Datasheet LTC3875 (Analog Devices)

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
Input Capacitance and Power Supply Induced Noise
switching jitter commonly found in low DCR applications. n Dual N-Channel MOSFET Synchronous Drive The LTC3875 features two high speed remote sense differ- n Wide VIN Range: 4.5V to 38V Operation 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 n A unique thermal balancing function adjusts per phase cur- Foldback Output Current Limiting n rent in order to minimize the thermal stress for multichip Clock Input and Output for Up to 12-Phase Operation n single output applications. The LTC3875 also features a Short-Circuit Soft Recovery n precise 0.6V reference with guaranteed accuracy of ±0.5% Output Overvoltage Protection n that provides an accurate output voltage from 0.6V to 3.5V. Power Good Output Voltage Monitor n A 4.5V to 38V input voltage range allows it to support a 40-Lead QFN Packages wide variety of bus voltages. The LTC3875 is available
APPLICATIONS
in a low profile 40-lead 6mm × 6mm (0.5mm pitch) and 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 Telecom Systems are registered trademarks and No RSENSE is a trademark of Linear Technology Corporation. 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
VIN INTV 6V TO 14V
Efficiency and Power Loss
CC 22µF 4.7µF V 16V ×4 IN INTVCC PHASMD
vs Load Current
CLKOUT (OPTIONAL) RUN1,2 PGOOD (OPTIONAL) 100 14 THERMAL ILIM IFAST THERMAL 12VIN ENTMPB MODE/PLLIN SENSOR SENSOR 1.8V TG1 TG2 O 95 12 ~400kHz 0.3µH 0.3µH BOOST1 BOOST2 CCM (0.32mΩ DCR) (0.32mΩ DCR) 10 POWER LOSS (W) SW1 LTC3875 SW2 90 EXTVCC 8 BG1 BG2 TAVG 85 PGND TRSET1 6 TRSET2 SNSA1+ EFFICIENCY (%) SNSA2+ 80 SNS1– 4 SNS2– 0.32mΩ SNSD1+ SNSD2+ 75 1.5mΩ TCOMP1 2 TCOMP2 0.32mΩ PLOSS VOUT V + OSNS1 FREQ 20k VOUT 1.5mΩ PLOSS V – OSNS1 V + 1.2V 70 0 + OSNS2 ITH1 0 10 20 30 40 50 60 470µF V – OSNS2 60A 2.5V ×2 TK/SS1 TK/SS2 I 1500pF LOAD CURRENT (A) TH2 + SP 470µF 122k 15k 20k 2.5V ×2 3875 TA01b 0.1µF SP 3875 TA01a 3875fb For more information www.linear.com/LTC3875 1 Document Outline Features Applications Description Typical Application Absolute Maximum Ratings Pin Configuration Order Information Electrical Characteristics Typical Performance Characteristics Pin Functions Block Diagram Operation Applications Information Typical Applications Related Parts