Texas Instruments LM385D-1-2

Overview

LM385D-1-2 from Texas Instruments is a micropower, two-terminal, band-gap voltage reference IC operating over 15 μA to 20 mA cathode current, delivering 1.235 V nominal output with ±20 ppm/°C temperature coefficient and 1.5 Ω max reference impedance across 0°C to 70°C. It serves as a precision shunt reference in portable test instruments and battery-operated analog signal chains.

For engineers reviewing the LM385D-1-2 datasheet, LM385D-1-2 pinout, LM385D-1-2 application, or LM385D-1-2 equivalent, this page provides verified electrical specs, SOIC-8 package details, real-world use cases, and validated alternative parts for low-power reference design.

Technical Context

The LM385D-1-2 implements a floating shunt topology using an internal band-gap core with high-gain amplifier and shunt pass element, enabling stable regulation without external components. Its on-chip trimming achieves tight initial tolerance (±2%) and low long-term drift (±20 ppm/khr).

Designed for capacitive loading tolerance, it features internal frequency compensation ensuring stability with ≥0.1 μF ceramic bypass capacitance at the cathode. It operates exclusively in fixed-voltage reference mode-no adjustment capability-and requires minimum 15 μA cathode current for regulation.

Key Specifications

Pinout & Package

LM385D-1-2 is housed in an 8-pin SOIC (Package Drawing D), body size 4.90 mm × 3.91 mm, with 1.75 mm max height and RoHS-compliant NiPdAu lead finish. The device uses a two-terminal shunt configuration with unused pins internally disconnected.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LM385BDR-1-2, the LM385D-1-2 trades ±1% accuracy for lower cost and broader legacy compatibility; versus TLVH431ACDBVR, it offers lower power and fixed-output simplicity at the expense of adjustability and package size.

Availability

LM385D-1-2 is available at Aetrix Electronics and suitable for portable test instruments, battery-operated systems, and current-loop instrumentation requiring stable component supply with guaranteed long-term continuity.

Supply support for LM385D-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 leader specializing in analog and embedded processing technologies, with over 50 years of innovation in precision analog ICs.

The LM385 series belongs to TI's micropower voltage reference product line, engineered specifically for battery-critical and portable instrumentation applications demanding ultra-low I_Q, tight tempco, and robust capacitive-load stability.

FAQ

What is the minimum cathode current required for regulation in the LM385D-1-2?

The LM385D-1-2 requires a minimum cathode current of 15 μA to achieve proper regulation and maintain its specified 1.235 V output. Below this threshold, the reference voltage becomes unstable and deviates significantly from nominal. This value is confirmed in the Electrical Characteristics table under "Minimum reference current" for the LM385-1.2 variant at 0°C to 70°C.

Can the LM385D-1-2 be used in place of the LM285-1.2 in existing designs?

Yes, the LM385D-1-2 is functionally and pin-compatible with the LM285-1.2 in SOIC-8 packaging, sharing identical pinout, cathode/anode terminal roles, and operating current range (15–20 mA upper limit). However, note that LM285-1.2 supports −40°C to 85°C operation while LM385D-1-2 is rated for 0°C to 70°C - verify ambient temperature compliance before substitution.

What is the maximum capacitive load the LM385D-1-2 can drive without oscillation?

The LM385D-1-2 is designed to remain stable with ≥0.1 μF ceramic bypass capacitance directly at the cathode pin, as recommended in Layout Guidelines. No upper limit is specified because internal compensation ensures unconditional stability across all practical capacitor values and ESR ranges encountered in portable instrumentation layouts.

Does the LM385D-1-2 have built-in ESD protection, and what level is rated?

Yes, the LM385D-1-2 features built-in ESD protection rated per JEDEC standards: ±2000 V HBM (Human Body Model) and ±1000 V CDM (Charged Device Model) on all pins. These ratings are documented in Section 7.2 of the SLVS075J datasheet and reflect TI's standard process-level protection for precision analog devices.

How does the reference impedance of the LM385D-1-2 affect accuracy in a ratiometric ADC system?

The LM385D-1-2's 1.5 Ω max reference impedance directly contributes to output voltage error under load: at 1 mA load current, it introduces ≤1.5 mV drop, translating to ~0.12% gain error in a 1.235 V-referenced 12-bit ADC. This is well within typical system tolerances and is mitigated by keeping load currents below 100 μA in high-accuracy implementations.