1.235 V shunt reference — what the ±1% tolerance buys you
The Texas Instruments LM385BYM-1.2/NOPB is a micropower shunt voltage reference that delivers a fixed 1.235 V output with a ±1% initial tolerance. It is designed for precision analog circuits — ADC/DAC references, comparator thresholds, and regulator feedback dividers — where a stable, low-drift voltage is needed without a series regulator. The 50 ppm/°C temperature coefficient keeps the output within roughly 6 mV across the full 0°C to 70°C range, which is tight enough for 8- to 10-bit systems but not for 12-bit+ designs without calibration.
20 mA output, 15 µA cathode — biasing the shunt
As a shunt reference, the LM385BYM-1.2/NOPB sinks current through the cathode to regulate the output voltage. The 20 mA maximum output current sets the load-driving ceiling; the 15 µA minimum cathode current defines the bias resistor value needed to keep the device in regulation at no load. For a typical 5 V supply rail, a 1.8 kΩ bias resistor delivers about 2 mA to the reference — well above the 15 µA floor and leaving headroom for the load.
8-SOIC package — rework-friendly footprint
No hidden pads, no underfill needed. The 1.27 mm pitch gives good clearance for hand-soldering touch-ups.