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PARAMETER DEFINITIONS

STATIC PERFORMANCE

Resolution

Full-Scale Error

Offset Error

Least Significant Bit (LSB)

Zero-Code Error

Most Significant Bit (MSB)

Relative Accuracy or Integral Nonlinearity (INL)

Gain Error

Full-Scale Error Drift

Differential Nonlinearity (DNL)

Offset Error Drift

DAC8564

SBAS403A – JUNE 2007 – REVISED NOVEMBER 2007

With the increased complexity of many different specifications listed in product data sheets, this section

summarizes selected specifications related to digital-to-analog converters.

Static performance parameters are specifications such as differential nonlinearity (DNL) or integral nonlinearity

(INL). Those are dc specifications and provide information on the accuracy of the DAC. They are most important

in applications where the signal is slowly changing and accuracy is required.

Generally, the DAC resolution can be expressed in

Full-scale error is defined as the deviation of the real

different forms. Specifications such as IEC 60748-4

full-scale output voltage from the ideal output voltage

recognize

the

numerical,

analog,

and

relative

while the DAC register is loaded with the full-scale

resolution. The numerical resolution is defined as the

number of digits in the chosen numbering system

LSB. The full-scale error is expressed in percent of

necessary to express the total number of steps of the

full-scale range (%FSR).

transfer characteristic, where a step represents both

a digital input code and the corresponding discrete

analogue output value. The most commonly-used

The offset error is defined as the difference between

definition of resolution provided in data sheets is the

actual output voltage and the ideal output voltage in

numerical resolution expressed in bits.

the linear region of the transfer function. This

difference is calculated by using a straight line

defined by two codes (code 485 and 64714). Since

The least significant bit (LSB) is defined as the

the offset error is defined by a straight line, it can

smallest value in a binary coded system. The value of

have a negative or positve value. Offset error is

the LSB can be calculated by dividing the full-scale

measured in mV.

converter.

The zero-code error is defined as the DAC output

voltage, when all '0's are loaded into the DAC

The most significant bit (MSB) is defined as the

register. Zero-scale error is a measure of the

largest value in a binary coded system. The value of

difference between actual output voltage and ideal

the MSB can be calculated by dividing the full-scale

output voltage (0V). It is expressed in mV. It is

output voltage by 2. Its value is one-half of full-scale.

primarily caused by offsets in the output amplifier.

Relative accuracy or integral nonlinearity (INL) is

Gain error is defined as the deviation in the slope of

defined as the maximum deviation between the real

the real DAC transfer characteristic from the ideal

transfer function and a straight line passing through

transfer function. Gain error is expressed as a

the endpoints of the ideal DAC transfer function. DNL

percentage of full-scale range (%FSR).

is measured in LSBs.

Full-scale error drift is defined as the change in

Differential nonlinearity (DNL) is defined as the

full-scale

error

with

a

change

in

temperature.

maximum deviation of the real LSB step from the

Full-scale

error

drift

is

expressed

in

units

of

ideal 1LSB step. Ideally, any two adjacent digital

%FSR/

°C.

codes correspond to output analog voltages that are

exactly one LSB apart. If the DNL is less than 1LSB,

the DAC is said to be monotonic.

Offset error drift is defined as the change in offset

error with a change in temperature. Offset error drift

is expressed in

µV/°C.

Copyright © 2007, Texas Instruments Incorporated

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