MCP4725 datasheet(11/42 Pages) MICROCHIP

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DS22039C-page 11

MCP4725

4.0

TERMINOLOGY

4.1

Resolution

The resolution is the number of DAC output states that

divide the full-scale range. For the 12-bit DAC, the

resolution is 212 or the DAC code ranges from 0 to

4095.

4.2

LSB

The least significant bit or the ideal voltage difference

between two successive codes.

EQUATION 4-1:

4.3

Integral Nonlinearity (INL) or

Relative Accuracy

INL error is the maximum deviation between an actual

code transition point and its corresponding ideal

transition point (straight line). Figure 2-5 shows the INL

curve of the MCP4725. The end-point method is used

for the calculation. The INL error at a given input DAC

code is calculated as:

EQUATION 4-2:

FIGURE 4-1:

INL Accuracy.

4.4

Differential Nonlinearity (DNL)

Differential

nonlinearity

error

(Figure 4-2)

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:

EQUATION 4-3:

LSB

Ideal

REF

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

Full

Scale

–

Zero

Scale

–

()

–

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

Where:

VREF

The reference voltage = VDD in the

MCP4725. This VREF is the ideal

full-scale voltage range

The number of digital input bits.

(n = 12 for MCP4725)

INL

OUT

Ideal

–

()

LSB

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

Where:

VIdeal

Code*LSB

VOUT

The output voltage measured at

the given input code

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

DNL

ΔV

OUT

LSB

–

LSB

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

Where:

ΔV

OUT

The measured DAC output

voltage difference between two

adjacent input codes.

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