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I'm currently using a MCP73871 (datasheet) to charge a LiPo battery and power my core circuit. However, I'm noticing parasitic power on my VIN pin even when no input is connected. This is affecting the circuitry before the battery charger.

I'm looking at ways to resolve this. One idea is putting a diode before the VIN pin on the MCP73871. My concern is that according to the datasheet, they recommend a value of Vreg + 0.3 for VIN. I'm not exactly sure what Vreg is - I'm assuming that is the regulated voltage my battery is being charged at. If so, knowing that I need to charge my battery at 4.2V, that would mean I require a minimum VIN of 4.5V. If I put a diode before VIN, the forward voltage drop means the voltage at VIN when connected would be 4.3V (which is less than 4.5).

Does anybody know if this is a legitimate concern / issue, or would the MCP73871 work properly? Am I reading this datasheet wrong?

Also - if anybody has any alternative suggestions to combating the parasitic power at the VIN, I'm all ears

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    \$\begingroup\$ Is this more than the specified 350 uA maximum quiescence current during "Charging Complete" operation? Are you seeing the current due to status LEDs being turned on? What is your quiescent current? \$\endgroup\$ – user2943160 Jun 9 '16 at 0:33
  • \$\begingroup\$ What circuitry do you have before the charger, and how is the 'parasitic power' affecting it? \$\endgroup\$ – Bruce Abbott Jun 9 '16 at 2:06

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