Texas Instruments LM385M

Overview

LM385M from Texas Instruments is a 3-terminal adjustable micropower band-gap voltage reference diode, operating from 1.24 V to 5.30 V with 1% initial tolerance, 1 Ω dynamic impedance, and 0°C to 70°C temperature range - used in precision shunt regulators, portable metering, and low-power analog circuitry.

For engineers reviewing the LM385M datasheet, LM385M pinout, LM385M application, or LM385M equivalent, this page delivers verified electrical specs, SOIC-8 package details, thermal characteristics, real-world use cases including 10V reference generation and current detection, and two validated alternative parts for design flexibility.

Technical Context

The LM385M implements a band-gap reference architecture using only transistors and resistors, enabling low noise, excellent long-term stability, and tolerance to capacitive loading without external compensation. Its 3-terminal configuration functions as a 2-pin shunt device with an adjustable output set by external resistor dividers.

It operates over a wide dynamic current range (10 μA to 20 mA), allowing replacement of older references with tighter tolerance while maintaining compatibility with varying supply conditions. The device exhibits 30 ppm/°C typical temperature coefficient and 50 μV_RMS wideband output noise at 100 Hz–10 kHz.

Key Specifications

Pinout & Package

LM385M is housed in an 8-pin SOIC package (Package Drawing D), with pin 1 marked by a beveled corner or dot. The device functions as a 3-terminal shunt reference: Cathode, Anode, and Adjust (ADJ) pins are used; five pins are NC (no connect) per TI's internal die layout and pin map.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar adjustable shunt voltage reference applications.

Compared with LM385M, LM385BXZ/NOPB offers identical electrical performance in a through-hole package but lacks SOIC manufacturability; TLVH431ACDBVR provides superior accuracy and voltage range at the cost of higher quiescent current and different pinout - both require schematic and layout updates.

Availability

LM385M is available at Aetrix Electronics and suitable for precision shunt regulators, portable instrumentation, voltage level detectors, and floating current sensing applications requiring stable component supply across production lifecycles.

Supply support for LM385M includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Texas Instruments is a global semiconductor leader specializing in analog, embedded processing, and connectivity technologies, with over 50 years of innovation in precision analog ICs.

The LM385M belongs to TI's micropower voltage reference product line, designed specifically for low-power, high-stability shunt reference applications in commercial-grade instrumentation and portable electronics.

FAQ

What is the maximum output voltage achievable with LM385M?

The LM385M supports an adjustable output voltage range from 1.24 V to 5.30 V, determined by external resistor values connected between its ADJ, Cathode, and Anode terminals. This upper limit is defined by the internal band-gap core and absolute maximum ratings - exceeding 5.30 V risks violating safe operating area and invalidating specifications. The LM385M datasheet confirms this range applies across its full 0°C to 70°C operating temperature span.

Does LM385M require external capacitors for stability?

No, the LM385M is explicitly designed to be tolerant of capacitive loading and does not require external output capacitors for stability. TI's datasheet states "careful design… makes the device tolerant of capacitive loading, making it easy to use in almost any reference application." This eliminates the need for series isolation resistors or compensation networks in typical PCB layouts, though a small ceramic capacitor (e.g., 100 nF) may still be added for local noise suppression if system EMI requirements demand it.

Can LM385M replace LM336Z-2.5 in existing designs?

The LM385M is not a direct functional or pin-compatible replacement for LM336Z-2.5. While both are 2.5 V shunt references, the LM336Z-2.5 is a fixed-output device in TO-92, whereas the LM385M is adjustable, requires three external connections (Cathode/Anode/ADJ), and uses an SOIC-8 package with five NC pins. Substituting LM385M would require modifying the resistor network, updating PCB layout, and verifying thermal performance due to differing θ_JA (170°C/W vs. ~200°C/W for TO-92).

What is the thermal resistance (θ_JA) of LM385M in SOIC package?

The LM385M in SOIC-8 package has a junction-to-ambient thermal resistance (θ_JA) of 170°C/W under standard JEDEC test conditions (0.125″ lead length). This value assumes a 2-layer board with minimal copper; actual thermal performance improves with increased copper area or thermal vias. TI's Thermal Characteristics table confirms this figure applies specifically to the LM385 series in SOIC, distinguishing it from TO-92 (440°C/W) and TO-46 (165°C/W) variants.

Is LM385M RoHS compliant and lead-free?

Yes, the LM385M/NOPB variant is RoHS compliant and lead-free, with "Green (RoHS & no Sb/Br)" eco plan designation and CU SN (copper-tin) lead finish. TI's Packaging Information confirms LM385M/NOPB meets current EU RoHS requirements for all 10 restricted substances, including ≤0.1% by weight for lead, cadmium, mercury, hexavalent chromium, PBB, and PBDE - verified per TI's 23-Aug-2017 Package Option Addendum.