Texas Instruments LM431CIM3

Overview

LM431CIM3 from Texas Instruments is a precision adjustable shunt voltage regulator in SOT-23-3 package, featuring 2.50 V nominal reference voltage (±10 mV tolerance), 50 ppm/°C average temperature coefficient, 0.5 Ω typical dynamic output impedance, and guaranteed operation from –40°C to +85°C. It replaces Zener diodes in linear power supplies, voltage monitors, and current sink circuits requiring stable 2.5–36 V programmable regulation.

For engineers reviewing the LM431CIM3 datasheet, LM431CIM3 pinout, LM431CIM3 application, or LM431CIM3 equivalent, key selection criteria include its industrial-grade temperature range, low-reference-input-current (2–4 μA), fast turn-on response, low-output-noise performance, and compatibility with standard resistor-divider feedback networks for precise output programming.

Technical Context

The LM431CIM3 operates as a 3-terminal shunt regulator using an internal bandgap reference and transconductance amplifier to maintain cathode voltage via controlled current shunting. Its reference pin senses a fraction of cathode voltage through external resistors, enabling programmable output from 2.5 V to 36 V with minimal quiescent current.

It functions in closed-loop regulation mode (with resistor divider feedback) or open-loop comparator mode. Regulation requires cathode current between 1 mA and 100 mA; minimum operating current is 0.4 mA at full temperature range. Thermal hysteresis is induced by package stress, not circuit design.

Key Specifications

Pinout & Package

SOT-23-3 package (DBZ drawing), 2.92 mm × 1.30 mm body size, single-row 3-pin surface-mount format with gull-wing leads. RoHS-compliant, lead-free CU SN finish, MSL Level-1.

Key Features

Applications

Equivalent & Alternatives

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

Compared with TL431CDBVR and AS431ASTU, the LM431CIM3 provides superior thermal stability (50 ppm/°C vs. 60/100 ppm/°C) and lower dynamic impedance (0.5 Ω vs. 0.75/1.2 Ω), making it preferred for industrial power supplies and precision monitoring where long-term accuracy and transient immunity matter.

Availability

LM431CIM3 is available at Aetrix Electronics and suitable for industrial power supplies, automotive voltage monitors, LED current sinks, and precision reference circuits requiring stable component supply across extended temperature ranges.

Supply support for LM431CIM3 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 headquartered in Dallas, Texas, delivering analog and embedded processing solutions for industrial, automotive, and personal electronics markets.

The LM431 product line was designed as a precision, temperature-stable alternative to Zener diodes for shunt regulation in space-constrained, high-reliability applications - emphasizing low drift, low noise, and flexible programmability.

FAQ

What is the maximum cathode voltage rating for the LM431CIM3?

The LM431CIM3 has an absolute maximum cathode voltage rating of 37 V. Operation above this level risks permanent damage. The recommended operating range extends from V_REF (2.5 V) up to 36 V, ensuring safe and specified performance across the full industrial temperature range of –40°C to +85°C. Always observe derating curves for thermal management at elevated ambient temperatures.

Can the LM431CIM3 be used as a comparator?

Yes, the LM431CIM3 can operate in open-loop comparator mode. When the reference pin is driven by an external voltage source instead of a resistor divider, the device switches its cathode current based on whether the reference voltage exceeds 2.5 V. This enables overvoltage/undervoltage detection, delay timers, or crowbar circuits - though propagation delay and hysteresis are not characterized in the datasheet.

What is the minimum cathode current required for regulation in the LM431CIM3?

The LM431CIM3 requires a minimum cathode current of 1 mA for guaranteed regulation across its full operating temperature range (–40°C to +85°C). At 25°C, regulation begins at 0.4 mA, but design margins must account for the 1 mA minimum to ensure stability under worst-case conditions including temperature extremes and parameter variation.

How does the LM431CIM3 differ from the LM431AIM3?

The LM431CIM3 and LM431AIM3 share identical SOT-23-3 packaging and pinout, but differ in reference voltage tolerance and temperature grade. The LM431CIM3 has a 2.50 V reference with ±10 mV max deviation (C-grade), while the LM431AIM3 is A-grade (±5 mV) and also rated for –40°C to +85°C. Both use the same DBZ package and electrical architecture.

Is a bypass capacitor required for stable operation of the LM431CIM3?

A bypass capacitor is not strictly required for basic regulation, but Texas Instruments recommends a 0.1 µF ceramic capacitor placed physically close to the cathode pin to suppress high-frequency noise and improve stability - especially in switching power supply feedback paths or noisy industrial environments. Layout guidelines emphasize minimizing trace length to the cathode and reference pins.