paralleling SPI ADC's

Mar 26, 2008 3 Replies
J

Hi,



I'd like to put two ADC's and a DAC on the same SPI bus, all with



200kHz sampling, but I think I may need to use three separate SPI buses to do this as the SCLK frequencies as specified in the datasheets I've seen so far are too low. Anyone know of some 12bit or higher SPI ADC's/DAC's with fast (40MHz+) SCLK frequencies?

cheers, Jamie


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M

12 bits * 200K = 2.4Mbits/sec 3 devices = 7.2Mhz

Find three devices that can handle 10 MHz SPI bus speed and your set. Any 12 bit 1MS/S SPI ADC must at a minimum support 12 MHz SPI bus. Use a MUX for the CS\\ signal.

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D

SPI ports are 8-bit !

You need to use 16 bits * 200K = 3.2Mbits/sec

3 devices = 9.6Mhz

Not much margin for errors.

10Mhz SPI ports may not be able to handle it.

donald

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J

Also the sampling isn't spaced evenly, I need to run the samples close together and then there is sampling deadtime.

I found a 1MSPS 12bit ADC with 20MHz max SCLK:

formatting link

cheers, Jamie

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