Texas Instruments LM4121IM5-1.2

Overview

LM4121IM5-1.2 from Texas Instruments (formerly National Semiconductor) is a precision micropower low-dropout voltage reference IC delivering a fixed 1.25 V output with ±0.5% initial accuracy, 50 ppm/°C temperature coefficient, and ±5 mA source/sink capability in SOT-23-5 package. 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). It is used in portable instrumentation, battery-powered data acquisition, and precision regulators where stable low-power reference voltage is critical.

For engineers reviewing the LM4121IM5-1.2 datasheet, LM4121IM5-1.2 pinout, LM4121IM5-1.2 application, or LM4121IM5-1.2 equivalent, key selection criteria include its 1.25 V fixed output, industrial temperature range (−40°C to +85°C), low dropout operation down to 1.5 V input at full load, enable-controlled power-down, and SOT-23-5 footprint compatibility with space-constrained PCB layouts.

Technical Context

The LM4121IM5-1.2 implements a bandgap-based reference core with internal trimming for initial accuracy and thermal compensation to achieve guaranteed 50 ppm/°C drift over −40°C to +125°C. Its enable pin controls a high-impedance shutdown path that reduces ground current to <2 µA while maintaining fast wake-up response.

Designed for low-voltage systems, it maintains regulation with as little as 1.5 V input at 5 mA load (dropout ≤300 mV), supports bidirectional load current (±5 mA), and achieves 0.012%/V line regulation and 0.17%/mA load regulation - enabling use in precision ADC biasing, sensor excitation, and closed-loop regulator feedback without external buffering.

Key Specifications

Pinout & Package

SOT-23-5 surface-mount package (2.92 mm × 1.6 mm × 1.1 mm), tape-and-reel packaging, RoHS-compliant, rated for industrial temperature range (−40°C to +85°C).

Key Features

Applications

Equivalent & Alternatives

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

Compared with LM4121IM5-1.2, LM4040CIM3-ADJ requires external biasing and offers no enable control, while MAX6012AEUR+T improves accuracy and tempco but sacrifices shutdown functionality and uses a 3-pin package - making LM4121IM5-1.2 uniquely suited for battery-powered systems needing both precision and dynamic power gating.

Availability

LM4121IM5-1.2 is available at Aetrix Electronics and suitable for portable instrumentation, precision data acquisition, and medical sensor modules requiring stable component supply, long-lifecycle support, and consistent parametric performance across production batches.

Supply support for LM4121IM5-1.2 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 delivering analog and embedded processing solutions, with deep heritage in precision analog from its acquisition of National Semiconductor in 2011.

The LM4121 product line was developed to address demand for micropower, low-dropout, enable-capable voltage references in space- and energy-constrained applications - particularly portable test equipment, battery management, and industrial sensors.

FAQ

What is the maximum load current the LM4121IM5-1.2 can source or sink?

The LM4121IM5-1.2 is specified to source and sink up to ±5 mA continuously while maintaining output voltage accuracy within datasheet limits. This bidirectional capability allows direct interfacing with op-amp inputs, comparator references, or small logic loads without external buffers. At 5 mA sink, minimum input voltage rises to 1.5 V; derating applies beyond this point per the dropout voltage curve in the datasheet.

Does the LM4121IM5-1.2 require an output capacitor, and if so, what value and type?

Yes - the LM4121IM5-1.2 requires a minimum 0.022 µF ceramic capacitor (X7R or better) between VOUT and GND for stability, as confirmed in the datasheet's Application Hints section. Values up to 0.047 µF ceramic are fully supported; larger values (up to 1 µF) require tantalum construction and additional 50 pF capacitor between VOUT and REF pins. Omitting the capacitor risks oscillation and degraded noise performance.

What is the function of Pin 1 (REF) on the LM4121IM5-1.2, and how should it be connected?

Pin 1 (REF) is unused in the LM4121IM5-1.2 fixed 1.25 V version and must be left unconnected (open circuit). It is reserved for the adjustable variant (LM4121IM5-ADJ), where it serves as the reference node for external resistor feedback. Connecting or loading Pin 1 on the -1.2 version may cause output inaccuracy or instability due to internal node contention.

How does the enable pin (Pin 3) of the LM4121IM5-1.2 behave during power-down?

When Pin 3 (EN) is pulled to ≤0.4 V, the LM4121IM5-1.2 enters power-down mode, disabling the reference output and reducing total supply current to <2 µA (at VIN = 12 V). The output goes into high-impedance state; recovery time to full regulation is typically <10 µs after EN rises above 1.5 V. No external pull-up is required - EN may be driven directly from CMOS/TTL logic outputs.

Is the LM4121IM5-1.2 rated for operation beyond the industrial temperature range?

The LM4121IM5-1.2 is characterized and guaranteed over the industrial temperature range of −40°C to +85°C. While certain parameters - including temperature coefficient (50 ppm/°C) - are guaranteed from −40°C to +125°C, full electrical specifications (e.g., initial accuracy, line/load regulation) are not validated above +85°C. For extended-range operation, consult TI's official documentation or consider the LM4121AIM5-1.2 (A-grade) with tighter initial tolerance.