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BQ25620: Thermal regulation question

Roy Chou1
Genius 16055 points
Part Number: BQ25620

Tool/software:

Hi Team,

Our condition is VBUS = 5.16V, VBAT = 3.4V and VSYS is 3.76V.

Currently, we are doing the high temperature test. but meet the issue and the BQ25620 reported the thermal regulation status, but not reported the thermal shutdown.

The behavior we observed was VSYS = VBAT and 0x2A(IBAT) = 0mA, but the VBAT is quickly lower down.

The behavior is different from the datasheet showing.

Do you have any comment for the observation? Can we disable the Thermal regulation?

Regards,

Roy

  • 0
    TI__Mastermind 31120 points

    Hi Roy,

    Please see my comments below. 

    Roy Chou1 said:
    Can we disable the Thermal regulation?

    Thermal regulation & thermal shutdown protections cannot be disabled on the BQ25620 battery charger IC. 

    Roy Chou1 said:

    The behavior we observed was VSYS = VBAT and 0x2A(IBAT) = 0mA, but the VBAT is quickly lower down.

    The behavior is different from the datasheet showing.

    The reported behavior indicates the device is entering supplement mode where battery discharges to power SYS. When in supplement mode VSYS = VBAT and IBAT_ADC measurement will output 0A.

    This can happen when in thermal regulation status because depending on temperature charge current can be reduced all the way to 0A and if IC is still too hot converter duty cycle can reduce even further such that input can no longer support SYS load on its own. 

    What was SYS load during the test? Also I am not sure what you mean by "the VBAT is quickly lower down". 

    Best Regards,

    Garrett

  • 0 in reply to Garrett Kreger
    TI__Genius 16055 points

    Hi Garrett,

    1. VSYS is around 850mA

    2. The meaning of "VBAT is quickly lower down" is that we think battery voltage is discharged. Like you said, it should provide the power to Vsys entering supplement mode.

    Regards,

    Roy

  • 0 in reply to Roy Chou1
    TI__Mastermind 31120 points

    Hi Roy, 

    Thank you for your response. Based on this info I have confidence the device is entering supplement mode where battery discharges to support SYS load due to thermal regulation reducing duty cycle of the converter such that input supply can no longer support the 850mA SYS load. 

    If your customer is able to more closely control the temperature environment or remove the SYS load they should be able to observe charge current reduction when BQ25620 first reaches thermal regulation threshold. 

    Please let me know if they have any further questions. 

    Best Regards,

    Garrett