SCPS267B March 2017 – February 2020 TCA9803
IEXT-I is a current source that is external to the TCA980x B-side, but leaks current into the device. This type of input leakage may not exceed the IEXT-I maximum spec, or else the minimum IILC value does not apply.
As shown in Figure 13, IEXT-I is a source of additional current into the device, shown as a leaky ESD cell. The user must keep IEXT-I as close to 0 as possible, since the TCA980x has a current source as a pull-up internally, and uses this current source to help detect which side is driving a low. As IEXT-I increases, it increases the minimum IILC value, requiring that an external device sink more current from the TCA980x in order to transmit a low. There must be no external pull-up resistor on the B-side to contribute to IEXT-I.