How to generate Frame Clock(FR) of the ADC?

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Lukas12

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Hello everyone,

I'm using a FMC board card with ADC - LTC2174. After powered on，I can detect Data output clock (DCO) signal of the ADC with Oscilloscope. However I can't detect Frame Clock (FR) signal.

1. I think that FR signal will be automatic generated after ADC powered on (just like DCO signal). Is that actually true?

2. I don't connect analog inputs of ADC. Must analog inputs be connected in order to generate FR signal?

Thanks
 

1 yes 2 no. There's no way to disable FRC separately.
 
Thanks FvM. So is this means that ADC may be destroyed?
 

That's a possible explanation. Or shorted FRC output. Not sure if an ENC input signal outside specified frequency and level range may cause a similar effect too.
 

Hi,

I used the LTC2170, which has an identical interface.

Defective IC is possible, but I think it´s not very likely.
You know that they are LVDS signals and thus only have a small differential voltage level. Relatively hard to measure with a scope, but for sure possible.
Is your scope able to trigger at the differential voltage between the FR-pair?

Klaus
 

I tested the line on FMC. It seems that the problem lies in the connection of the line.

- - - Updated - - -

Hi Klaus,

I think the scope that I used can capture differential FR signal. Becaues it has detected DCO signal which is also LVDS signal and has the same voltage level as FR. Anyway, I found that there is a problem on the line connection of FMC board card.
Thanks for your reply.
 

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