DAC6578: I2C address misread

Toshihiro Watanabe

Part Number: DAC6578
Other Parts Discussed in Thread: DAC7568

Hello,

We use DAC6578 and ADDR1=Float, ADDR0=0. Slave address should be 1001100 but Ack respond when address 1001010. From this, ADDR1 seems changed from Float to 1. We see this issue in low temp, -20C condition.

I found the discussion DAC7568 has a similar issue and suggested address pin set intermediate voltage but it doesn't work.

Why does DAC6578 address changed in low temp condition?

Best regards,

Toshihiro Watanabe

over 7 years ago

0 Toshihiro Watanabe over 7 years ago

TI__Genius 10235 points

Hello,

I missed the post I saw. it is below.

https://e2e.ti.com/support/data-converters/f/73/t/710017?tisearch=e2e-sitesearch&keymatch=dac7578

Best regards,

Toshihiro Watanabe

0 Paul_Frost over 7 years ago in reply to Toshihiro Watanabe

TI__Guru 57313 points

Watanabe-san,

Uttam will get back to you tonight.

Thanks,
Paul

0 Uttam Sahu over 7 years ago in reply to Paul_Frost

TI__Genius 14220 points

Hi Watanabe-san,

Thank you for your query. There are usually weak internal pull-up and pull-down resistors on these pins. We have seen issues with the floating conditions unless strong pull-up and pull-down resistors are put externally so that the pin is held at the mid-voltage.

Sometimes due to many factors like a shift in the ground potential, noise, or temperature, the weak pull-ups drift and the floating value gets detected as either LOW or HIGH. We recommend putting external resistors to keep the ADDRx pin at mid-voltage in order to get them detected as expected.

Hope that answers your question.

Regards,

Uttam Sahu

Applications Engineer, Precision DAC

0 Toshihiro Watanabe over 7 years ago in reply to Uttam Sahu

TI__Genius 10235 points

Hello Sahu-san,

Do you have a recommended resister value? We did 1Mohm pull-up and 1Mohm pull-down but it does not help the issue.

I think 1Mohm may be too big. It would be helpful if there is a recommended value. My idea is like 10kohm or less.

Best regards,

Toshihiro Watanabe

0 Uttam Sahu over 7 years ago in reply to Toshihiro Watanabe

TI__Genius 14220 points

Watanabe-san,

Any value around 10k or less is a good choice.

Regards,

Uttam

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DAC6578: I2C address misread