CS7620 datasheet(35/70 Pages) CIRRUS

35 / 70 page

CS7620

DS301PP2

4.12

Gain Calibration - Offset 3

Default = 00h; Read/Write (address 11h)

Gain Calibration - Fix Gains

Default = 00h; Read/Write (address 16h)

Bit Number

765432

Bit Name

gain_offset

Default

0000000

Bit

Mnemonic

Function

gain_offset37

Gain Calibration Offset 3: Offset added to 1x gain segment. Values are in

2’s complement.

These registers are used to report some of the calibration settings. After cal-

ibration is performed the gain offset registers are automatically updated with

values needed for the DRX circuitry to operate correctly. These registers

should not be written to since this will remove the proper settings found during

calibration. The gain offset values are used to add an offset to the output of

the ADC when using different analog gain settings (See equations below).

The purpose of this is to produce a continuous transition between the different

gain settings so that the final 13 bit output is monotonic and has no undesired

artifacts. (See Figure 26)

{ADC_outif in the 8x gain segment}

dout[12:0] ={ADC_out*2+Offset1if in the 4x gain segment}

{ADC_out*4+Offset2*2if in the 2x gain segment}

{ADC_out*8+Offset3*4if in the 1x gain segment}

gain_offset36

gain_offset35

gain_offset34

gain_offset33

gain_offset32

gain_offset31

gain_offset30

Bit Number

543

Bit Name

Reserved

fixed_gain2

fixed_gain1

fixed_gain0

Reserved

Default

000

---

Bit

Mnemonic

Function

7:6

Reserved

fixed_gain2

Fixed Gain: This is used to turn off the DRX functionality and apply a fixed

gain to the input before reaching the ADC. A setting of 000 is used for normal

operation this will yield the largest dynamic range by switching the front end

gain relative to the amplitude of the input signal. The settings 001, 010, 011,

and 100 are for fixed gains of 1x, 2x, 4x, and 8x respectively. Figure 27 shows

the transfer function of the output of the ADC for a given input with the various

fixed gain settings.

fixed_gain1

fixed_gain0

2:0

Reserved

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