0 Replies Latest reply on Jun 9, 2016 8:09 AM by Bansal

    Circuit to turn-on Edison from battery when USB power removed

    Bansal

      Hello all,

       

      For one of my projects I needed a circuit to turn on the Edison module from battery when 5V USB power is removed. Something like when Edison based device is unplugged from USB charger. I built and tested my circuit on a custom PCB which I am posting here.

      1. If Edison is OFF and +5V USB is plugged in. That will turn ON Q1.1 and turn OFF Q2.1 resulting in logic high for PWRBTN# on Edison. Basically that will do nothing for Edison and it will stay OFF.

      2. Note that since the Edison module is OFF, the gate of p-channel FET Q1.2 is 0 volts and the pin 2 of R4 is at VBAT while pin 1 of R4 is ground because Q1.1 is ON.

      3. Now removing the +5V USB will make the gate of Q2.1 to VBAT thereby turning it ON. This will pull down PWRBTN# pin on Edison module.

      4. Once Edison is turned on, net V3P3_Edison will become 3.3V turning OFF p-channel FET Q1.2. This will lead to the gate of Q2.1 pull down to GND by R5. This will bring back the PWRBTN# of Edison high.

      5. Note that once Edison is turned on, if you insert +5V USB, nothing will happen.

       

      I hope it helps someone.

       

      Best,

      - Aditya