Three programmable parameters control the TPS53676 input undervoltage protection. More detail is shown in the figure below.

• Turn-on voltage (VIN_ON) is the input voltage at which TPS53676 allows power conversion to be enabled. Program this threshold through the VIN_ON command. The input undervoltage fault and warning are masked until the turn-on voltage is exceeded the first time during power-up. TPS53676 does not act on commands to enable power conversion while the input voltage is below this limit. No action is taken when the input voltage falls below this threshold during power conversion. Detection is based on input voltage telemetry. TPS53676 supports values from 4.25 V to 11.5 V.
• Input undervoltage fault (VIN_UVF) is the input voltage at which power conversion stops. Program this threshold through the VIN_UV_FAULT_LIMIT command. This command is also forced equal to the turn-off voltage (VIN_OFF). Detection is based on input voltage telemetry. When the sensed input voltage falls below this limit, the input undervoltage fault condition is detected. This fault is masked until the sensed input voltage exceeds the turn-on voltage VIN_ON for the first time. TPS53676 supports values from 4.00 V to 11.25 V.
• Input undervoltage warning (VIN_UVW) is a programmable threshold which sets a warning based on the input voltage sense telemetry for a channel. Detection is based on input voltage sense telemetry. When the sensed input voltage below this limit, the input undervoltage warning is detected. Program this threshold using the VOUT_UV_WARN_LIMIT command. TPS53676 supports values of 4.0 V to 11.25 V.

The input undervoltage fault is triggered when the sensed input voltage falls below the VIN_UV_FAULT_LIMIT threshold, and considered to be cleared when the sensed input voltage exceeds the VIN_ON limit. The input undervoltage fault is enabled only when either of the channels is enabled. Toggling the enable for both channels at the same time with the input voltage above the VIN_UV_FAULT_LIMIT threshold clears the fault, and enables power conversion to begin automatically after the input voltage exceeds the VIN_ON limit. In the case where the enable for each channel is independent, commanding one channel to enable conversion does not clear the input undervoltage condition and power conversion may not start automatically when the input voltage exceeds the VIN_ON thresholds. TI recommends to enable power conversion only after the input voltage exceeds the VIN_ON as shown in the figure below.

Figure 7-32 Input undervoltage protection (VR_EN active high control)