LTC3731 - 3-Phase, 600kHz, Synchronous Buck Switching Regulator Controller

The LTC3731 is a PolyPhase synchronous step-down switching regulator controller that drives all N-channel external power MOSFET stages in a phase-lockable fixed frequency architecture. The 3-phase controller drives its output stages with 120° phase separation at frequencies of up to 600kHz per phase to minimize the RMS current losses in both the input and output filter capacitors. The 3-phase technique effectively triples the fundamental frequency, improving transient response while operating each controller at an optimal frequency for efficiency and ease of thermal design. Light load efficiency is optimized by using a choice of output Stage Shedding or Burst Mode operation.

A differential amplifier provides true remote sensing of both the high and low side of the output voltage at the point of load. The precision reference supports output voltages from 0.6V to 6V.

Soft-start and a defeatable, timed short-circuit shutdown protect the MOSFETs and the load. Current foldback provides protection for the external MOSFETs under short-circuit or overload conditions.

Features

3-Phase Current Mode Controller with Onboard MOSFET Drivers
±5% Output Current Matching Optimizes Thermal Performance and Size of Inductors and MOSFETs
Differential Amplifier Accurately Senses VOUT
±1% VREF Accuracy Over Temperature
VOUT Range: 0.6V to 5.5V without Diffamp
VOUT Range: 0.6V to (VCC – 1.2V) with Diffamp
250kHz to 600kHz Per Phase, PLL, Fixed Frequency
PWM, Stage Shedding™ or Burst Mode® Operation
OPTI-LOOP® Compensation Minimizes COUT
Adjustable Soft-Start Current Ramping
Short-Circuit Shutdown Timer with Defeat Option
Overvoltage Soft Latch
Adjustable Undervoltage Lockout Threshold
Selectable Phase Output for Up to 12-Phase Operation
Available in 5mm × 5mm QFN and 36-Pin Narrow (0.209") SSOP Packages

Typical Application

Applications

Desktop Computers and Servers
High Performance Notebook Computers
High Output Current DC/DC Power Supplies

Packaging

Order Information

Part Number	Package	Temp	Price(1-99)	Price (1k)*
LTC3731CG#PBF	SSOP-24	C	$6.16	$4.35
LTC3731CG#TRPBF	SSOP-24	C		$4.45
LTC3731CUH#PBF	5x5 QFN-32	C	$6.52	$4.55
LTC3731CUH#TRPBF	5x5 QFN-32	C		$4.65
LTC3731IG#PBF	SSOP-24	I	$6.88	$4.80
LTC3731IG#TRPBF	SSOP-24	I		$4.90
LTC3731IUH#PBF	5x5 QFN-32	I	$5.89	$4.95
LTC3731IUH#TRPBF	5x5 QFN-32	I		$5.05

Demo Boards

Part Number	Description	Price
DC438A	LTC3731CG \| 3-Phase, Vin = 9V to 14V, Vout = 2.5V/1.8V @ 60A	$150.00
DC558A	LTC3731CUH Demo Board \| 3-Phase, Vin = 5V to 14V, Vout = 1.5V/60A	Contact Factory
DC561A-A	LTC3731CUH (x4) \| 12-Phase, 10V - 14Vin, 1.5Vout @ 180A	$175.00
DC561A-B	LTC3731CUH (x2) \| 6-Phase, 10V - 14Vin, 1.5Vout @ 90A	Contact Factory
DC721A-A	LTC3738CUHF/LTC3731CUH Demo Board \| 6-Phase, 8V ≤ VIN ≤ 14V, Vout = VRM9.X / 10.X @ 120A	Contact Factory