Part A
ADR421ARZ
Analog Devices Inc.
- Lifecycle
- Active
- Stock
- 1276 PCS
- Package
- SOIC-8
- Series
- PMIC - Voltage Reference
Replacement verdict
Compatible functional replacement candidate
The ADR421ARZ and ADR420AR are both precision low-noise voltage references from the same ADR42x family, sharing a common SOIC-8 footprint and series-mode topology, but they differ in output voltage (2.500 V vs 2.048 V) and initial accuracy grade. The ADR421ARZ is a viable functional replacement candidate for the ADR420AR only where the 2.500 V reference level and the associated accuracy, drift, and thermal specifications are acceptable for the target circuit; designers must confirm the output voltage change and revalidate accuracy budget before substitution.
Output Voltage
Validation required
Package Type
High match
Initial Accuracy
Validation required
Operating Temperature Range
High match
Key differences
Rows are prioritized by design impact. Highlighted values require attention during substitution.
Key electrical and mechanical differences between the two devices
| Parameter | ADR421ARZ | ADR420AR | Why it matters |
|---|---|---|---|
| Initial Accuracy | ±0.04% (max) | ±0.15% (max) | Tighter initial tolerance reduces system calibration effort and directly affects output voltage precision at room temperature. |
| Output Voltage | 2.500 V | 2.048 V | The nominal reference voltage must match the ADC/DAC full-scale requirement; these parts are not directly interchangeable without redesign. |
| Temperature Coefficient | 3 ppm/°C (max) | 3 ppm/°C (max) | Drift over temperature determines accuracy stability in precision measurement systems across the operating range. |
| Initial Accuracy Grade | A grade | A grade | Grade designation indicates the binning level for tolerance and drift; matching grades ensures comparable precision performance. |
| Output Current Capability | 10 mA (source/sink) | 10 mA (source/sink) | Drive capability determines whether the reference can supply the load current required by the downstream converter or ADC. |
| Supply Voltage Range | 4.5 V to 18 V | 4.5 V to 18 V | The allowable supply range must encompass the system rail to ensure proper regulation and headroom. |
| Package | 8-Lead SOIC | 8-Lead SOIC | Package compatibility affects PCB footprint and assembly; identical packages simplify board-level substitution. |
| Operating Temperature Range | -40°C to +125°C | -40°C to +125°C | The temperature range must cover the application environment to guarantee specified performance limits. |
| Long-Term Drift | 50 ppm/1000 hr (typ) | 50 ppm/1000 hr (typ) | Long-term stability affects recalibration intervals and accuracy retention over the product lifetime. |
Need help validating a replacement?
Send your BOM and application constraints for technical and sourcing review.
Full specification comparison
Use manufacturer datasheets as the final authority.
| Specification | ADR421ARZ | ADR420AR |
|---|---|---|
| Series | XFET® | XFET® |
| Part Status | Active | Obsolete |
| Mounting Type | Surface Mount | Surface Mount |
| Reference Type | Series | - |
| Output Type | Fixed | - |
| Voltage - Output (Min/Fixed) | 2.5V | - |
| Current - Output | 10 mA | - |
| Tolerance | ±0.12% | - |
| Temperature Coefficient | 10ppm/°C | - |
| Noise - 01 Hzto10 Hz | 1.75µVp-p | - |
| Voltage - Input | 4.5V ~ 18V | - |
| Supply Current | 600µA | - |
| Operating Temperature | -40°C ~ 125°C (TA) | - |
Frequently asked questions
What are the key differences between the ADR421ARZ and ADR420AR?
The ADR421ARZ is a 2.500 V precision voltage reference with an initial accuracy of ±0.04% (max) and a temperature coefficient of 1 ppm/°C (max, A grade). The ADR420AR is a 2.048 V precision voltage reference with an initial accuracy of ±0.05% (max) and a temperature coefficient of 3 ppm/°C (max, A grade). The primary differences are output voltage (2.500 V vs 2.048 V) and temperature drift specification.
Are the ADR421ARZ and ADR420AR pin-compatible?
Yes. Both devices are offered in the same 8-lead SOIC package (R-8 suffix) with identical pin functions, including VOUT, GND, VIN, and TRIM. This allows a common PCB footprint, but the different output voltages must be accounted for in the design.
What is the output voltage of each device?
The ADR421ARZ provides a fixed 2.500 V output, while the ADR420AR provides a fixed 2.048 V output. Both are available in A and B grades, with the A grade offering the wider specified tolerance.
How do the initial accuracy and temperature coefficient specifications compare?
The ADR421ARZ A grade specifies ±0.04% maximum initial accuracy and 1 ppm/°C maximum temperature coefficient. The ADR420AR A grade specifies ±0.05% maximum initial accuracy and 3 ppm/°C maximum temperature coefficient. The ADR421ARZ therefore offers tighter drift performance, while both provide comparable initial accuracy.
What is the operating temperature range for both references?
Both the ADR421ARZ and ADR420AR are specified over the industrial temperature range of −40°C to +125°C, making them suitable for industrial and instrumentation applications.
What are the supply voltage and quiescent current requirements?
Both devices operate from a supply voltage of 4.5 V to 18 V and typically draw approximately 0.8 mA of quiescent current. The minimum supply headroom must be observed relative to the respective output voltage.
Can the ADR421ARZ and ADR420AR be used interchangeably in an existing design?
They are not directly interchangeable without design review because their output voltages differ (2.500 V vs 2.048 V). Pin compatibility and similar package options allow substitution only after verifying that the system tolerates the different reference voltage and that accuracy and drift requirements are met.
What package options are available for these references?
Both the ADR421ARZ and ADR420AR are available in an 8-lead SOIC package. The "RZ" suffix on the ADR421ARZ denotes the SOIC package in tape and reel or tube form per the manufacturer's ordering guide.