CS5376A datasheet(59/107 Pages) CIRRUS

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CS5376A

15. GAIN AND OFFSET CORRECTION

The CS5376A digital filter can apply independent

gain and offset corrections to the data of each mea-

surement channel. Also, an offset calibration algo-

rithm can automatically calculate offset correction

values for each channel.

Gain correction values are written to the GAINx

registers (0x21-0x24), while offset correction val-

ues are written to the OFFSETx registers (0x25-

0x28). Gain and offset corrections are enabled by

the USEGR and USEOR bits in the FILTCFG reg-

ister (0x20).

When enabled, the offset calibration algorithm will

automatically calculate offset correction values for

each channel and write them into the OFFSETx

registers. Offset calibration is enabled by writing

the EXP and ORCAL bits in FILTCFG.

15.1 Gain Correction

Gain correction in the CS5376A normalizes sensor

gains in multi-sensor networks. It requires exter-

nally calculated correction values to be written into

the GAINx registers (0x21-0x24).

Gain correction values are 24-bit two’s comple-

ment with unity gain defined as full scale,

0x7FFFFF. Gain correction always scales to a frac-

tional value, and can never gain the digital filter

data greater than one.

Output Value = Data * (GAIN / 0x7FFFFF)

Unity Gain: GAIN = 0x7FFFFF

50% Gain: GAIN = 0x3FFFFF

Zero Gain: GAIN = 0x000000

Once the GAIN registers are written, the USEGR

bit in the FILTCFG register enables gain correc-

tion.

15.2 Offset Correction

Offset correction in the CS5376A cancels the DC

bias of a measurement channel by subtracting the

Figure 32. Gain and Offset Correction

FIR

IIR

Filters

Filter

Output to High Speed Serial Data Port (SD Port)

Offset

Correction

Output Rate 4000 SPS ~ 1 SPS

SINC

Filter

MDI Input

512 kHz

Correction

Gain

Offset

Calibration

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