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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...
#4: Post edited
by
Carl
·
2025-12-22T11:23:26Z (9 months ago)
- 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 - are they useful here?
- 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?
#3: Post edited
by
Carl
·
2025-12-22T11:20:27Z (9 months ago)
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 from my PC and to provide communication. 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 - are they useful here?
- 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 - are they useful here?
#2: Post edited
by
Carl
·
2025-12-22T11:19:10Z (9 months ago)
Using USB-B to power 5 V microcontroller and peripherals
- How to use USB-B to power 5 V microcontroller and peripherals
#1: Initial revision
by
Carl
·
2025-12-22T11:18:22Z (9 months ago)
Using USB-B to power 5 V microcontroller and peripherals
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 from my PC and to provide communication. 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 - are they useful here?