9.4.1.1.1 V_ILC & I_ILC

The I_ILC parameter is the minimum amount of current that the external device must sink from the TCA980x in order for the TCA980x to accept the low on the B-side.

In order for the TCA980x to accept a low on the B-side, both V_IL and I_ILC parameters must be satisfied. In an idle bus condition (both A and B sides are high), meeting the V_IL threshold with an external device pull-down meets the I_ILC requirement, since the pull-down has to sink the entire I_CS (current source value) current before the voltage on the pin falls.

In a contention situation (the A-side is being driven low externally, and the B-side is driven low by the TCA980x), the V_IL requirement is already satisfied by the TCA980x alone (Since the output low voltage is less than the V_IL threshold). In order for a device on the B-side to over-drive the A-side, it must sink the I_ILC value for the TCA980x to accept that the low is now being driven by the B-side. This helps reduce or eliminate overshoot during the hand off between a slave an master during a clock-stretching event, or an acknowledge.

External pull-up resistors on the B-side are not allowed for this reason. As the additional current provided by them may hinder an external device from being able to satisfy the TCA980x's I_ILC requirement. For more information on this and allowed external current into the device, see the Input and Output Leakage Current (IEXT-I/IEXT-O) section.