As shown in Figure 7-3, 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. During normal operation, the DIAG pin is in high-impedance (Hi-Z) state and is pulled high through an external pullup resistor. 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). In this case, the amplifier outputs are driven to the V_FAILSAFE value, see Figure 7-2.
• 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 (brown-out). 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 V_FAILSAFE value, see Figure 7-2.

Figure 7-3 DIAG Output Under Different Operating Conditions

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