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BQ24210: VBat 0V even with 5V input and ~EN tied to ~PG.

Sander Baten NL
Prodigy 50 points
Part Number: BQ24210
Other Parts Discussed in Thread: BQ24040

Hello,

We have a problem with the BQ24210. We use the following schematic:

Whenever we connect a USB wall charger we measure Vbus = 5V, ~EN = ~PG = 0V (J8 is mounted) but the battery(1S2P or 1S3P), connected to K6, is not being charged.
Vbat = 0V, due to the battery being in protection mode. Protection mode will release when a charger is connected. This is tested; applying a positive voltage to the battery + terminal releases the protection.

VDPM, ~PG(and so ~EN_CHR) and ~CHG are connected to high impedance uC inputs.

Can someone please advise on this?

If needed, I can provide additional measurement data, please let me know.

Thanks in advance,

Sander Baten
Embedded System Engineer

  • 0
    TI__Guru 65716 points

    Hello Sander

    When you apply USB power (+5V) do you see any voltage out? If viewed with a scope do you seen voltage increase at all?

    Unit should enter battery detect mode and try to apply power.

    The device has a battery short protection feature, if the battery voltage is below 0.8V output current is limited to 17mA.  If OUT / Battery has a load on it during start up that draws more than 17mA voltage will not increase and output will remain at 0V.

  • 0 in reply to Bill Johns
    Prodigy 50 points

    Hello Bill,

    Thanks for your answers.
    I measured at the Vbat, and there was no rise in voltage.

    However, we found out that there is a voltage present in both of the following situations:

    - Attaching USB Power
    - OR Connect VDPM to VSS for short time
    - OR Connect Vbus to Vbat for a short time

    As long as we don't disconnect the VBus, the systems keeps delivering power, even without battery.

    Can you explain this?

    Triggering VDPM every time a battery is 0V could be an option for the on-board controller, but we would like to know what is going on to make sure we do the right thing.

    Sander

  • 0 in reply to Sander Baten NL
    Prodigy 50 points

    Hi Bill,

    We have changed our PCB layout to support the VDPM tying to VSS with the microcontroller to start the system when this situation occurs.
    We can program this, but we want to make sure that this is not causing any other problems or that the problem is caused by something else.

    Hoping to hear from you soon,

    Sander Baten

  • 0 in reply to Sander Baten NL
    TI__Guru 65716 points

    Hello Sander

    "As long as we don't disconnect the VBus, the systems keeps delivering power, even without battery. Can you explain this?"  -- This could be BATTERY DETECTON see Figure 9 of data sheet.  The same circuit is used on BQ24040 and data sheet has better scope capture see figure 23.

    VDPM

    "Triggering VDPM every time a battery is 0V could be an option for the on-board controller, but we would like to know what is going on to make sure we do the right thing."  --- The VDPM resistor is 7.35k for 4.6V, if "VDPM" signal is grounded.  If "VDPM" is floating the then DPM is in battery track  3.6V or VBAT + 100mV.  Both would work and should not cause problems.