Input low spec. of TCA9517's B-side pins

user446310155

Other Parts Discussed in Thread: TCA9517

Hi Supporter,

Two parameters talking about the input low spec. on TCA9517's B-side, one is VIL and the other is VILC. And there is a foot note following 7.3 of the datasheet's page-5 says VIL is only for the first low seen by B-side signals whereas VILC is applied by the 2nd and subsequent lows.

Can you kindly explain what is the difference between the first low and the following low seen by TCA9517's B-side signals in detail and why the first low can apply a less strict spec. (<0.3VCCB)?

Regards,

SP Lin@Adlink

over 9 years ago

0 fhoude over 9 years ago

TI__Mastermind 23806 points

Hello SP Lin,
Let me put some diagrams together to explain this. I will send an update soon.
-Francis Houde

0 user446310155 over 9 years ago in reply to fhoude

Intellectual 460 points

Hi Mr. Houde,

Thanks for your reply. I am looking forward your explanation for that question.

Regards,
S.P. Lin@Adlink

0 user446310155 over 9 years ago in reply to fhoude

Intellectual 460 points

Hi Mr. Houde,

Do you have any update for this question?

Regards,
S.P. Lin@Adlink

0 fhoude over 9 years ago

TI__Mastermind 23806 points

Hello SP Lin,

Sorry for delay and thanks for the reminder. The TCA9517 is a buffered translator and in order to support the bidirectional communication and the buffer capabilities we need to understand how the static voltage offset works. Here is the diagram of the transitions.

When B signal goes below 0.3*Vcc (VIL) then the device relays a logic zero to the A side. After this occurs, the new VIL is VILC or 0.4V in this diagram. If a device continues to pull low on the bus below 0.4V then the A side get pulled low. It is necessary to have the toggling of the reference comparator for the B side due to the static offset voltage which allows a input low from the B side to propagate back to the A side.

0 user446310155 over 8 years ago in reply to fhoude

Intellectual 460 points

Hi Supporter,

According to your clarification, it seems there are two methods to pass a low from B-side to A-side: one is to identify 0.3VCCB and the other is to identify VILC around 0.4V. Can you let me know why two methods are required? Why not to keep only one method that just to identify 0.4V VILC?

Regards,
Lin, S.P.

0 user446310155 over 8 years ago in reply to user446310155

Intellectual 460 points

Hi Supporter,

Do you have any comment for this question?

Regards,
Lin, S.P.

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Input low spec. of TCA9517's B-side pins