Datasheet

DAC7568
DAC8168
DAC8568
www.ti.com SBAS430D –JANUARY 2009–REVISED MAY 2012
PARAMETER DEFINITIONS
With the increased complexity of many different
Full-Scale Error
specifications listed in product data sheets, this
section summarizes selected specifications related to
Full-scale error is defined as the deviation of the real
digital-to-analog converters.
full-scale output voltage from the ideal output voltage
while the DAC register is loaded with the full-scale
STATIC PERFORMANCE
code (0xFFFF). Ideally, the output should be AV
DD
–
1 LSB. The full-scale error is expressed in percent of
Static performance parameters are specifications
full-scale 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
are most important in applications where the signal
The offset error is defined as the difference between
changes slowly and accuracy is required.
actual output voltage and the ideal output voltage in
the linear region of the transfer function. This
Resolution
difference is calculated by using a straight line
defined by two codes (code 485 and 64714). Since
Generally, the DAC resolution can be expressed in
the offset error is defined by a straight line, it can
different forms. Specifications such as IEC 60748-4
have a negative or positive value. Offset error is
recognize the numerical, analog, and relative
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
transfer characteristic, where a step represents both
The zero-code error is defined as the DAC output
a digital input code and the corresponding discrete
voltage, when all '0's are loaded into the DAC
analogue output value. The most commonly-used
register. Zero-scale error is a measure of the
definition of resolution provided in data sheets is the
difference between actual output voltage and ideal
numerical resolution expressed in bits.
output voltage (0V). It is expressed in mV. It is
primarily caused by offsets in the output amplifier.
Least Significant Bit (LSB)
Gain Error
The least significant bit (LSB) is defined as the
smallest value in a binary coded system. The value of
Gain error is defined as the deviation in the slope of
the LSB can be calculated by dividing the full-scale
the real DAC transfer characteristic from the ideal
output voltage by 2
n
, where n is the resolution of the
transfer function. Gain error is expressed as a
converter.
percentage of full-scale range (%FSR).
Most Significant Bit (MSB)
Full-Scale Error Drift
The most significant bit (MSB) is defined as the
Full-scale error drift is defined as the change in full-
largest value in a binary coded system. The value of
scale error with a change in temperature. Full-scale
the MSB can be calculated by dividing the full-scale
error drift is expressed in units of %FSR/°C.
output voltage by 2. Its value is one-half of full-scale.
Offset Error Drift
Relative Accuracy or Integral Nonlinearity (INL)
Offset error drift is defined as the change in offset
Relative accuracy or integral nonlinearity (INL) is
error with a change in temperature. Offset error drift
defined as the maximum deviation between the real
is expressed in μV/°C.
transfer function and a straight line passing through
the endpoints of the ideal DAC transfer function. DNL
Zero-Code Error Drift
is measured in LSBs.
Zero-code error drift is defined as the change in zero-
code error with a change in temperature. Zero-code
Differential Nonlinearity (DNL)
error drift is expressed in μV/°C.
Differential nonlinearity (DNL) is defined as the
maximum deviation of the real LSB step from the
Gain Temperature Coefficient
ideal 1LSB step. Ideally, any two adjacent digital
The gain temperature coefficient is defined as the
codes correspond to output analog voltages that are
change in gain error with changes in temperature.
exactly one LSB apart. If the DNL is less than 1LSB,
The gain temperature coefficient is expressed in ppm
the DAC is said to be monotonic.
of FSR/°C.
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