Mxtronics Data Converter Selection Guide
Selecting the right data converter is critical for achieving optimal system performance in aerospace and defense applications. This guide walks through the key selection criteria and provides recommendations for common application scenarios.
Resolution Selection: For general sensor monitoring and control applications, 12-bit resolution is typically sufficient. For precision instrumentation requiring high dynamic range, 16-bit converters provide 96dB of dynamic range. For the most demanding measurement applications such as test equipment and scientific instruments, 24-bit sigma-delta converters offer exceptional precision.
Speed Considerations: SAR ADCs offer the fastest sampling rates, up to 1 MSPS in the Mxtronics portfolio. These are ideal for multiplexed systems and applications requiring fast transient capture. Sigma-delta ADCs trade speed for resolution, with rates up to 500 kSPS for 16-bit devices and lower rates for higher resolution. Consider the bandwidth requirements of your signals when selecting sampling rate.
Environmental Requirements: For commercial aviation and ground-based military systems, industrial temperature range (-40°C to +85°C) may be sufficient. For military aircraft, missiles, and space applications, extended temperature range (-55°C to +125°C) is required. Engine compartment and high-temperature applications require the full military temperature range (-55°C to +175°C).
Radiation Tolerance: For space applications, select radiation-tolerant versions with TID rating appropriate for your mission. LEO missions typically require 30-50 krad(Si), while GEO and deep space missions may require 100 krad(Si) or higher. All Mxtronics radiation-tolerant devices are characterized for single event effects.
Interface Selection: SPI interface offers the highest flexibility and is supported by most microcontrollers and FPGAs. Parallel interfaces provide the highest throughput for very high-speed applications but require more I/O pins. Consider your system architecture and available interface resources when selecting.
💡 FAE Insights
📋 Customer Cases
Commercial Space Company
Challenge
Selecting the right ADC for a high-resolution imaging payload with strict power and reliability requirements.
Solution
Selected MXD1604 16-bit SAR ADC based on radiation tolerance, low power, and precision requirements.
Customer Feedback
"Customer reported excellent performance and has standardized on Mxtronics for future missions."
Frequently Asked Questions
1. What is the difference between SAR and sigma-delta ADCs?
SAR (Successive Approximation Register) ADCs offer fast conversion speeds and are ideal for applications requiring high sampling rates or multiplexed channel acquisition. They provide good accuracy with lower latency. Sigma-delta ADCs use oversampling and noise shaping to achieve very high resolution (up to 24 bits) with excellent noise performance, making them ideal for precision measurement applications. However, they have higher latency due to digital filtering requirements. Choose SAR for speed, sigma-delta for precision.
2. How do I calculate the effective number of bits (ENOB) I need?
To determine required ENOB, first identify your system's dynamic range requirement in dB. For example, if you need to resolve signals from 1mV to 10V (80dB range), add 6dB for headroom, giving 86dB required dynamic range. Divide by 6.02 to convert to bits: 86/6.02 = 14.3 bits. Round up to the next standard resolution: 16 bits. Remember that ENOB is typically 1-2 bits less than the ADC's resolution specification due to noise and distortion, so a 16-bit ADC may provide 14-bit ENOB.
3. When do I need radiation-tolerant data converters?
Radiation-tolerant data converters are required for any application operating in radiation environments. This includes all space applications (LEO, MEO, GEO, deep space), nuclear environments, and some high-altitude aviation. Standard commercial components may fail at 5-10 krad(Si) total dose, while Mxtronics radiation-tolerant devices are rated for 100 krad(Si). radiation-tolerant devices are characterized for single event effects (SEE) which can cause upset or latchup in standard components. For mission-critical applications in these environments, radiation-tolerant components are essential.
4. What power supply considerations are important for precision ADCs?
Precision ADCs are sensitive to power supply noise and ripple. For best performance, use low-noise LDO regulators rather than switching supplies for the analog supply. If DC-DC converters must be used, implement adequate filtering and keep switching frequency away from the ADC sampling frequency to avoid aliasing. Separate analog and digital supplies are recommended, with the analog supply powering the ADC reference and analog circuits. Use proper decoupling with ceramic capacitors (0.1µF and 10µF) placed close to the ADC power pins. Mxtronics provides recommended power supply designs in our application notes.
5. How do I interface an ADC with my microcontroller or FPGA?
Mxtronics ADCs use standard SPI interface which is supported by virtually all modern microcontrollers and FPGAs. The interface typically requires 3-4 signals: SCLK (serial clock), SDI (data input), SDO (data output), and CS (chip select). Some devices also provide a BUSY or DRDY (data ready) signal for conversion status. For microcontrollers, use the hardware SPI peripheral with CPOL=0, CPHA=0 mode. For FPGAs, implement a simple SPI master state machine. Reference code examples are available from Mxtronics for popular microcontroller platforms including STM32, TI C2000, and Microchip dsPIC.