TXS0108 used in I2C, 1.7V rather than 3.3V when bus is idle

Michael Huang3

Hi SC colleague,

My customer starnet is using TXS0108 to translate I2C between 2.5V and 3.3V. But they have an issue. with our devices connected, the bus voltage is down to 1.7V at B side(3.3V side).

They have tested

1 With or withou external pull-up resistor, the problem existed.

2 OE is pulled down, it is 3.3V on the bus. but when oe is pulled up, the 3.3V drops to 1.7V.

Do you have the same problems before?

Regards

Michael

over 10 years ago

0 Wei Lang over 10 years ago

TI__Expert 6430 points

Hi Michael,

Could you please check the voltage on A1/A2? If it is possible, could you remove R56, R58 and test it again?

Thanks

0 Michael Huang3 over 10 years ago in reply to Wei Lang

TI__Intellectual 2460 points

Hi Wei,

They tested it before. It is ok when they remove R56 R58, the TXS0108 wit CPU. when removed, the voltage of CPU I2C and TXS part are both 3.3V.

Regards

Michael

0 Michael Huang3 over 10 years ago in reply to Wei Lang

TI__Intellectual 2460 points

Hi Buddy,

The problem is solved by reducing the fly-wire.

As far as i know, TXB products can not drive lengthy cable, and TXS can. I read the datasheet and the there's push-pull output structure like TXB. Is it the cause of the problem? Do we have application note or some materials to look into this?

Thanks for the support.

Michael Huang

Logic

Logic forum

TXS0108 used in I2C, 1.7V rather than 3.3V when bus is idle