Please help me.
First, I use DRVDD = 1.8V, differential clock input, and the output test mode is OK.
Then I swith to use DRVDD = 3.3V, single end clock input.
The SPI read is OK, and I can read out Chip ID (address 0x01)
But when I try output test mode, outputs are all high.
I'm wondering if the clock is not accept by AD9640, so please check the clock waveform for me.
Datasheet reference design:
The waveform of point A is:
And the waveform of point B is:
At point B,
(1) Low level is 480mV, high level is 1.88V.
(2) Vpp is 2.02V
(3) Duty cycle is 49.59%
(4) Vrms is 1.407V
Is the clock not good or there may be other mistakes?
Please give me a direction to debug.