TCA9536: Weak Pull-up

Marco Rojas

Part Number: TCA9536
Other Parts Discussed in Thread: TCA9537

Tool/software:

Hi team,

I have a customer with the below inquiry, see below for the full excerpt. Let me know what you think and thanks in advance!

"We noticed this blurb in the TCA9536 datasheet that the pins have a “weak” pull-up during power on. This could cause serious issues for us since the expectation is that GPIOs are either low/high-Z be default.

Im curious what TI’s recommended implementation is since I would suspect many others would also run into issues having GPIOs default high. Adding external pull downs (<10 kohm) appears to be the only solution but this would cause constant leakage through the resistor when we eventually want to toggle them high. Any suggestions?"

Marco

over 1 year ago

0 Clemens Ladisch over 1 year ago

Guru 316690 points

Figures 8-2/8-3 show the 100 kΩ pull-up resistors. Table 8-7 shows that they are enabled by default.

The TCA9537 does not have internal pull-ups.

0 Tyler Townsend over 1 year ago

TI__Mastermind 47328 points

Hi Marco,

TCA9536 has weak 100k pull-ups enabled at power up with GPIO's default to input. This is to ensure non of the pins upon power up are left as floating inputs which could cause significant increase in leakage.

A possible solution the customer could take is upon powerup, write to register 0x50 to disable the pull-up resistors. See table 8-7 in the datasheet.

Set S6 to "1" on power up.

As Clemens has already stated, TCA9537 could be another option, and does not have internal 100k pull-ups .

Regards,

Tyler

0 Marco Rojas over 1 year ago in reply to Tyler Townsend

TI__Intellectual 2770 points

Hi Tyler & Clemens,

Thanks for the responses! My customer is asking if there are any plans for the 9537 to come in a similar X2SON package as the TCA9536, as small solution size is key for this project.

Marco

0 Tyler Townsend over 1 year ago in reply to Marco Rojas

TI__Mastermind 47328 points

Hi Marco,

No plans at the moment.

Lets continue this conversation offline to determine business case.

t-townsend@ti.com

Regards,

Tyler

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TCA9536: Weak Pull-up