Microchip | MIC4043YM4-TR

The MIC4043 is a shunt regulator optimized for secondary-side regulation in low-voltage power supplies. Featuring a output stage guaranteed to swing within 400 mV of ground, the MIC4043 can be used in power supplies operating down to 1.5 V, even with optoisolators requiring greater than 1.2 V of headroom.

The MIC4043 normally drives the LED of an optically isolated feedback circuit. The MIC4043 monitors a resistively-divided output voltage and sinks error current through the optoisolator’s LED (secondary side); the optoisolator’s transistor (primary side) provides this signal to the controller’s feedback input. The MIC4043 is also practical for other voltage-monitoring applications requiring an open-collector output.

The MIC4043 replaces conventional ’431-type shunt regulators to allow low-voltage applications where there is inadequate headroom for a 2.5 V regulator in series with an optoisolator. Replacing ’431-type devices requires only a minor change to the way that the resistive-divider values are calculated.

Features:

• Ideal for 1.8 V switching converters
• Low-voltage operation
• 400 mV maximum saturation over operating temperature range
• Easy to use
• voltage in, current out
• 2% voltage tolerance over operating temperature range

Applications:

• Optically isolated low-volage power supplies
• Low-voltage discrete regulator control