TXS0102: Low-levels are relatively high

franziskus

Part Number: TXS0102
Other Parts Discussed in Thread: TCA9800

Team,

my customer uses TXS0102 to convert 1.8V I2C signals to 3.3V I2C signals (I2C_SCL, I2C_SDA).
The I2C master is an FPGA. There are 3 slaves connected to the TXS0102.

The low-levels are

0.5V with external 2.2kOhm pull-ups
0.4V without external pull-ups

Are those (relatively high) low-levels normal for TXS0102?

I see a comment in the datasheet that this device is meant for point-to-point topology.
Could the 3 slaves be causing this behavior?

Thanks!

over 5 years ago

0 Clemens Ladisch over 5 years ago

Guru 317060 points

The TXS is a passive switch. The voltage at the output pin is the voltage at the input pin plus the voltage drop over the switch, which has a typical resistance of about 25 Ω.

Measure the voltage at both pins of the TXS to check whether the TXS itself contributes to the high voltage. I suspect that the FPGA and/or the slaves do not have very strong output drivers.

If you want lower voltages, use an I²C buffer like the TCA9800.

0 franziskus over 5 years ago in reply to Clemens Ladisch

TI__Expert 8339 points

Thank you Clemens, this is helpful feedback!

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TXS0102: Low-levels are relatively high