Analog Devices Inc./Maxim Integrated LM4040BEX3-2.5

Overview

LM4040BEX3-2.5 from Maxim Integrated is a precision 2.500V two-terminal shunt voltage reference in SC70-3 package, featuring 0.2% initial accuracy, ±15 ppm/°C temperature coefficient over –40°C to +125°C, 60µA to 15mA operating current range, and 35 µVRMS wideband noise (10Hz–10kHz). It serves as a stable reference in battery-powered ADCs, portable instrumentation, and industrial sensor signal conditioning circuits.

For engineers reviewing the LM4040BEX3-2.5 datasheet, LM4040BEX3-2.5 pinout, LM4040BEX3-2.5 application, or LM4040BEX3-2.5 equivalent, key selection considerations include guaranteed operation across automotive-grade temperature range, no external capacitor requirement, low dynamic impedance (≤0.8Ω), micropower compatibility down to 60µA, and SC70 footprint constraints for space-constrained PCB layouts.

Technical Context

The LM4040BEX3-2.5 uses a bandgap-based shunt architecture to maintain a precise 2.500V reverse breakdown voltage without series regulation. Its internal pass transistor sinks variable current to hold V_SHUNT constant across load and supply variations, enabling simple biasing with a single source resistor (R_S).

It operates stably with any capacitive load and requires no output capacitor-unlike many series references-due to inherent low-output-impedance design and optimized internal compensation. Temperature drift is bounded by ±15 ppm/°C max over full –40°C to +125°C range, with typical long-term stability of 120 ppm after 1000 hours.

Key Specifications

Pinout & Package

The LM4040BEX3-2.5 is housed in a 3-pin SC70 surface-mount package (1.8mm × 1.8mm), 50% smaller than SOT23 equivalents. Pin 3 is unconnected (N.C.) and must be left floating or tied to pin 2 per datasheet guidance.

Key Features

Applications

Equivalent & Alternatives

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

Compared with TLVH431ACDBVR and MAX6008BEUR+T, the LM4040BEX3-2.5 delivers superior thermal stability (±15 ppm/°C vs. 100/50 ppm/°C), smallest PCB footprint (SC70), and lowest noise (35 µVRMS), making it optimal for high-accuracy, space-constrained, wide-temperature applications.

Availability

LM4040BEX3-2.5 is available at Aetrix Electronics and suitable for portable instrumentation, industrial sensor transmitters, and automotive cabin control modules requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for LM4040BEX3-2.5 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

Maxim Integrated (now part of Analog Devices) is a semiconductor company specializing in precision analog, mixed-signal, and power management ICs for industrial, automotive, and communications markets.

The LM4040 product line delivers micropower, high-accuracy shunt voltage references optimized for space-constrained, battery-operated, and wide-temperature applications where stability, low noise, and minimal external components are essential.

FAQ

What is the guaranteed operating temperature range for LM4040BEX3-2.5?

The LM4040BEX3-2.5 is specified and guaranteed over –40°C to +125°C ambient temperature. This extended range qualifies it for under-hood automotive, industrial process control, and outdoor equipment applications where thermal robustness is mandatory. The device maintains its 0.2% initial accuracy and ±15 ppm/°C tempco performance across this full range, as validated in production testing per datasheet Rev 8.

Does LM4040BEX3-2.5 require an external output capacitor for stability?

No, the LM4040BEX3-2.5 does not require an external output capacitor and remains stable with any capacitive load-including zero capacitance or multi-microfarad bulk caps. This is due to its internally compensated shunt architecture and low dynamic impedance (<0.8Ω). Adding a capacitor provides no stability benefit but may marginally reduce high-frequency noise; the design intentionally eliminates capacitor dependency to simplify BOM and layout.

What is the minimum operating current for LM4040BEX3-2.5, and why does it matter?

The LM4040BEX3-2.5 has a guaranteed minimum operating current (I_RMIN) of 60 µA across temperature. Below this, regulation is not assured and output voltage may deviate significantly. This low threshold enables use in ultra-low-power systems-such as coin-cell IoT sensors-that spend most time in deep-sleep mode while keeping the reference active for rapid wake-up ADC conversions without startup delay.

How does the pin configuration of LM4040BEX3-2.5 differ from standard three-terminal references?

The LM4040BEX3-2.5 uses a two-terminal functional configuration implemented in a 3-pin SC70 package: pin 1 is anode (+), pin 2 is cathode (–/output), and pin 3 is N.C. (no connection). Pin 3 must be left unconnected or tied to pin 2-never driven-because it has no internal bond wire or circuit function. This differs from traditional three-terminal references that use all pins for input/output/control, allowing simpler routing and eliminating misconnection risk.

Can LM4040BEX3-2.5 replace LM4040CIX3-2.5 in an existing design?

Yes, the LM4040BEX3-2.5 can directly replace LM4040CIX3-2.5 in most designs because both share identical SC70-3 package, pinout, and electrical behavior-except for tighter initial accuracy (0.2% vs. 0.5%) and same ±15 ppm/°C tempco. No PCB or schematic changes are needed; the upgrade improves reference precision without affecting layout, thermal performance, or supply current requirements.