Datasheet

DAC7565
www.ti.com SBAS412B –FEBRUARY 2008–REVISED MARCH 2011
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. Ideally, the output should be V
DD
– 1 LSB. The
STATIC PERFORMANCE
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. Since the offset error is defined
Generally, the DAC resolution can be expressed in
by a straight line, it can have a negative or positve
different forms. Specifications such as IEC 60748-4
value. Offset error is measured in mV.
recognize the numerical, analog, and relative
resolution. The numerical resolution is defined as the
Zero-Code Error
number of digits in the chosen numbering system
The zero-code error is defined as the DAC output
necessary to express the total number of steps of the
voltage, when all '0's are loaded into the DAC
transfer characteristic, where a step represents both
register. Zero-scale error is a measure of the
a digital input code and the corresponding discrete
difference between actual output voltage and ideal
analogue output value. The most commonly-used
output voltage (0V). It is expressed in mV. It is
definition of resolution provided in data sheets is the
primarily caused by offsets in the output amplifier.
numerical resolution expressed in bits.
Gain Error
Least Significant Bit (LSB)
Gain error is defined as the deviation in the slope of
The least significant bit (LSB) is defined as the
the real DAC transfer characteristic from the ideal
smallest value in a binary coded system. The value of
transfer function. Gain error is expressed as a
the LSB can be calculated by dividing the full-scale
percentage of full-scale range (%FSR).
output voltage by 2
n
, where n is the resolution of the
converter.
Full-Scale Error Drift
Most Significant Bit (MSB)
Full-scale error drift is defined as the change in
full-scale error with a change in temperature.
The most significant bit (MSB) is defined as the
Full-scale error drift is expressed in units
largest value in a binary coded system. The value of
of %FSR/°C.
the MSB can be calculated by dividing the full-scale
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
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
transfer function and a straight line passing through
Zero-Code Error Drift
the endpoints of the ideal DAC transfer function. DNL
is measured in LSBs.
Zero-code error drift is defined as the change in
zero-code error with a change in temperature.
Differential Nonlinearity (DNL)
Zero-code error drift is expressed in μV/°C.
Differential nonlinearity (DNL) is defined as the
Gain Temperature Coefficient
maximum deviation of the real LSB step from the
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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