Fixed 1.235V shunt reference — obsolete, but still spec'd into legacy BOMs
The Texas Instruments LM385PSRG4-1-2 is a fixed 1.235V shunt voltage reference in an 8-SOIC package. Minimum cathode current is 15 µA, and the device can sink up to 20 mA.
If you are qualifying a replacement, the search starts with the 1.235V fixed output, shunt topology, and 8-SOIC footprint. The base product number LM385 family includes multiple tolerance and temperature-grade variants — but this specific PSRG4 suffix is the one that matches the original BOM line.
Noise and drift — where the 60µVrms matters
The 60µVrms noise figure (10 Hz to 10 kHz) is a genuine differentiator for a shunt reference in this voltage class. It keeps the reference contribution below 1 LSB for a 12-bit ADC with a 2.5V full-scale range, which is why this part shows up in older instrumentation and sensor-conditioning boards. The 20ppm/°C typical drift adds about 25 µV over a 70°C span — acceptable for 0.1% system accuracy but not for 16-bit designs without calibration.