How do you choose the right integrated ADC for your sensing application?
The search term "analog-to-digital converter selection" has generated thousands of results, showing that this task remains a challenge for many engineers working on advanced sensing solutions. From basic 10-bit ADCs found in 8-bit microcontrollers to high-speed ADCs capable of GHz sampling rates, there are countless options available in the market.
If you're not designing a custom front-end for your sensor, you're likely looking for an integrated ADC that offers excellent performance without compromising power efficiency or system flexibility. In this article, I’ll walk you through key parameters that can help narrow down your ADC choices—though your specific application might require additional considerations.
Resolution is one of the most frequently discussed ADC parameters. While the number of bits directly affects the resolution and accuracy, it's important to consider what the data will be used for after conversion. For instance, if you're measuring temperature changes, a 10-bit or 12-bit ADC may be sufficient, as the measurement is relative. However, in applications like electric meters, where precise current measurements determine energy billing, higher-resolution ADCs—often 16-bit or more—such as delta-sigma ADCs, are essential for accuracy.
Sampling rate is another critical factor. According to the Nyquist theorem, the ADC must sample at more than twice the input signal frequency. For example, a 100 kHz signal needs a minimum sampling rate of 200 kHz. However, the datasheet’s stated sampling rate only refers to the actual sampling and conversion time, not including setup time or post-processing. These factors are equally important because they impact how much time you have for data processing and decision-making between samples.
For example, an ADC with a 1 MSPS (Mega Samples Per Second) rate can collect 1,000 16-bit samples in just 1 millisecond. If using double buffering, you have up to 1 ms to process the data, make decisions, and transfer the data before the next batch is ready. This timing margin is crucial for real-time applications.
Reference voltage selection is also a key consideration. Many ADCs come with internal precision references, which simplify design and improve accuracy. The ability to adjust reference voltage ranges adds flexibility, especially when dealing with varying input signal levels.
Operating voltage range is another parameter to evaluate. Some ADCs function within a limited portion of the supply voltage, which can be a concern in battery-powered systems. For example, in low-power applications, it’s often necessary to operate at lower voltages (like 1.8V or even below 1.72V in some cases), ensuring reliable operation until the device is powered off.
Input channel count isn't just about the number of pins available. It also involves the ADC's flexibility in handling multiple channels, especially when sequencing inputs. Features like configurable differential inputs, dedicated interrupts, and customizable data formats can significantly reduce system overhead and improve overall efficiency.
As mentioned earlier, your ADC selection criteria may vary depending on your application. If you're interested in exploring high-precision ADCs, TI’s MSP432P4 series offers up to 16-bit accuracy. You can get started with the MSP432P4 LaunchPad Development Kit and access tutorials on precision ADC usage through the SimpleLink Academy training portal.
If you want to dive deeper into ADC selection, check out how TI’s MSP432P4 high-precision ADC compares with other leading ADCs on the market. Refer to Figure 1 below and explore our application report for useful tips on interpreting ADC datasheet parameters. Whether you're designing a simple sensor or a complex system, choosing the right ADC is a critical step in achieving accurate and reliable performance.
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