In IR Mode, the target LED current is equal to the value stored in the LED1/2/3/4 Flash Brightness Registers. When IR mode is enabled on any of the outputs, the boost converter turns on and set the output equal to the input (pass-mode) or to the selected voltage mode depending upon the state of the voltage mode settings. At this point, toggling the STROBE pins enables and disables the LED1/2/3/4 current sources (if enabled via the Dx Mode bits). The strobe pins can only be set to be Level sensitive, meaning all timing of the IR pulse is externally controlled. If the strobe pin is set to edge mode, the LM3645 device times out after the end of the set duration. In IR Mode, the current sources either ramp quickly or do not ramp the LED outputs to the target based upon the ramp time setting chosen.

Figure 6-6 IR Mode with Boost

Figure 6-7 IR Mode Pass Only

Figure 6-8 IR Mode Voltage Mode Enabled