UC3907 CONTROLLER IC Chip

UC3907(LOAD SHARE CONTROLLER)

Introduction

The UCx907 family – UC1907/UC2907/UC3907 of load share controller ICs offers all the necessary features to enable the paralleling of multiple independent power modules. This configuration ensures that each module supplies only its proportionate share of the total load current.

Controlling the power stage of each module is achieved by using a command from a voltage-feedback amplifier. The reference of this amplifier can be adjusted independently in response to a common-share-bus voltage. By monitoring the current from each module, the current share bus circuitry identifies the module with the highest output current as the master. It then adjusts all other modules to increase their output current to within 25% of the master’s output.

The current share bus signal, connecting all paralleled modules, is a low-impedance, noise-insensitive line. This ensures that each module can operate independently if the bus becomes open or shorted to ground. The UC3907 controller, located on the output side of each power module, functions to provide a voltage feedback loop. The specific architecture of the power stage is not crucial; however, both switching and linear designs are applicable. Furthermore, methods such as an optocoupler or other isolated medium can be utilized to directly couple or isolate the control signal.

Other features of the UC3907 include 1.25% accurate reference: a low-loss, fixed-gain current- sense amplifier, a fully differential, high-impedance voltage sensing capability, and a status indicator to designate which module is performing as master.

Feature

• Fully Differential High Impedance Voltag Sensing
• Accurate Current Amplifier for Precise Current Sharing
• Opto Coupler Driving Capability
• 1.25% Trimmed Reference
• Master Status Indication
• 4.5V to 35V Operation

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