One of my customers is investigating AD9833 DDS for sine wave generator.
His application frequency is relative low as 0.9 kHz to 22.2 kHz range. (0.9kHz, 1.8kHz, 2.8kHz, 6kHz, 12kHz, 15kHz, 18kHz, 21kHz, 5kHz, 7kHz, 9kHz, 11kHz, 13kHz, 15.1kHz, 17.3kHz, 19.7kHz, 22.2kHz, etc)
His design point is switching the output frequency from one to another at near zero-cross phase angle point.
For example, he first generates 5 kHz sine wave and switch to 7 kHz sine wave at near zero-cross phase angle point after reception of command signal from MCU.
It is not important that delay time between reception of command and actual occurrence of frequency switching. Most important is switching at zero-crossing phase angle point, he said.
I asked that it is acceptable the frequency switch is made with keeping continuous phase, but not zero-crossing point. His reply was negative.
Could you advise me how to do it using AD9833?
Is it possible with some external components in addition to AD9833?