SN74AVC4T774: OE pin design issue

The OE pin is referenced to V_CCA. This sounds as if V_CCA and V_CCB got accidentally exchanged.

Hi Anne,

Can we get a schematic and some scope shots of the issue. 

May I know what is "V_CCA and V_CCB got accidentally exchanged" means?

Did you see this phenomenon before?

I will ask customer to provide the waveform by OE# / A port / B port / VCCA

Do you have any suggestions to make us to investigate the issue in advance before we capture the waveform?

The OE pin disables the outputs when it goes near V_CCA, so if 1.8 V does not work, V_CCA must be higher.

But it's hard to tell without a schematic; it's possible that something else pulls the voltage down.

If at all possible, measure the voltages directly at the pins.

Hi Anne,

A schematic will be a good start, Clemens and I both share the same hypothesis on what the issue could be. Other than that, the 4 signals you requested to see from the customer is spot on.

Hi Dylan,

Here is the schematic from customer's board,

Customer said if the OE pin connect to VCCB, the output of A2/3/4 can be Hi-Z

But if customer OE pin connect to VCCA, the output of A2/3/4 will still pass threw B2/3/4 signal to A side.

from our datasheet said, The OE pin is referenced to V_CCA.

May I have your confirm that OE pin is reference to VCCA or VCCi ?

Or please let us know OE pin need to reference which voltage level from customer's schematc.

Thanks

Hi Dylan,

Here is the schematic from customer's board,

Customer said if the OE pin connect to VCCB, the output of A2/3/4 can be Hi-Z

But if customer OE pin connect to VCCA, the output of A2/3/4 will still pass threw B2/3/4 signal to A side.

from our datasheet said, The OE pin is referenced to V_CCA.

May I have your confirm that OE pin is reference to VCCA or VCCi ?

Or please let us know OE pin need to reference which voltage level from customer's schematc.

Thanks

Hi Dylan,

Here is the schematic from customer's board,

Customer said if the OE pin connect to VCCB, the output of A2/3/4 can be Hi-Z

But if customer OE pin connect to VCCA, the output of A2/3/4 will still pass threw B2/3/4 signal to A side.

from our datasheet said, The OE pin is referenced to V_CCA.

May I have your confirm that OE pin is reference to VCCA or VCCi ?

Or please let us know OE pin need to reference which voltage level from customer's schematc.

Thanks

Hi Dylan,

Here is the schematic from customer's board,

Customer said if the OE pin connect to VCCB, the output of A2/3/4 can be Hi-Z

But if customer OE pin connect to VCCA, the output of A2/3/4 will still pass threw B2/3/4 signal to A side.

from our datasheet said, The OE pin is referenced to V_CCA.

May I have your confirm that OE pin is reference to VCCA or VCCi ?

Or please let us know OE pin need to reference which voltage level from customer's schematc.

Thanks

The OE pin is refererenced to V_CCA. With V_CCA = 1.8 V, any voltage below 0.63 V enables the outputs, and any voltage between 1.17 V and 3.6 V disables the outputs.

What is the voltage at the OE pin?

Hi Anne,

Do they have any scope shots of the OE signal that shows it meeting the required voltages Clemens mentioned?

Hi Clemens,

From the spec VCCI means the Transceiver  A-side or B-side input port ?

It refers to whatever side is currently configured as input by the DIRx pin.

So the OE# pin VIH/VIL will be changed depend on the VCCI voltage level?