DS90UB948-Q1: Is there any requirement about DS90UB948's PDB?

Lian Wu

Part Number: DS90UB948-Q1

Dears:

We are testing the eye diagram of the communication between DS90UB947 and DS90UB948 in the Infotainment system.

After the system is powered on and Screen is powered on, if 948's PDB is Low, we can get a good eye diagram.

However, after the system is powered on and Screen is powered on, if DS90UB948 is working firstly, then let DS90USB948's PDB Low, we can not get eye diagram.

Is there any requirement about DS90UB948's PDB?

Btw, after power on, if 948's PDB is Low, 947 can be got a good eye diagram.

And if 948's PDB is High firstly, then is low, 948 can not be got a eye diagram.

best regards

Luck Wu

over 7 years ago

0 Palaniappan Manickam over 7 years ago

TI__Genius 10475 points

Luck,
The 948 PDB should be asserted after valid data is being received at the 948 input from the 947 serializer.

PDB should only be activated after all the power supplies have ramped up and reached the steady state value. On the 947 side ensure the input PCLK is stable for atleast 1us without any frequency drifts before applying PDB.

0 Lian Wu over 7 years ago in reply to Palaniappan Manickam

Genius 5250 points

Dears:
Could you kindly help to check the below issue?

Btw, after power on, if 948's PDB is Low, 947 can be got a good eye diagram.

And if 948's PDB is High firstly, then is low, 948 can not be got a eye diagram.

Thanks a lot!
Best regards
Luck Wu

0 Palaniappan Manickam over 7 years ago in reply to Lian Wu

TI__Genius 10475 points

Luck,
Not sure if I understand the question properly.
Where is this good/bad eye diagram measured at - at the output of 947? And what do you mean by good or not good?
As I mentioned the PDB of 948 side should be activated (low -> high) after the 947 is transmitting valid data to the 948.

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DS90UB948-Q1: Is there any requirement about DS90UB948's PDB?