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BQ24073: Fails to Reset Active PCM

Shahab Davoodabadi
Prodigy 10 points
Part Number: BQ24073

Tool/software:

Hi TI Team,

I am encountering an issue with the BQ24073 Li-ion battery management IC when trying to reset an active PCM (Protection Circuit Module) on a Li-ion battery. Here are the observations:

  1. Setup Details:

    • The PCM activates due to low battery voltage (below 3V) and disables the battery output (0V).
    • During power-up, I observe a transient voltage rise from 0V to 3.5V on the BAT and BAT1 pins for ~200ms.

  2. Current Measurement:

    • Using a 10Ω resistor in series with the battery, I measured:
      • 156mV drop (15.6mA) for 28ms.
      • 662mV drop (66.2mA) for 25ms.

  3. Additional Observation:

    • When I connect the battery directly to a bench power supply at 3V, the PCM wakes up, and the battery output is restored. This confirms that the battery and PCM are functioning correctly.

  4. Issue:

    • Despite the transient voltage rise from the BQ24073, the PCM remains in its locked state, and the battery output stays at 0V.
    • The BQ24073 seems unable to reliably trigger the PCM to reset and restore the battery's normal operation.

  5. Questions:

    • What are the best practices to configure the BQ24073 for triggering PCM reset, especially for transient scenarios?
    • Are there specific considerations for timing, voltage, or current to ensure the PCM is reset properly?
    • Could any additional circuitry (e.g., pre-charge or capacitor adjustments) help sustain the transient and meet the PCM's requirements?
    • Are there any known limitations of the BQ24073 in handling PCM reset functionality?

I have attached oscilloscope screenshots showing the voltage and current behaviour during the event.




Thank you in advance for your support!

  • 0
    TI__Mastermind 31930 points

    Hi Shahab, 

    Thank you for reaching out via E2E. 

    Can you please help to confirm what is the requirement to reset the PCM used in your system? You mention connection to a 3V supply worked, but what is the required time voltage must be applied? 

    Shahab Davoodabadi said:
    Are there any known limitations of the BQ24073 in handling PCM reset functionality?

    In general there is no known limitations of the BQ24073 releasing a battery protection circuit. It has been on the market for some time and functions with various battery protectors.  

    Best Regards,

    Garrett

  • 0 in reply to Garrett Kreger
    Prodigy 10 points

    Hi Garrett,

    Thanks for getting back to me!

    More Findings on PCM Wake-Up Behaviour:

    I've noticed that the PCM wake-up issue mostly happens when the battery is slowly discharged with a low current. In these cases:

    • After a slow discharge, the battery voltage stays low when the PCM kicks in, and the BQ24073’s transient pulse (53ms - 100ms) doesn’t seem long enough to bring it back to life.
    • If I apply 3.6V, some batteries take around 40 seconds to wake up—starting at 12mA before jumping to 60mA when fully active.
    • If I apply 4.3V, the wake-up time is much shorter (~5 seconds).
    • The HiMax(battery) datasheet doesn’t specify how long voltage needs to be applied, only that it must be above 3V.

      Also,
    • When the battery is discharged with a higher current, its voltage drops more significantly under load. But once the PCM activates, the battery cell voltage rebounds slightly (since there’s no longer a load).
    • In these cases, the BQ24073 wakes up the battery just fine, and everything works as expected.

      A Couple of Questions:
    1. Is there a way to extend the BQ24073’s power-up pulse to help the PCM reset more reliably after a slow discharge?
    2. Do you have any recommended approaches for making sure the PCM wakes up properly in these cases?

      HIMAX-SPE-LIPO503138-610-3.7V 1.pdf



    Looking forward to your thoughts!

    Best Regards,
    Shahab

    Garrett Kreger said:

    Hi Shahab, 

    Thank you for reaching out via E2E. 

    Can you please help to confirm what is the requirement to reset the PCM used in your system? You mention connection to a 3V supply worked, but what is the required time voltage must be applied? 

    Shahab Davoodabadi said:
    Are there any known limitations of the BQ24073 in handling PCM reset functionality?

    In general there is no known limitations of the BQ24073 releasing a battery protection circuit. It has been on the market for some time and functions with various battery protectors.

  • 0 in reply to Shahab Davoodabadi
    TI__Mastermind 31930 points

    Hi Shahab, 

    Thank you for your response. 

    In general 40sec seems quite a long time to exit the under voltage protection on your battery pack. I would expect trigger to close protector to be much shorter. Please check with the battery manufacturer.

    When BQ24073 initially measures 0V at bat pin it will perform battery detection procedure where is provides approx. 7.5mA current to BAT pin for 250ms. This is shown in waveform below as well as figure 10-3 in the datasheet. 

    One way to prevent this battery detection procedure from being performed is connecting TD pin to logic high. Can you please check if this works to close your protection circuit? Other than changing status of TD pin there is no way to extend the on time (approx. 250ms) for battery detection when BQ24073 IC initially measures 0V at BAT.

    Best Regards,

    Garrett