODE .. to 6V Storage Temperature Range .. 65 C to 150 C. INTVCC, (BOOST1 - SW1), (BOOST2 - SW2) .. to 6V. PIN CONFIGURATION. TOP VIEW TOP VIEW. SENSE1 . SENSE1+. PGOOD. ILIM 1 28 PGOOD. SW1. ILIM. TG1. SENSE1+ 2 27 SW1. SENSE1 3 26 TG1 28 27 26 25 24 23. FREQ 4 25 BOOST1 FREQ 1 22 BOOST1. PHASMD 5 24 BG1 PHASMD 2 21 BG1. CLKOUT 3 20 VBIAS.

5 CLKOUT 6 23 VBIAS. PLLIN/MODE 7 22 PGND PLLIN/MODE 4 29 19 PGND. GND 18 EXTVCC. SGND 5. SGND 8 21 EXTVCC. RUN 6 17 INTVCC. RUN 9 20 INTVCC. SS 7 16 BG2. SS 10 19 BG2. SENSE2 8 15 BOOST2. SENSE2 11 18 BOOST2. 9 10 11 12 13 14. SENSE2+ 12 17 TG2. SENSE2+. VFB. ITH. NC. SW2. TG2. VFB 13 16 SW2. ITH 14 15 NC. UFD PACKAGE. GN PACKAGE 28-LEAD (4mm s 5mm) PLASTIC QFN. 28-LEAD PLASTIC SSOP TJMAX = 125 C, JA = 43 C/W. TJMAX = 125 C, JA = 90 C/W EXPOSED PAD (PIN 29) IS GND, MUST BE CONNECTED TO GND. ORDER INFORMATION. LEAD FREE FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE. LTC3787 EUFD#PBF LTC3787 EUFD#TRPBF 3787 28-Lead (4mm 5mm) Plastic QFN 40 C to 125 C. LTC3787 IUFD#PBF LTC3787 IUFD#TRPBF 3787 28-Lead (4mm 5mm) Plastic QFN 40 C to 125 C. LTC3787 HUFD#PBF LTC3787 HUFD#TRPBF 3787 28-Lead (4mm 5mm) Plastic QFN 40 C to 150 C. LTC3787 MPUFD#PBF LTC3787 MPUFD#TRPBF 3787 28-Lead (4mm 5mm) Plastic QFN 55 C to 150 C.

6 LTC3787 EGN#PBF LTC3787 EGN#TRPBF LTC3787GN 28-Lead Plastic SSOP 40 C to 125 C. LTC3787 IGN#PBF LTC3787 IGN#TRPBF LTC3787GN 28-Lead Plastic SSOP 40 C to 125 C. LTC3787 HGN#PBF LTC3787 HGN#TRPBF LTC3787GN 28-Lead Plastic SSOP 40 C to 150 C. LTC3787 MPGN#PBF LTC3787 MPGN#TRPBF LTC3787GN 28-Lead Plastic SSOP 55 C to 150 C. Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container. For more information on lead free part marking, go to: For more information on tape and reel specifications, go to: 3787fc 2. LTC3787 . ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the specified operating junction temperature range, otherwise specifications are at TA = 25 C, VBIAS = 12V, unless otherwise noted (Note 2). SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS. Main Control Loop VBIAS Chip Bias Voltage Operating Range 38 V.

7 VFB Regulated Feedback Voltage ITH = (Note 4) l V. IFB Feedback Current (Note 4) 5 50 nA. VREFLNREG Reference Line Voltage Regulation VBIAS = 6V to 38V %/V. VLOADREG Output Voltage Load Regulation Measured in Servo Loop; l %. (Note 4) ITH Voltage = to Measured in Servo Loop; l %. ITH Voltage = to 2V. gm Error Amplifier Transconductance ITH = 2 mmho IQ Input DC Supply Current (Note 5). Pulse-Skipping or Forced Continuous Mode RUN = 5V; VFB = (No Load) mA. Sleep Mode RUN = 5V; VFB = (No Load) 135 300 A. Shutdown RUN = 0V 8 20 A. UVLO INTVCC Undervoltage Lockout Thresholds VINTVCC Ramping Up l V. VINTVCC Ramping Down l V. VRUN RUN Pin ON Threshold VRUN Rising l V. VRUNHYS RUN Pin Hysteresis 100 mV. IRUNHYS RUN Pin Hysteresis Current VRUN > A. IRUN RUN Pin Current VRUN < A. ISS Soft-Start Charge Current VSS = GND 7 10 13 A. VSENSE1,2(MAX) Maximum Current Sense Threshold VFB = , ILIM = INTVCC l 90 100 110 mV.

8 VFB = , ILIM = Float l 68 75 82 mV. VFB = , ILIM = GND l 42 50 56 mV. VSENSE(MATCH) Matching Between VSENSE1(MAX) and VFB = , ILIM = INTVCC l 12 0 12 mV. VSENSE2(MAX) VFB = , ILIM = Float l 10 0 10 mV. VFB = , ILIM = GND l 9 0 9 mV. VSENSE(CM) SENSE Pins Common Mode Range ( Boost 38 V. Converter Input Supply Voltage VIN). ISENSE1,2+ SENSE+ Pin Current VFB = , ILIM = Float 200 300 A. ISENSE1,2 SENSE Pin Current VFB = , ILIM = Float 1 A. tr(TG1,2) Top Gate Rise Time CLOAD = 3300pF (Note 6) 20 ns tf(TG1,2) Top Gate Fall Time CLOAD = 3300pF (Note 6) 20 ns tr(BG1,2) Bottom Gate Rise Time CLOAD = 3300pF (Note 6) 20 ns tr(BG1,2) Bottom Gate Fall Time CLOAD = 3300pF (Note 6) 20 ns RUP(TG1,2) Top Gate Pull-Up Resistance . RDN(TG1,2) Top Gate Pull-Down Resistance . RUP(TG1,2) Bottom Gate Pull-Up Resistance . RDN(TG1,2) Bottom Gate Pull-Down Resistance . tD(TG/BG) Top Gate Off to Bottom Gate On Switch-On CLOAD = 3300pF (Each Driver) 70 ns Delay Time tD(BG/TG) Bottom Gate Off to Top Gate On Switch-On CLOAD = 3300pF (Each Driver) 70 ns Delay Time DFBG1,2(MAX) Maximum BG Duty Factor 96 %.

9 TON(MIN) Minimum BG On-Time (Note 7) 110 ns 3787fc 3. LTC3787 . ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the specified operating junction temperature range, otherwise specifications are at TA = 25 C, VBIAS = 12V, unless otherwise noted (Note 2). SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS. INTVCC Linear Regulator VINTVCC(VIN) Internal VCC Voltage 6V < VBIAS < 38V, VEXTVCC = 0 V. VLDO INT INTVCC Load Regulation ICC = 0mA to 50mA 2 %. VINTVCC(EXT) Internal VCC Voltage VEXTVCC = 6V V. VLDO EXT INTVCC Load Regulation ICC = 0mA to 40mA, VEXTVCC = 6V 2 %. VEXTVCC EXTVCC Switchover Voltage EXTVCC Ramping Positive l 5 V. VLDOHYS EXTVCC Hysteresis 250 mV. Oscillator and Phase-Locked Loop fPROG Programmable Frequency RFREQ = 25k 105 kHz RFREQ = 60k 335 400 465 kHz RFREQ = 100k 760 kHz fLOW Lowest Fixed Frequency VFREQ = 0V 320 350 380 kHz fHIGH Highest Fixed Frequency VFREQ = INTVCC 488 535 585 kHz fSYNC Synchronizable Frequency PLLIN/MODE = External Clock l 75 850 kHz PGOOD Output VPGL PGOOD Voltage Low IPGOOD = 2mA V.

10 IPGOOD PGOOD Leakage Current VPGOOD = 5V 1 A. VPGOOD PGOOD Trip Level VFB with Respect to Set Regulated Voltage VFB Ramping Negative 12 10 8 %. Hysteresis %. VFB Ramping Positive 8 10 12 %. Hysteresis %. tPGOOD(DELAY) PGOOD Delay PGOOD Going High to Low 25 s BOOST1 and BOOST2 Charge Pump IBOOST1,2 Boost Charge Pump Available Output VSW1,2 = 12V; VBOOST1,2 VSW1,2 = ; 55 A. Current FREQ = 0V, Forced Continuous or Pulse-Skipping Mode Note 1: Stresses beyond those listed under Absolute Maximum Ratings temperature (TA, in C) and power dissipation (PD, in Watts) according to may cause permanent damage to the device. Exposure to any Absolute the formula: TJ = TA + (PD JA), where JA = 43 C/W for the QFN package Maximum Rating condition for extended periods may affect device and JA = 90 C/W for the SSOP package. reliability and lifetime. Note 3: This IC includes overtemperature protection that is intended to Note 2: The LTC3787 is tested under pulsed load conditions such that protect the device during momentary overload conditions.