MXD2420
High-resolution 24-bit sigma-delta ADC with integrated PGA, 8kSPS sampling, and exceptional noise performance.
Product Overview
Description
The MXD2420 is a precision 24-bit sigma-delta analog-to-digital converter featuring an integrated programmable gain amplifier (PGA) for high-resolution sensor measurement.
With programmable data rates from 10 SPS to 8kSPS and integrated digital filtering, this ADC achieves exceptional noise performance for precision instrumentation.
The device includes an internal reference, temperature sensor, and burnout current sources for sensor diagnostics.
Product Series
MXD
Primary Application
Satellite sensor systems
Key Features
- 24-bit resolution with 20 effective bits
- Programmable gain amplifier (1x to 128x)
- Low noise 0.1μVrms at gain=128
- Excellent offset drift 5nV/°C
- Internal 2.5V reference
- Integrated temperature sensor
- Burnout current sources for sensor diagnostics
- Flexible SPI interface
- Extended temperature range
Specifications
| Resolution | 24-bit |
|---|---|
| Data Rate | 10 SPS to 8 kSPS |
| PGA Gain | 1 to 128 |
| ENOB | 20 bits at 10 SPS |
| Noise | 0.1 μVrms (gain=128) |
| Offset Drift | 5 nV/°C |
| Gain Drift | 0.5 ppm/°C |
| Supply Voltage | 3.3V or 5V |
| Interface | SPI |
| Temperature Range | -55°C to +125°C |
| Package | CERDIP-24, QFP-32 |
Applications
Satellite sensor systems
Sensor signal conditioning
Precision weigh scales
Electronic system design
Temperature measurement
Data acquisition and conversion
Pressure sensors
Sensor signal conditioning
Strain gauge interfaces
Communication and interface
Scientific instrumentation
Electronic system design
FAE Expert Insights
"The MXD2420 is my go-to recommendation for precision sensor measurement in aerospace applications. The integrated PGA eliminates the need for external instrumentation amplifiers, reducing component count and improving reliability. With 20 effective bits at 10 SPS, it provides exceptional resolution for weigh scales, pressure sensors, and thermocouple measurement. The low offset drift (5nV/°C) is critical for long-term stability in satellite systems where calibration opportunities are limited. I've successfully used this part in satellite propulsion system pressure monitoring where 0.01% accuracy was required over 15-year mission life. The burnout current sources are valuable for sensor health monitoring - you can detect open or shorted sensors before they cause system failures. For thermocouple applications, use the internal temperature sensor for cold junction compensation. One tip: for lowest noise, use the lowest data rate your application can tolerate - noise decreases with the square root of averaging time."
Exceptional 24-bit precision ADC for aerospace sensor applications
— Dr. Li Ming, BeiLuo
Frequently Asked Questions
How do I optimize noise performance with MXD2420?
Noise optimization for MXD2420: 1) Use the lowest data rate your application allows - noise decreases with 1/√(data rate). At 10 SPS, noise is 3x lower than at 100 SPS. 2) Use higher PGA gain for small signals - input-referred noise decreases with gain. 3) Provide clean power supply with adequate decoupling - use separate analog and digital supplies if possible. 4) Minimize external noise pickup - use shielded cables and proper grounding. 5) Enable digital filter for additional noise reduction. 6) Use external reference with lower noise than internal reference for critical applications.
Use lowest data rate possible. Use appropriate PGA gain. Ensure clean power and proper shielding.
What is the best way to use the PGA in MXD2420?
MXD2420 PGA provides gains from 1x to 128x. Best practices: 1) Use the highest gain that keeps the output within full-scale range - this minimizes input-referred noise. 2) For bridge sensors, gain of 64x or 128x is typically optimal. 3) For thermocouples, gain of 32x to 64x works well. 4) Ensure input common-mode voltage stays within specified range (typically AVDD/2 ± 0.5V). 5) For ratiometric measurement with bridge sensors, use the same reference for both sensor excitation and ADC reference - this cancels out reference drift. 6) Consider offset voltage at high gains - auto-zero calibration may be needed for highest accuracy.
Use highest gain within full-scale range. Consider common-mode limits. Use ratiometric measurement for bridges.
How do I perform sensor diagnostics with MXD2420?
MXD2420 includes burnout current sources for sensor diagnostics. Two 500nA current sources can be programmed to flow into or out of the input pins. Diagnostic modes: 1) Open sensor detection - both currents source into inputs, open sensor causes full-scale reading. 2) Shorted sensor detection - one sources, one sinks, shorted sensor causes near-zero reading. 3) Normal mode - currents disabled for measurement. Enable diagnostics via SPI command before taking reading. This feature is valuable for detecting sensor failures in remote or inaccessible systems like satellites.
Use burnout currents to detect open or shorted sensors. Enable diagnostics periodically or before critical measurements.
What is the settling time for different PGA gains?
MXD2420 settling time varies with PGA gain due to bandwidth limitations. Typical settling times: 1x gain: 10μs, 8x gain: 20μs, 32x gain: 50μs, 128x gain: 150μs. Settling time must be considered when switching channels or changing gain. Allow sufficient settling time before starting conversion. For multiplexed systems, add settling delay between channel switches. The internal digital filter also contributes to effective settling - higher output data rates have shorter filter settling but more noise.
Allow adequate settling time after gain changes or channel switching. Higher gains require longer settling.
How do I use the internal temperature sensor?
MXD2420 includes an internal temperature sensor for monitoring die temperature or cold junction compensation. Temperature sensor output is approximately 0.1V at 25°C with slope of 0.3mV/°C. To use: 1) Select temperature sensor input via multiplexer (typically channel 7 or via special command). 2) Set PGA to 1x (sensor output is large enough). 3) Perform conversion and calculate temperature. Accuracy is typically ±2°C. For cold junction compensation in thermocouple applications, place the ADC close to the connection terminals to ensure thermal coupling. Calibrate offset at known temperature for improved accuracy.
Use for die temperature monitoring or cold junction compensation. Place ADC close to thermocouple terminals for best CJC accuracy.