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BQ76952: BQ going from rest to sleep，BQ was reset.

Che Liu
Prodigy 100 points
Part Number: BQ76952

Dear:

         During the process of BQ going from rest to sleep, we suddenly pulled up RST to wake up BQ (60ms), but occasionally found that BQ was reset directly (the SETTING register data entered in CONFIG_UPDATE was lost) (small probability), what might be the reason for this? 

        Looking forward to your reply.

  • 0
    TI__Expert 8451 points

    Hi Che,

    The RST_SHUT pin also serves as a reset pin for the device.  If a high signal is sent to the RST_SHUT pin for < 1 sec, a partial reset of the device will occur.  Applying a high signal at RST_SHUT for > 1 sec will send a SHUTDOWN signal to the device.  I will attach a link to the datasheet here: BQ76952 3-Series to 16-Series High Accuracy Battery Monitor and Protector for Li-Ion, Li-Polymer, and LiFePO4 Battery Packs datasheet (Rev. B) (ti.com).  Section 12.6 RST_SHUT Pin Operation should have some useful information.  I will also attach an image from the datasheet that shows how to transition between states.  I hope this helps!

    Best,

    Andria

  • 0 in reply to Andria McIntyre
    Prodigy 100 points

            I have confirmed these, and the confirmation result is: if I am in the configupdate mode, the RAM setting content will be lost, but if I have exited this mode, the 100ms short-time RST pulling action will not be cleared. At the same time, I can more accurately test the abnormal point.   

           If I use the 100ms PWM to flip the control, it will not clear the RAM, but if I use the contact plug and pull a 3.3V signal, If the pulse waveform of about 100ms is produced, it is easy to lose RAM. 

           Does ESD affect its logic?

  • 0 in reply to Andria McIntyre
    Prodigy 100 points

            I have confirmed these, and the confirmation result is: if I am in the configupdate mode, the RAM setting content will be lost, but if I have exited this mode, the 100ms short-time RST pulling action will not be cleared. At the same time, I can more accurately test the abnormal point.   

           If I use the 100ms PWM to flip the control, it will not clear the RAM, but if I use the contact plug and pull a 3.3V signal, If the pulse waveform of about 100ms is produced, it is easy to lose RAM. 

           Does ESD affect its logic?

  • 0 in reply to Che Liu
    TI__Expert 8451 points

    Hi Che,

    I am not sure I understand some points in your statement, but ESD should not affect the device's logic. 

    I would recommend not using the RST_SHUT pin for waking up from sleep mode.  If the device was in the midst of updating something in RAM when the RST_SHUT is asserted, it might cause the RAM to fail its integrity check and do a full reset.  This could be why you are seeing full RAM resets seemingly randomly.

    It would be better to use SLEEP_DISABLE to wake from SLEEP, or the wake current detection.  If you are waking from SLEEP because you want to get data, and you are communicating with the device.  You can simply send the SLEEP_DISABLE command to wake the BQ76952.

    Best,

    Andria

  • 0 in reply to Andria McIntyre
    Prodigy 100 points

    Hi,

          Sleep_disable causes the sleep function to shut down, which directly leads to the failure of the BQ itself autosleep. The logic of timing sleep is broken, and you need to find a node to sleep_enable. Is there any other way to quit sleep instead of turning off the sleep module?

         The accompanying drawings are state switching diagrams, which describe that RST feet can be used for this function, and after the method is disabled, it seems that there is no other method from the description.

            

  • 0 in reply to Che Liu
    TI__Expert 8451 points

    Hi Che,

    Sending a HIGH signal to the RST_SHUT pin for < 1 sec will wake the pin, but it does cause a partial reset of the device.  It is recommended by the data sheet because some users do not care about the partial reset functionality of this pin. 

    Since you are concerned about device reset, sending a sleep_disable command, then sending a sleep_enable command is probably your best option. I think your device should stay awake for the sleep hysteresis time after sending the sleep disabled followed by enable.

    Best,

    Andria