Texas Instruments LM385M3-1.2

Overview

LM385M3-1.2 from Texas Instruments is a micropower 2-terminal band-gap voltage reference diode delivering a precise 1.235 V output with ±1% initial tolerance, 1 Ω dynamic impedance, and operation over 10 μA to 20 mA current range. It serves as a low-drift, low-noise reference in battery-powered analog circuits, portable meters, and precision current sources.

For engineers reviewing the LM385M3-1.2 datasheet, LM385M3-1.2 pinout, LM385M3-1.2 application, or LM385M3-1.2 equivalent, key selection criteria include its SOT-23 package, 0°C to 70°C operating temperature range, 30 ppm/°C typical temperature coefficient (X-suffix), and compatibility with capacitive loading up to 10 nF without instability.

Technical Context

The LM385M3-1.2 implements a band-gap reference architecture using only transistors and resistors, enabling low noise (60 μV_rms, 10 Hz–10 kHz) and excellent long-term stability (20 ppm/1000 hr). Its two-terminal configuration simplifies design by eliminating separate input/output pins and requiring only a single series resistor for biasing.

It operates across a wide reverse current range (10 μA–20 mA), allowing flexible supply voltage selection and direct replacement of older references. On-chip trimming ensures tight voltage tolerance, while its low 1 Ω dynamic impedance supports stable regulation under varying load conditions.

Key Specifications

Pinout & Package

SOT-23 (DBZ) package: 3-pin surface-mount, 1.12 mm max height, footprint compatible with IPC-7351 standard land pattern. Pin 1 = Anode, Pin 2 = Cathode, Pin 3 = Die Attach Pad (DAP), electrically connected to Pin 2 and intended for thermal and electrical grounding.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LM385BZ-1.2/NOPB and LM385BM-1.2/NOPB, the LM385M3-1.2 offers the smallest PCB footprint and lowest thermal resistance among 1.235 V variants, making it optimal for space-constrained, battery-operated devices where thermal management and size are critical.

Availability

LM385M3-1.2 is available at Aetrix Electronics and suitable for portable instrumentation, precision sensor interfaces, and micropower industrial monitoring requiring stable component supply and RoHS-compliant packaging.

Supply support for LM385M3-1.2 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 company specializing in analog and embedded processing technologies, with leadership in precision analog ICs and power management solutions.

The LM385 family was designed for micropower, low-drift voltage referencing in battery-critical and portable applications-emphasizing minimal quiescent current, robust capacitive-load stability, and tight initial tolerance without external components.

FAQ

What is the exact reference voltage of LM385M3-1.2 and how tightly is it specified?

The LM385M3-1.2 delivers a nominal reference voltage of 1.235 V, with an initial tolerance of ±1% at 25°C. Electrical Characteristics tables confirm minimum and maximum values of 1.223 V and 1.247 V respectively under 10 μA ≤ I_R ≤ 20 mA conditions. This specification applies directly to the LM385M3-1.2/NOPB variant per TI's SNVS742E datasheet.

Can LM385M3-1.2 operate from a 1.5 V battery, and what is the minimum required headroom?

Yes, the LM385M3-1.2 can operate from a 1.5 V battery. Its minimum operating current is 10 μA, and Figure 16 in the datasheet explicitly shows "Micropower Reference from 1.5V Battery" using LM385-1.2-N. The device requires no headroom beyond its 1.235 V output-only sufficient series resistance to limit current into the 2-terminal device, as confirmed in LM385M3-1.2 application schematics.

What is the thermal resistance (θ_JA) of LM385M3-1.2 in its SOT-23 package?

The thermal resistance from junction to ambient (θ_JA) for LM385M3-1.2 in the SOT-23 (DBZ) package is 283°C/W, as documented in the Thermal Characteristics table of SNVS742E. This value assumes standard JEDEC 2-layer board conditions and is specific to the LM385M3-1.2 variant-not extrapolated from TO-92 or SOIC versions.

Does LM385M3-1.2 require an external capacitor for stability, and what is its capacitive load limit?

No, the LM385M3-1.2 does not require an external capacitor for stability. Its datasheet states "exceptionally tolerant of capacitive loading" and shows stable operation with ≥10 nF output capacitance in typical performance curves. This behavior is intrinsic to the LM385M3-1.2's internal design and eliminates the need for isolation resistors in most applications.

What is the long-term stability specification for LM385M3-1.2, and under what conditions is it measured?

The long-term stability of LM385M3-1.2 is specified as 20 ppm over 1000 hours, measured at I_R = 100 μA and T_A = 25°C ±0.1°C. This parameter appears in the Electrical Characteristics table of SNVS742E and applies specifically to the LM385M3-1.2/NOPB part, confirming predictable aging behavior in precision calibration circuits.