MCP47DA1 datasheet(70/76 Pages) MICROCHIP

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MCP47DA1

DS25118D-page 70

 2012-2013 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 MCP47DA1, INL is calculated using two end

points (zero and full scale). 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-4 shows how to calculate the INL error in

LSb and Figure B-4 shows an example of INL accu-

racy.

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 0x00-0x20 to 0x60-0x7F for the MCP47DA1.

Refer to Figure B-4.

Positive INL means higher VOUT voltage than ideal.

Negative INL means lower VOUT voltage than ideal.

See Figure 2-1 through Figure 2-11 and Figure 2-67

through Figure 2-70 for INL characterization graphs.

EQUATION B-4:

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 2-12 through Figure 2-22 and Figure 2-71

through Figure 2-74 for DNL characterization graphs.

EQUATION B-5:

DNL ERROR

FIGURE B-5:

DNL ACCURACY.

INL

VOUT VIdeal

–



LSb

---------------------------------------

Where:

INL is expressed in LSb.

VIdeal

Code*LSb

VOUT

The output voltage measured with

a given DAC input code

111

110

101

100

011

010

001

000

Wiper

Code

Actual

transfer

function

INL < 0

Ideal transfer

function

INL < 0

VOUT Output Voltage

DNL

V

OUT

LSb

–

LSb

----------------------------------

Where:

DNL is expressed in LSb.

VOUT

The measured DAC output

voltage difference between two

adjacent input codes.

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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