MCP4821 datasheet(17/48 Pages) MICROCHIP

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 2010 Microchip Technology Inc.

DS22244B-page 17

MCP4801/4811/4821

4.0

GENERAL OVERVIEW

The MCP4801, MCP4811 and MCP4821 are single

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

devices, respectively. These devices include rail-to-rail

output amplifier, internal voltage reference, shutdown

and reset-management circuitry. The devices use an

SPI serial communication interface and operate with a

single 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:

• MCP4801 (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.

•MCP4811 (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.

• MCP4821 (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 is the maximum

deviation between an actual code transition point and

its corresponding ideal transition point once offset and

gain errors have been removed. The two endpoints

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) ear-

lier than ideal.

FIGURE 4-1:

Example for INL Error.

Note:

See the output swing voltage specification in

Section 1.0 “Electrical Characteristics”.

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 MCP4801

=10 for MCP4811

12 for MCP4821

TABLE 4-1:

LSb OF EACH DEVICE

Device

Gain

Selection

LSb Size

MCP4801

(n = 8)

2.048V/256 = 8 mV

4.096V/256 = 16 mV

MCP4811

(n = 10)

2.048V/1024 = 2 mV

4.096V/1024 = 4 mV

MCP4821

(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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