LM385SM-1.2

Overview

The LM385SM-1.2 is a micropower voltage reference diode manufactured by National Semiconductor, now part of Texas Instruments. It functions as a two-terminal bandgap reference providing a nominal output voltage of 1.235 V. The device operates within a wide current range from 10 µA to 20 mA, ensuring stable performance with low dynamic impedance and low noise. Designed for precision applications, it features tight initial voltage tolerances achieved through on-wafer trimming. The component is housed in an 8-pin SOIC surface-mount package, suitable for space-constrained designs requiring reliable voltage referencing.

Feature Summary

• Provides precise 1.235 V reference using bandgap technology
• Operates efficiently across a wide current range from 10 µA to 20 mA
• Features low dynamic impedance and low noise characteristics
• Available in compact 8-pin SOIC surface-mount packaging

Applications

• Battery-powered portable instrumentation
• Precision analog-to-digital converter references
• Micropower regulator circuits
• Temperature sensing systems

Procurement Notes

Verify the manufacturer origin, as National Semiconductor assets were acquired by Texas Instruments. Confirm the specific suffix indicates the SOIC package and 1.235 V output. Check for RoHS compliance status, as older National Semiconductor parts may not meet current environmental standards. Ensure the ordering part number matches the required package type and tolerance grade for your design.

Selection Notes

Select this component when a fixed 1.235 V reference is needed in a surface-mount format. It is suitable for designs requiring low quiescent current operation down to 10 µA. Compare against the LM385Z-1.2 for through-hole alternatives or LM385M-1.2/NOPB for updated lead-free versions. Ensure the input voltage allows sufficient headroom for the series resistor to maintain current within the 10 µA to 20 mA operating window.

Part Context

The LM385 series includes adjustable and fixed voltage references like the LM185 and LM285. The LM385 specifically offers fixed outputs such as 1.235 V and 2.5 V. These devices are bipolar, two-terminal bandgap references known for high precision and low cost. They are widely used in industrial and consumer electronics where stable voltage referencing is critical for analog signal processing.

Replacement Considerations

The LM385M-1.2/NOPB is a direct lead-free replacement for the LM385SM-1.2, offering identical electrical specifications in the same SOIC package. Verify pinout compatibility and thermal characteristics when substituting. Other variants like LM385MX-1.2 may also serve as equivalents depending on availability and specific tolerance requirements.