The OPA838 includes a power-down feature. Under logic control, the amplifier can switch from normal operation to a standby current of less than 1 µA. When the PD pin is connected high (greater than or equal to 1.5 V over the negative supply), the amplifier is active. Connecting the PD pin low (less than or equal to 0.55 V over the negative supply) disables the amplifier. To protect the input stage of the amplifier, the device uses internal, back-to-back diodes (two in series each way) between the inverting and noninverting input pins. If the differential voltage in shutdown exceeds 1.2 V, those diodes turn on.

Actively drive the PD pin high or low; do not float this pin. If the power-down mode is not used, tie the PD pin to the positive supply rail.

When the op amp is powered from a single-supply and ground, with PD driven from logic devices with similar V_DD voltages to the op amp, no special considerations are required. When the op amp is powered from a split-supply with V_S– less than ground, an open-collector type of interface with a pullup resistor is more appropriate. Pullup resistor values must be less than 100 kΩ. Recovery from power down is illustrated in Figure 6-53 and Figure 6-54 for several gains. In single-supply mode, with the gain resistor at ground, the output approaches the positive supply on initial power-up until the internal nodes charge, and then recover to the target output voltage; see Figure 6-51 and Figure 6-52.