TCA9539: The status of GPIO before power on

Mike Yu

Part Number: TCA9539

Hi Team,

According to the DS, the GPIO config at power on is config as input. The customer wants to know the config before power on. I guess it should be Hi-z mode, please kindly help to double confirm.

The reason why the customer asking is that they are using these GPIO ports to output.
They’re afraid the floating and impact the design function if the port setup to output before configure.

However, it should be okay, if the port config is input before power on. Thank you.

Best regards,

Mike

over 4 years ago

0 Clemens Ladisch over 4 years ago

Guru 316960 points

As shown in the absolute maximum ratings, the I/O pins are clamped to V_CC. So when V_CC = GND, they are not Hi-Z.

0 Mike Yu over 4 years ago in reply to Clemens Ladisch

TI__Intellectual 2320 points

Hi Ladisch,

Since, the GPIOs are not Hi-Z when Vcc=Gnd. Are them floating? or is there any other status? Thank you.

Best regards,

Mike

0 Clemens Ladisch over 4 years ago in reply to Mike Yu

Guru 316960 points

There is a diode between the pin and VCC. This prevents the output from going higher than VCC + 0.6 V. (If VCC is floating, a high voltage on the pin will make a current flow into VCC.)

0 BOBBY over 4 years ago in reply to Mike Yu

TI__Guru 73201 points

Hi Mike,

The GPIOs are HI-Z when Vcc is GND.

The protection diodes on the GPIOs are actually 2 facing each other (from pin to Vcc) so inorder to bias both, you would need to put enough voltage to reverse bias one and forward bias the other. I believe this to occur outside the absolute maximum ratings we spec.

-Bobby

0 Mike Yu over 4 years ago in reply to BOBBY

TI__Intellectual 2320 points

Hi Ladisch and Bobby,

Thanks for the information, it is clear to me.

Best regards,

Mike

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TCA9539: The status of GPIO before power on