Texas Instruments LM4128CMF-3.3

Overview

LM4128CMF-3.3 from Texas Instruments (formerly National Semiconductor) is a precision micropower series voltage reference in SOT-23-5 package, delivering 3.3 V output with ±0.5% initial accuracy, 100 ppm/°C temperature coefficient, and 60 µA quiescent current. It features an enable pin for shutdown mode (3 µA), supports up to 20 mA load, and operates across −40°C to +125°C - ideal for battery-powered instrumentation and portable data acquisition.

For engineers reviewing the LM4128CMF-3.3 datasheet, LM4128CMF-3.3 pinout, LM4128CMF-3.3 application, or LM4128CMF-3.3 equivalent, key selection considerations include its low dropout (400 mV @10 mA), stability with capacitive loads up to 10 µF, absence of required external stabilization capacitor, and grade-specific tempco/accuracy trade-offs for cost-sensitive industrial designs.

Technical Context

The LM4128CMF-3.3 uses a band-gap–derived reference core optimized for micropower operation, with internal circuitry eliminating need for external stabilization capacitance while maintaining stability into 10 µF capacitive loads. Its series architecture avoids idle current waste typical of shunt references, enabling efficient use in low-power systems.

It integrates an enable input (EN) that controls biasing of the reference core, reducing supply current to 3–7 µA in shutdown. The device maintains regulation over VIN = VREF + 400 mV to 5.5 V, with line regulation of 85 ppm/V and load regulation of 25–120 ppm/mA - critical for precision ADC biasing and sensor excitation circuits.

Key Specifications

Pinout & Package

SOT-23-5 package (NS package number MF05A), surface-mount, 5-pin plastic small-outline transistor outline with exposed pad not present; footprint compatible with standard SOT-23-5 land patterns.

Key Features

Applications

Equivalent & Alternatives

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

Compared with REF3033AIDBZR and MAX6029AEUR+T, the LM4128CMF-3.3 uniquely combines grade-tailored accuracy/tempco, integrated enable for ultra-low standby power, and capacitor-free stability - making it optimal for cost-sensitive, battery-operated industrial and portable instrumentation where dynamic power management is essential.

Availability

LM4128CMF-3.3 is available at Aetrix Electronics and suitable for portable medical monitors, industrial sensor transmitters, battery-powered data loggers, and automotive cabin sensors requiring stable component supply with consistent parametric performance across production lots.

Supply support for LM4128CMF-3.3 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 acquired National Semiconductor in 2011 and maintains full product continuity, quality assurance, and technical documentation for the LM4128 family.

The LM4128 series was designed as a micropower, precision series voltage reference targeting space-constrained, battery-operated instrumentation and industrial sensing applications where low dropout, enable control, and capacitor-free stability are critical.

FAQ

What is the maximum load current supported by the LM4128CMF-3.3?

The LM4128CMF-3.3 supports up to 20 mA output current while maintaining regulation within specified accuracy and dropout limits. This enables direct driving of moderate-current analog circuitry such as op-amp bias networks or low-power DACs without external buffering - verified across −40°C to +125°C per Electrical Characteristics table.

Does the LM4128CMF-3.3 require an external output capacitor?

No, the LM4128CMF-3.3 is stable without an external output capacitor and remains stable with capacitive loads up to 10 µF. An output capacitor is optional and used only to improve load transient response - the device's internal design eliminates the need for mandatory stabilization capacitance, reducing BOM count and PCB area.

What is the purpose of Pin 1 (N/C) on the LM4128CMF-3.3?

Pin 1 of the LM4128CMF-3.3 is a no-connect (N/C) terminal with no internal connection. It must be left unconnected and floating - neither tied to ground nor used for thermal relief. This pin exists due to SOT-23-5 package constraints and has zero electrical function in the LM4128CMF-3.3.

How does the enable (EN) pin function on the LM4128CMF-3.3?

The EN pin (Pin 3) is an active-high digital control input. When driven above 65% of VIN, the LM4128CMF-3.3 operates normally; when below 35% of VIN, it enters shutdown mode drawing only 3–7 µA. The pin features an internal ~2 µA pull-up, allowing direct connection to VIN for always-on operation or microcontroller GPIO for dynamic power gating.

What is the minimum input voltage required for the LM4128CMF-3.3 to regulate at 3.3 V?

The LM4128CMF-3.3 requires VIN ≥ VREF + 400 mV = 3.7 V to maintain regulation at full load (10 mA). At lighter loads, dropout decreases - e.g., 175 mV at 10 mA for 3.3 V variants per Electrical Characteristics - but 3.7 V is the guaranteed minimum for specified accuracy across temperature and load conditions.