The AD7175-2BRUZ is a 24-bit Σ-Δ ADC with a programmable output data rate ranging from 5 SPS to 250 kSPS. In precision data acquisition systems, digital filter selection affects more than just noise performance. It also influences output data rate, settling time, channel-switching efficiency, and power-line interference rejection. As a result, the same ADC can exhibit noticeably different system behavior under different filter configurations.
1. Three digital filter options for different acquisition requirements
The AD7175-2BRUZ provides sinc5 + sinc1, sinc3, and enhanced 50 Hz/60 Hz rejection filters. Filter selection should begin with the system requirement: whether the priority is fast channel switching, lower noise, or stronger rejection of power-line interference, rather than simply choosing the lowest available output data rate.
The sinc5 + sinc1 filter is particularly suitable for multiplexed multichannel applications. When several analog inputs must be scanned sequentially, filter settling time directly affects the effective channel update rate. This filter is optimized for fast multiplexing and can achieve single-cycle settling at output data rates of 10 kSPS and below. It is therefore well suited to multi-sensor acquisition systems and applications that require relatively fast channel switching.
The sinc3 filter is more appropriate for low-speed, single-channel precision measurements. ADI positions it as an option for achieving improved single-channel noise performance at lower data rates, with a settling time equal to 3 / output data rate. For pressure, temperature, or other slowly changing signals, sinc3 is often worth considering when stable measurements are more important than rapid channel switching.
2. There is no single optimum point between speed and noise
Increasing the output data rate provides faster response, but it also widens the effective digital filter bandwidth, which can allow more noise into the conversion result. According to the AD7175-2 specifications, its noise-free resolution is 17.2 bits at 250 kSPS, 20 bits at 2.5 kSPS, and up to 24 bits at 20 SPS. These figures show why a 24-bit ADC should not be evaluated by nominal resolution alone. Actual output data rate, noise level, and target signal bandwidth all need to be considered.
For control systems or rapidly changing signals, a higher data update rate may be more important than achieving the lowest possible noise. In weighing, temperature measurement, or high-precision instrumentation, a lower data rate may be a better trade-off if it provides improved noise performance. Filter selection is therefore a balance among response speed, effective resolution, and signal bandwidth rather than a simple choice between maximum sampling speed and minimum noise.
Digital filter settings should also be evaluated together with the analog front end. If the sensor, amplifier, or front-end RC network has limited bandwidth, configuring the ADC for a higher output data rate will not necessarily improve overall system response. Conversely, an unnecessarily high data rate may capture more high-frequency noise and reduce effective resolution. ADC configuration should therefore be coordinated with front-end bandwidth, signal dynamics, and target measurement accuracy.
The AD7175-2BRUZ also allows different channels to use different setup configurations, enabling each channel to operate with its own filter and output data rate. This is particularly useful in mixed-sensor systems. Fast-changing channels can prioritize response time, while slower precision channels can use stronger digital filtering without forcing the entire system to follow a single acquisition strategy. In multichannel designs, settling time after channel switching should also be included in the timing budget rather than estimating overall acquisition efficiency from the single-channel output data rate alone.
3. 50/60 Hz rejection should be selected according to the application environment
Industrial environments and precision measurement systems are often exposed to 50 Hz or 60 Hz power-line interference. Simply reducing the output data rate does not always provide the most effective solution. The AD7175-2BRUZ includes enhanced 50 Hz/60 Hz rejection filters designed specifically to suppress this type of interference. According to the device specifications, the enhanced filter can provide 85 dB simultaneous rejection of 50 Hz ±1 Hz and 60 Hz ±1 Hz interference at 20 SPS, with a 50 ms settling time. The enhanced filters can also operate at up to 27.27 SPS, where the specified simultaneous rejection is 47 dB with a 36.67 ms settling time.
This configuration is particularly useful in industrial sensing, process control, and laboratory instrumentation where power-line coupling can affect measurement quality. Stronger interference rejection, however, generally comes with a longer response time. If the system operates in a relatively low-noise environment and requires faster data updates, maximizing 50/60 Hz rejection may not be the most appropriate design choice.
Filter selection for the AD7175-2BRUZ is best approached from the requirements of the specific application. For fast multichannel scanning, sinc5 + sinc1 is a strong candidate. For low-speed, single-channel precision measurement, sinc3 may be more suitable. Systems exposed to significant power-line interference should evaluate the enhanced 50/60 Hz rejection mode. The final configuration should also account for input signal bandwidth, channel count, allowable settling time, and target noise performance.
For precision acquisition systems built around the AD7175-2BRUZ, understanding these filter trade-offs is more useful than focusing only on the highest data rate or the lowest noise figure. In component selection and supply support, WIN SOURCE also considers how device specifications align with actual application requirements, helping engineering and procurement teams make more informed decisions across design needs, component availability, and system-level constraints.
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