MCP48FVB21 datasheet(79/84 Pages) MICROCHIP

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DS20005466A-page 79

MCP48FVBXX

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) passing through the

defined end points of the DAC transfer function (after

offset and gain errors have been removed).

In the MCP48FVBXX, INL is calculated using the

defined end points, DAC code 100 and code 4000.

INL can

expressed

percentage

full-scale range (FSR) or in LSb. INL is also called

Relative Accuracy. Equation B-6 shows how to

calculate the INL error in LSb and Figure B-4 shows an

example of INL accuracy.

Positive INL means higher VOUT voltage than ideal.

Negative INL means lower VOUT voltage than ideal.

EQUATION B-6:

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. Equation B-7 shows how to calculate

the DNL error between any two adjacent codes in LSb.

EQUATION B-7:

DNL ERROR

FIGURE B-5:

DNL ACCURACY.

Where:

EINL 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(4000) - VOUT(100))/3900

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:

EDNL is expressed in LSb.

VOUT(Code = n) = The measured DAC output voltage

with a given DAC register code.

VLSb(Measured) = For Measured:

(VOUT(4000) - VOUT(100))/3900

EDNL =

- 1

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

VLSb(Measured)

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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