Q.
What is the correct equation for the determining the corner frequencies associated with the rms averaging and the offset control loop in the AD8362 RMS Detector?
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A.
There are some errors in the Rev. D datasheet. Under the heading “TIME-DOMAIN RESPONSE OF THE CLOSED LOOP” there is an equation
fLP = 1/(CLPF x 1.1 KΩ)
This is incorrect. The correct equation is:
FLP = 1/(CLPF x 1.1 KΩ x 2π)
In the section “CHOOSING A VALUE FOR CLPF”, the equation is written as:
CLPF = 900 μF/(2π x FLP).
This expresses the correct equation in a slightly different format
Equation 13 on page 21 of the Rev. D datasheet is also incorrect. The correct equation for determining CHPF, which sets the high-pass corner of the offset control loop is:
CHPF = 200uF/Fhp
