The LT1009IS8#TRPBF is a 2.5 V fixed-output shunt voltage reference from Analog Devices, in an 8-SOIC surface-mount package. As a shunt reference, it regulates voltage by shunting current through the cathode — the load and the reference share the same current path, so the 10 mA output current is the total current the reference can source to the load while maintaining regulation. The 400 µA minimum cathode current is the bias floor: the external resistor must be sized so that the cathode current never drops below this level, or the output voltage drifts out of spec. The ±0.4 % initial tolerance sets the accuracy of the reference voltage at 25 °C — for a 2.5 V rail, the output sits between 2.490 V and 2.510 V at first power-up. This matters for an ADC reference or a comparator threshold where the system accuracy depends on the reference staying tight over the enclosure's ambient swing.
It is ROHS3 compliant, covering the full RoHS exemption list including lead in high-melting-temperature solders.