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AD9913.. Timing on serial programming

Question asked by RedDragon on Nov 22, 2013
Latest reply on Nov 29, 2013 by RedDragon

I dont have an EVB of this DDS.

But i have implemented the AD9913 on my hardware, handled with an uC Freescale (S08QE128) by a SPI peripheral in bidirectional mode (only one line for i/o data).

The AD9913 conditions: External 25 MHz crystal mode, 10x PLL multiplier to frequency on VCO of 250MHz, serial programming (SCLK of about 2 MHz). The use of DDS is to make a BPSK (0/180°) modulator of an IF frequency of 10.7 or 13 MHz in Direct Switch Mode on proper pin, (bitrate about 33kbps..) to switch the preconfigured profiles...

I have noted a very difficulty to proper programming the AD9913 registers, several tries to obtain the right value...

May be critical the timing of serial communication?

At page 3 of Rev.A data sheet, i read 22ns for MAX of DataValidTime in Read mode, but this require a minimum frequency of 22.7 MHz on SCLK (?!) and the minimum value is omissis...

Also 2ns for MAX Rise/Fall Time on SCLK.. may be a MIN (or TYPical) ?

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