The TL431 is a three-terminal adjustable shunt regulator with specified thermal stability over applicable automotive temperature ranges. The output voltage can be set to any value between Vref (approximately 2.5 V) and 36 V, with two external resistors (see Figure 17). This device has a typical output impedance of 0.2 Ω. Active output circuitry provides a sharp turn-on characteristic, making this device an excellent replacement for Zener diodes in many applications, such as onboard regulation, adjustable power supplies, and switching power supplies.
