AM5728: Power-down sequence issue

Denny%20Yang99373

Part Number: AM5728
Other Parts Discussed in Thread: TPS659037

Hi all,

Customer follow am5728 datasheet do power down the chip. But they meet a issue.

Just because the Vcore is power down earlier than Vdd_IO. It will make GPIO misoperation like below picture(GPIO will power down follow VDD_IO not Vcore). And PMIC can not adjust the timing(make vcore/vdd_IO power down at the same time). Are their any other methods to fix this? thanks!

BR,

Denny

over 7 years ago

0 Biser Gatchev-XID over 7 years ago

TI__Guru**** 393215 points

Hi,

Aren't they using the TPS659037? They shouldn't have this sort of issue with it.

0 Denny%20Yang99373 over 7 years ago in reply to Biser Gatchev-XID

TI__Expert 3805 points

Hi,

Yes, they use TPS659037.

BR,
Denny

0 Biser Gatchev-XID over 7 years ago in reply to Denny%20Yang99373

TI__Guru**** 393215 points

Can you describe what is the issue in more detail? What is connected on this pin?

0 Denny%20Yang99373 over 7 years ago in reply to Biser Gatchev-XID

TI__Expert 3805 points

Confirmed by customer, this picture has been capture from am5728 EVM.
Customer board has the same issue, they will connect the pin to other board to control the motor motion.

0 Biser Gatchev-XID over 7 years ago in reply to Denny%20Yang99373

TI__Guru**** 393215 points

I have asked the factory team to comment. They will respond here.

0 Biser Gatchev-XID over 7 years ago in reply to Biser Gatchev-XID

TI__Guru**** 393215 points

Feedback from the factory team:

Are they expecting GPIOs to remain valid until the respective VDDSHVx supply begins to fall? If so, this is not possible because the internal logic sourcing the GPIO buffers is powered from the core supply. GPIOs are only valid while all power rails are valid.

0 Denny%20Yang99373 over 7 years ago in reply to Biser Gatchev-XID

TI__Expert 3805 points

Customer hope GPIO fall to 0 when vdd_core down, but it seems GPIO will keep voltage for a while.

This voltage will goes down with VDD_IO. Customer hope it go with VDD_CORE.

0 peaves over 7 years ago in reply to Denny%20Yang99373

TI__Guru 58155 points

The state of any AM5728 output is not defined when any voltage rail is outside the recommended operating range. If the system requires a signal to be low during power-up or power-down sequencing, an external circuit powered from an auxiliary power source will be required to detect this condition and force the signal low.

Regards,

Paul

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AM5728: Power-down sequence issue