Working mode: 250MPS, 2scomplement, found that when outputting an unbiased standard sine wave, it is found that glitches (output errors) occur after a period of time (about 25ms) The level of the burr is a fixed position, which appears at the position of 0, 1/2, -1/2 full amplitude, as shown in the figure below:
there is a probability of error when the digital code jumps from 0x0000(0) to 0xffff(-1). The following is the waveform when the error is output from 0x0000 to 0xffff every 10us:
- the code value 0 is the center of the sine wave. The output common mode has been corrected correctly.
- Customer can’t verify with EVM because they don’t have EVM now.
- Have not bypass DLL. Check the value of the DLL lock register to confirm that the DLL is locked.
- Adjust the phase offset in the register from maximum to minimum, and the error has not been improved.
In addition, this error does not occur all the time. It occurs once in about 20ms and lasts for several hundred us.
Could please help to analysis the reason why glitches appear? Thanks for your help!