DAC7578SPW datasheet(43/55 Pages) TI

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DAC5578

DAC6578

DAC7578

www.ti.com

SBAS496A – MARCH 2010 – REVISED AUGUST 2010

PARAMETER DEFINITIONS

With the increased complexity of many different

Full-Scale Error

specifications listed in product data sheets, this

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

section summarizes selected specifications related to

full-scale output voltage from the ideal output voltage

digital-to-analog converters.

while the DAC register is loaded with the full-scale

code (for example, for 12 bit resolution 0xFFF).

STATIC PERFORMANCE

Ideally, the output should be AVDD – 1 LSB. The

full-scale error is expressed in percent of full-scale

Static performance parameters are specifications

range (%FSR).

such as differential nonlinearity (DNL) or integral

nonlinearity (INL). These are dc specifications and

Offset Error

provide information on the accuracy of the DAC. They

The offset error is defined as the difference between

are most important in applications where the signal

actual output voltage and the ideal output voltage in

changes slowly and accuracy is required.

the linear region of the transfer function. This

difference is calculated by using a straight line

Resolution

defined by two codes (for example, for 12 bit

Generally, the DAC resolution can be expressed in

resolution code 30 and 4050). Since the offset error is

different forms. Specifications such as IEC 60748-4

defined by a straight line, it can have a negative or

recognize

the

numerical,

analog,

and

relative

positive value. Offset error is measured in mV.

resolution. The numerical resolution is defined as the

number of digits in the chosen numbering system

Zero-Code Error

necessary to express the total number of steps of the

The zero-code error is defined as the DAC output

transfer characteristic, where a step represents both

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

a digital input code and the corresponding discrete

analogue output value. The most commonly-used

difference between actual output voltage and ideal

definition of resolution provided in data sheets is the

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

numerical resolution expressed in bits.

primarily caused by offsets in the output amplifier.

Least Significant Bit (LSB)

Gain Error

The least significant bit (LSB) is defined as the

Gain error is defined as the deviation in the slope of

smallest value in a binary coded system. The value of

the real DAC transfer characteristic from the ideal

the LSB can be calculated by dividing the full-scale

transfer function. Gain error is expressed as a

output voltage by 2n, where n is the resolution of the

percentage of full-scale range (%FSR).

converter.

Full-Scale Error Drift

Most Significant Bit (MSB)

Full-scale error drift is defined as the change in

The most significant bit (MSB) is defined as the

full-scale

error

with

change

temperature.

largest value in a binary coded system. The value of

Full-scale error drift is expressed in units of µV/°C.

the MSB can be calculated by dividing the full-scale

Offset Error Drift

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

Offset error drift is defined as the change in offset

Relative Accuracy or Integral Nonlinearity (INL)

error with a change in temperature. Offset error drift

Relative accuracy or integral nonlinearity (INL) is

is expressed in µV/°C.

defined as the maximum deviation between the real

Zero-Code Error Drift

transfer function and a straight line passing through

Zero-code error drift is defined as the change in

the endpoints of the ideal DAC transfer function. INL

zero-code error with a change in temperature.

is measured in LSBs.

Zero-code error drift is expressed in µV/°C.

Differential Nonlinearity (DNL)

Gain Temperature Coefficient

Differential nonlinearity (DNL) is defined as the

The gain temperature coefficient is defined as the

maximum deviation of the real LSB step from the

change in gain error with changes in temperature.

ideal 1LSB step. Ideally, any two adjacent digital

The gain temperature coefficient is expressed in ppm

codes correspond to output analog voltages that are

of FSR/°C.

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

the DAC is said to be monotonic.

Power-Supply Rejection Ratio (PSRR)

Power-supply rejection ratio (PSRR) is defined as the

empty para to force Full-Scale Error to next col

ratio of change in output voltage to a change in

empty para to force Full-Scale Error to next col

supply voltage for a full-scale output of the DAC. The

PSRR of a device indicates how the output of the

DAC is affected by changes in the supply voltage.

PSRR is measured in decibels (dB).

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