Small Schematic Review - MCP73831

Discussion in 'The Projects Forum' started by Robert Seal, Jan 27, 2016.

  1. Robert Seal

    Thread Starter New Member

    Jan 22, 2015
    11
    0
    Greetings,

    I am unfortunately at a very novice level in my electronics hobbyist skill-set but trying diligently to make forward progress. I am currently working on a small part of a much larger project, but am looking for some level of comfort with what I've done thus far before moving on. Enclosed is a small schematic that includes all necessary wiring for an MCP73831 LiPo charging circuit. I feel like I've met the requirements of the datasheet for a 500mA charging circuit (my single cell battery is a 18650 - 3.7v - 2.6Ah) but honestly datasheets are still written in a language that feel I only pretend to understand.

    Anyway, if someone with more experience wouldn't mind just peeking and making sure things look right, I would really appreciate it. VBATT will go to the battery + and the battery - will connect to the common ground.

    The only thing I'm not really understanding about what I've done in this circuit is the STAT to two LED wiring. Page 15 of (http://ww1.microchip.com/downloads/en/DeviceDoc/20001984g.pdf) says STAT is a tri-state (High, Low, and High Impedance) but I still do not see how the red (D1) LED doesn't come on in both situations.

    Thank you in advance!

    View attachment MCP73831_1.pdf
     
  2. wayneh

    Expert

    Sep 9, 2010
    12,119
    3,043
    Check your connection to Vbatt. The cap needs to be parallel, not series as drawn.

    I don't understand you question about the state indicator. Why would the LED light when there is no voltage across it?
     
    Last edited: Jan 27, 2016
  3. Robert Seal

    Thread Starter New Member

    Jan 22, 2015
    11
    0
    Wayneh,

    Not sure how something that simple slipped by the radar. I've updated the schematic and included it below. Thank you very much for taking the time to look at it and provide feedback!
     
  4. Robert Seal

    Thread Starter New Member

    Jan 22, 2015
    11
    0
    Sorry, I missed the second part of your message. The circuit is designed to operate as a LiPo battery charger using a USB as the source. So when the USB (micro in this case if it makes a difference) is plugged in and supplies +5V to the VDD, the LED's would have voltage across them.

    What I do not understand however is why both of them wouldn't illuminate? The only thing I could imagine is the +5V from the USB wouldn't have the power necessary to illuminate the second LED, but the STAT pin would on HIGH assuming it too would be putting out +5V.
     
  5. wayneh

    Expert

    Sep 9, 2010
    12,119
    3,043
    Yes, I assumed that the LEDs would not light at all with 5V applied to two in series. This puts complete control at the STAT pin. You can certainly test this easily enough.
     
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