SCPS267B March 2017 – February 2020 TCA9803
Some translators are based on pass-gates for translation support. In most of the use cases, external pull-up resistors are required to pull the bus to the voltage rail.
As shown in Figure 15, it may appear that this use case is valid, but actually it is not. When either the TCA980x B-side or the slave pull down on the bus, the FET isolating the bus closes (low RDS_ON) and current from the 5-kΩ resistor is observed by the TCA980x, violating IEXT-I. See the IEXT-I section for more information.
Figure 16 shows the correct way to pair with a FET base translator (connecting to the A-side).
Rather than using a FET-based translator, it is recommended that a buffered translator be used, such as another TCA980x or a TCA9517. See the Typical Application section for single device for more information on concerns with B-side connections to buffered translators.