TLK2711-SP: TLK2711-SP: Seeing voltage on VDD/VDDA

Part Number: TLK2711-SP

Tool/software:

Hello,

Im using the TLK2711-SP in transmit only mode and I am seeing voltage on the VDD/VDDA pin even though it is not powered.

Here is the setup:

• The TLK2711-SP is setup to be in only transmit mode, the interface to the TX pins and the CLK are 3.3V from the FPGA. RX pins are left floating.
• During normal operation, the TLK2711-SP would run off of 2.6V.

Now here is what the setup is when we see the issue:

1. On initial power up of the board, the FPGA turns on first, and has not yet configured the TLK2711-SP. However the 3.3V interface is already powered.
2. The 2.6V LDO is turned on by the FPGA but, on initial power up the 2.6V LDO should also be off.
3. When probing VDD and VDDA, we get a reading of about 0.9V on VDD and VDDA.
4. We still see the 0.9V on VDD and VDDA when we isolate the TLK2711-SP and completely disconnect the 2V6 LDO

Is the reason why we are seeing voltage on VDD/VDDA because we have voltage at the interface before the device is turned on? And what we are seeing is the voltage drop across the ESD Diode?

Or is it because we haven't properly configured it and need it to go through a power-on Reset?

Thank you

Wenchau