Analog Devices Inc. ADR421BR

Overview

ADR421BR from Analog Devices is an ultraprecision XFET® voltage reference delivering 2.500 V output with ±1 mV (±0.04%) initial accuracy, 3 ppm/°C max temperature coefficient, and 1.75 μV p-p (0.1 Hz to 10 Hz) low-frequency noise. It operates from 4.5 V to 18 V supply, supports 10 mA output current, and is used in high-resolution ADC/DAC biasing for optical network control circuits and portable medical instrumentation.

For engineers reviewing the ADR421BR datasheet, ADR421BR pinout, ADR421BR application, or ADR421BR equivalent, this page provides verified specifications, SOIC/MSOP package details, trim-adjustable output functionality, load/line regulation behavior, and validated alternative options for precision analog signal chains requiring stable 2.5 V references.

Technical Context

The ADR421BR employs patented XFET architecture-using two JFETs with differential pinch-off voltage-to generate a ~0.5 V intrinsic reference, then applies PTAT-based curvature correction for ultra-low drift. Its 3 ppm/°C max TCVOUT over −40°C to +125°C is achieved without buried Zener power overhead or bandgap compensation noise penalties.

It features a dedicated TRIM pin enabling ±0.5% output adjustment without degrading temperature coefficient or long-term stability, and integrates internal circuitry that maintains 70 ppm/mA load regulation and 35 ppm/V line regulation across full temperature and load range-critical for metrology-grade data acquisition systems.

Key Specifications

Pinout & Package

ADR421BR is available in both 8-lead SOIC (R) and 8-lead MSOP (RM) packages. Both share identical pinout and thermal characteristics (θJA = 130°C/W for SOIC, 190°C/W for MSOP).

Key Features

Applications

Equivalent & Alternatives

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

Compared with REF5025AIDR and MAX6126BASA25+, the ADR421BR delivers optimal balance of ultra-low noise (1.75 μV p-p), 10 mA drive, and 500 µA quiescent current - making it preferred for portable, high-resolution, multi-channel data loggers where power, precision, and loading headroom are jointly constrained.

Availability

ADR421BR is available at Aetrix Electronics and suitable for precision data acquisition systems, optical network control circuits, and battery-powered instrumentation requiring stable component supply with traceable lot history and extended lifecycle support.

Supply support for ADR421BR 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

Analog Devices, Inc. is a global leader in high-performance analog, mixed-signal, and digital signal processing semiconductors, headquartered in Norwood, MA, with R&D and manufacturing facilities worldwide.

The ADR42x series was designed specifically for ultraprecision voltage reference applications demanding low noise, low drift, and high stability in compact SOIC/MSOP packages - targeting high-end test equipment, medical imaging, and aerospace data converters.

FAQ

What is the maximum load current supported by the ADR421BR?

The ADR421BR supports up to 10 mA of continuous output current while maintaining all specifications including load regulation (70 ppm/mA) and output voltage accuracy. This allows direct driving of multiple op-amps, ADC reference inputs, or DACs without external buffering - confirmed in Table 3 of the Rev. J datasheet under "LOAD REGULATION" and "SHORT CIRCUIT TO GND" (27 mA short-circuit current limit).

Can the ADR421BR operate from a 3.3 V supply?

No, the ADR421BR requires a minimum supply voltage of 4.5 V to ensure proper operation and specified performance. Its minimum supply headroom is 2 V (VIN − VOUT ≥ 2 V), so with a 2.500 V output, VIN must be ≥4.5 V - verified in Table 3 ("SUPPLY VOLTAGE HEADROOM") and General Description section of the Rev. J datasheet.

Does the ADR421BR require an output capacitor for stability?

No, the ADR421BR is internally compensated and remains stable with or without an output capacitor. A 0.1 µF ceramic capacitor is recommended solely to reduce broadband noise; larger capacitors (e.g., 1–10 µF) improve load transient response but increase turn-on settling time - detailed in the "Output Capacitor" section on page 16 of the Rev. J datasheet.

How does the TRIM pin on the ADR421BR function?

The TRIM pin allows adjustment of the ADR421BR's output voltage over a ±0.5% range using an external resistor divider, without degrading temperature coefficient, long-term stability, or noise performance. The configuration follows Figure 39 in the Rev. J datasheet and requires no additional components beyond two precision resistors - confirmed in the "Output Adjustment" subsection on page 18.

What is the long-term stability specification for the ADR421BR?

The ADR421BR exhibits 50 ppm maximum output voltage shift after 1000 hours of operation at 125°C - equivalent to ±0.125 mV drift for the 2.500 V output. This value is measured at 25°C before and after accelerated life testing and is specified in Table 3 ("LONG-TERM STABILITY") of the Rev. J datasheet.