My goal is to power a Raspberry Pi Zero W using an IP5306 charging IC which would receive its power input from a 3.7v 18650. The Raspberry Pi Zero requires 5V and can draw as much as 120mA without HDMI running.

The IP5306 should be able to power the raspberry pi from its battery source in theory. The issue I am running into is the following scenario...

The Raspberry Pi Zero W is currently on and is being powered by the IP5306 Charging IC. The 18650 is running out of juice so it is now time to charge the battery using an external 5V power supply. As soon as the external 5V is applied to the IP5306 to charge the 18650, there is a VERY brief interrupt in the voltage output of the IP5306. This interrupt is brief enough where you wouldn't even see an LED flicker but it is long enough to cause a Raspberry Pi and even an MCU to reboot.

This brief voltage output interrupt is a trait of the IP5306 itself.

I would like to know what I can do to prevent the Raspberry Pi Zero W from losing power when the external 5V is applied to the IP5306. Would I need to add a shottkey diode with some ceramic capacitors in parallel between the IP5306 and the Pi? If so, how many capacitors and what would their values have to be.

I don't know the exact duration of the output interrupt in ms.

  • \$\begingroup\$ The question has been answered here electronics.stackexchange.com/a/171531/260528 \$\endgroup\$ Oct 2 '20 at 13:47
  • \$\begingroup\$ See answer mentioned by George, but: C ~= time_off x current / Voltage-droop. || So for eg 100 mS, 125 mA and 1V acceptable drop : C = 0.1s x 0.125A / 1v = 0.0125 F = 12,500 uF. \$\endgroup\$
    – Russell McMahon
    Oct 3 '20 at 10:10

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