ADR421BRZ - 2.5V Ultraprecision Low Noise Voltage Reference | Analog Devices
MPN： ADR421BRZ ✓ 啟用中ADR421BRZ 概覽
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.
直接替換替代品，適用於 ADR421BRZ — 相同封裝，腳位對腳位相容。需重新設計 PCB 的不同封裝零件不列入。
此系列的變體
與下列產品可直接替換的同系列型號： ADR421BRZ （相同外形與佔位） — 差異在於 Package, Temperature Coefficient.
ADR421BRZ-REEL7
✅ 直接替換聯絡詢價
查看資料表 →ADR421ARZ
✅ 直接替換📋 參考替代品（不在目錄中）
ADR420ARZ
✅ 直接替換 ⚠️ 規格未經驗證📋 參考替代品（不在目錄中）
ADR425ARZ
✅ 直接替換📋 參考替代品（不在目錄中）
REF5025AIDR
✅ 直接替換📋 參考替代品（不在目錄中）
ADR431ARZ
✅ 直接替換📋 參考替代品（不在目錄中）
ADR421BRZ 規格
| Reference Type | Series, XFET |
| 輸出電壓 | 2.500 V (fixed) |
| Initial Accuracy (B grade) | ±0.04% (±1 mV max) |
| Output Current (Source) | 10 mA |
| 輸入電壓範圍 | 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 |
| 工作溫度範圍 | -40 °C to +125 °C |
| 封裝 | 8-pin SOIC (R-8, SOIC-8 narrow body) |
| 安裝類型 | Surface Mount |
| RoHS 狀態 | Compliant |
ADR421BRZ 腳位配置
| 腳位 1 | NC — Not connected (per datasheet) |
| 腳位 2 | +IN — Positive supply input (4.5 V to 18 V) |
| 腳位 3 | NC — Not connected (per datasheet) |
| 腳位 4 | GND — Ground return |
| 腳位 5 | TRIM — Output voltage trim (optional adjustment) |
| 腳位 6 | VOUT — Reference output (2.500 V fixed) |
| 腳位 7 | NC — Not connected (per datasheet) |
| 腳位 8 | NC — Not connected (per datasheet) |
典型應用
ADR421BRZ 適用於 6 應用s: 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.
推薦
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.
推薦
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.
推薦
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.
推薦
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.
推薦
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.
推薦
推薦產品摘要
工程參考資料，適用於 ADR421BRZ — 比較、設計指引及合規資訊。
選型指南
與替代品比較
| 參數 | 本產品 | 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 |
主要差異化特點
- Best-in-class 0.1 Hz to 10 Hz noise (1.75 µV p-p) (對比REF5025AIDR)
- Tighter B-grade initial accuracy (±0.04% vs ±0.05%) (對比ADR421ARZ)
- Higher output current drive (30 mA vs 10 mA) (對比ADR431ARZ)
- Wide input supply range (4.5 V to 18 V) (對比ADR425ARZ)
設計說明
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%.
合規資訊
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.
