The EN pin of the REF70 has an internal 16 MΩ pull-up resistor (R_EN) to VIN. This allows the EN pin of the REF70 to be left floating. When the EN pin of the REF70 is pulled high, the device is in active mode. The device must be in active mode for normal operation. The REF70 can be placed in shutdown mode by pulling the EN pin low. When in shutdown mode, the output of the device becomes high impedance and the quiescent current of the device reduces to 12 µA in shutdown mode. The EN pin must not be pulled higher than VIN supply voltage. See the Section 7.6 for logic high and logic low voltage levels.