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Problem with AD5263

Hello,

For an application, I use 2 AD5263 in SPI (see attach, "Capture.PNG).

The frequency of the SPI input signal (SDIMESURES) is 2,5Mhz (see attach SDIMESURES2,5MHz).

The problem I have is that my signal is damaged on the output of the first AD5263 (SDOMESESURES2,5MHz, see attach) and even more on the output of the second AD5263 (POT2,5MHz, see attach).

How can I do to have steep fronts? I saw in the datasheet :

" It is recommended to increase the clock period when using a pull-up resistor to the SDI pin of the following device because capacitive loading at the daisy-chain node (SDO to SDI) between devices may induce time delay to subsequent devices"

I try to change my frequency to 1,25MHz, but nothing change, my fronts are also longer (SDOMESURES1,25MHz, see attach).

If you have any suggestions, I would be very happy :-). Excuse my poor English, I'm French.

Regards, Florian

attachments.zip
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  • Hi Florian,

    As per the datasheet you only need 20 bits in a frame to set the position of the wiper in the digipot for both device.

    I would like to know what data are you sending into the device.

    How many bits are you sending in a single frame?

    Can you share the waveform of CSb, SCLK, SDI and SDO in a single screen and send it? 

    Regards,

    Koushik

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  • Hi Florian,

    As per the datasheet you only need 20 bits in a frame to set the position of the wiper in the digipot for both device.

    I would like to know what data are you sending into the device.

    How many bits are you sending in a single frame?

    Can you share the waveform of CSb, SCLK, SDI and SDO in a single screen and send it? 

    Regards,

    Koushik

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