To enable the I/O pins, the EN input should be tied directly to V_{ref_B} during operation and both pins must be pulled up to the HIGH side (V_CCB) through a bias resistor (typically 200 kΩ). To ensure the high impedance state during power-up, power-down, or during operation, the EN pin must be LOW. The EN pin should always be tied directly to the V_{ref_B} pin and is recommended to be disabled by an open-drain driver without a pullup resistor. This allows V_{ref_B} to regulate the EN input and bias the channels for proper translation. A filter capacitor on V_{ref_B} is recommended for a stable supply at the device.

Figure 8-1 EN Pin Tied to V_{ref_B} Directly and to V_CCB Through a Pull-Up Resistor

The supply voltage of open drain I/O devices can be completely different from the supplies used for the LSF and has no impact on the operation. For additional details on how to use the enable pin, see the Using the Enable Pin with the LSF Family video.