8.3.2 Quick Output Discharge (QOD)

The TPS22810-Q1 includes a QOD feature. The QOD pin can be configured in one of three ways:

• QOD pin shorted to VOUT pin. Using this method, the discharge rate after the switch becomes disabled is controlled with the value of the internal pull-down resistance (R_PD). The value of this resistance is listed in the Electrical Characteristics table.
• QOD pin connected to VOUT pin using an external resistor R_EXT. After the switch becomes disabled, the discharge rate is controlled by the value of the total resistance of the QOD. To adjust the total QOD resistance, Equation 1 can be used.
Equation 1. R_QOD = R_PD + R_EXT
where
• R_QOD is the total output discharge resistance
• R_PD is the internal pulldown resistance
• R_EXT is the external resistance placed between the VOUT and QOD pin.
• QOD pin is unused and left floating. Using this method, there is no quick output discharge functionality, and the output remains floating after the switch is disabled.

Note that during thermal shutdown, the QOD functionality is not available. The device does not discharge the load because R_PD does not become engaged.

The fall times of the device depend on many factors including the total resistance of the QOD, V_IN, and the output capacitance. When QOD is connected to VOUT, the fall time changes over V_IN because the internal R_PD varies over V_IN. To calculate the approximate fall time of V_OUT for a given R_QOD, use Equation 2 and Table 1.

The fall time's dependency on V_IN becomes minimal because the QOD value increases with additional external resistance. See Table 1 for QOD fall times.