BQ76952: Device not entering Shutdown mode when RST_SHUT is pulled high

Hello Vic,

What is the voltage measured at your REG18 pin? Is it around 1.8V or 0V?

From an initial inquiry, it seems like your device is entering the soft shutdown state. This typically occurs when either the TS2 pin is held low, or the LD pin is held high after attempting to enter the shutdown state. 

For more information on soft shutdown, I would recommend taking a look at this thread. It will detail what the soft shutdown state is, what causes a device to enter this state, and how to then exit the soft shutdown state. If anything is unclear or you have any additional questions, feel free to reply on this thread.

Regards,

Rohin Nair

Dear Rohin,

Thank you very much for your continued support.

I have rechecked the shutdown conditions as follows:

TS2 is pulled high by default
LD is at 0V
REG2 is at 2.2V
However, after attempting to shut down the device, REG18 still remains at 1.8V.
I also reviewed the reference you shared and tried pulling RST_SHUT high for 300 milliseconds, but unfortunately, the device still does not enter shutdown mode, and I am unable to communicate with it afterward.

Is there anything else I can try to further troubleshoot this issue?
Any suggestions would be greatly appreciated.

Best regards,
Vic

Dear Rohin,

I hope you're doing well.

I have one more question regarding the BQ76952. When exiting Shutdown mode by pulling the WAKE pin low, is there a specific duration that the WAKE pin must be held low to ensure the device wakes up properly?

If there is a minimum low-level time requirement, could you please let me know the recommended value?

Thank you very much for your support!

Best regards,

Vic

Hello Vic,

Apologies for the delayed response. REG18 remaining at 1.8V even though you have attempted to enter shutdown does indicate that your device is stuck in a soft shutdown state.

Just to clarify, when you say TS2 is pulled high by default, you have measured the voltage and it reaches the pull-up voltage of 5V? Is there anything else connected to your TS2 pin like a thermistor? This can prevent your device from ever fully entering shutdown mode.

Other suggestions I have would be to drive the TS2 pin above Vwakeonts2 and LD pin below Vwakeonld and force the device into shutdown. Again, you can double check this by measuring the voltage at the REG18 pin and confirming it is 0V.

There is no specified duration for holding the WAKE pin low to ensure the device wakes up properly.

Regards,
Rohin Nair

Dear Rohin Nair,

Thank you very much for your previous detailed explanation regarding the REG18 voltage and shutdown behavior of the bq79652. Your support has been very helpful in troubleshooting our system.

I have a follow-up question:
Could you please confirm whether the bq79652 is only unable to communicate via I²C in Shutdown and Soft Shutdown modes?
In other words, are these the only two modes in which the device’s I²C interface is disabled and unable to respond to communication from the host?

I would like to confirm that the device can still communicate normally via I²C in other states such as Standby, Active, or Init, so that we can further refine our system’s power management and communication logic.

Looking forward to your response. Thank you again for your continued support!

Best regards,

Vic