The OPAx863 includes a power-down mode for low-power standby operation with a quiescent current of only 1.5 μA (maximum) with a 3-V supply and high output impedance. Many low-power systems are active for only a small time interval when the parameters of interest are measured and remain in low-power standby mode for a majority of the time and an overall small average power consumption. The OPAx863 enables such a low-power operation with quick turn-on within less than 6.5 μs. See the Electrical Characteristics tables for power-down pin control thresholds.

Always drive PD pin to avoid false triggering and oscillations. If power-down mode is not used, then connect the PD pin to V_S+. For applications that need power-down mode, use an external pull-up resistor from the PD pin to V_S+ (driven with an open-collector power-down control logic).

Figure 8-2 Power Down Control

Figure 8-2 shows the choice of value of the pull-up resistor R_PU, which impacts the current consumption in power-down mode. Using a large RPU reduces power consumption, but increases the noise at the PD pin, which can cause the amplifier to power down. A 1‑nF capacitor can be used in parallel with RPU to avoid coupling of external noise and false triggering. For the case of the PD pin driven to V_S-, the I_PU current through R_PU is given as:

Equation 1.