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AD8310 slope temperature stability

Question asked by JGerber on Apr 18, 2014
Latest reply on Apr 18, 2014 by jdobler

Hi there,

 

We are busy with a cost saving exercise on one of our design. Part of the change is moving from a dual AD640 log amp set to a single AD8310.

The AD8310 gives a RSSI slope variations of 23.8 mV/dB at 10 MHz to ~ 22.8 mV/dB at 400 MHz (Figure 16). Our application is at 60±5 MHz, so this does not have much of an effect. However, the datasheet does specify the total variance of the slope of 20-26 mV/dB over temperature and frequency. How much would this change over temperature for this the smaller frequency range and how much of the change is over different the batches of components and not over temperature?

 

We are increasing the video slope in the design (to 37 mV/dB) and I would like to know how much temperature compensation is required, if any. We did not use extra temperature compensation on the AD640 design, but that may have been an oversight. The secondary question would be, do I need a trim pot in the slope increase circuit to allow for batch variation or how much would it change if I left it at a fixed scaling.

* If extra temperature compensation is required, what is the change in slope (negative / positive, etc).

 

Thanks for your support.

 

Regards,

Johann

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