The TLVH431B-EP device is a low-voltage, 3-terminal, adjustable voltage reference with specified thermal stability over applicable industrial and commercial temperature ranges. Output voltage can be set to any value between VREF (1.24 V) and 18 V with two external resistors (see Figure 24). This device operates from a lower voltage (1.24 V) than the widely used TL431 and TL1431 shunt-regulator references. When used with an optocoupler, the TLVH431B-EP device is ideal for voltage references in isolated feedback circuits designed for 3-V to 3.3-V switching-mode power supplies. It has a typical output impedance of 0.25 Ω. Active output circuitry provides a very sharp turn-on characteristic, making the TLVH431B-EP device an excellent replacement for low-voltage Zener diodes in many applications, including on-board regulation and adjustable power supplies.