Update: I resoldered a new IC and everything works.

I have designed a charging circuit for a device that I am building. The circuit uses a MCP73831-2ACI/MC (datasheet). These are the schematics:

enter image description here

The problem I am having is that the battery is not being charged. Very little current (0.5mA) is being drawn from the USB (VIN). When the USB is connected, the RLED will turn on, but very dim. However, the LED will stay turned on even if the battery is disconnected or connected. To me, this looks like the charger IC is not detecting the battery and therefore entering shutdown mode. This circuit is essentially a replica of what the manufacture provided in the datasheet.

There is a common ground plane on the board, however, VBAT and VIN are routed directly to their respective pins.

Why will the battery not charge? Does this have something to do with the rest of the device drawing current while charging?? Any help is much appreciated (and sorry if I missed any important info).

I have measured the following things on my circuit: VIN = 5.18v VBAT = 3.887v VIN current = 0.5 mA

  • \$\begingroup\$ You show Vbat on 3+2. Should be 3+4. May just be a typo or MAY reflect your actual cct. \$\endgroup\$
    – Russell McMahon
    Apr 17, 2021 at 12:43
  • \$\begingroup\$ Are you sure all pins (pads) in the ic are soldered? \$\endgroup\$
    – Kartman
    Apr 17, 2021 at 13:53
  • \$\begingroup\$ Sorry I think that is just a typo... I am somewhat confident all pins are soldered. I have been probing around with a multimeter and confirmed continuity from the pins to the PCB. Although, I might try resolder as the ic is a DFN package so hard to test. Thanks for the input. \$\endgroup\$ Apr 17, 2021 at 20:39

1 Answer 1


Well, I resoldered a new ic and everything works.

  • \$\begingroup\$ Jayden Clark - Hi, Thanks for coming back with the answer to your question. To mark the topic as solved, please "accept" an answer (click the "tick mark" next to an answer, to turn it green) - which could be your answer, if a better one isn't provided. Then it is shown as having an accepted answer in various lists, and we don't get nagged for it having an unaccepted answer. Note that you must wait 48 hours after you asked the question before you can accept your own answer. So please come back in a couple of days to accept it. Thanks! \$\endgroup\$
    – SamGibson
    Apr 18, 2021 at 1:40

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