ADR421BRZ-REEL7 - 2.5V Ultraprecision XFET Voltage Reference | Analog Devices
MPN: ADR421BRZ-REEL7 ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $5.74 | $5.74 |
| 10 | $5.16 | $51.60 |
| 100 | $4.59 | $459.00 |
| 500 | $4.13 | $2,065.00 |
| 1,000 | $3.71 | $3,710.00 |
| 2,500 | $3.45 | $8,625.00 |
ADR421BRZ-REEL7 Overview
A voltage reference is a precision circuit that produces a stable, known DC voltage independent of supply variations, temperature, and load current. Voltage references sit at the base of the signal chain in data acquisition, instrumentation, and precision analog systems: their absolute accuracy and noise floor set the ultimate performance limit of downstream ADCs, DACs, sensor bridges, and weighing scales. The ADR421 belongs to the XFET (eXtra implanted junction FET) family, which uses a junction FET reference cell rather than a buried Zener or bandgap to achieve sub-2 µV p-p noise and excellent thermal hysteresis of 40 ppm typical.
Key features include 4.5 V to 18 V supply range, low supply current of 0.5 mA typical, line regulation of 35 ppm/V, load regulation of 70 ppm/mA, and -40 °C to +125 °C operating temperature. The SOIC-8 (R-8) package is the industry-standard precision reference footprint, allowing direct substitution on most reference layouts. Unlike buried-Zener references that need 10 V minimum, the XFET architecture operates from as low as 4.5 V, suiting it to 5 V and ±5 V or +5 V/-12 V system rails. The ADR421 is offered in three grades (A: ±0.05%, B: ±0.04%, C: ±0.12%) and three packages (8-lead SOIC, 8-lead MSOP, TO-92).
Typical applications include precision data acquisition system references, high-resolution ADC and DAC reference inputs, industrial process control calibration, precision weighing scales, medical instrumentation, and instrumentation amplifiers. The 2.500 V output matches the full-scale range of many 16-bit and 24-bit sigma-delta ADCs (e.g., AD7799/AD7730 families) and is compatible with 5 V reference-input DACs.
When designing with the ADR421, add a 0.1 µF ceramic bypass capacitor close to the supply pin and a 1 µF to 10 µF tantalum or ceramic capacitor on the output for stable load-transient response. The trim pin (pin 5) allows ±0.5% fine adjustment of the output using a 10 kΩ/1 kΩ divider; leave it open if trimming is not required.
This page synthesizes distributor pricing, drop-in same-brand and cross-brand alternatives, and practical design notes not found in the manufacturer datasheet alone.
Drop-in alternatives for ADR421BRZ-REEL7 — 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 ADR421BRZ-REEL7 (same form factor and footprint) — differing in Package, Temperature Coefficient.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
ADR421ARZ
✅ Drop-In📋 Reference alternative (not in catalog)
ADR421BRZ
✅ Drop-In✓ In Stock
$4.58 / Unit
View Datasheet →ADR421BRZ-REEL7 Specifications
| Output Voltage | 2.500 V (fixed) |
| Initial Accuracy | ±0.04% (B grade) |
| Output Current | 10 mA |
| Input Voltage Range | 4.5 V to 18 V |
| Temperature Coefficient | 3 ppm/°C |
| Noise (0.1 Hz to 10 Hz) | 1.75 µV p-p |
| Long-Term Stability | 50 ppm / 1000 hours |
| Line Regulation | 35 ppm/V |
| Load Regulation | 70 ppm/mA |
| Quiescent Current | 0.5 mA typical |
| Hysteresis | 40 ppm typical |
| Operating Temperature | -40 °C to +125 °C |
| Package | 8-pin SOIC (R-8) |
| Mounting Type | Surface Mount |
| MSL Level | 1 |
| Lead-Free / RoHS | Yes (RoHS compliant) |
| Reference Type | Series, XFET |
| Trim Pin | Yes (pin 5) |
| Reel Size | 7-inch (REEL7) |
ADR421BRZ-REEL7 Pin Configuration
| Pin 1 | NC — Not connected (per datasheet) |
| Pin 2 | NC — Not connected (per datasheet) |
| Pin 3 | GND — Ground |
| Pin 4 | NC — Not connected (per datasheet) |
| Pin 5 | TRIM — Output trim / fine adjust (~±0.5%) |
| Pin 6 | VIN — Supply input (4.5 V to 18 V) |
| Pin 7 | NC — Not connected (per datasheet) |
| Pin 8 | VOUT — Reference output 2.500 V |
Typical Applications
ADR421BRZ-REEL7 is suitable for 6 applications: Precision ADC Reference Input, Industrial Process Control and Weighing Scales, Portable Battery-Powered Instrumentation, Precision Data Acquisition Systems (DAQ), Medical Instrumentation and Patient Monitoring, Precision DAC Output Scaling.
Precision ADC Reference Input
The ADR421BRZ-REEL7's 2.500 V ±0.04% output drives the REFIN pin of 16-bit and 24-bit sigma-delta ADCs such as the AD7799, AD7730 and AD7190, where the absolute accuracy of the reference directly sets the converter's full-scale precision. With 1.75 µV p-p noise (0.1 Hz–10 Hz) and 3 ppm/°C drift, the ADR421 contributes less than 5 LSBs of error at 16 bits over industrial temperature ranges. It is placed close to the ADC with a 1 µF to 10 µF low-ESR output capacitor to absorb charge-injection transients and preserve INL. Compared to buried-Zener references, the XFET design runs cold on 5 V and needs no ±15 V rail.
Recommended
Industrial Process Control and Weighing Scales
Bridge-based load-cell weighing scales demand a high-stability 2.5 V or 5 V reference to amplify millivolt-level strain-gauge signals with sub-ppm resolution; the ADR421BRZ-REEL7's 50 ppm/1000-hour long-term stability keeps the calibration accurate over years of continuous operation. The 70 ppm/mA load regulation and 0.5 mA quiescent current let the part share the bridge excitation rail without impacting measurement accuracy. Operating temperature spans -40 °C to +125 °C, suiting outdoor and factory-floor PLC modules. The SOIC-8 footprint is compatible with REF5025 layouts, enabling a quick cross-brand swap if supply is constrained.
Recommended
Portable Battery-Powered Instrumentation
The low 0.5 mA quiescent current makes the ADR421BRZ-REEL7 attractive for handheld DMMs, data loggers, and medical telemetry that run from a single 5 V USB rail or two AA cells with a boost. Unlike Zener references needing 10 V minimum, the ADR421 works from 4.5 V and adds only 2.5 mW quiescent overhead at full load. Low hysteresis of 40 ppm typical preserves accuracy across daily temperature swings between hot vehicle interiors and air-conditioned labs. Surface-mount SOIC-8 fits compact 2-layer sensor boards, and the trim pin can be used to trim out PCB-level offsets.
Recommended
Precision Data Acquisition Systems (DAQ)
Multi-channel DAQ cards for vibration, audio, and seismic test use the ADR421BRZ-REEL7 as a system-wide reference, where its 35 ppm/V line regulation rejects ripple on the +12 V or +24 V factory rail. Pairing with a 24-bit ADC and an instrumentation front-end such as the AD8421 or INA128 enables 7.5-digit DC measurements on bench-top multimeters. The 1.75 µV p-p 0.1 Hz–10 Hz noise floor is competitive with the AD588 and ADR01 while drawing 20× less current. Trim pin implementation uses a 5 kΩ multi-turn potentiometer for a one-time calibration after PCB assembly.
Recommended
Medical Instrumentation and Patient Monitoring
Patient monitors, defibrillators, and infusion pumps need predictable references for ECG, SpO2, and impedance-measurement front ends. The ADR421BRZ-REEL7's ±0.04% initial accuracy and 3 ppm/°C drift support the 0.1% gain-error budgets of medical-grade analog front ends. Wideband noise of 1.75 µV p-p does not dominate over the 50 Hz/60 Hz power-line interference filtered by the front end. The RoHS-compliant SOIC-8 supports long design-life certification cycles for IEC 60601-1 medical safety standards, and the part is rated for continuous operation from -40 °C to +125 °C body-proximate housing environments.
Recommended
Precision DAC Output Scaling
In audio and industrial 4-20 mA transmitter designs, the 4 mA to 20 mA loop current must be accurate to within 0.1% of full scale. The ADR421BRZ-REEL7 sets the reference for 16-bit DACs such as the AD5420 or AD5755, where each LSB is 38 µV at 2.5 V FS. With 3 ppm/°C drift, the DAC's mid-scale accuracy stays calibrated across -40 °C to +85 °C outdoor installations. SOIC-8 keeps the PCB bill of materials lean and avoids the larger TO-99 footprint that legacy references occupy. Designers can also use the trim pin to absorb PCB-scale offsets between the reference and the rest of the analog chain.
Recommended
Recommended Products Summary
Engineering reference data for ADR421BRZ-REEL7 — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | ADR421ARZ | ADR421BRZ | REF5025AIDR |
|---|---|---|---|---|
| Package | SOIC-8 (R-8) | SOIC-8 (R-8) - same | SOIC-8 (R-8) - same | SOIC-8 (R-8) - same |
| Brand | Analog Devices | Analog Devices | Analog Devices | Texas Instruments |
| Output Voltage | 2.500 V | 2.500 V | 2.500 V | 2.500 V |
| Initial Accuracy | ±0.04% (B grade) | ±0.05% (A grade) | ±0.04% (B grade) | ±0.05% |
| Temperature Coefficient | 3 ppm/°C | 5 ppm/°C | 3 ppm/°C | 3 ppm/°C |
| Input Voltage Range | 4.5 V to 18 V | 4.5 V to 18 V | 4.5 V to 18 V | 2.7 V to 18 V |
| Quiescent Current | 0.5 mA | 0.5 mA | 0.5 mA | 0.8 mA |
| Output Noise (0.1 Hz – 10 Hz) | 1.75 µV p-p | 1.75 µV p-p | 1.75 µV p-p | 3 µV p-p |
| Load Regulation | 70 ppm/mA | 70 ppm/mA | 70 ppm/mA | 25 ppm/mA |
| Line Regulation | 35 ppm/V | 35 ppm/V | 35 ppm/V | 5 ppm/V |
| AEC-Q100 | No | No | No | No |
Key Differentiators
- B-grade accuracy ±0.04% with 3 ppm/°C (vs ADR421ARZ)
- Trim pin for ±0.5% fine adjustment (vs REF5025AIDR)
- Wide 4.5 V–18 V input range (vs ADR423BRZ)
- 0.5 mA typical quiescent current (vs REF5025AIDR)
Design Notes
Place the ADR421BRZ-REEL7 as close as possible to the ADC reference input (or DAC reference input) to minimize PCB trace resistance and IR drop. Keep analog ground separate from digital ground, joining them only at the ADC AGND pin (star-ground topology). The 8-pin SOIC has thermal resistance of 160 °C/W with a standard 1 oz 2-layer board; route the inner copper layer as a GND pour under the part for better heat spreading.
Use a 0.1 µF X7R ceramic capacitor within 3 mm of the VIN pin (pin 6) for high-frequency decoupling. Then place a 1 µF to 10 µF low-ESR output capacitor (tantalum or X7R ceramic in series with a small ESR of 0.5 Ω–2 Ω) between VOUT (pin 8) and GND. Avoid ceramic-only output capacitance below 0.1 µF, and avoid pure MLCC stacks at 10 µF which can produce sub-Hz oscillations; the Analog Devices datasheet performance was characterized with this 0.1 µF + 1-10 µF combination.
Estimated: at 5 V supply and 10 mA load the ADR421 dissipates roughly 25 mW – far below the 250 mW SOIC-8 absolute max, so no heatsink is needed. Do NOT apply supply voltage above 18 V (instant damage), and do NOT reverse the supply. Do NOT exceed 10 mA continuous sink/source on VOUT; operation below 0.5 mA load produces poor line-transient rejection. If the trim pin is unused, leave pin 5 floating or tied to VOUT with a 1 nF capacitor to reject noise – do NOT ground pin 5 as this can cause the internal feedback loop to misbehave.
The 1.75 µV p-p 0.1 Hz to 10 Hz noise is dominated by flicker noise; for spectrum analyzers and audio ADC reference paths, add a passive RC low-pass (1 kΩ + 1 µF = ~160 Hz cutoff) between the ADR421 output and the ADC REFIN pin to attenuate any high-frequency spurs from the upstream LDO. The trim pin (pin 5) can pick up digital switching noise – guard it with a 10 nF capacitor and never run noisy digital traces near pin 5.
Compliance Information
RoHS and REACH compliant per Analog Devices product page and DigiKey listing. Not AEC-Q100 qualified – industrial/commercial grade. Pb-free reflow compatible per JEDEC J-STD-020. Lead finish per supplier data: NiPdAu.
