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BQ24192 stop charging at 4.0V

Andreas Riesner
Prodigy 180 points
Other Parts Discussed in Thread: BQ24192

Hello,

i use the BQ24192 as a standalone Battery Charger. It works fine, but the BQ stops charging at 4.02 - 4.03 Voltage.
Used Battery is a Samsung 1200mAh 3.7V Li-Ion Cell from a Smartphone.

Following my schematic:

As you can see i used it with a input current limit of 500mA and it should work with the parameters from Table 4 (SLUSAW5A) for the bq24192. I don't use a temperature Sensor and thought that could be the problem, but with ~2.4V at TS1/2 it is between VLTF and VTCO.

VCHG is at the moment a power supply with 5V and 500mA, while loading you can see the BQ consumed around 460mA and both LEDs are on. After it stops at 4V, STAT is off and it just forwards 120mA to the load circuit. +VBAT is the trace to the Battery.

Do you have any Ideas?

Best regards,

Andreas

Layout:

  • 0
    TI__Genius 13700 points
    Hello Andreas,

    Where are you measuring the battery voltage to get 4.02V?

    Also what is the content of REG04? This is where the charging voltage is set.

    Also is the thermal pad connected to GND? I do not see it in the layout. You might have a voltage offset due to a offset due to GND potentials.
  • 0 in reply to Ryan May
    Prodigy 180 points
    Hello Ryan,

    thank you for your answer. I measure the Voltage direct at the Battery after the LED on STAT (PIN4) goes off.

    Because I use the BQ as standalone Charger I have no access to the register settings. I hope the settings are the one from the "Table 4. Charging Parameter Default Setting". I have the same behavior at all the five pcb i tested. I also measure the same ~4.02V at the unconnected Battery.

    At the Shematic you can see the EXP (Exposed Pad) is connected to GND. I just hide the TOP GND plane so you get a better view of the BOTTOM Layout. The nine VIAs goes direct to the GND TOP plane.

    Regards,
    Andreas