AD4080BBCZ datasheet(71/95 Pages) AD

71 / 95 page

Data Sheet

AD4080

DIGITAL FEATURES

analog.com

Rev. 0 | 71 of 95

SYSTEM ERROR CORRECTION

COEFFICIENTS

Systematic gain and offset errors exist in all practical data acquis-

ition circuits, and thus, the need for correction is essential to

maximize the precision of the measurement channel. While these

quantities can be corrected for in the host processor, implementa-

tion can be inefficient and consume more power than if integrated

within the data converter. To minimize these challenges for the end

user, the AD4080 has integrated both gain and offset correction on

a per sample basis.

To describe the available error corrections, consider that the trans-

fer function of an ideal ADC can be described by the straight line

equation.

y = mx + c

(2)

This equation can be applied to the ADC transfer function where:

y is the corrected ADC result.

m is the gain or slope of the line.

x is the uncorrected ADC result.

c is the offset.

The gain or slop of the line can be described as follows:

m = (y2 − y1)/(x2 − x1)

where the following are in volts:

y2 is the input voltage at close to the positive full-scale input.

y1 is the input voltage at close to the negative full-scale input.

x2 is the converted voltage with the y2 voltage applied at the input.

x1 is the converted voltage with the y1 voltage applied at the input.

The ideal slope or gain is m = 1 V/V

The system error correction coefficients in the Offset Error Correc-

tion and Gain Error Correction sections detail how signal chain

errors in offset (c) and gain (m) can be corrected using the configu-

ration registers of the AD4080.

Offset Error Correction

The AD4080 is factory calibrated to give low zero error. To account

for system offset errors that may be present in a users application

signal chain, an offset error correction function was included, which

allows users to correct for system offsets in their application by

applying a code to the OFFSET bit field in the offset Register at

Address 0x24 and Address 0x25, Bits[11:0]. This bit field is a 12-bit

value in a twos compliment data format.

The bit field is a 12-bit value in a twos compliment data format and

OFFSET LSB represents the value of the ADC LSB as defined in

the Transfer Function section. The range of offset error correction is

therefore defined as −2048 × LSB (0x800) to +2047 × LSB (0x7FF).

This represents a voltage range of ±11.71 mV for the specified

VREFIN = 3.0 V. The default value for this register, after power on,

or after a software reset, is 0x000, which represents the zero offset

correction applied.

Gain Error Correction

The AD4080 is a high precision ADC with factory calibrated, gain

error correction. To allow a user to correct for any signal chain

gain error within their application, the GAIN register (see the Gain

Correction Register, Address 0x27 and Address 0x28) can be used.

The GAIN bit field is a 10-bit value that allows a nominal gain error

correction of ±1.5594% of full scale. The 10-bit register is coded in

a straight binary data format, where the default value after power

on, or software reset, is 0x200. This value represents no gain error

correction being applied to the ADC results.

With the GAIN register first set to the default 0x200 value, the user

can perform a two-point voltage measurement, preferably close

to positive and negative full-scale inputs, and use the slope or

gain equation in the System Error Correction Coefficients section

to determine their system gain error. This system error can then

be adjusted with a resolution of 1.5594%/512 = 0.00305%. The

required correction calculated can be input to the GAIN register.

AD4080BBCZ データシート(PDF) 71 Page - Analog Devices

AD4080BBCZ データシート(HTML) 71 Page - Analog Devices

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95

データシートダウンロード