Synchronous buck converter improvements

Abstract

A synchronous buck converter which provides an improved output current sensing circuit (608) and improved transient behavior during output current stepdown. Also disclosed is a multi-phase synchronous buck converter having improved output current sharing capability, and a multi-phase synchronous buck converter having improved load balancing capability. For improved output current sensing (608), a sensing circuit includes a sampling switch which operates synchronously on and off with the shunt MOSFET to sample the voltage across the RDS-ON of the shunt MOSFET, and to provide the sampled voltage to a variable gain amplifier. The sensing circuit also includes n RC circuit which implements a low pass filter whereby the output of the variable gain amplifier is substantially independent of the value of the inductor and the magnitude of any time varying component of the signal input to the sampling switch. When the device is packaged an MCM, the current sense circuit (608) gain can be trimmed based on the RDS-ON value. The current sense gain can also be adjusted according to the module temperature by using temperature sensitive devices inside the IC to eliminate the RDS-ON temperature variation, and according to the gate voltage to eliminate the RDS-ON variation due to gate voltage changes. For improved output current sharing (608), a sensing circuit for each converter stage generates an output signal representative of the output current provided by that converter stage. A master controller provides duty cycle control signals in a predetermined phase relationship for the switching transistors of the individual converter stages according to the difference between the output voltage from the multi-phase converter and a reference signal representing a desired voltage at the output node. A duty cycle trimming for each converter stage modifies the duty cycle control signals from the master controller to equalize as nearly as possible the currents provided by each stage.

Description

[0001] related application

[0002] This application is based on and claims priority to U.S. Provisional Application No. 30 / 370,007, filed April 3, 2002, entitled MULTI-CHIPMODULE CIRCUIT IMPROVEMENTS, the contents of which are incorporated herein by reference. technical field

[0003] The present invention relates to improvements in multi-phase synchronous buck converters, and in particular, to having improved transient performance for output current sensing, for current sharing between components, and during fast load changes. improved technology. The invention is described and illustrated in the context of a multi-chip module (MCM) implementation, but the disclosed improvements can also be applied to different component implementations. Background technique

[0004] An MCM is an electronic package that includes multiple integrated circuits (ICs) formed on a common substrate with multiple interconnect layers separated by insulating material. Package entire assemblies, no...

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