MCP47CMB02 datasheet(118/124 Pages) MICROCHIP

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MCP47CXBXX

DS20006089B-page 118

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C.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), passing through the

defined end-points of the DAC transfer function (after

Offset and Gain Errors have been removed).

For the MCP47CXBXX, INL is calculated using the

defined end points, DAC code 64 and code 4032. INL

can be expressed as a percentage of Full-Scale Range

(FSR) or in LSb. INL is also called relative accuracy.

Equation C-6 shows how to calculate the INL error in

LSb and Figure C-4 shows an example of INL accuracy.

Positive INL means a VOUT voltage higher than the

ideal one. Negative INL means a VOUT voltage lower

than the ideal one.

EQUATION C-6:

INL ERROR

FIGURE C-4:

INL Accuracy.

C.12

Differential Nonlinearity (DNL)

The

Differential

Nonlinearity

(DNL)

error

(see

Figure C-5) is the measure of step-size between codes

in an 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 ensures monotonic

output and no missing codes. Equation C-7 shows how

to calculate the DNL error between any two adjacent

codes in LSb.

EQUATION C-7:

DNL ERROR

FIGURE C-5:

DNL Accuracy.

Where:

INL is expressed in LSb

VCalc_Ideal = Code * VLSb(Measured) + VOS

VOUT(Code = n) = The measured DAC output

voltage with a given DAC

VLSb(Measured) = For Measured:

(VOUT(4032) – VOUT(64))/3968

VOS = Measured offset voltage

EINL

VOUT VCalc_Ideal

–



VLSb Measured



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

010

001

000

Analog

Output

(LSb)

DAC Input Code

011

111

100 101

110

Ideal Transfer Function

Actual Transfer Function

INL = < -1 LSb

INL = 0.5 LSb

INL = -1 LSb

Where:

DNL is expressed in LSb.

VOUT(Code = n) = The measured DAC output

voltage with a given DAC

VLSb(Measured) = For Measured:

(VOUT(4032) – VOUT(64))/3968

EDNL

VOUT(code = n+1) VOUT(code = n)

–



VLSb Measured



------------------------------------------------------------------------------------1

–

010

001

000

Analog

Output

(LSb)

DAC Input Code

011

111

100 101

DNL = 2 LSb

DNL = 0.5 LSb

110

Ideal Transfer Function

Actual Transfer Function

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