ADR421BRZ - 2.5V Ultraprecision Low Noise Voltage Reference | Analog Devices
MPN: ADR421BRZ ✓ AktifADR421BRZ Genel Bakış
An XFET voltage reference is a specialized series-mode reference that uses an externally modulated JFET pair to generate a temperature-compensated bandgap-like voltage, achieving lower noise and better long-term stability than conventional buried-Zener references. It occupies the product hierarchy of voltage reference -> series reference -> precision reference -> power management IC, serving as the stable potential against which ADCs, DACs, and precision analog signal chains are calibrated.
Key features include sub-2 µV p-p low-frequency noise, 50 ppm/1000 hrs long-term stability, 40 ppm typical hysteresis, and a wide 4.5 V to 18 V supply operating range with low quiescent current. The XFET architecture also eliminates the need for a resistor in series with the supply pin required by older Zener designs, simplifying PCB layout and improving turn-on settling.
Architecturally, the XFET cell pairs a JFET reference transistor with a second JFET biased to cancel temperature drift. A precision op-amp servos the bandgap-like cell to maintain constant VOUT, while the trim network programs the initial accuracy. This topology trades the higher pre-trim noise of bandgap references for far better long-term drift and thermal hysteresis.
Typical applications include precision 16-bit and 24-bit ADC and DAC reference inputs, industrial process control calibration, automatic test equipment (ATE) system references, and precision data acquisition systems in medical imaging, weighing scales, and 6.5-digit digital multimeters. The 2.5 V output makes it an ideal companion to devices such as the AD8628, AD8629, and ADI's AD57xx, AD76xx, and ADuM-series converter families.
When designing with the ADR421BRZ, route the output node directly to the reference pin of the target converter with a 0.1 µF ceramic plus 1 µF tantalum bypass network within 5 mm of the reference pin to preserve noise and load regulation. Avoid running digital or switching traces under the reference - injected charge can deteriorate 0.1 Hz to 10 Hz noise performance.
This page synthesizes distributor pricing across nine channels, parametric drop-in alternatives, and practical layout notes not consolidated on the manufacturer datasheet.
Drop-in alternatifler için ADR421BRZ — aynı paket, pin-başına uyumlu. PCB yeniden montajı gerektiren farklı paket bileşenleri dışlanmıştır.
Bu Serideki Variantlar
Yedek parça uyumlu olan aynı serideki modeller ADR421BRZ (aynı form faktörü ve ayağa oturma) — farklı olan Package, Temperature Coefficient.
ADR421BRZ-REEL7
✅ YerleştirmeFiyat için iletişime geçin
Veri Şablonunu Görüntüle →ADR421ARZ
✅ Yerleştirme📋 Katalogda Olmayan Referans Alternatifi
ADR420ARZ
✅ Yerleştirme ⚠️ Onaylanmamış Özellikler📋 Katalogda Olmayan Referans Alternatifi
ADR425ARZ
✅ Yerleştirme📋 Katalogda Olmayan Referans Alternatifi
REF5025AIDR
✅ Yerleştirme📋 Katalogda Olmayan Referans Alternatifi
ADR431ARZ
✅ Yerleştirme📋 Katalogda Olmayan Referans Alternatifi
ADR421BRZ Özellikler
| Reference Type | Series, XFET |
| Çıkış Gerilimi | 2.500 V (fixed) |
| Initial Accuracy (B grade) | ±0.04% (±1 mV max) |
| Output Current (Source) | 10 mA |
| Giriş电压范围 | 4.5 V to 18 V |
| Noise (0.1 Hz to 10 Hz) | 1.75 µV p-p |
| Temperature Coefficient | 3 ppm/°C max |
| Load Regulation | 70 ppm/mA |
| Line Regulation | 35 ppm/V |
| Long-Term Stability | 50 ppm / 1000 hours |
| Hysteresis | 40 ppm typical |
| İşletim Sıcaklığı Aralığı | -40 °C to +125 °C |
| Paket | 8-pin SOIC (R-8, SOIC-8 narrow body) |
| Montaj Türü | Surface Mount |
| RoHS Durumu | Compliant |
ADR421BRZ Pin Yapısı
| Pin 1 | NC — Not connected (per datasheet) |
| Pin 2 | +IN — Positive supply input (4.5 V to 18 V) |
| Pin 3 | NC — Not connected (per datasheet) |
| Pin 4 | GND — Ground return |
| Pin 5 | TRIM — Output voltage trim (optional adjustment) |
| Pin 6 | VOUT — Reference output (2.500 V fixed) |
| Pin 7 | NC — Not connected (per datasheet) |
| Pin 8 | NC — Not connected (per datasheet) |
Tipik Uygulamalar
ADR421BRZ için uygundur 6 uygulamas: Precision 16-Bit and 24-Bit ADC Reference, Automatic Test Equipment (ATE) Calibration Reference, Industrial Weighing Scale Front-End, Medical Imaging Signal Chain, 6.5-Digit Digital Multimeter Reference, Precision Data Acquisition Modules.
Precision 16-Bit and 24-Bit ADC Reference
The ADR421BRZ's 2.500 V output, ±0.04% initial accuracy, and 1.75 µV p-p 0.1 Hz to 10 Hz noise suit it as the reference for 16-bit and 24-bit SAR and sigma-delta ADCs. Its 3 ppm/°C drift remains within a single LSB over a 100 °C excursion at 14-bit resolution (5 V full scale), eliminating the need for periodic software gain calibration. Placed within 5 mm of the REF pin and bypassed with 0.1 µF + 1 µF ceramic caps, it preserves the noise floor of converters such as AD7606, AD7768, and AD7124. Compared to a Zener reference, the XFET topology offers lower flicker noise, faster settling, and the elimination of the series supply resistor required by older designs.
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Automatic Test Equipment (ATE) Calibration Reference
In ATE source-measurement units and digital multimeter calibrators, the ADR421BRZ provides a stable 2.500 V anchor for multimode DAC systems and divider networks. Its 50 ppm/1000 hr long-term stability and 40 ppm hysteresis allow calibration cycles to extend from days to months without service interruption. The 4.5 V to 18 V supply range covers standard +5 V and +15 V analog rails used in bench and rack instruments. Buffering with a low-offset amplifier such as the AD8628 preserves the noise floor under dynamic load while keeping the reference itself isolated from the output drive current.
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Industrial Weighing Scale Front-End
Weighing scales operating from load cells in the millivolt range digitize via 24-bit sigma-delta ADCs whose absolute accuracy depends on the reference rail. The ADR421BRZ's 1.75 µV p-p noise is well below the ADC's quantization noise, and its 3 ppm/°C drift keeps within the OIML R76 resolution class III limits across the operating temperature range. Routing 4-wire Kelvin sensing back to the reference output absorbs PCB IR drop in long cable harnesses common to bench and floor scales.
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Medical Imaging Signal Chain
Ultrasound, CT, and MRI analog front ends require absolute amplitude calibration for beam-forming and image reconstruction. The ADR421BRZ anchored at 2.500 V provides the GND-referenced voltage for ADC reference pins that span a 5 V differential range. Its low hysteresis (40 ppm typical) means that warm-up drift does not repeat across scan cycles - critical for image co-registration. Drive the reference pin through a low-noise buffer to keep the noise current out of the sensing channel.
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6.5-Digit Digital Multimeter Reference
Bench and handheld 6.5-digit DMMs require DC references with ppm-class stability on every range. The ADR421BRZ's 2.500 V tap feeds both the ADC reference and divider networks for 2.5 V, 25 V, and 250 V ranges. Its 50 ppm/1000 hr long-term drift and 35 ppm/V line rejection hold accuracy over humidity and load variations that typically pollute handheld meter designs. Operating temperature of -40 °C to +125 °C suits both indoor bench and outdoor field instruments.
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Precision Data Acquisition Modules
DAQ modules used in aerospace test rigs, structural health monitoring, and vibration analysis leverage the ADR421BRZ's XFET technology for unsurpassed long-term stability. The 4.5 V to 18 V supply range accommodates both 5 V USB-powered and 24 V industrial backplane designs. Use the ADR421BRZ as the reference for the module's main 16-bit converter and as the bias generator for cold-junction compensation thermocouple front-ends. Decoupling with a 0.1 µF ceramic + 10 µF tantalum pair suppresses both high-frequency noise and load-transient events triggered by multiplexed channel switching.
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Önerilen Ürünler Özeti
Mühendislik referans verileri: ADR421BRZ — karşılaştırma, tasarım rehberi ve uyumluluk bilgileri.
Seçim Kılavuzu
Alternatiflerle Karşılaştırma
| Parametre | Bu Ürün | ADR421BRZ-REEL7 | ADR421ARZ | ADR420ARZ | ADR425ARZ | REF5025AIDR | ADR431ARZ |
|---|---|---|---|---|---|---|---|
| Brand | Analog Devices | Analog Devices | Analog Devices | Analog Devices | Analog Devices | Texas Instruments | Analog Devices |
| Package | SOIC-8 (R-8) | SOIC-8 (R-8) - same | SOIC-8 (R-8) - same | SOIC-8 (R-8) - same | SOIC-8 (R-8) - same | SOIC-8 - same | SOIC-8 (R-8) - same |
| Output Voltage | 2.500 V | 2.500 V | 2.500 V | 2.048 V | 5.000 V | 2.500 V | 2.500 V |
| Initial Accuracy (B grade) | ±0.04% | ±0.04% | ±0.05% | ±0.05% | ±0.12% | ±0.05% | ±0.05% |
| Noise (0.1 Hz to 10 Hz) | 1.75 µV p-p | 1.75 µV p-p | 1.75 µV p-p | 1.75 µV p-p | 3.4 µV p-p | 3.0 µV p-p | 3.5 µV p-p |
| Temperature Coefficient | 3 ppm/°C | 3 ppm/°C | 3 ppm/°C | 3 ppm/°C | 3 ppm/°C | 3 ppm/°C | 10 ppm/°C |
| Long-Term Stability | 50 ppm/1000 hr | 50 ppm/1000 hr | 50 ppm/1000 hr | 50 ppm/1000 hr | 50 ppm/1000 hr | 30 ppm/1000 hr | 100 ppm/1000 hr |
| Input Voltage Range | 4.5 V to 18 V | 4.5 V to 18 V | 4.5 V to 18 V | 4 V to 18 V | 7 V to 18 V | 2.7 V to 18 V | 4.5 V to 18 V |
| Output Current | 10 mA | 10 mA | 10 mA | 10 mA | 10 mA | 10 mA | 30 mA |
Ana Farklılayıcılar
- Best-in-class 0.1 Hz to 10 Hz noise (1.75 µV p-p) (karşılaştırma:REF5025AIDR)
- Tighter B-grade initial accuracy (±0.04% vs ±0.05%) (karşılaştırma:ADR421ARZ)
- Higher output current drive (30 mA vs 10 mA) (karşılaştırma:ADR431ARZ)
- Wide input supply range (4.5 V to 18 V) (karşılaştırma:ADR425ARZ)
Tasarım Notları
Place a 0.1 µF ceramic bypass on the +IN pin within 5 mm, and a 1 µF to 10 µF low-ESR tantalum or ceramic on VOUT also within 5 mm. The added output capacitance also improves load-transient response when the reference is buffered by a switched gain stage. Keep the VOUT trace short and direct to the destination ADC reference pin - every additional millimeter of trace adds parasitic inductance that couples noise from neighboring lines into the 0.1 Hz to 10 Hz band.
Use a single-point analog ground star at the ADR421BRZ GND pin (pin 4) and route digital ground back to this star via a ferrite bead. Avoid routing high-current digital return paths (from processors, FPGAs, or switching converters) within 6 mm of the reference output trace. Load regulation is specified at 70 ppm/mA; a 1 mA change in load current due to digital noise directly translates to 0.175 mV reference error.
Do not draw more than 10 mA from VOUT - the reference cannot self-protect and reliability degrades under overload. If the destination ADC draws more than 5 mA dynamic current, buffer the reference with a low-offset, low-noise op-amp such as the AD8628 or OP177 to isolate the reference. Also, note that the TRIM pin (pin 5) is for optional fine adjustment - leave it floating if no trim is needed; a 10 kΩ pot from VOUT to TRIM to GND adjusts ±0.5%.
Uyumluluk Bilgisi
RoHS compliant per Analog Devices product page. AEC-Q100 not applicable - this is a precision analog reference, not an automotive-qualified part. For automotive (AEC-Q100) reference needs see ADR425WHARSZ or equivalent.
