I built a small breakout board of for an ATmega328p microcontroller. It included an AMS1117 5 V regulator and a CP2102 USB-UART bridge for programming and serial communication. On the board I use a USB-B receptacle to provide power, and for communication purposes. Both the microcontroller and the bridge run on 5 V.

The simplified schematic without other peripherals looks like this.

I have learned that my AMS1117 5 V regulator is a bad idea, because the dropout voltage is around 1 V, leaving at best 4 V for my microcontroller and bridge.

What is the correct approach to use here? I need 5 V for the bridge and micro. Should I just feed the unregulated USB Vbus into both ICs? Should there be a mechanism to limit inrush current? I have heard about polyfuses / resettable fuses - are they useful here?

posted 9 months ago

CC BY-SA 4.0

9mo ago

Carl‭

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