I'm looking at incorporating a LSF0108 level shifter into a design to convert bidirectional GPIO signals from a 1.8V CPLD (Vcca) to an off-board device via ribbon cable. The header contains a voltage reference at one of several known voltages (1.8V, 2.5V, 3.3V, and 5V possible), which I have connected to Vccb.
The issue I'm running into is the datasheet calls for the enable pin to be connected via pull-up resistor to Vccb. Because there is an offboard connector, Vccb may not always be present when power is applied to Vcca. The suggested layout also calls for a .1uF decoupling capacitor on both the Vcca and Vccb rails. The datasheet also mentions that if either Vcca or Vccb are grounded, then this will also disable translation.
On to my question: how can I ensure that Vcca or Vccb are effectively grounded when a cable isn't attached? Using a pull-down doesn't seem right especially since the enable pin is pulled up when Vccb is present.
(Apologies in advance, I'm a hobbyist trying to step up his game and I'll gladly read any reference you can put in front of me!)