AnsweredAssumed Answered

AD9883 on a video board

Question asked by PGerva Employee on Oct 3, 2016
Latest reply on Oct 26, 2016 by joe.triggs

We are using  AD9883ABSTZ-110 on a video board.
Input to the converter is a video signal from -300 mV to + 700 mV (where -300 is the sync level and + 700 is the white level).


Question 1

With reference to Figure 2  of the data sheet in attachment (gain and offset control), we don't understand clearly what are the correct setting for the corresponding register.




Question 2

We have checked that delivering the same video signal to different board, results in different reconstructed video signal (without any changes to the register setting).

We have monitored four different board measuring the following internal reference voltage: 1.23, 1.26, 1.27 and 1.29 Volt.

Is it possible that these difference in the internal reference voltage can cause so big difference on the reconstructed video signal?

See image below.


===================================================================

Blue signal is the input signal.

Cyan signal is the reconstructed signal.

Board equipped with AD9883ABSTZ-110 with internal reference voltage 1.29
 

Figure 1

 

FIGURE 1
===========================================================================


Blue signal is the input signal.

Cyan signal is the reconstructed signal.

Board equipped with AD9883ABSTZ-110 with internal reference voltage 1.26

Figure 2
FIGURE 2
=========================================================================


If yes, how is possible to mitigate this effect?
Data sheet suggests to use an external voltage reference. But how to connect it to the AD9883ABSTZ-110?

 

Kind regards

PG

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