The OPAx375S devices feature SHDN pins that disable the op amp, placing it into a low-power standby mode. In this mode, the op amp typically consumes less than 1 µA. The SHDN pins are active-low, meaning that shutdown mode is enabled when the input to the SHDN pin is a valid logic low.

The SHDN pins are referenced to the negative supply voltage of the op amp. The threshold of the shutdown feature lies around 800 mV (typical) above the negative rail. Hysteresis has been included in the switching threshold to ensure smooth switching characteristics. To ensure optimal shutdown behavior, the SHDN pins should be driven with valid logic signals. A valid logic low is defined as a voltage between V– and V– + 0.2 V. A valid logic high is defined as a voltage between V– + 1.2 V and V+. The shutdown pin must either be connected to a valid high or a low voltage or driven, and not left as an open circuit. There is no internal pull-up to enable the amplifier.

The SHDN pins are high-impedance CMOS inputs. Dual op amp versions are independently controlled, and quad op amp versions are controlled in pairs with logic inputs. For battery-operated applications, this feature may be used to greatly reduce the average current and extend battery life. The enable time is 15 µs for full shutdown of all channels; disable time is 3 µs. When disabled, the output assumes a high-impedance state. This architecture allows the OPAx375S to be operated as a gated amplifier (or to have the device output multiplexed onto a common analog output bus). Shutdown time (t_OFF) depends on loading conditions and increases as load resistance increases. To ensure shutdown (disable) within a specific shutdown time, the specified 10-kΩ load to midsupply (V_S / 2) is required. If using the OPAx375S without a load, the resulting turnoff time is significantly increased.