TAD5142: Pull-up or pull-down resistors for BCLK, FSYNC, and DIN

Hi Jeff-san,

Thank you for your answer.

Do BCLK, FSYNC and DIN have built-in pull-down resistors like MDx?

Best Regards,
Ishiwata

Hi Ishiwata-san,

I am not familiar with MDx. I2S is generated with push/pull topology normally so no pull up or pull down resistors, but transistors to drive the output. Even then the exact nature of the clock generation is generally not important. Series termination to prevent ringing is the only addition that might be necessary. For our devices 33-50ohms is typically the best value.

Best regards,
Jeff McPherson

Hi Jeff-san,

Thank you for your reply.

Is it correct to understand that the pull-down resistors listed below in the data sheet are not built into the BCLK/FSYNC/DIN terminals?

Which terminals have the pull-down resistors listed above built in?

Best Regards,
Ishiwata

Hi Ishiwata-san,

My apologies. That is a new spec that I have not normally seen before. Let me confirm internally some more details on that. Can I ask what is the specific concern around the pulldown resistance from your design point of view?

Thank you,
Jeff McPherson

Hi Jeff-san,

A customer has inquired about how to handle the BCLKt / FSYNC / DIN input signals.

Is it better to pull up? Or pull down? The customer asked.

I thought it was unnecessary because there is an internal pull-down resistor, but I didn't know which terminal digital I/O indicated, so I asked you.

Best Regards,
Ishiwata

Hi Ishiwata-san,

There should be no pull up or pull down used externally to the device. I'm still looking into the meaning of the pull-down spec, but I do know that the customer should not use any pull ups or pull downs outside of the device. The clock is not like I2C which requires pull up.

Best regards,
Jeff McPherson