TCA9517-Q1: multiple B-side connection application

Shih Stone said:

Part Number: TCA9517-Q1

Dear,

We got a problem on TCA9517 application. 

It seems TCA9517 not allow to have B side to B side connection.

But we have same application(other board) have same B side to B side connection and it works good.

 

So we want to know~~

1. Any workaround to avoid oscillation if we have to connect two B-side together ?
   [Bobby] The easiest way is to disable the parallel 9517 that is not essential to communicating with the master/slave for that transaction.
   One other potential solution you could try is swapping  two of the TCA9517s with a TCA9509 (PVT2 and PVT3) or three of them (PVT2, PVT3, and VT1). The TCA9509 has its offset side on A side and is pin to pin with the TCA9517. It has different voltage rules though and you may want to remove/change pull up resistances on A side of TCA9509.
2. Does TCA9517 has min RC constant for pull-up resistor and bus capacitance?
   [Bobby] Not exactly but this is likely the reason why you are seeing B side being connected to work in some boards and not others (plus differences in prop delays). The device has an unwrapping affect when B side releases, it waits until A side is above a certain threshold before B side can fully release (it will sit at its VoLB until this time). Since the A side on VT 15 is connected to another B side of TCA9517 which are also in parallel, it makes it harder to support this kind of set up. You may be able to try to modify the RC constant on PVT2 and PVT3 to be faster to see if that helps.

 

 

 

Application diagram show as below.

VT15,VT1,PVT2 and PVT1 are TCA9517.

 

Scope waveform -  the probe are measure on VT15 A side and B-side.