AD5330_08 datasheet(11/28 Pages) AD

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AD5330/AD5331/AD5340/AD5341

Rev. A | Page 11 of 28

TERMINOLOGY

OUTPUT

VOLTAGE

DAC CODE

POSITIVE

OFFSET

GAIN ERROR

AND

OFFSET ERROR

ACTUAL

IDEAL

Relative Accuracy or Integral Nonlinearity (INL)

For the DAC, relative accuracy or INL is a measure of the

maximum deviation, in LSBs, from a straight line passing

through the actual endpoints of the DAC transfer function.

Typical INL vs. code plots can be seen in Figure 14, Figure 15,

and Figure 16.

Differential Nonlinearity (DNL)

DNL is the difference between the measured change and the

ideal 1 LSB change between any two adjacent codes. A specified

differential nonlinearity of ±1 LSB maximum ensures mono-

tonicity. This DAC is guaranteed monotonic by design. Typical

DNL vs. code plots can be seen in Figure 17, Figure 18, and

Figure 19.

Gain Error

This is a measure of the span error of the DAC (including any

error in the gain of the buffer amplifier). It is the deviation in

slope of the actual DAC transfer characteristic from the ideal,

expressed as a percentage of the full-scale range. This is

illustrated in Figure 11.

Figure 12. Positive Offset Error and Gain Error

OUTPUT

VOLTAGE

DAC CODE

NEGATIVE

OFFSET

GAIN ERROR

AND

OFFSET ERROR

ACTUAL

IDEAL

AMPLIFIER

FOOTROOM

(~1mV)

NEGATIVE

OFFSET

DEADBAND CODES

Offset Error

This is a measure of the offset error of the DAC and the output

amplifier. It is expressed as a percentage of the full-scale range.

If the offset voltage is positive, the output voltage is still positive

at zero input code. This is shown in Figure 12. Because the

DACs operate from a single supply, a negative offset cannot

appear at the output of the buffer amplifier. Instead, there is

a code close to zero at which the amplifier output saturates

(amplifier footroom). Below this code, there is a deadband over

which the output voltage does not change. This is illustrated in

Figure 13.

OUTPUT

VOLTAGE

DAC CODE

POSITIVE

GAIN ERROR

ACTUAL

IDEAL

NEGATIVE

GAIN ERROR

Figure 13. Negative Offset Error and Gain Error

Figure 11. Gain Error

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