DS90UB948-Q1: PDB discharge

Roy Chou1

Part Number: DS90UB948-Q1
Other Parts Discussed in Thread: TPS3840-Q1

Hi Team,

My customer is now using DS90UB948-Q1 and face a issue. We connect a RC circuit before PDB pin to achieve power sequence.

But when we turn off the system for 2s and then turn it on, the system is startup fail.

We find that the reason is VPDB voltage is discharge so slow that system will start up fail.

Is there any work around for this issue?

Regards,

Roy

over 5 years ago

0 Casey McCrea over 5 years ago

TI__Guru** 103215 points

Hello Roy,

If the system need to tolerate fast startup/shutdown configurations we would recommend controlling PDB via an external MCU or voltage supervisor device to ensure that the power sequence can be met.

Best Regards,

Casey

0 Roy Chou1 over 5 years ago in reply to Casey McCrea

TI__Genius 16900 points

Hi Casey,

Thank you for your reply.

Just would like to double check a point again. Do you mean that we could use reset for discharge path function?

By the way, have you ever see the issue in worldwide? Or most of customers use discharge path function to avoid re-power on startup fail?

Regards,

Roy

0 Casey McCrea over 5 years ago in reply to Roy Chou1

TI__Guru** 103215 points

Hello Roy,

I mean you could use a supervisor IC to control the PDB pin and make sure it is only asserted during valid power rail conditions. TI provides supervisor ICs with push-push type outputs which can actively pull the pin low when supply voltage is falling in order to quickly discharge the pin. Can you also find ICs with programmable power up delay to ensure sequencing is met at the system level. An example would be TPS3840-Q1

Best Regards,

Casey

0 Roy Chou1 over 5 years ago in reply to Casey McCrea

TI__Genius 16900 points

Hi Casey,

Got it. Thank you for your quick support.

Regards,

Roy

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DS90UB948-Q1: PDB discharge