SBOS659B January 2022 – August 2022 OPA593
The OPA593 incorporates an enable and disable feature that uses the E/D pin to disable the output stage of the amplifier, which lowers the power consumption of the op amp and switches the output to a high-impedance state.
The E/D pin is referenced to the E/D Com pin. If left floating, the E/D pin is internally pulled up to enable the device. If externally controlled, the E/D pin must be supplied with a voltage between 2.5 V and 5 V greater than the E/D Com pin voltage. Even though the OPA593 output is enabled with a floating E/D pin, a moderately fast, negative-going signal capacitively coupled to the E/D pin can overpower the internal pullup and cause device shutdown. If the enable function is not used, a conservative and recommended approach is to connect E/D through a 30-pF capacitor to a low-impedance source. Another alternative is to connect an external current source from V+ (positive supply) that is sufficient to hold the enable level greater than the shutdown threshold. Figure 7-3 shows a circuit that connects E/D and E/D Com.
When the E/D pin is dropped to a voltage between 0 V and 0.65 V greater than the E/D Com pin voltage, the output of the OPA593 is disabled. Because the inputs are still active, an input signal can be passed to the output of the amplifier, despite being in a high-output-impedance state. The voltage at the amplifier output is reduced because of a drop across this output impedance, and can appear distorted compared to a normal operation output.