TCA9545A: TCA9545A has below POR requirements issue

Hi Johnney,

"TCA9545A has below POR requirements but PCA9545A doesn’t."

PCA9545A does have POR requirements which is seen in section 11 (page 20 of the datasheet)

"Why the TCA9545A need POR requirements?"

Both devices have POR requirements because they have a state machine which requires a proper power up/reset inorder to set default values and ensure the state machine does not power up in an unknown state.

"How to verify the POR requirements by pins signal?"

Check the registers for default values, do they match the datasheet?

Can you communicate with the device?

-Bobby

Hi Bobby:

  Thanks for your reply.

I  didn't clearly about PCA9545A.

The PCA9545A of Vendor is NXP, not TI.

NXP PCA9545A don't has POR requirements.

We want lead-in TI TCA9545A.

Could the VCC power rail meet the VCC_FT and VCC_RT spec for VCC pin of TCA9545A?

Thanks a lot.

Hi Johnney,

Thanks for clarifying, the NXP version doesn't include the PoR requirements in their datasheet but I would think there is some kind of requirement for their power up sequence even if they don't specify it. [Note: I haven't done testing with NXP's device to look for their boundaries.]

Do you have a scopeshot of what your Vcc ramp rates look like so we can compare it to our requirements?

Thanks,

-Bobby

Hi Bobby:

   I measured the VCC rising/fall timing as below picture.

The reference level is 1.2V to 3.3V.

Please help check if VCC meet POR requirements.

Thanks a lot.