Shunt reference for the feedback loop
It provides a precision 2.495 V reference at the cathode when the reference pin is tied to the cathode, and can be set to any higher output voltage up to 36 V with two external resistors. The ±1% tolerance on the internal reference keeps the regulation tight across temperature, which matters when you are setting the feedback divider on a flyback converter or a linear regulator.
100 mA cathode current — sink capacity for the rail
Rated for 100 mA continuous output current, the TL432AQDBVT can sink enough current to drive the optocoupler LED in an isolated power supply feedback loop or to bias a pass transistor.
The SOT-23-5 package — also known as SC-74A — is a compact footprint that fits tight PCB layouts, but the small body means the power dissipation is limited; at 100 mA and a 5 V cathode-to-anode drop the die sees 500 mW, which exceeds the package's thermal capacity without a copper pour. For continuous high-current operation, budget a larger copper pad or a bigger package variant.
For dual-sourcing flexibility, the TL432BIDBVT is a pin-compatible sibling with the same SOT-23-5 footprint and similar electrical characteristics; the main difference is the temperature grade, so confirm the operating range matches your application before substituting.