LM4040AIM3-2.5/NOPB - 2.5V Shunt Voltage Reference | Texas Instruments
MPN: LM4040AIM3-2.5/NOPB ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $0.97 | $0.97 |
| 10 | $0.87 | $8.70 |
| 100 | $0.72 | $72.00 |
| 500 | $0.58 | $290.00 |
| 1,000 | $0.48 | $480.00 |
LM4040AIM3-2.5/NOPB Overview
A shunt voltage reference is a two-terminal (plus a third pin for the SOT-23 package outline) analog building block that operates like a precision zener diode. When biased with a small current sourced through a series resistor from a higher supply rail, it produces a stable, low-noise reference voltage. Within the broader hierarchy, the LM4040 sits below adjustable references (e.g., LM4041) and series references (e.g., TL431) and above simple zener diodes, providing far better temperature stability, lower noise, and tighter initial tolerance for analog signal-chain design.
Key features of the LM4040AIM3-2.5/NOPB include ±0.1% initial accuracy (A-grade), 100 ppm/°C maximum temperature coefficient, 45 µA typical cathode current, low dynamic impedance, and stable operation with any capacitive load - no external stabilizing capacitor is required. The fixed 2.5 V output is compatible with 12-bit and 16-bit ADC full-scale references and is a common system reference in mixed-signal designs.
The device uses a band-gap core that compensates curvature across temperature, achieving 100 ppm/°C drift from -40 °C to +125 °C. The SOT-23-3 (DBZ) package is approximately 50% smaller than comparable SC70 packages from some second sources, freeing PCB area for space-constrained designs such as portable instrumentation.
Typical applications include ADC/DAC reference rails, precision threshold detectors, battery monitoring in portable equipment, power-supply supervisory circuits, and loop control for industrial sensors. The fixed 2.5 V output maps directly onto many ADCs whose LSB quantization matches this reference.
When biasing the LM4040AIM3-2.5/NOPB, choose a series resistor that supplies at least 45 µA at minimum cathode current and limits the current to under 15 mA across all input and temperature conditions. Place the device close to the load to minimize ground-loop noise.
This page synthesizes distributor pricing, drop-in alternatives, and practical design notes not found in the manufacturer datasheet, enabling faster selection and second-source qualification for production engineers.
Drop-in alternatives for LM4040AIM3-2.5/NOPB — 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 LM4040AIM3-2.5/NOPB (same form factor and footprint) — differing in Dynamic Impedance, Output Voltage, Package.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
LM4040BIM3-2.5/NOPB
✅ Drop-In📋 Reference alternative (not in catalog)
LM4040CIM3-2.5/NOPB
✅ Drop-In📋 Reference alternative (not in catalog)
LM4040DIM3-2.5/NOPB
✅ Drop-In📋 Reference alternative (not in catalog)
LM4040AIM3X-2.5/NOPB
✅ Drop-In📋 Reference alternative (not in catalog)
LM4040AIM3-2.5+T
✅ Drop-In📋 Reference alternative (not in catalog)
LM4040AIM3-2.5/NOPB Specifications
| Reference Type | Shunt Voltage Reference |
| Output Voltage | 2.5 V (fixed) |
| Initial Accuracy (A-grade) | ±0.1% |
| Temperature Coefficient | 100 ppm/°C (maximum) |
| Minimum Cathode Current | 45 µA (typical) |
| Maximum Cathode Current | 15 mA |
| Dynamic Impedance | Low (per datasheet curve) |
| Operating Temperature Range | -40 °C to +125 °C |
| Package | SOT-23-3 (DBZ) |
| Pin Count | 3 |
| Mounting Type | Surface Mount |
| External Capacitor Required | No - stable with any capacitive load |
| MSL Level | 1 (per JEDEC J-STD-020) |
| RoHS Status | Compliant |
| Lead-Free (NOPB suffix) | Yes |
LM4040AIM3-2.5/NOPB Pin Configuration
| Pin 1 | CATHODE — Cathode (reference output / bias input) |
| Pin 2 | ANODE — Anode (ground reference) |
| Pin 3 | NC — Not connected (mechanical mounting pin per SOT-23-3 outline) |
Typical Applications
LM4040AIM3-2.5/NOPB is suitable for 7 applications: 12-bit/16-bit ADC Reference Rail, Precision Comparator Reference, Portable Battery Monitor, Power Supply Supervisory Circuit, Industrial Process Control Loop, Data Acquisition System Reference, Digital Multimeter Reference.
12-bit/16-bit ADC Reference Rail
The LM4040AIM3-2.5/NOPB's fixed 2.5 V output maps directly onto 12-bit and 16-bit ADC full-scale reference inputs, providing a stable low-noise rail that directly determines conversion accuracy. With ±0.1% A-grade initial tolerance and 100 ppm/°C drift, the reference contributes less than 1 LSB of gain error across the operating temperature range for a 12-bit ADC. Placed at the ADC REFIN pin with a 1 kΩ to 10 kΩ bias resistor from the analog 5 V rail and a 0.1 µF local bypass, the LM4040AIM3-2.5/NOPB eliminates the need for a buffer amplifier and the associated offset error. Compared to a TL431 adjustable reference, no external resistor divider is required, reducing BOM cost and drift contribution.
Recommended
Precision Comparator Reference
The LM4040AIM3-2.5/NOPB provides a stable 2.5 V threshold reference for window detectors, over-voltage protection circuits, and precision comparator rails. The ±0.1% initial accuracy ensures consistent trip-point thresholds across production units, while the 100 ppm/°C drift maintains accuracy across the -40 °C to +125 °C automotive and industrial temperature range. Used at the inverting input of a comparator paired with a resistive divider, the device produces a clean, low-noise threshold. Unlike a resistor divider alone, the LM4040 holds the threshold steady across supply variations, ensuring reliable operation in industrial control and battery-management systems where supply rails vary widely.
Recommended
Portable Battery Monitor
The LM4040AIM3-2.5/NOPB's micropower 45 µA typical minimum cathode current makes it ideal for battery-powered portable equipment where standby current directly drains cell capacity. Operating from a 3.3 V or 5 V rail through a series bias resistor, the device provides a stable 2.5 V reference for the ADC inside a battery-fuel-gauge IC, enabling coulomb-counting accuracy within 1% across the discharge curve. The SOT-23-3 (DBZ) footprint measures only 2.9 mm × 1.6 mm, taking minimal PCB area inside handheld medical, fitness, and IoT sensor devices. The reference draws essentially zero extra current when the host is in sleep mode, supporting multi-year coin-cell operation.
Recommended
Power Supply Supervisory Circuit
The LM4040AIM3-2.5/NOPB serves as a precision reference rail in power-supply supervisory circuits, where it produces a stable 2.5 V reference against which a supervisor IC compares the main supply rail. This enables accurate under-voltage, over-voltage, and power-good detection in industrial PLCs, telecom equipment, and server motherboards. The 100 ppm/°C temperature coefficient keeps the supervisory threshold stable across ambient temperature swings from cold boot to full operation, preventing nuisance resets in field-deployed equipment. With its 15 mA maximum cathode current, the LM4040 can directly drive the reference input of multiple supervisory comparators on the same rail.
Recommended
Industrial Process Control Loop
The LM4040AIM3-2.5/NOPB provides a precision 2.5 V reference for 4-20 mA current-loop transmitters, RTD excitation, and strain-gauge bridge excitation in industrial process control. The ±0.1% initial accuracy combined with 100 ppm/°C drift ensures loop accuracy better than 0.2% across the -40 °C to +85 °C industrial range, sufficient for Class I and Class II process instrumentation. Operating as a stable excitation source for a 2.5 V-referenced bridge, the device enables ratiometric ADC readings where bridge output is scaled directly to the reference, eliminating absolute reference drift from the measurement. The shunt topology allows direct connection to a current-source bias network in 2-wire loop-powered field transmitters.
Recommended
Data Acquisition System Reference
The LM4040AIM3-2.5/NOPB provides a stable 2.5 V system reference inside multi-channel data acquisition systems, where a single reference drives multiple ADC channels simultaneously. The low output impedance across the 45 µA to 15 mA cathode current range holds the reference steady as multiple ADC sample-and-hold capacitors switch, preventing channel-to-channel crosstalk via the reference rail. The 2.5 V output is a common full-scale reference for many precision ADCs (e.g., the ADS1256 family) and enables direct interface without divider resistors. The SOT-23-3 package allows tight placement near the ADC reference pin, minimizing PCB trace impedance for lowest reference-noise coupling into the conversion result.
Recommended
Digital Multimeter Reference
The LM4040AIM3-2.5/NOPB provides a precision 2.5 V reference for handheld and benchtop digital multimeters (DMMs), where it serves as the absolute voltage reference against which the ADC measures unknown inputs. With ±0.1% initial accuracy and 100 ppm/°C drift, the LM4040 supports DMM accuracy classes up to 0.5% on DC voltage ranges without requiring periodic user calibration. The shunt topology allows the reference to share a bias network with the ohms-measurement current source, simplifying the analog signal path. Operating from a 9 V or 12 V internal battery through a series bias resistor, the LM4040 maintains regulation even as battery voltage sags during field use.
Recommended
Recommended Products Summary
Engineering reference data for LM4040AIM3-2.5/NOPB — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | LM4040BIM3-2.5/NOPB | LM4040CIM3-2.5/NOPB | LM4040DIM3-2.5/NOPB | LM4040AIM3X-2.5/NOPB | LM4040AIM3-2.5+T |
|---|---|---|---|---|---|---|
| Package | SOT-23-3 (DBZ) | SOT-23-3 (DBZ) | SOT-23-3 (DBZ) | SOT-23-3 (DBZ) | SOT-23-3 (DBZ) | SOT-23-3 |
| Brand | Texas Instruments | Texas Instruments | Texas Instruments | Texas Instruments | Texas Instruments | Analog Devices |
| Output Voltage | 2.5 V | 2.5 V | 2.5 V | 2.5 V | 2.5 V | 2.5 V |
| Initial Accuracy | ±0.1% (A-grade) | ±0.2% (B-grade) | ±0.5% (C-grade) | ±1.0% (D-grade) | ±0.1% (A-grade) | ±0.1% (A-grade) |
| Temperature Coefficient | 100 ppm/°C max | 100 ppm/°C max | 100 ppm/°C max | 100 ppm/°C max | 100 ppm/°C max | 100 ppm/°C max |
| Maximum Cathode Current | 15 mA | 15 mA | 15 mA | 15 mA | 15 mA | 15 mA |
| Minimum Cathode Current (typ) | 45 µA | 45 µA | 45 µA | 45 µA | 45 µA | 45 µA |
| External Capacitor Required | No | No | No | No | No | No |
Key Differentiators
- A-grade ±0.1% initial accuracy vs C-grade ±0.5% alternative (vs LM4040CIM3-2.5/NOPB)
- Qualified cross-brand second source available (vs LM4040AIM3-2.5+T)
- Industry-standard SOT-23-3 footprint with multiple voltage options in same package (vs TL431 (TO-92 adjustable shunt reference))
Design Notes
Estimate: For a 5 V analog rail driving the LM4040AIM3-2.5/NOPB to 2.5 V reference output at 1 mA cathode current, the series bias resistor R = (VIN - VREF) / IKA = (5 V - 2.5 V) / 1 mA = 2.5 kΩ. At minimum VIN of 3.3 V, IKA = (3.3 - 2.5) / 2.5 kΩ = 0.32 mA, well above the 45 µA minimum. At maximum VIN of 5.5 V, IKA = (5.5 - 2.5) / 2.5 kΩ = 1.2 mA, well below the 15 mA maximum. Standard 2.4 kΩ E96 resistor provides adequate margin. Estimated calculation; refer to TI datasheet for production design.
Place the LM4040AIM3-2.5/NOPB as close as possible to the load (typically an ADC REFIN pin) to minimize PCB trace impedance. Keep the trace from the LM4040 cathode to the load short and isolated from digital switching traces. A small 0.1 µF ceramic bypass capacitor at the load pin (not directly across the LM4040) absorbs transient current demands from the ADC sample-and-hold switching, even though the LM4040 itself is stable with any capacitive load.
Do not operate the LM4040AIM3-2.5/NOPB below its 45 µA minimum cathode current - the reference output becomes nonlinear and noisy in this region. Do not exceed the 15 mA maximum cathode current without current limiting - the device will dissipate excessive heat (PD = (VIN - 2.5 V) × IKA). Also note that pin 3 of the SOT-23-3 (DBZ) package is not electrically connected internally; do not use it as a signal pin or connect it to the cathode (this may cause internal stress in some second-source parts).
Compliance Information
NOPB suffix indicates lead-free RoHS-compliant per TI product page. AEC-Q100 grade (LM4040QIM3-2.5/NOPB) is available separately for automotive; the standard LM4040AIM3-2.5/NOPB is industrial grade.
