TCA9539-Q1: GPIO status after Vcc is powered (IC power supplied) before reset is actived

Vincent Chiu

Part Number: TCA9539-Q1

I need TI's expert to confirm the status of TCA9539-Q1's GPIO (P0-P7, P10-P17) after Vcc is powered but bedore reset is enabled.

Regards,

Vincent

over 2 years ago

0 Clemens Ladisch over 2 years ago

Guru 318760 points

While the device is powering up or while /RESET is low, all I/Os are in the high-impedance state.

0 Tyler Townsend over 2 years ago

TI__Guru 53278 points

Hi Vincent,

Assuming that your case is VCC is powered, /RESET = HIGH, state of the p-ports will be high-impedance inputs.

Regards,

Tyler

0 Vincent Chiu over 2 years ago in reply to Tyler Townsend

Prodigy 200 points

Hi Tyler

Due to our design use TCA9539-Q1's P0-P7 & P10-P17 to be the enable control signal for the DC-DC converter, we are worried about the P0-P7 & P10-P17 will be "unknown state" or "pull-up ouput" when IC's VCC is on but the /RESET=L. Should we add the pull low resistor on the output pins?

Vincent

0 Clemens Ladisch over 2 years ago in reply to Vincent Chiu

Guru 318760 points

As long as the I/Os are not yet configured as outputs, they will be floating. So you definitely need pull-downs.

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TCA9539-Q1: GPIO status after Vcc is powered (IC power supplied) before reset is actived