TCA9802: TCA9802 for 1.8v to 1.8v Level-Translating Buffer problem

Hey Kevin,

Are you sure the device is soldering on properly? (Make sure the device wasn't soldered on 180 degrees rotated by accident).

I would suggest double checking your connections.

Probe the Enable pin and make sure the pin is high.

Thanks,

-Bobby

Hi Bobby

We have tried to replace the new unit, and check that there is no direction error, there is no signal output,

Does device support 1.8v to 1.8v?

P.S  Enable pin make sure the pin is high.

Sincerely

Kevin

Hey Kevin,

"Does device support 1.8v to 1.8v?"

Yes it does.

From the scopeshots, it also shows B side is powered on correctly because the signals are sitting at 1.8V meaning that if there are no pulls ups on B side then B side is sourcing current out.

Can you do me a favor and drive Side A to GND after powering up and looking at B side? (Just short A side with a jumper wire to GND) See if B side goes low.

-Bobby

HI Bobby

I have shorted to GND, there is a reaction on the B side, please refer to the waveform.
Measuring the TCA9802 Ch1 (A side) touches the GND waveform as follows, why does the Ch1 touch the GND see Ch2 (B side) measure Low to 1.44V?   

(B side is not connected to the device).

For my application, is there any other suggestion that chips can replace?

Sincerely

Kevin

Hey Kevin,

That's an interesting result....

This suggest to me that either:

1) there is another strong pull up on the B side (Not entirely confident on this theory as the NFET of the device would be broken at that high of a VoL)

2) there is a pull up resistor on the bus and a diode being conducted when you are driving the B side "low"

3) the device is damaged

"(B side is not connected to the device)."

What is B side connected to?

Are you able to provide me with the side B I2C bus schematic? (duynguyen@ti.com). I'd like to look at it and make sure there isn't something on that side which is causing issues.

"For my application, is there any other suggestion that chips can replace?"

For this device we do not have a pin to pin solution that would support 1.8V to 1.8V

-Bobby

Hi Booby

if I put a pull down100k resistor on the output? Is this suggestion?
I have sent the circuit diagram to you mail, please check it. thanks

Sincerely

Kevin

Hey Kevin,

I sent a response Via Email.

Adding a 100k pull down shouldn't hurt but at the same time, I do not see it helping us at all either. I am currently wondering if the TVS diodes on the bus are somehow affecting us.

-Bobby