Two external synchronization Strobe pins are available to enable the four LED outputs in either Flash or IR mode. Each of the four outputs can be assigned to either Strobe pin via the Strobe Control Register (bits [7:0] in reg 0x03). Each output assigned to a strobe pin must be set to the same LED mode, either all Flash or all IR. Additionally, no output should be assigned to both strobe pins. If D1 is assigned to STR1, it should not be assigned to STR2 as well.

If the LM3645 is already enabled, the minimum strobe duration in either level or edge mode must be 10 µs. This restriction applies to both flash and IR mode operation. If the LM3645 is in standby and either strobe pin is asserted, it is recommended that the strobe duration be no less than 1ms to ensure that the boost has enough time to reach the proper level to ensure current into the LED can regulate.