Adjustable shunt reference, 1.24 V to 6 V rail
15 mA output, 80 µA cathode — the bias budget
Rated for 15 mA maximum output current, the TLV431IDBZR can sink enough current to drive an optocoupler LED in a primary-side regulated flyback supply or to pull down a feedback node. The ±1.5% tolerance on the internal reference voltage is tighter than the standard ±2% grade found on many general-purpose shunt references. For a 3.3 V rail that needs a 1.24 V threshold, that tolerance keeps the set point within roughly 19 mV, which is acceptable for most power-good and overvoltage detection circuits without additional trimming.
Active production, SOT-23-3 footprint
The SOT-23-3 package (TO-236-3 / SC-59 compatible) is a common three-pin footprint shared with the TL431 family, so the board layout is straightforward and the part can be dropped into existing TL431 pads with a check on the pin assignment.