The internal AD converter of TPS92910-Q1 continuously monitors the supply voltage and compares the results with internal threshold V_{(ADCLOWSUPTH)} set by CONF_ADCLOWSUPTH as described in Register Maps. If the supply voltage is lower than threshold, the device pulls ERR pin down with one pulsed current sink for 50 µs to report the fault and set flag registers including FLAG_ADCLOWSUP to 1. The master controller can write register CLR_FAULT to 1 to reset this flag, and the CLR_FAULT bit automatically returns to 0. The internal ADC monitors supply voltage and converters to 8-bit binary code in every conversion cycle T_(CONV) when it is in idle. After each AD conversion-cycle time on supply, the ADC_SUPPLY is automatically updated with the latest result.

The low-supply warning is also used to disable the LED open-circuit detection and single-LED short-circuit detection. When the voltage applied on SUPPLY pin is higher than the threshold V_{(ADCLOWSUPTH)}, the TPS929121-Q1 enables LED open-circuit and single-LED short-circuit diagnosis. When V_(SUPPLY) is lower than the threshold V_{(ADCLOWSUPTH)}, the device disables LED-open-circuit detection and single-LED short-circuit diagnosis. Because when V_(SUPPLY) drops below the maximum total LED forward voltage plus required V_(DROPOUT) at required current, the TPS929121-Q1 is not able to deliver sufficient current output to pull the voltage of each output channel as close as possible to the V_(SUPPLY). In this condition, the LED open-circuit fault or single-LED short-circuit fault might be detected and reported by mistake. Setting the low-supply warning threshold high enough can avoid the LED open-circuit and single LED short-circuit fault being detected when V_(SUPPLY) drops to low. The V_{(ADCLOWSUPTH)} is programmable from 5 V to 20 V.