MCP4921 datasheet(19/50 Pages) MICROCHIP

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DS22248A-page 19

MCP4901/4911/4921

4.0

GENERAL OVERVIEW

The MCP4901, MCP4911 and MCP4921 are single

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

devices, respectively. These devices include a VREF

input buffer, a rail-to-rail output amplifier, 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:

• MCP4901 (n = 8)

(a) 0V to 255/256*VREF when gain setting = 1x.

(b) 0V to 255/256*2*VREF when gain setting = 2x.

•MCP4911 (n = 10)

(a) 0V to 1023/1024*VREF when gain setting = 1x.

(b) 0V to 1023/1024*2*VREF when gain setting = 2x.

• MCP4921 (n = 12)

(a) 0V to 4095/4096*VREF when gain setting = 1x.

(b) 0V to 4095/4096*2*VREF 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.

4.1

DC Accuracy

4.1.1

INL ACCURACY

Integral Non-Linearity (INL) error is the maximum

deviation between an actual code transition point and

its corresponding ideal transition point, after offset and

gain errors have been removed. The two endpoints

(from 0x000 and 0xFFF) method is used for the calcu-

lation. 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.

4.1.2

DNL ACCURACY

A Differential Non-Linearity (DNL) error is the measure

of variations in code widths from the ideal code width.

A DNL error of zero indicates that every code is exactly

1 LSB wide.

Note:

See the output swing voltage specification

in Section 1.0 “Electrical Characteris-

tics”.

OUT

REF





-------------------------------G

Where:

VREF =EXternal voltage reference

DAC input code

Gain Selection

2 for <GA> bit = 0

1 for <GA> bit = 1

DAC Resolution

8 for MCP4901

10 for MCP4911

12 for MCP4912

TABLE 4-1:

LSb OF EACH DEVICE

Device

Gain

Selection

LSb Size

MCP4901

(n = 8)

VREF/256

(2*VREF)/256

MCP4911

(n = 10)

VREF/1024

(2*VREF)/1024

MCP4921

(n = 12)

VREF/4096

(2*VREF)/4096

where VREF is the external voltage reference.

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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