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AD8436 RMS-to-DC

Question asked by SouthPacific on Aug 1, 2012
Latest reply on Sep 7, 2012 by jstaley

Hi JS,

 

I've now had time to look at the AD8436 Data Sheet.

 

In my AD737 post, you wondered why people still have interest in an AVERAGE result. Possibly its because as engineers, we want to be able to flick a switch and actually see how poor the AVERAGE reading is - as in, its for educational, rather than practical reasons.

 

On the AD737, it is suggested to pre-boost the user supplied input signal by 111%, if an AVERAGE reading is to be done. Is that still the case with the AD8436?

 

Some data sheet comments.

 

Page 16 of 20 Figure 41. Slightly below top, left text, bottom line - word RECTIFIED is spelt incorrectly.

 

Page 11 of 20 FET Input Buffer. Add the word CORE so it reads - the input resistance of the AD8436 core is 8k,

 

Page 13 of 20 Capacitor Construction - Mention that a Metalized Polyester cap is optimal (it didn't say Metalized Polypropylene MKT - which might be best for timing - yet huge). These types of capacitors in 10u are not so common - and I don't believe any film capacitors come in surface mount. However, in development of the AD8436, the designers probably came across some really "nice" types (smallish, affordable, performed well). Are you able to give information of what those types were?     (Digikey, Mouser...)

 

Page 15 of 20 Converting to Average Rectified 4th line down, ...appears at the output... I think it could say appears at OUT (I wondered whether it was the core or the output opamp).

 

Cheers,

 

Peter

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