MCP4822-ESLASHMS datasheet(15/36 Pages) MICROCHIP

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DS21953A-page 15

MCP4821/MCP4822

4.0

GENERAL OVERVIEW

The MCP482X devices are voltage-output string DACs.

These devices include rail-to-rail output amplifiers,

internal voltage reference, shutdown and reset-man-

agement circuitry. Serial communication conforms to

the SPI protocol. The MCP482X devices operate from

2.7V to 5.5V supplies.

The coding of these devices is straight binary, with the

ideal output voltage given by Equation 4-1, where G is

the selected gain (1x or 2x), DN represents the digital

input value and n represents the number of bits of

resolution (n = 12).

EQUATION 4-1:

LSb SIZE

1 LSb is the ideal voltage difference between two

successive codes. Table 4-1 illustrates how to calculate

LSb.

4.0.1

INL ACCURACY

INL error for these devices is the maximum deviation

between an actual code transition point and its corre-

sponding ideal transition point once offset and gain

errors have been removed. These endpoints are from

0x000 to 0xFFF. Refer to Figure 4-1.

Positive INL represents transition(s) later than ideal.

Negative INL represents transition(s) earlier than ideal.

FIGURE 4-1:

INL Accuracy.

4.0.2

DNL ACCURACY

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.

FIGURE 4-2:

DNL Accuracy.

4.0.3

OFFSET ERROR

Offset error is the deviation from zero voltage output

when the digital input code is zero.

4.0.4

GAIN ERROR

Gain error is the deviation from the ideal output,

VREF – 1 LSb, excluding the effects of offset error.

TABLE 4-1:

LSb SIZES

Device

Gain

LSb Size

MCP482X

2.048V/4096

MCP482X

4.096V/4096

OUT

2.048V G D

⋅⋅

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

111

110

101

100

011

010

001

000

Digital

Input

Code

Actual

Transfer

Function

INL < 0

Ideal Transfer

Function

INL < 0

DAC Output

111

110

101

100

011

010

001

000

Digital

Input

Code

Actual

Transfer

Function

Ideal Transfer

Function

Narrow Code < 1 LSb

DAC Output

Wide Code > 1 LSb

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