I encounter a problem about DS90UB925 and DS90UB926. Could you kindly give me some advise?
My block diagram as follow. There is a DS90UB926 on my board, which get data stream from DS90UB925 from the car.
But the system doesn't work well. The Lock pin of 926 only got high for about 300ms when power up, then it got low, and the RGB pins have no output. The wave form of VDD(channel 1)and Lock PIN of 926(Channel 2) as follow:
And we have do some testing as follow:
1、the I2C of 926 is OK. After Writing some registers I can read the same data. So the IC is working
2、Only in the mode 9, the 926 can lock, but the data and clock is not right. The output of HS and VS are all 16M.
3、We have tried another piece of 926, the result is the same.
4、We have another kind of good 926 PCB。Connecting it to the 925 source from the car is OK。 So the 925 source is OK。
5、We compare the singal of RIN+/-(near the pin of 926) between our PCB and the good PCB. We found the singal is a little different(Not we don't have a differential oscilloprobe, so we measure RIN+/- to GND), the main differen si peak-to-peak value. Our value is about double the good board. does it affect?
Our board
Reference board
6、On the reference design I see a CM inductor and resistor on the line, which I don't have in my design ,is it important?
my design
reference design
