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AD5930 strange behavior

Question asked by HSGIMAT on Oct 4, 2011
Latest reply on Oct 20, 2011 by LiamR

Hi all,

 

I'm currently using the AD5930 as a function generator on a development board. The AD5930 is clocked with a 41.94304MHz clock signal resultig in a frequency increment of 2.5Hz.

The AD5930 allows fixed frequency mode as described in AN-1044. Furthermore the AD5930 supports burst mode by setting the burst time register (TBURST). I now wanted to combine both modes in a fixed frequency burst.

Therefor the AD5930 is configured as described in the datasheet and the application note to a fixed number of output waveform cycles. This works well up to the point the number of "on" cycles plus "off" cycles exceed the value of 48.

For example a 1MHz burst signal with 24 cycles (24µs) and further 24 cycles off time (further 24µs) works well, but the combination 25 cycles burst (25µs) and 24 cycles off time (further 24µs) doesn't work.

I've also tried to manually set the register values to exclude a bug in my software, the result is the same.

Up to now I couldn't find a correlation to explain this behavior.

 

Can anyone confirm that the AD5930 behaves this way? Is there a possible work around know?

 

Thanks for your reply.

Kind regards, HSGIMAT

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