MCP4921 datasheet(17/50 Pages) MICROCHIP

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DS20002249B-page 17

MCP4802/4812/4822

4.0

GENERAL OVERVIEW

The MCP4802, MCP4812 and MCP4822 are dual

voltage output 8-bit, 10-bit and 12-bit DAC devices,

respectively. These devices include rail-to-rail output

amplifiers, internal voltage reference, shutdown and

reset-management circuitry. The devices use an SPI

serial communication interface and operate with a sin-

gle supply voltage from 2.7V to 5.5V.

The DAC input coding of these devices is straight

binary. Equation 4-1 shows the DAC analog output

voltage calculation.

EQUATION 4-1:

ANALOG OUTPUT

VOLTAGE (VOUT)

The ideal output range of each device is:

• MCP4802 (n = 8)

(a) 0.0V to 255/256 * 2.048V when gain setting = 1x.

(b) 0.0V to 255/256 * 4.096V when gain setting = 2x.

• MCP4812 (n = 10)

(a) 0.0V to 1023/1024 * 2.048V when gain setting = 1x.

(b) 0.0V to 1023/1024 * 4.096V when gain setting = 2x.

• MCP4822 (n = 12)

(a) 0.0V to 4095/4096 * 2.048V when gain setting = 1x.

(b) 0.0V to 4095/4096 * 4.096V when gain setting = 2x.

1 LSb is the ideal voltage difference between two

successive

codes.

Table 4-1

illustrates

the

LSb

calculation of each device.

4.0.1

INL ACCURACY

Integral Non-Linearity (INL) error for these devices is

the maximum deviation between an actual code transi-

tion point and its corresponding ideal transition point

once offset and gain errors have been removed. The

two end points method (from 0x000 to 0xFFF) is used

for the calculation. Figure 4-1 shows the details.

A positive INL error represents transition(s) later than

ideal. A negative INL error represents transition(s)

earlier than ideal.

FIGURE 4-1:

Example for INL Error.

Note:

See the output swing voltage specification in

Section 1.0

“Electrical

Characteris-

tics”.

OUT

2.048V





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



Where:

2.048V

Internal voltage reference

DAC input code

Gain selection

=2 for <GA> bit = 0

=1 for <GA> bit = 1

DAC Resolution

=8 for MCP4802

10 for MCP4812

12 for MCP4822

TABLE 4-1:

LSb OF EACH DEVICE

Device

Gain

Selection

LSb Size

MCP4802

(n = 8)

2.048V/256 = 8 mV

4.096V/256 = 16 mV

MCP4812

(n = 10)

2.048V/1024 = 2 mV

4.096V/1024 = 4 mV

MCP4822

(n = 12)

2.048V/4096 = 0.5 mV

4.096V/4096 = 1 mV

111

110

101

100

011

010

001

000

Digital

Input

Code

Actual

Transfer

Function

INL < 0

Ideal Transfer

Function

INL < 0

DAC Output

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