Texas Instruments LM4121AIM5X-1.2

Overview

LM4121AIM5X-1.2 from Texas Instruments (formerly National Semiconductor) is a precision micropower low-dropout voltage reference IC delivering a fixed 1.25 V output with ±0.2% initial accuracy, 50 ppm/°C temperature coefficient, and ±5 mA source/sink capability in SOT-23-5 packaging. It operates from 1.8 V to 12 V input, draws only 160 µA typical supply current, and features an enable pin for power-down mode (<2 µA), making it ideal for battery-powered instrumentation and portable data acquisition systems.

For engineers reviewing the LM4121AIM5X-1.2 datasheet, LM4121AIM5X-1.2 pinout, LM4121AIM5X-1.2 application, or LM4121AIM5X-1.2 equivalent, key selection considerations include its guaranteed industrial temperature range (−40°C to +85°C), low-noise performance (20 µV_PP, 0.1–10 Hz), load regulation (0.01%/mA over 1–5 mA), and compatibility with ceramic output capacitors as small as 0.022 µF.

Technical Context

The LM4121AIM5X-1.2 implements a bandgap-based reference core with integrated enable control and low-quiescent-current biasing. Its architecture supports operation down to 1.5 V input at full 5 mA load while maintaining 0.012%/V line regulation and 0.17%/mA load regulation across the full industrial temperature range.

It uses a dedicated REF pin (Pin 1) for the 1.25 V version-unconnected in normal operation-and an active Enable pin (Pin 3) requiring <0.4 V logic-low to enter power-down mode. Ground pin (Pin 2) carries both quiescent and load-dependent current, necessitating careful PCB layout to minimize mechanical stress-induced drift.

Key Specifications

Pinout & Package

SOT-23-5 surface-mount package (2.92 mm × 1.6 mm × 1.1 mm), tape-and-reel delivery (3000 units), RoHS-compliant, with top marking "R19A" indicating 1.25 V option, A-grade tolerance.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LM4121AIM5X-1.2, REF3012AIDBZR offers lower supply current but sacrifices programmable shutdown and exact 1.25 V compliance, while ADR3412ARJZ-R7 delivers tighter tempco and accuracy at the cost of disable capability-making LM4121AIM5X-1.2 optimal for battery-gated, 1.25 V–dependent precision systems.

Availability

LM4121AIM5X-1.2 is available at Aetrix Electronics and suitable for portable instrumentation, industrial process transmitters, and medical point-of-care devices requiring stable component supply with guaranteed A-grade specifications and SOT-23-5 footprint compatibility.

Supply support for LM4121AIM5X-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 (TI) is a global semiconductor leader specializing in analog and embedded processing technologies, with legacy expertise in precision analog ICs inherited from National Semiconductor.

The LM4121 series was designed specifically for micropower, low-voltage reference applications in portable and battery-constrained systems-emphasizing minimal dropout, enable-controlled shutdown, and robust performance across industrial temperatures.

FAQ

What is the guaranteed temperature range for LM4121AIM5X-1.2 initial accuracy?

The LM4121AIM5X-1.2 guarantees ±0.2% initial output voltage accuracy over the industrial temperature range of −40°C to +85°C. While the temperature coefficient (50 ppm/°C) is specified from −40°C to +125°C, the full initial accuracy specification applies only within the −40°C to +85°C ambient range per the official datasheet. Extended-range validation requires direct consultation with TI.

Can LM4121AIM5X-1.2 operate with a 1.5 V supply?

Yes, LM4121AIM5X-1.2 can operate with a 1.5 V supply under light load conditions. The datasheet specifies a minimum input voltage of 1.5 V at 5 mA load; at zero or low load, it functions down to ~1.3 V. However, regulation degrades below 1.5 V, and output accuracy is not guaranteed outside the 1.8–12 V recommended range. For reliable 1.25 V output, maintain VIN ≥ 1.8 V.

Is the REF pin on LM4121AIM5X-1.2 required to be connected?

No, the REF pin (Pin 1) on LM4121AIM5X-1.2 must remain unconnected. It is an internal tap of the 1.25 V bandgap node and is provided only for the fixed-output variant-no external connection is permitted or necessary. Connecting it may disrupt regulation or damage the device. This differs from the adjustable LM4121-ADJ variant, where Pin 1 serves as the ADJ terminal.

How does LM4121AIM5X-1.2 behave during power-down mode?

In power-down mode (EN pin ≤ 0.4 V), LM4121AIM5X-1.2 reduces supply current to <2 µA and disconnects the output from the internal reference, forcing V_OUT to float near GND. The device retains its ability to resume regulation within 10 µs of EN rising above 1.5 V. During shutdown, the REF pin remains inactive and must stay unconnected; no output voltage is delivered until enable is reasserted.

What output capacitor is required for stable operation of LM4121AIM5X-1.2?

LM4121AIM5X-1.2 requires a minimum 0.022 µF ceramic output capacitor (X7R or C0G dielectric) placed close to the OUT and GND pins. Stability is maintained up to 0.047 µF ceramic; larger values (up to 1 µF) require tantalum construction and a 50 pF capacitor between OUT and REF pins. Using capacitors outside this range risks oscillation or degraded transient response.