Datasheet LTC3856 (Analog Devices)

LTC3856 2-Phase Synchronous Step-Down DC/DC Controller with Diffamp
FeaTures DescripTion
n
PolyPhase® Controller Reduces Input and Output
The LTC®3856 is a single output, dual channel PolyPhase
Capacitance and Power Supply Induced Noise
synchronous step-down DC/DC controller that drives all n
Wide VIN Range: 4.5V to 38V Operation
N-channel power MOSFET stages. This device includes a n
±0.75%, 0.6V Reference Voltage Accuracy
high speed differential amplifier for remote output volt- n
High Efficiency: Up to 95%
age sense. Power loss and supply noise are minimized by n
Programmable Burst Mode® Operation or
operating the two controller output stages out-of-phase
Stage Shedding
™
for Highest Light Load Efficiency
and up to 12-phase operation can be achieved. n
Active Voltage Positioning (AVP)
The LTC3856 monitors the output current by sensing n
RSENSE or DCR Current Sensing
the voltage drop across the output inductor (DCR) or by n
Programmable DCR Temperature Compensation
using a sense resistor. DCR temperature compensation n
Phase-Lockable Fixed Frequency: 250kHz to 770kHz
maintains an accurate current sense threshold over a n
True Remote Sense Differential Amplifier
broad temperature range. A constant-frequency, current n
Dual N-Channel MOSFET Synchronous Drive
mode architecture allows a phase-lockable frequency of n VOUT Range: 0.6V to 5V without Differential Amplifier up to 770kHz. n VOUT Range: 0.6V to 3.3V with Differential Amplifier n Adjustable Soft-Start or V A wide 4.5V to 38V input supply range encompasses OUT Tracking n Stackable for Up to 12-Phase Operation most intermediate bus voltages and battery chemistries. n 32-Pin (5mm × 5mm) QFN and 38-Pin TSSOP Packages Burst Mode operation, continuous or Stage Shedding modes are supported. A TK/SS pin shared by both chan-
applicaTions
nels ramps the output voltage during start-up. n Telecom and Datacom Systems L, LT, LTC, LTM, Linear Technology, the Linear logo, PolyPhase, Burst Mode and OPTI-LOOP n Industrial and Medical Instruments are registered trademarks and Stage Shedding 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, 6498466, 6580258, 6611131, 6674274. n Computer Systems
Typical applicaTion Efficiency and Power Loss High Efficiency 1.5V/50A Step-Down Converter vs Output Current
VIN 100 100 4.5V TO V 30.1k 10µF IN = 12V × 4 20V 90 DIFFOUT V TG1 V IN OUT = 1.5V S 0.33µH S VFB BOOST1 0.1µF 80 Burst Mode 20k ILIM SW1 OPERATION 10 LTC3856 S POWER LOSS (W) 70 RUN BG1 PGOOD PLLIN S S 60 CLKOUT SENSE1+ 50 1 PHASMD SENSE1– MODE TG2 S 40 ITEMP BOOST2 0.33µH VOUT EFFICIENCY (%) 0.1µF 1.5V 30 FREQ SW2 S 50A S 0 BG2 20 122k EXTVCC INTVCC S S S 100µF 10 DIFFN SENSE2+ 4.7µF × 8 DIFFP SENSE2– 0 –1 ITH TK/SS GND AVP ISET 0.1 1 10 100 2200pF LOAD CURRENT (A) 1.5k 0.1µF 3856 TA01b S 3856 TA01a 3856fa For more information www.linear.com/LTC3856 1 Document Outline Features Applications Description Typical Application Absolute Maximum Ratings Pin Configuration Order Information Electrical Characteristics Typical Performance Characteristics Pin Functions FUNCTIONAL Diagram Operation Applications Information Typical Application Typical Application Related Parts