AD7606C-16: The relationship between SCLK frequency and sampling rate

Dear Technical Support Team,

Is there relationship between SCLK frequency and sampling rate?

According to the datasheet, 60MHz(VDRIVE > 2.7 V) is the max frequency.

My microcontroller is max 16MHz for SCLK. 

My target is over 200ksps and 8ch simultaneous sampling. SPI is serial interface.

Best Regards,

ttd



Add "SPI I/F is serial mode."
[edited by: ttd at 11:10 PM (GMT -4) on 25 May 2021]
  • +1
    •  Analog Employees 
    on May 26, 2021 6:10 AM

    Hi ttd,

    The sample rate comes dictated by the CNVST signal frequency. However, you need to clock out the data in between two CNVST pulses.

    So, if your SCLK is 16 MHz, but you need to clock out 8ch*16bits=128 clocks, that means you max sampling frequency is 125kSPS.

    But if you have four channels in ADCa and four channels in ADCb plus you can handle two MISO lines(DOUTa and DOUTb), you can run duplicate that speed. Another alternative is to use the parallel interface for faster throughputs.

    Regards,

    Lluis.

  • Hi Lluis,

    Thank you for your reply.

    I calculated that SCLK is 25.6MHz for 200ksps (8ch*16bits=128 clock).

    >But if you have four channels in ADCa and four channels in ADCb plus you can handle two MISO lines(DOUTa and >DOUTb), you can run duplicate that speed.

    →Dose it mean this two Doutx lines mode for Serial Interface?

       Is this case sampling rate 250kSPS with 16MHz SCLK?

    Best Regards,

    ttd

  • +1
    •  Analog Employees 
    on May 31, 2021 6:28 AM in reply to ttd

    Hi ttd,

    Short answer is yes, if you have two DOUT lines, with half the SCLK you can clock out the same number of channels. Or with same SCLK, achieve twice throughput rate.

    Please, dismiss what I said about 'ADCa and ADCb', I was thinking on AD7616. But the comment on two DOUT lines applies here too.

    Regards,

    Lluis.

  • So, im using the ad7606c-18 insteado of the -16, and I use a SCLK with 16.67 MHz and works correctly, but when I increase it to 25 MHz it does not work.

    Another question that I have, if you know if the FlexSPI from NXP LS1028 can be adapted to this serial protocol, I think we cannot, and what SPI protocol has more than one MISO signal?

    Thanks.

  • 0
    •  Analog Employees 
    on Sep 2, 2021 12:12 PM in reply to aaganza

    Hi aaganza, you're right. The classic spi on MCU may have just one MISO line. The 4DOUT mode is not that standard, easier to interface with FPGAs instead.

    Regards,

    Lluis.