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AD7608 Spi with microcontroller

Question asked by Golden21 on Jul 5, 2017
Latest reply on Sep 24, 2017 by jcolao


I have some questions about the ad7608 18 bit converter SPI interface :

- From what I understood reading the datasheet, the SCLK digital input (spi master clock) frequency is ajustable by providing Vdrive, is this right ?

- if so, I see 4 possibles values for sclk frequency : 23,5Mhz, 17Mhz, 14.5Mhz and 11.5Mhz : I cant find any information if those are exact frequency sclk signal must reach or the maximum frequency allowed for sclk ? I assume it's max but i am not sure...

- if it is a max frequency, no problem. If not, as I wont be able to reach perfectly those frequencies with my microcontroller clock prescaler, what is a "close enough" frequency ? (I can reach 11.428, close to 11.5 ..)

-  my microcontroller  (TMS5701224) SPI module can read words which length is 16 bits max. The adc provides 18 bits data. Is that ok to configure the microcontroller with 9bits word length and to proceed like : set SS active (low logical), read 9 bits, set SS inactive, reset SS active, read the 9 bits lefts and so on... ? If not, would you have any idea of how should I proceed ?

- fourth and last question : From the datasheet, I understood that I can use only the DoutA line, and reading it 8 times will give me the 8  18 bits data values for each channel, is this right ?


Thanks a lot to any one who could help me !