Synchronous buck converter with output current sensing

摘要

A synchronous buck converter manufacturable as an MCM having an output current sensing circuit. The device employs MOSFETS as the switching transistors, and a sensing circuit including a sampling switch operated synchronously on and off with the shunt MOSFET, a variable gain amplifier, the sampling switch being coupled to provide a signal to the variable gain amplifier representing the voltage across the R_DS-ON of the shunt MOSFET, and a circuit, e.g., an RC circuit, associated with the variable gain amplifier implementing 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 gain can be trimmed based on the R_DS-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 R_DS-ON temperature variation, and according to the gate voltage to eliminate the R_DS-ON variation due to gate voltage changes.