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BQ24230: Charge Current Higher than expected

Luke Mills29
Prodigy 125 points
Part Number: BQ24230

Hi,

Im using a bq24230 in my design.

Riset = 2k94

Riterm = 2k94

Rilim = NC

EN1 and EN2 are set to USB500 mode

According to the datasheet my battery charging current should be limited to 296mA at nominal Kiset to a maximum of 330mA at the highest Kiset.

In CC mode I am charging at around a rate of 370mA and I haven't been able to explain why. the charger appears to be functioning properly.

Has anyone encountered a similar issue to this?

Thanks,

Luke

  • 0
    TI__Mastermind 21590 points
    Hello Luke,
    Can you measure the resistance value of RISET on the board. Also what voltage do you measure on the ISET pin during charging?
  • 0 in reply to Raheem
    Expert 1230 points
    Hello Raheem,

    I am working in the project Luke is and I checked what you asked:

    RIset (measured) = 2941 ohm
    VIset = 2.04 V (DC RMS)
    I at time of measurement = 322 mA

    Thanks for your help!
  • 0 in reply to leinho
    TI__Guru* 75656 points
    Hi Leinho and Luke

    I am assisting Raheem with this question.

    When the BQ24230 is in CC mode, battery less than 4.2V the current control loop will regulate ISET pin to 2.25V.
    Also ratio of ISET current mirror to battery current is 1 to 380.

    With VISET = 2.04V the unit is not in current regulation, voltage needs to be higher.
    Battery current is measured at 322mA, with 1 to 380 ratio and 2941 R-ISET the voltage should be about 2.5V --- (322mA/380)*2941 ohms = 2.49V. Something is not right in the circuit.

    How many units show this problem?

    Do you have a schematic you can send?
    Layout will help also?
    We can set up a private conversion on the forum PM feature if you do not want to share in a public forum.
  • 0 in reply to Bill Johns
    Expert 1230 points
    Thanks for your help Bill. This is happening in at least 4 units. Due to high resistance between the battery and the BQ24230's VBat Pin, when the battery voltage is 3898 mV, the charger ic measures 4121mV and provides 357 mA. It should be in CC... The charger terminates correctly (as set).
    How does the forum PM feature would work?
  • 0 in reply to leinho
    TI__Guru* 75656 points

    Hi

    I will try to send something tonight to set up conversation.

  • 0 in reply to Bill Johns
    TI__Guru* 75656 points
    Hi
    We worked off line on this problem.
    If you have any more question contact me using conversation please.