Applications Information

Definitions

Integral Nonlinearity (INL)

Integral nonlinearity (Figure 6a) is the deviation of the val-

ues on an actual transfer function from a straight line.

This straight line can be either a best-straight-line fit

(closest approximation to the actual transfer curve) or a

line drawn between the endpoints of the transfer func-

tion, once offset and gain errors have been nullified. For

a DAC, the deviations are measured at every single step.

Differential Nonlinearity (DNL)

Differential nonlinearity (Figure 6b) is the difference

between an actual step height and the ideal value of

1LSB. If the magnitude of the DNL is less than 1LSB, the

DAC guarantees no missing codes and is monotonic.

Offset Error

The offset error (Figure 6c) is the difference between

the ideal and the actual offset point. For a DAC, the off-

set point is the step value when the digital input is zero.

This error affects all codes by the same amount and

can usually be compensated for by trimming.

Gain Error

Gain error (Figure 6d) is the difference between the

ideal and the actual full-scale output voltage on the

transfer curve, after nullifying the offset error. This error

alters the slope of the transfer function and corre-

sponds to the same percentage error in each step.

Settling Time

The settling time is the amount of time required from the

start of a transition, until the DAC output settles to its new

output value within the converter’s specified accuracy.

3V/5V, 10-Bit, Serial Voltage-Output Dual DACs

with Internal Reference

14

______________________________________________________________________________________

0

2

1

4

3

7

6

5

000

010

001

011

100

101

110

AT STEP

011 (1/2LSB )

AT STEP

001 (1/4LSB )

111

DIGITAL INPUT CODE

Figure 6a. Integral Nonlinearity

0

2

1

4

3

6

5

000

010

001

011

100

101

DIFFERENTIAL LINEARITY

ERROR (-1/4LSB)

DIFFERENTIAL

LINEARITY ERROR (+1/4LSB)

1LSB

1LSB

DIGITAL INPUT CODE

Figure 6b. Differential Nonlinearity

0

2

1

3

000

010

001

011

ACTUAL

DIAGRAM

IDEAL DIAGRAM

ACTUAL

OFFSET

POINT

OFFSET ERROR

(+1 1/4LSB)

IDEAL OFFSET

POINT

DIGITAL INPUT CODE

Figure 6c. Offset Error

0

5

4

6

7

000

101

100

110

111

IDEAL DIAGRAM

GAIN ERROR

(-1 1/4LSB)

IDEAL FULL-SCALE OUTPUT

ACTUAL

FULL-SCALE

OUTPUT

DIGITAL INPUT CODE

Figure 6d. Gain Error