What's the actual ADC sampling rates of AD5940 and ADUCM355, and how to make a choice?

Hi BlingBling,

The sampling rate of the ADC depends on the configuration you choose for the digital filters that perform post processing. The 800k samples per second specification indicates this is available with no filtering.

The 400 kSPS and 200 kSPS specification are when the Sinc3 filter is enabled with an OSR of 4 (I assume four samples are low-passed with an FIR/IIR into a single value). This is the "decimation factor" to the right of the BASIC ADC SPECIFICATIONS.

Each functional block may impact your actual sample rate. I recommend profiling interrupts, or the time it takes to fill up the FIFO to verify sampling rates for your settings.

To answer your second question, the ADuCM355 has an integrated Cortex-M3 processor. The AD5940 is just an analog front end, bring your own micro.

Best,

Matt

Thanks for your answer,

What about the choice between EVAL-AD5940 and EVAL-ADUCM355? I think ADUCM355 has better performance and integration. However, EVAL-AD5940 is much more expensive than EVAL-ADUCM355. What‘s the cause?

Hi,

The eval-AD5940 kit comes with EVAL-ADICUP3029 base board (containing microcontroller for testing and verification), hence the cost.

Both IC's use the same analog front-end. From EVAL-ADuCM355QSPZ UG-1308: 

"The ADuCM355 is a dual-die device that has a Cortex-M3 digital die and an analog front-end (AFE) die. The AFE die and the AD5940 are the same except for some differences in which pins are bonded out, and both devices share a common library interface to simplify firmware development."