MCP4716 datasheet(59/86 Pages) MICROCHIP

59 / 86 page

DS22272A-page 59

MCP4706/4716/4726

7.0

TERMINOLOGY

7.1

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, meaning the DAC code ranges from 0

to 4095.

7.2

Least Significant bit (LSb)

Normally this is thought of as the ideal voltage

difference between two successive codes. This bit has

the smallest value or weight of all bits in the register.

For a given output voltage range, which is typically the

voltage between the Full-Scale voltage and the Zero-

Scale voltage (VOUT(FS) - VOUT(ZS)), it is divided by the

resolution of the device (Equation 7-1).

EQUATION 7-1:

LSb VOLTAGE

CALCULATION

7.3

Monotonicity

Normally this is thought of as the VOUT voltage never

decreasing, as the DAC Register code is continuously

incremented by 1 code step (LSb).

7.4

Full-Scale Error (FSE)

The Full-scale error (see Figure 7-4) is the sum of

offset error plus gain error. It is the difference between

the ideal and measured DAC output voltage with all bits

set to one (DAC input code = FFFh for 12-bit DAC).

EQUATION 7-2:

FULL SCALE ERROR

7.5

Zero-Scale Error (ZSE)

The Zero-Scale Error (see Figure 7-4) is the difference

between the ideal and measured VOUT voltage with the

volatile DAC Register equal to 000h. The Zero-Scale

Error is the same as the Offset Error for this case

(volatile DAC Register = 000h).

EQUATION 7-3:

ZERO SCALE ERROR

7.6

Offset Error

The Offset error (see Figure 7-1) is the deviation from

zero voltage output when the volatile DAC Register

value = 000h (zero scale voltage). This error affects all

codes by the same amount. The offset error can be

calibrated by software in application circuits.

FIGURE 7-1:

Offset Error Example.

VLSb =

VOUT(FS) - VOUT(ZS)

2N - 1

2N = 4096 (MCP4726)

1024 (MCP4716)

256 (MCP4706)

FSE =

VOUT(@FS) - VIDEAL(@FS)

VLSb

Where:

FSE is expressed in LSb

VOUT(@FS) is the VOUT voltage when the DAC

VIDEAL(@FS) is the ideal output voltage when the

DAC register code is at Full-scale.

VLSb is the delta voltage of one DAC register code

step (such as code 000h to code 001h).

ZSE =

VOUT(@ZS)

VLSb

Where:

FSE is expressed in LSb

VOUT(@ZS) is the VOUT voltage when the DAC

VLSb is the delta voltage of one DAC register code

step (such as code 000h to code 001h).

Analog

Output

Ideal Transfer Function

Actual Transfer Function

DAC Input Code

Offset

Error

(ZSE)

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