LM4040D25FTA - 2.5V Shunt Voltage Reference, ±1%, 15mA
MPN: LM4040D25FTA ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $0.36 | $0.36 |
| 10 | $0.32 | $3.20 |
| 100 | $0.27 | $27.00 |
| 500 | $0.23 | $115.00 |
| 1,000 | $0.19 | $190.00 |
| 3,000 | $0.16 | $480.00 |
LM4040D25FTA Overview
A shunt voltage reference is a two-terminal device that behaves like a precision zener diode: current flows through it in the reverse direction and the device holds its terminal voltage constant over a wide range of operating current. Compared with a series (3-terminal) reference such as the TL431, the LM4040 is simpler — no feedback resistors, no minimum dropout voltage drop across a series pass element — and is the standard building block for power management ICs -> voltage references -> shunt references. Its sub-1 mA quiescent capability makes it ideal for battery-powered and micropower designs.
Key features include ±1% initial tolerance at +25 °C (D-grade), typical 20 ppm/°C temperature coefficient, 45 µVrms output noise (10 Hz to 10 kHz), and excellent line/load stability. The SOT-23-3 footprint occupies roughly 8 mm² of board area, making the device the smallest precision reference in the LM4040 family. Operating temperature range is -40 °C to +85 °C (commercial) or -40 to +125 °C (automotive Q-grade, see LM4040Q datasheet).
Architecturally, the LM4040 uses a curvature-compensated bandgap reference with on-chip op-amp buffering, then presents the buffered reference at the cathode pin. The two-terminal topology is the simplest reference architecture: the user simply chooses a series resistor from the supply rail, sized so that the worst-case quiescent and load current together keep the device above 60 µA and below 15 mA across temperature. Because the bandgap loop is internally compensated, the device is unconditionally stable with 0 nF to 10 µF of load capacitance — a major advantage over many 3-terminal LDOs repurposed as references.
Typical applications include ADC and DAC reference inputs, precision threshold detectors, solar/battery monitoring circuits, instrumentation loop power, and as a precision reference for 4-20 mA loops. Designers should also use the LM4040 as a stable pull-up for opto-isolators or as a low-noise reference for portable instrumentation where TL431 quiescent current is excessive. For audio or RF signal chains the 45 µVrms noise is adequate for most 16-bit systems; for higher resolution consider the LT1460 or ADR45xx families.
When designing with this device, calculate the series resistor for worst-case supply, load, and temperature so the LM4040 stays above 60 µA and below 15 mA. A 1 mA midpoint with a 5 V supply and 2.5 V reference drops 2.5 V across a 2.5 kΩ resistor, dissipating 2.5 mW. Reverse-polarity protection on the supply side is recommended if the input can be replaced.
This page synthesizes distributor pricing, drop-in alternatives, and practical design notes not found in the manufacturer datasheet.
Drop-in alternatives for LM4040D25FTA — same package, pin-to-pin compatible. Different-package parts requiring PCB rework are excluded.
Variants in this series
Same-series models that are drop-in compatible with LM4040D25FTA (same form factor and footprint) — differing in Output Voltage.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
LM4040DIM3-2.5/NOPB
✅ Drop-In📋 Reference alternative (not in catalog)
LM4040BIM3-2.5/NOPB
✅ Drop-In📋 Reference alternative (not in catalog)
LM4040CIM3-2.5/NOPB
✅ Drop-In📋 Reference alternative (not in catalog)
LM4040DEM3-2.5/NOPB
✅ Drop-In📋 Reference alternative (not in catalog)
ADR425ARZ
✅ Drop-In📋 Reference alternative (not in catalog)
LM4040D25FTA Specifications
| Reference Type | Shunt Voltage Reference |
| Output Voltage | 2.5 V (fixed) |
| Initial Accuracy (D-grade) | ±1% (at +25 °C) |
| Cathode Operating Current | 60 µA to 15 mA |
| Reverse Dynamic Impedance | 0.5 ohm (at 1 mA, typ) |
| Output Noise (10 Hz to 10 kHz) | 45 µVrms (typ) |
| Temperature Coefficient | 20 ppm/°C (typ), 150 ppm/°C max (D-grade) |
| Operating Temperature Range | -40 °C to +85 °C |
| Power Dissipation | 330 mW |
| Package | SOT-23-3 |
| Pin Count | 3 |
| Topology | 2-terminal shunt (no series pass element) |
| Output Capacitor Required | No (stable with 0 to 10 µF load) |
| Pin-to-Pin Compatible With | LM4040-2.5 family |
| RoHS Status | Compliant |
LM4040D25FTA Pin Configuration
| Pin 1 | K (Cathode) — Cathode - reference output, internally shorted to pin 3 |
| Pin 2 | A (Anode) — Anode - reference ground, connect to system GND |
| Pin 3 | K (Cathode) — Cathode - reference output, internally shorted to pin 1 |
Typical Applications
LM4040D25FTA is suitable for 6 applications: ADC/DAC Voltage Reference, Portable Battery Monitoring Circuit, Precision Threshold Detector, 4-20 mA Current Loop Reference, Solar Panel / Energy Harvesting Reference, Instrumentation Loop Power Reference.
ADC/DAC Voltage Reference
The LM4040D25FTA provides a clean, stable 2.5 V rail for 12- to 16-bit ADC and DAC reference pins, where any reference noise or drift directly becomes measurement error. The device's 45 µVrms noise (10 Hz to 10 kHz) and 20 ppm/°C typical temperature coefficient keep the reference stable over the operating range. Placed between the analog supply rail and the ADC REFIN pin via a series resistor biased at 1 mA, the LM4040D25FTA eliminates the need for a separate reference IC in many data-acquisition designs. Unlike a 3-terminal reference, no bypass cap is required because the device is unconditionally stable with 0 to 10 µF of load capacitance.
Recommended
Portable Battery Monitoring Circuit
In Li-ion and LiPo battery monitoring designs, the LM4040D25FTA supplies the reference for the ADC that monitors cell voltage, enabling accurate state-of-charge calculations. Its 60 µA minimum operating current means it can be left permanently biased without draining the cell, while its 15 mA maximum permits direct connection to multiple analog inputs. The wide cathode current range lets a single series resistor handle worst-case load transients from 60 µA to 15 mA without losing regulation. Compared with a TL431, the LM4040D25FTA's micropower capability extends battery life by approximately 70% in always-on monitoring designs.
Recommended
Precision Threshold Detector
The LM4040D25FTA combined with a low-offset comparator forms a precision threshold detector with a switching point stable across temperature. By tying the comparator reference input to the LM4040's 2.5 V rail, the threshold is immune to supply drift, and 20 ppm/°C typical temperature coefficient gives sub-100 µV drift over -40 to +85 °C. This topology is widely used in industrial control loops, over-voltage protection circuits, and precision window comparators. The shunt topology allows the LM4040 to be biased from the same rail as the comparator, simplifying PCB layout and reducing component count.
Recommended
4-20 mA Current Loop Reference
In 4-20 mA industrial current-loop designs, the LM4040D25FTA provides a stable 2.5 V reference for the sense resistor and ADC input, where loop accuracy depends directly on reference stability. Its 0.5 ohm typical dynamic impedance at 1 mA keeps the reference stable even when the loop current varies with load. The 15 mA maximum cathode current allows the device to be biased directly from the loop supply. Operating across -40 to +85 °C, the LM4040D25FTA maintains reference accuracy over the full industrial temperature range required by IEC 61131-2.
Recommended
Solar Panel / Energy Harvesting Reference
In solar and energy-harvesting systems the LM4040D25FTA biases the MPPT controller's voltage sense circuit, where the 60 µA minimum cathode current allows the reference to remain stable from the harvested current even at low light levels. With 20 ppm/°C typical temperature coefficient, the reference remains accurate across outdoor temperature swings. The shunt device is particularly suited to variable-input energy-harvesting because its two-terminal nature means the series resistor can absorb wide input voltage variations without affecting the reference voltage. This makes the LM4040D25FTA ideal for solar-powered IoT sensor nodes.
Recommended
Instrumentation Loop Power Reference
In medical and industrial instrumentation, the LM4040D25FTA provides a 2.5 V rail for transducer excitation circuits, including strain-gauge bridges, RTD signal conditioning, and thermistor networks. Its low 45 µVrms noise floor ensures the excitation does not couple noise into the sensor signal path, preserving measurement resolution. The 330 mW dissipation rating allows the device to be biased at several mA for low-impedance sensors. Combined with a precision op-amp such as the INA128, the LM4040D25FTA forms a complete, accurate analog front-end for weighing scales and process-control instrumentation.
Recommended
Recommended Products Summary
Engineering reference data for LM4040D25FTA — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | LM4040DIM3-2.5/NOPB | LM4040BIM3-2.5/NOPB | LM4040CIM3-2.5/NOPB | LM4040DEM3-2.5/NOPB | ADR425ARZ |
|---|---|---|---|---|---|---|
| Brand | Diodes Incorporated | Texas Instruments | Texas Instruments | Texas Instruments | Texas Instruments | Analog Devices |
| Package | SOT-23-3 | SOT-23-3 - same | SOT-23-3 - same | SOT-23-3 - same | SOT-23-3 - same | SOT-23-3 (SOIC-8 / TO-92 also avail) - same |
| Output Voltage | 2.5 V | 2.5 V | 2.5 V | 2.5 V | 2.5 V | 2.5 V |
| Initial Accuracy | ±1% (D-grade) | ±1% (D) | ±0.2% (B) | ±0.5% (C) | ±1% (D) | ±0.2% |
| Cathode Current Range | 60 µA to 15 mA | 60 µA to 15 mA | 60 µA to 15 mA | 60 µA to 15 mA | 60 µA to 15 mA | 0.5 mA to 3 mA (lower max current) |
| Max Cathode Current | 15 mA | 15 mA | 15 mA | 15 mA | 15 mA | 3 mA |
| Temperature Coefficient (typ) | 20 ppm/°C | 20 ppm/°C | 20 ppm/°C | 20 ppm/°C | 20 ppm/°C | 5 ppm/°C (better) |
| Operating Temperature | -40 to +85 °C | -40 to +85 °C | -40 to +85 °C | -40 to +85 °C | -40 to +125 °C (extended/automotive) | -40 to +125 °C |
| Output Capacitor Required | No (stable with 0 to 10 µF) | No | No | No | No | No |
Key Differentiators
- Active mass-production status with broad distributor stock (vs LM4040D25IDCKR (SC-70-5))
- Pin-for-pin compatible with TI LM4040-2.5 family (vs ADR425ARZ (Analog Devices))
- 15 mA maximum cathode current — 5× higher than ADR425 (vs ADR425ARZ (Analog Devices))
- No output capacitor required — unconditionally stable (vs Most 3-terminal references)
Design Notes
Calculate the series bias resistor R_series = (V_SUPPLY - V_REF) / I_KA. For a 5 V supply, 2.5 V reference, and 1 mA midpoint: R_series = (5 - 2.5) / 1 mA = 2.5 kΩ, dissipating 2.5 mW. Verify the worst-case end of regulation: at low temperature I_KA_min may rise to 80 µA; at high temperature it may drop to 50 µA. Always bias above 60 µA at worst case (lowest temperature, maximum load). At maximum I_KA = 15 mA, power dissipation = 2.5 V × 15 mA = 37.5 mW, well below the 330 mW SOT-23-3 limit.
The SOT-23-3 package has a typical θJA of approximately 250 °C/W on a standard 1-oz 4-layer JEDEC test board, so 37.5 mW worst-case dissipation raises the junction only 9 °C above ambient — no heatsinking is required. However, if the user mounts the device on a 2-layer board with minimal copper pour, θJA can rise to 400 °C/W. Always check the actual PCB thermal resistance for high-I_KA designs. For continuous 15 mA operation at +85 °C ambient, prefer a small copper pour (≥10 mm²) on the cathode pads to keep junction temperature within safe limits.
Place the LM4040D25FTA close to the load (ADC reference pin) to minimize PCB trace resistance, which appears in series with the device's dynamic impedance and degrades load regulation. Keep high-current switching traces (DC-DC converters, motor drivers) away from the reference, since their switching noise can couple through parasitic capacitance into the high-impedance cathode node. A guard ring connected to the anode pin around the cathode pin can reduce leakage by 10× in high-impedance precision applications. Keep the series bias resistor close to the cathode pin to minimize the high-impedance trace length.
Do NOT apply reverse voltages exceeding -6 V to the LM4040D25FTA — the device is not reverse-polarity tolerant and will be damaged. Do NOT exceed 15 mA cathode current or 330 mW power dissipation. Do NOT bypass the cathode with a large capacitor (>10 µF) without verifying current-limit behavior — although the datasheet claims capacitive-load stability, the combination of high cathode current and large cap can cause oscillation on some lots. Do NOT rely on the SC-70-5 LM4040D25IDCKR for new designs — Diodes has EOL'd the SC-70-5 variants and only the SOT-23-3 LM4040D25FTA remains in active production.
Compliance Information
RoHS compliant per DigiKey product listing. SOT-23-3 is lead-free matte-tin plated per JEDEC J-STD-020 MSL1. Not AEC-Q100 qualified — for automotive applications use the LM4040Q family (Diodes LM4040 datasheet mentions AEC-Q100 approval for Q-grade). SC-70-5 variants are EOL.
