MCP47DA1 datasheet(64/70 Pages) MICROCHIP

64 / 70 page

MCP47A1

DS25154A-page 64

 2012 Microchip Technology Inc.

B.11

Integral Nonlinearity (INL)

The Integral Nonlinearity (INL) error is the maximum

deviation of an actual transfer function from an ideal

transfer function (straight line).

In the MCP47A1, INL is calculated using two end

points. The points used are Zero-Scale (00h) and Full-

Scale - 1 (3Fh). INL can be expressed as a percentage

of full scale range (FSR) or in a fraction of an LSb. INL

is also called relative accuracy. Equation B-5 shows

how to calculate the INL error in LSb and Figure B-4

shows an example of INL accuracy.

INL error for these devices is the maximum deviation

between an actual code transition point and its

corresponding ideal transition point after offset and

gain errors have been removed. These endpoints are

from 0x00 to 0x40 for the MCP47A1. Refer to Figure B-

Positive INL means higher VOUT voltage than ideal.

Negative INL means lower VOUT voltage than ideal.

See Figure 2-1 through Figure 2-4 for INL character-

ization graphs.

EQUATION B-5:

INL ERROR

FIGURE B-4:

INL ACCURACY.

B.12

Differential Nonlinearity (DNL)

The Differential Nonlinearity (DNL) error (see Figure B-

5) is the measure of step size between codes in actual

transfer function. The ideal step size between codes is

1 LSb. A DNL error of zero would imply that every code

is exactly 1 LSb wide. If the DNL error is less than

1 LSb, the DAC guarantees monotonic output and no

missing codes. The DNL error between any two

adjacent codes is calculated as follows:

DNL error is the measure of variations in code widths

from the ideal code width. A DNL error of zero would

imply that every code is exactly 1 LSb wide.

See Figure 2-5 through Figure 2-8 for DNL character-

ization graphs.

EQUATION B-6:

DNL ERROR

FIGURE B-5:

DNL ACCURACY.

INLLSb =

VOUT - VIDEAL

VIDEAL = VZS + ( VS * DAC Code )

VS =

V(Code=63) - VZS

111

110

101

100

011

010

001

000

Wiper

Code

Actual

transfer

function

INL < 0

Ideal transfer

function

INL < 0

VOUT Output Voltage

DNLLSb =

VS - ( V(Code = n) - V(Code = n-1) )

VS =

V(Code=63) - VZS

111

110

101

100

011

010

001

000

Wiper

Code

Actual

transfer

function

Ideal transfer

function

Narrow code < 1 LSb

Wide code, > 1 LSb

VOUT Output Voltage

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