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BQ24230: Charger LEDs do not come on, schematic review requested.

Jean Rintoul
Prodigy 60 points
Part Number: BQ24230

I've set up a BQ23240 the same way as the data sheet suggests but PGOOD and PCHG LEDs never come on. I can power via USB DC as well as via Battery however, it's just that the LED's do not come on. Attached is my schematic set up of the charger. Any ideas what I've done wrong in setting it up? 

  • 0
    TI__Guru* 75656 points
    The circuit looks correct.
    Have you verified that the battery is charging and in that condition the /CHG and /PG pin is low.
    Also test that grounding the /CHG and /PG pin will turn on the LED.
  • 0 in reply to Bill Johns
    Prodigy 60 points

    Although the battery can power the circuit when USB power is not plugged in, it appears not to be charging. I tested it over a few hours. The battery reads 3.79V, and has been the same for a few hours with the USB plugged in.  When I first plug in the USB power, the /CHG LED momentarily flashes then goes dead. 

    Both /CHG and /PG are low. 

    Grounding the CHG pin turns on the LED.

    Grounding PG does not turn on the LED. 

    Do you have any ideas what else I should check? 

    Thanks.

  • 0 in reply to Jean Rintoul
    TI__Guru* 75656 points
    Double check the CHG and PG pin grounding test, both should turn on. PG did not turn on, this would point to the voltage at OUT possibly low.
    Input current should be a max of 500mA --- check what input current is running.
    Current into the battery should be 200mA --- measure with a current meter or measure ISET---Current at ISET pin is mirror of battery current see section 8.4.1.1
    If the current at OUT is over 500mA no current is available for the battery to charge.
  • 0 in reply to Bill Johns
    Prodigy 60 points
    Due to how small the proto board is I have limited access to OUT pin at this time.

    I am using a USB3.0 port which can supply more than 500mA. Do you think this could be a problem? If so, is there another charger which is USB 2.0 and USB 3.0 compatible?
  • 0 in reply to Jean Rintoul
    TI__Guru* 75656 points
    Hello
    To trouble shoot the problem we need to determine how much current is going into the IN pin. A power supply could be used to power the device, it would be easier to measure current.
    Things we are looking for.
    1.) Battery should be charging at about 200mA, with no load input current would be 200mA.
    2.) The Max allowed input current is 500mA, if all of this is going to the load none is available to charge the battery . Load gets current first then battery. Also what is voltage at load, OUT.
    3.) The battery current can be measured at ISET pin, voltage will represent current to battery. ISET is a current source and voltage developed across R-ISET.
  • 0 in reply to Bill Johns
    Prodigy 60 points

    Thanks.

    I ordered another board assembled by a different manufacturer(same schematic/layout exactly) and this one works perfectly. LEDs come on when expected, and it charges as expected. I think there is an assembly/part sourcing issue as I cannot read anything on the 0402's which were sourced by the fabricator in China. 

    Thanks again for your efforts in trying to resolve this problem - much appreciated.