Dear TI team,
Acc. to the datasheet of DS90UB954 (SNLS570B):
"The VPOC noise must be kept to 10 mVp-p or lower on the source / deserializer side of the system. The VPOC fluctuations on the serializer side, caused by the transient current draw of the sensor and the DC resistance of cables and PoC components,must be kept at minimum as well. Increasing the VPOC voltage and adding extra decoupling capacitance (> 10 µF) help reduce the amplitude and slew rate of the VPOC fluctuations."
Currently we are using an active differential probe and limiting the BW of the oscilloscope to 20MHz in order to focus in the noise produced due to load changes (in our case it is due to increase of consumption of the cameras when sending the frames).
The measuring point used is right before the inductor of the Vpoc network.
Currently we have a floor noise of ~15mVpp with some spikes produced by the loads (cameras). Noise Vpp is around 50mVpp (measured in the described test point, with BW limited to 20MHz and using active differential probe).
I'd like to ask the following:
- What is your recommended measuring method for this voltage noise in the VPOC?
- How strict is this requirement to have a proper link in our system? Is it possible to "relax this requirement" and still be in a good position to ensure a proper FPD-link functionality? We have also measured the eye diagram of back-channel and forward-channel and they are both inside specs.
BR,
Vicent Climent