The ADR421ARZ is a high-precision, low-noise voltage reference (VR) device manufactured by Analog Devices (ADI). It belongs to ADI’s family of ultra-stable, shunt-mode voltage references, designed to provide a fixed, accurate output voltage with minimal temperature drift and noise—critical for applications requiring precise voltage calibration, measurement, or biasing.
The ADR421ARZ is engineered to solve challenges related to voltage stability, noise reduction, and temperature resilience. Its key functional features are detailed below:
- Fixed Output Voltage: Provides a nominal output voltage of 2.5 V (the "ARZ" variant is specifically calibrated for this value; other ADR421 variants offer 1.25 V, 2.048 V, etc.).
- Initial Accuracy: Boasts an extremely tight initial output voltage tolerance of ±0.02% (max) at 25°C (room temperature). This eliminates the need for post-production trimming in most precision systems, reducing design complexity and cost.
- Stability Across Temperatures: Exhibits ultra-low temperature coefficient (tempco), a key metric for voltage reference performance. The typical tempco is 1.5 ppm/°C (parts per million per degree Celsius) over the industrial temperature range (-40°C to +85°C), with a maximum of 5 ppm/°C.
- Importance: Minimal temperature drift ensures the output voltage remains stable even in environments with significant temperature fluctuations (e.g., industrial equipment, automotive systems), preventing errors in measurements or calibration.
- Low Output Noise: Generates very low noise to avoid corrupting sensitive signals. The typical output noise density is 3.5 µV p-p (peak-to-peak) over the frequency range of 0.1 Hz to 10 Hz—a critical range for low-frequency precision applications (e.g., data acquisition, sensors).
- Noise Reduction Mechanism: Integrates internal circuitry to suppress both thermal noise and flicker noise (1/f noise), which are common sources of voltage instability in precision references.
- Shunt Configuration: Operates as a shunt voltage reference (unlike series references), meaning it is connected in parallel with the load. It requires an external current-limiting resistor to set the operating current.
- Operating Current Flexibility: Supports a wide operating current range of 10 µA to 10 mA. This flexibility allows it to adapt to low-power (e.g., battery-powered sensors) and higher-current (e.g., ADC biasing) applications alike.
- Reverse Voltage Protection: Includes built-in protection against reverse voltage connections, preventing device damage during system assembly or operation.
- No External Components Required: Beyond the mandatory current-limiting resistor, no additional external components (e.g., capacitors for stabilization) are needed for basic operation, simplifying PCB layout and reducing bill-of-materials (BOM) cost.
The ADR421ARZ’s combination of precision, low noise, and temperature stability makes it indispensable in systems where accurate voltage references are critical. Below are its primary application areas:
- Use Cases: Precision analog-to-digital converters (ADCs), digital-to-analog converters (DACs), and sensor signal conditioning circuits.
- Role: Provides the critical reference voltage for ADCs/DACs to ensure accurate signal conversion. For example, in a 16-bit or 24-bit high-resolution ADC, the ADR421ARZ’s 2.5 V reference sets the full-scale input range—any drift or noise in the reference directly degrades the ADC’s measurement accuracy.
- Use Cases: Digital multimeters (DMMs), oscilloscopes, signal generators, and calibration tools.
- Role: Serves as a calibration reference to maintain the precision of T&M instruments. For instance, a DMM uses the ADR421ARZ to calibrate its voltage measurement circuitry, ensuring readings remain accurate across temperature and time.
- Use Cases: Industrial sensors (pressure, temperature, flow), programmable logic controllers (PLCs), and process control transmitters.
- Role: Biases or calibrates industrial sensors to ensure reliable, repeatable data. For example, a 4-20 mA pressure transmitter uses the ADR421ARZ to set a precise reference voltage for its internal signal conditioning, ensuring the output current accurately reflects the measured pressure.
- Use Cases: Patient monitoring devices (blood pressure monitors, glucose meters), medical imaging equipment (ultrasound), and diagnostic instruments.
- Role: Enables precise measurements critical for patient safety. In a glucose meter, the ADR421ARZ provides a stable reference for the sensor’s electrochemical reaction, ensuring the device outputs accurate glucose level readings.
- Use Cases: Automotive sensors (engine knock sensors, air-fuel ratio sensors), advanced driver-assistance systems (ADAS) components, and infotainment calibration circuits.
- Role: Withstands automotive temperature ranges (-40°C to +85°C) while maintaining stability. For example, an air-fuel ratio sensor uses the ADR421ARZ to calibrate its output signal, helping the engine control unit (ECU) optimize fuel efficiency and reduce emissions.
- Use Cases: Portable test tools, wireless sensors, and IoT (Internet of Things) devices.
- Role: Operates efficiently at low currents (down to 10 µA), making it suitable for battery-powered systems where power conservation is critical. It provides stable voltage references for low-power ADCs in wireless sensors, ensuring accurate data transmission without draining the battery quickly.
The table below highlights critical electrical and mechanical specifications of the ADR421ARZ, contextualizing its performance:
In summary, the ADR421ARZ is a high-performance 2.5 V voltage reference that excels in precision, stability, and low noise. Its versatility makes it a cornerstone component in data acquisition, test equipment, industrial, medical, and automotive systems—where reliable, accurate voltage references are non-negotiable.
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ADR421ARZ is a low-noise voltage reference (VR) device manufactured by ADI Images
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