Recently, I have been using your AD5930 Evaluation Board for a prototype, and I have noticed an odd glitch during frequency sweeping. I am continually bursting two different frequencies using the "Saw-Sweep mode" in the "external increment, external burst control" option. (The same glitch was appearing in the "external increment, auto-burst control" option as well.)
What I have found is that intermittently, the sweep of the two frequencies (7.33 MHz and 8.33 MHz) jumps to a third, unknown frequency state. This state then changes the order at which the bursting occurs. Attached to this email is an oscilloscope screen-shot of the mysterious frequency.
My question, then, is have you seen this issue before? Are there ways I can correct it via programming or set up?
I can send any additional information you might need to replicate this glitch or help solve this problem. as well. Below are the SPI commands sent [in order] at power up to the AD5930 chip. (Note, the SPI frequency is 656 kHz, sweeping from 7.33 MHz to 8.33 MHz, one 1 MHz step.)
Cntrl_Register = 0x0F73 (24-bit, single register write; DAC enable; Sine wave mode; MSBout enable; burst mode w/ DC mid-point; Burst external; increment external; saw-sweep mode; syncsel disable; syncout disable; reserved bits)
Fstart_LSB = 0xC793 (7.33 MHz)
Fstart_MSB = 0xD258
DeltaF_LSB = 0x2EB8 (1 MHz step-size, increasing)
DeltaF_MSB = 0x3051
Num_INCR = 0x1001 (1 step)
** From this point, we let the values sit for 1 millisecond, then begin toggling the CTRL line at a frequency of 71.43 kHz (7 microseconds high, 7 microseconds low). The waveform between cursors "A" and "B" does not look like the other frequencies we were expecting.
Any help or direction would be appreciated. Thank you,