The open-drain DIAG pin can be monitored to confirm the device is operational, and the output voltage is valid. During power-up, the DIAG pin is actively held low until the high-side supply is in regulation and the device operates properly. The DIAG pin is actively pulled low if:

• The low-side does not receive data from the high-side (for example, because of a loss of power on the high-side). The amplifier outputs are driven to negative full-scale.
• The high-side DC/DC output voltage (DCDC_OUT) or the high-side LDO output voltage (HLDO_OUT) drop below their respective undervoltage detection thresholds V_DCDCUV and V_HLDOUV as sepecified in the Electrical Characteristics table. In this case, the low-side may still receive data from the high-side but the data may not be valid. The amplifier outputs are driven to negative full-scale.

During normal operation, the DIAG pin is in a high-impedance state. Connect the DIAG pin to a pull-up supply through a resistor or leave open if not used.