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Can we configure the AD7768-1 as an ADC with an adjustable sampling frequency?
Can we directly switch the sampling frequency of the chip through the program? I mean don't change the external hardware device. Simply use the FPGA to input a command to the ADC via SPI .Because I see that the AD7768-1 provides three power modes and kinds of modulator and filters.
Hi Lizhe,
The AD7768-1 is a Sigma-Delta ADC. The principal of operation is an over-sampled architecture followed by decimation and filtering. You can see more on how Sigma-Deltas work Here and also in the Theory of Operation section of the datasheet.
The sampling rate is determined by FMOD which is set by a combination of the MCLK and the internal divide set by MCLK_div. The MCLK is supplied by the user. The output data rate is also dependent on decimation rate which I have shown in my response above.
The maximum input signal bandwidth the AD7768-1 can digitize depends on the output data rate and filter selected. To see how all this works I suggest taking a look at the filter tool which appears on the AD7768-1 product page. You can see how the MCLK, MCLK_div and decimation rate affect the output rate, SNR and power consumed.
The AD7768-1 Product Page contains the Filter Model in the Tools and Simulations section. To be clear, the AD7768-1 can output data at rates as high as 1MSPS to as low as hundreds of Hz.
Regards
Niall
Hi Niall，
Thank you very much for helping me solve this problem！
Lizhe
Thank you very much for your answer！
There is another question I hope to get your help.
When we operat AD7768-1,if it works in the low power mode and using the sinc5 filter in the default?
And how can I find out the default state after the chip is powered on in the datasheet?