POWER LOSS (W) LTC3875 Dual, 2-Phase, Synchronous Controller with Low Value DCR Sensing and Temperature Compensation FEATURES DESCRIPTION n Low Value DCR Current Sensing The LTC 3875 is a dual output current mode synchronous n Programmable DCR Temperature Compensation step-down DC/DC controller that drives all N-channel n 0.5% 0.6V Output Voltage Accuracy synchronous power MOSFET stages. It employs a unique n Dual True Remote Sensing Differential Amplifiers architecture which enhances the signal-to-noise ratio of n Optional Fast Transient Operation the current sense signal, allowing the use of very low DC n Phase-Lockable Fixed Frequency 250kHz to 720kHz resistance power inductors to maximize the efficiency in n Dual, 180 Phased Controllers Reduce Required high current applications. This feature also reduces the switching jitter commonly found in low DCR applications. Input Capacitance and Power Supply Induced Noise n Dual N-Channel MOSFET Synchronous Drive The LTC3875 features two high speed remote sense differ- n Wide V Range: 4.5V to 38V Operation IN ential amplifiers, programmable current sense limits from n Output Voltage Range with Low DCR: 0.6V to 3.5V, 10mV to 30mV and DCR temperature compensation to limit without Low DCR: 0.6V to 5V the maximum output current precisely over temperature. n Adjustable Soft-Start Current Ramping or Tracking A unique thermal balancing function adjusts per phase cur- n Foldback Output Current Limiting rent in order to minimize the thermal stress for multichip n Clock Input and Output for Up to 12-Phase Operation single output applications. The LTC3875 also features a n Short-Circuit Soft Recovery precise 0.6V reference with guaranteed accuracy of 0.5% n Output Overvoltage Protection that provides an accurate output voltage from 0.6V to 3.5V. n Power Good Output Voltage Monitor A 4.5V to 38V input voltage range allows it to support a n 40-Lead QFN Packages wide variety of bus voltages. The LTC3875 is available in a low profile 40-lead 6mm 6mm (0.5mm pitch) and APPLICATIONS 40-lead 5mm 5mm (0.4mm pitch) QFN packages. n Servers and Instruments L, LT, LTC, LTM, Linear Technology, the Linear logo OPTI-LOOP, Burst Mode and PolyPhase n are registered trademarks and No R is a trademark of Linear Technology Corporation. Telecom Systems SENSE All other trademarks are the property of their respective owners. Protected by U.S. Patents n DC Power Distribution Systems including 5481178, 5705919, 5929620, 6100678, 6144194, 6177787, 6304066, 6580258. TYPICAL APPLICATION High Efficiency Dual Phase 1.2V/60A Step-Down Converter V IN 6V TO 14V INTV 22F Efficiency and Power Loss CC 16V 4 4.7F V INTV PHASMD IN CC vs Load Current CLKOUT (OPTIONAL) (OPTIONAL) RUN1,2 PGOOD 100 14 IFAST ILIM 12V THERMAL THERMAL IN ENTMPB MODE/PLLIN 1.8V SENSOR SENSOR O 12 TG1 TG2 95 ~400kHz 0.3H 0.3H CCM BOOST1 BOOST2 (0.32m DCR) (0.32m DCR) 10 90 SW1 LTC3875 SW2 EXTV CC 8 BG1 BG2 85 TAVG PGND 6 TRSET1 TRSET2 + SNSA1 80 + SNSA2 4 SNS1 SNS2 0.32m + SNSD1 + SNSD2 75 1.5m 2 TCOMP1 0.32m PLOSS TCOMP2 + V V OUT OSNS1 V 1.5m PLOSS FREQ 20k OUT V + 70 0 OSNS1 1.2V V OSNS2 0 10 20 30 40 50 60 I TH1 V 60A + 470F OSNS2 1500pF LOAD CURRENT (A) TK/SS1 TK/SS2 I 2.5V 2 TH2 + 470F 20k SP 3875 TA01b 122k 15k 2.5V 2 0.1F SP 3875 TA01a 3875fb 1 For more information www.linear.com/LTC3875 EFFICIENCY (%)LTC3875 ABSOLUTE MAXIMUM RATINGS (Note 1) Input Supply Voltage (V ) ......................... 40V to 0.3V MODE/PLLIN, ILIM, FREQ, IFAST, ENTMPB IN + Topside Driver Voltages V , V Voltages ...............INTV to 0.3V OSNS(s) OSNS(s) CC (BOOST1, BOOST2).................................... 46V to 0.3V I , I , PHASMD, TRSET1, TRSET2, TH1 TH2 Switch Voltage (SW1, SW2) .......................... 40V to 5V TCOMP1, TCOMP2, TAVG Voltages .......INTV to 0.3V CC INTV , RUN(s), PGOOD, EXTV INTV Peak Output Current ................................100mA CC CC CC (BOOST-SW1), (BOOST2-SW2).................... 6V to 0.3V Operating Junction Temperature Range + + SNSA (s), SNSD (s), (Notes 2, 3) ............................................ 40C to 125C SNS (s) Voltages ..................................INTV to 0.3V Storage Temperature Range .................. 65C to 125C CC PIN CONFIGURATION TOP VIEW TOP VIEW 40 39 38 37 36 35 34 33 32 31 40 39 38 37 36 35 34 33 32 31 TK/SS1 1 30 SW1 TK/SS1 1 30 SW1 + + V 2 29 TG1 V 2 29 TG1 OSNS1 OSNS1 V 3 28 BOOST1 V 3 28 BOOST1 OSNS1 OSNS1 I 4 27 BG1 I 4 27 BG1 TH1 TH1 I I 5 26 V 5 26 V TH2 IN TH2 IN 41 41 + + SGND/PGND SGND/PGND V 6 25 INTV V 6 25 INTV OSNS2 OSNS2 CC CC V 7 24 EXTV V 7 24 EXTV OSNS2 CC OSNS2 CC TK/SS2 8 23 BG2 TK/SS2 8 23 BG2 + + SNSA2 9 22 BOOST2 SNSA2 9 22 BOOST2 SNS2 10 21 SNS2 10 21 TG2 TG2 11 12 13 14 15 16 17 18 19 20 11 12 13 14 15 16 17 18 19 20 UJ PACKAGE UH PACKAGE 40-LEAD (6mm 6mm) PLASTIC QFN 40-LEAD (5mm 5mm) PLASTIC QFN T = 125C, = 33C/W, = 2.0C/W T = 125C, = 44C/W, = 7.3C/W JMAX JA JC JMAX JA JC EXPOSED PAD (PIN 41) IS SGND/PGND, MUST BE SOLDERED TO PCB EXPOSED PAD (PIN 41) IS SGND/PGND, MUST BE SOLDERED TO PCB 3875fb 2 For more information www.linear.com/LTC3875 + + SNSD2 SNSA1 TCOMP2/ITEMP2 SNS1 + TAVG SNSD1 TRSET2 TCOMP1/ITEMP1 FREQ TRSET1 RUN2 ILIM IFAST RUN1 ENTMPB MODE/PLLIN PGOOD PHASMD SW2 CLKOUT + + SNSD2 SNSA1 TCOMP2/ITEMP2 SNS1 + TAVG SNSD1 TRSET2 TCOMP1/ITEMP1 FREQ TRSET1 RUN2 ILIM IFAST RUN1 ENTMPB MODE/PLLIN PGOOD PHASMD SW2 CLKOUT