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BQ24210: the IC behaves as if the security timer had not been disabled using the LPCM feature

FranMartin
Intellectual 600 points
Part Number: BQ24210

Hello and thanks in advance.

I have a prototype where I use the bq24210 IC to charge a battery that will always be connected to the system. A solar panel is used to charge the battery. Next I expose the basic characteristics of the solar panel, battery and the average system consumption.

SOLAR PANEL

  • Voc = 5,8 V
  • Vmp = 4,35 V (Voc -25% approx.)
  • Isc = 170 mA

BATTERY

  • Type Li-Po 1 cell
  • Nominal Voltage 3.7 V
  • Nominal Capacity 2350 mAh
  • Standard Charge Current 450 mA
  • Max Charge Current 4750 mA
  • Charge cut-off Voltage 4.20+/-0.05 V
  • Discharge cut-off Voltage 2.75 V


LOAD CONSUMPTION

  • average current consumption < 22 mA

As the battery will always be connected to the system, it is necessary to deactivate the security timer, for this I use the LPCM feature and also, when using a solar panel I use the battery tracking mode.

In addition, I attach part of the schematic. As you can see, there are certain jumpers and additional elements but they are there to be able to use different modes of operation of the bq24210 (as if it were a custom EVM).

Based on the schematic, the J1, J3 and J4 jumpers are on. J2 is off.
J3 and J4 are jumpers to activate the lighting of LEDs to display the 'POWER_GOOD' indication (D5) and 'CHARGING' status (D6).
J2 is off for battery tracking mode
J1 is on to use the LPCM feature and therefore disable the safety timer.

Now, the problem is that after a time between 20-30 h (I could not limit the time interval anymore) the IC bq2410 stops charging while the battery is always below 3.8 V, so with that voltage shouldn't stop charging. In addition, it is a sunny day and the POWER_GOOD LED indicates the sufficient voltage level to continue charging the battery.
To start charging again I have to disconnect the battery for a time (usually less than a minute). Why does this happen?
However, I have done a test using this same configuration but instead of a solar panel, a power supply. In this case, it is observed that the safety timer remains inactive. I've had it for a week and the battery charges it up to 4.2 and then when the battery voltage drops to 3.95 a new charge starts and so indefinitely.

Best regards, 

Fran Martin

  • 0
    TI__Mastermind 19195 points

    Hi Fran,

    The test you performed makes me think this is related to the Vin DPM, can you determine what the voltage of the solar panel is when the charge is stopping?

    D/s states "When the regular timers are disabled there still is a 2 hour timer if the part is stuck in DPM above 4.1 V but outside of termination conditions at which point charging will terminate and re-start if the voltage falls below 4.1V." 

    From electrical specs table, tmaxterm: "Limited power charge mode, terminate charge when VIN DPM active, normal termination conditions met and this timer expires."

    I am going to try to replicate your issue, it seems like the d/s may need to be revised slightly if the VIN DPM timer can terminate charge when battery under 4.1V. Your schematic looks correct.

    Best,

  • 0 in reply to Nick Brylski
    Intellectual 600 points

    Hi Nick Brylski,

    thanks for your answer.

    Right now I can't give you the exact value of the solar panel voltage. I'm going to try to reproduce the problem and measure that value to give it to you exactly.
    What I can tell you is that one of the times I detected this problem, that is, the IC stopped charging, I proceeded to measure the voltage of the solar panel (connected to the PCB) and it was below the battery voltage , despite having a lot of solar intensity. So I disconnected a wire from the solar panel and measured that voltage and it was back to its typical open-circuit voltage. So I think the solar panel was working correctly.

    I also wanted to tell you that I have several prototype PCBs mounted and the problem is reproduced in all of them.
    I just purchased a difference solar panel and am going to test it to see if the problem reproduces on one of the prototype PCBs.

    I hope you can give me some ideas to try to solve the problem. Thanks for your time.

    Best regards,
    Fran Martin

  • 0 in reply to FranMartin
    TI__Mastermind 19195 points

    Hi Fran,

    For now you can try adding a 0.1 uF cap from TS pin to ground. This may help. 

    Best,

  • 0 in reply to Nick Brylski
    Intellectual 600 points

    Hello Nick and thanks.

    I've already soldered a capacitor of that value on a couple of PCBs. Looking in your support forum I read that it could help but it did not work in my design.
    I attached a picture. The 0.1 uF capacitor is soldered (on the bottom layer) between GND and the jumper J1 that is has its two pins also soldered, that is, it is set to ON.

    Thank you.

    Best regards,
    Fran Martín.

  • 0 in reply to FranMartin
    TI__Mastermind 19195 points

    Hi Fran,

    I thought this might be an issue with VIN DPM loop but test I ran didn't have any issues with charge terminating. I set VBat = 3.8V and lowered VIN until current started to be reduced (around 3.9V). Test ran for 30 hours.

    "What I can tell you is that one of the times I detected this problem, that is, the IC stopped charging, I proceeded to measure the voltage of the solar panel (connected to the PCB) and it was below the battery voltage " When VIN gets close to Vbat, VIN DPM will kick in and reduce current, if VIN continues to fall below 100mV charging will stop. When VIN goes up charging will start again, should not have to unplug/plug battery.

    Best,

  • 0 in reply to Nick Brylski
    TI__Mastermind 19195 points

    Hi Fran,

    Any updates on this?

    Best,

  • 0 in reply to Nick Brylski
    Intellectual 600 points

    Hello Nick ,

    the problem is still present. I have conducted tests with different types of solar panel and batteries combining them with each other. The power goog led and the charge led turn off after 20-30 hours and the system stops charging. Then, after days in full sun, the IC does not recharge despite almost completely discharging the battery. The only way is to disconnect the battery and wait a few seconds (less than a minute) and reconnect the battery.

    Also, as I think I told you, when this problem happens, the voltage of the solar panel is below the voltage of the battery (then it would be logical that both leds were off and the IC stopped charging), but then, I disconnect the positive panel cable sonar and its voltage rises to 5.5V (or more). The fact is as if the BQ24210 is driving the solar panel to a voltage below the battery voltage. I don't know if this fact can help you diagnose the problem.

    Thank you very much again Nick

    Best regards,
    Fran Martin.