CS5529-AP(1997) Ver la hoja de datos (PDF) - Cirrus Logic

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CS5529-AP
(Rev.:1997)

16-Bit, Programmable ∆Σ ADC with 6-Bit Latch

Cirrus Logic 

CS5529

FAQs

11) What do the numbers in the calibration registers actually mean?

A: There are two internal read/write calibration registers in the CS5525/26

(offset, and gain). One LSB in the offset register is 2-24 proportion of the

input span (bipolar span is 2 times the unipolar span). The MSB in the

offset register determines if the offset that is to be trimmed is either posi-

tive or negative. The converter can typically trim ±50% of the input span.

The gain register spans from 0 to (2 - 2-23). The decimal equivalent

meaning of the gain register is:

D = b020+ b12-1 + b22-2 + b32-3 + ... + bN2-N

where the binary numbers have a value of either zero or one. After a gain

calibration has been performed, the numeric value in the gain register

should not exceed the range of 0.5 to 2.0 (decimal) [400000(Hex) to

FFFFFF(Hex)].

12) How can the gain be calibrated if a full-scale signal is not available?

A: The CS5525/26 can be gain calibrated with some input signal other than

full scale. For example, when the converter is reset, the gain register’s

calibration word is 1.0 (decimal). If a signal representing ten percent of

full scale reads three percent less than it should, the value in the gain reg-

ister can be scaled up by three percent. Gain accuracy can be improved if

output words are averaged while using this technique. Use caution when

a calibration signal less than full scale is being used. If the transfer func-

tion of the transducer being used to generate the ten percent signal hap-

pens to have a major nonlinearity at the point at which calibration is

being performed, it will cause the rest of the transfer function to be incor-

rect.

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PI246PP1 OCT ‘97

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