The output voltage is limited to typically 5.7 V. In situations such as an open LED, the LM3645 raises the output voltage in order to try and keep the LED current at its target value. When V_OUT reaches 5.7 V (typical) the overvoltage comparator trips and turns off the internal N-channel MOSFET . When V_OUT falls below the “V_OVP Off Threshold”, the LM3645 begins switching again. The Dx_EN bits are cleared, and the OVP flag is set (bit[6] in reg 0x15), when an OVP condition is present for three rising OVP edges. This prevents momentary OVP events from forcing the device to shut down.

When operating in voltage mode, the OVP protection mechanism is enabled, however the fault reporting and shut down functions are not enabled.