DS90UB948-Q1: unused input

Shinji Tsuji

Genius 14139 points

Part Number: DS90UB948-Q1

Hi team,

I have a question about the unused pin of DS90UB948-Q1.

For pin #8 - #19, it seems all pin has internal weak pull down. Isn't it a need for external pull down resistor?

Or is it OK to just leave them open if these function are unused?

Is there any specific reason that needs external pull down resistor?

regards,

over 5 years ago

0 Casey McCrea over 5 years ago

TI__Guru** 103215 points

Hello Shinji,

Since they have internal pulldown, it is ok to leave them open generally, but for the most robust performance especially in terms of EMC it may be better to tie them with a stronger external pulldown to GND if unused.

Best Regards,

Casey

0 Shinji Tsuji over 5 years ago in reply to Casey McCrea

TI__Genius 14139 points

Hi Casey,

Thank you.

Is that OK to connect directly to GND without resister?

Or I should put some resistance to protect in case IO becomes Output and drive it High?

regards,

0 Casey McCrea over 5 years ago in reply to Shinji Tsuji

TI__Guru** 103215 points

Hello Shinji,

I would suggest using some weak pulldowns for the reason you stated. That way if your IO's go high they will not source a lot of current.

Best Regards,

Casey

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DS90UB948-Q1: unused input