SOT-89-3 footprint and thermal integration
The TLVH431QPK: This three-lead package has a large copper tab on the bottom that doubles as the cathode connection and the primary heat path. The tab must be soldered to a PCB copper plane; without it the 70 mA output current at elevated ambient will push the junction above the 125°C rated maximum. The 1.24V minimum reference voltage means the cathode-to-anode dropout is effectively the reference itself — the device regulates down to that floor. Output can be set anywhere from 1.24V up to 18V using two external resistors in the classic shunt configuration.
Tolerance and temperature range for the BOM line
For a power-supply feedback path that must hold ±2% regulation across temperature, this part delivers the margin without needing a precision series reference. The 100 µA minimum cathode current is the device's own operating floor — the external resistor string must pass at least this much current for the shunt to regulate. Below that the output drifts out of the ±1.5% window.