The shutdown (enable) function of the OPAx363 is referenced to the negative supply voltage of the operational amplifier. A logic level HIGH enables the op amp. A valid logic HIGH is defined as voltage greater than 75% of the positive supply applied to the enable pin. The valid logic HIGH signal can be as much as 5.5 V above the negative supply, independent of the positive supply voltage. A valid logic LOW is defined as less than 0.8 V above the negative supply pin. If dual or split power supplies are used, take care to ensure that logic input signals are properly referred to the negative supply voltage. This pin must be connected to a valid high or low voltage or driven, not left open-circuit.
The logic input is a high-impedance CMOS input. Dual op amps are provided separate logic inputs. For battery-operated applications, this feature reduces the average current and extend battery life. The enable time is 20 μs; disable time is 1 μs. When disabled, the output assumes a high-impedance state. This configuration allows the OPAx363 to operate as a gated amplifier, or to have the output multiplexed onto a common analog output bus.