Analog Devices Inc. ADR421ARZ

Overview

ADR421ARZ 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 ADR421ARZ datasheet, ADR421ARZ pinout, ADR421ARZ application, or ADR421ARZ equivalent, this page provides verified specifications, SOIC-8 pin mapping, real-world use cases in precision data acquisition, and validated alternative options for design continuity and sourcing flexibility.

Technical Context

The ADR421ARZ employs patented XFET architecture-using two matched JFETs with differential pinch-off voltage-to generate a stable ~0.5 V intrinsic reference, then applies PTAT-based curvature correction to achieve ultra-low 3 ppm/°C drift. Its core topology avoids bandgap compensation circuitry, directly enabling lower noise than conventional references.

It features a dedicated TRIM pin enabling ±0.5% output adjustment without degrading temperature coefficient or long-term stability, and includes two test pins (TP) and two no-connect terminals (NIC) for factory characterization-none of which are user-accessible in normal operation.

Key Specifications

Pinout & Package

ADR421ARZ is housed in an 8-lead SOIC package (body width 3.9 mm, JEDEC MS-012), with thermal resistance θ_JA = 130°C/W. Pin 1 and Pin 8 are test pins (TP); Pins 3 and 7 are no internal connection (NIC). GND (Pin 4) must be connected to system ground plane for optimal noise rejection.

Key Features

Applications

Equivalent & Alternatives

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

Compared with REF5025IDR and ADR441ARMZ, the ADR421ARZ delivers best-in-class noise-to-power ratio (1.75 μV p-p at 500 µA) and widest supply range (4.5 V–18 V), making it uniquely suited for portable, wide-input, and noise-critical applications without sacrificing long-term stability.

Availability

ADR421ARZ is available at Aetrix Electronics and suitable for precision data acquisition systems, optical network control circuits, and portable medical instruments requiring stable component supply across extended temperature ranges and multi-year production cycles.

Supply support for ADR421ARZ 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 centers worldwide.

The ADR42x series was designed specifically for ultraprecision voltage reference needs in high-resolution data converters, optical networking, and portable instrumentation-leveraging XFET® technology to surpass traditional bandgap and buried Zener performance limits.

FAQ

What is the maximum load current supported by the ADR421ARZ?

The ADR421ARZ delivers up to 10 mA of continuous output current while maintaining specified accuracy, load regulation (70 ppm/mA), and thermal stability. It sustains this performance across the full −40°C to +125°C temperature range and 4.5 V to 18 V input supply, making it suitable for driving multiple ADC references or op-amp bias networks without external buffers. Exceeding 10 mA may degrade output voltage accuracy and increase self-heating effects.

Can the ADR421ARZ operate from a 3.3 V supply rail?

No, the ADR421ARZ requires a minimum supply voltage of 4.5 V due to its 2 V minimum supply headroom specification (VIN − VOUT ≥ 2 V). With a 2.500 V output, the absolute minimum input is 4.5 V. Attempting operation from 3.3 V will result in loss of regulation and unpredictable output behavior. For 3.3 V systems, consider the ADR3425 or AD1582 instead.

Does the ADR421ARZ require an output capacitor for stability?

No, the ADR421ARZ is internally compensated and remains stable with or without an output capacitor under all load conditions. A 0.1 µF ceramic capacitor from VOUT to GND is recommended solely to reduce broadband noise-not for stability. Adding larger capacitors (e.g., 1 µF–10 µF) improves load transient response but increases turn-on settling time proportionally to capacitance value.

What is the purpose of the TRIM pin on the ADR421ARZ?

The TRIM pin (Pin 5) allows adjustment of the ADR421ARZ output voltage over a ±0.5% range (±12.5 mV around 2.500 V) using an external resistor divider. This adjustment does not compromise temperature coefficient, long-term stability, or noise performance. It enables final system-level calibration without requiring tighter initial tolerance parts or post-assembly trimming of resistors.

Are the TP (test) pins on the ADR421ARZ safe to connect to ground or leave unconnected?

The TP pins (Pins 1 and 8) are reserved exclusively for factory wafer-level testing and must remain unconnected in end-user applications. Connecting them to ground, supply, or any other node may disrupt internal biasing, cause functional failure, or invalidate specifications. They may be left floating or optionally tied to GND for mechanical reinforcement-but never for electrical purposes.