I'm working on bidirectional isolated I2C, from 1V8 to 3V3 or 5V voltage level.
I'm using TXS0108 with ISO1540. My schematic looks like:
I have tested this circuit, I2C lines have many self-oscilators. I2C transmission has a lot of distortions.
I tried to add capacitor to filtering it, but withou succes.
Will TXS0108 work together with ISO1540 isolator ? What will be proper configuration for this devices ?
@TI - Do hou have I2C isolator for 1V8 ?
tj,
TI does not have a 1.8V I2C isolator at the moment. We have the ISO1540 and ISO1541 that supports voltages down to 3.0V.
The Output Load Considerations Section of the TXS0108E datasheet discusses signal oscillation. Specifically, the recommendation is to reduce line length and line capacitance to avoid false triggering of the one-shots that can yield signal oscillation.
I would appreciate any oscillscope screen shots that you can send me for debug. Can you capture SCL and SDA at each point in the signal chain?
1. SCL and SDA on 1.8V side of TXS0108E
2. SCL and SDA on 3.3V/VDD1 side of TXS0108E/ISO1540
3. SCL and SDA on VDD2 side of ISO1540
Best Regards,
Nirav
Hello Nirav
I have short PCB lengths.
My test environment is:
Rasberry as I2C master 3V3 <-> 3V3 TXS0108E 5V <-> 5V ISO1540 3V3
SDA signal from Rasberry without TXS0108E connected:
SDA signal with connected TXS0108E:
SDA signal on second side TXS0108E
SDA signal after ISO1540
SDA/SCL signals from Raspberry without TXS0108E
SDA/SCL signals from Raspberry with TXS0108E connected
