The TORCH/TX pin is either a Power Amplifier Synchronization input, or external torch enable. In Tx mode, this function is designed to reduce the flash LED current and thus limit the battery current during high battery current conditions such as PA transmit events. When the LM3645 is engaged in a Flash event, and the TX pin is pulled high, the LED current is forced into Torch Mode at the programmed Torch current setting. If the TX pin is then pulled low before the Flash pulse terminates, the LED current returns to the previous Flash current level. At the end of the Flash time-out, whether the TX pin is high or low, the LED current turns off. If a Tx event occurs during a flash, a flag will be set in the FLAG_RPT_REG register (bit[5] in reg 0x14).