AD664
Table I. Transfer Functions
Mode = UNI
Mode = BIP
000000000000 = 0 V
Gain = 1 100000000000 = VREF/2
111111111111 = VREF – 1 LSB
000000000000 = – VREF/2
100000000000 = 0 V
111111111111 = VREF/2 –1 LSB
000000000000 = 0 V
Gain = 2 100000000000 = VREF
111111111111 = 2 × VREF – 1 LSB
000000000000 = VREF
100000000000 = 0 V
111111111111 = +VREF – 1 LSB
DEFINITIONS OF SPECIFICATIONS
UNIPOLAR OFFSET ERROR: Unipolar offset error is the dif-
ference between the ideal output (0 V) and the actual output of
a DAC when the input is loaded with all “0s” and the MODE is
unipolar.
LINEARITY ERROR: Analog Devices defines linearity error as
the maximum deviation of the actual, adjusted DAC output
from the ideal analog output (a straight line drawn from 0 to FS
– 1 LSB) for any bit combination. This is also referred to as
relative accuracy. The AD664 is laser-trimmed to typically
maintain linearity errors at less than ±1/4 LSB.
BIPOLAR ZERO ERROR: Bipolar zero error is the difference
between the ideal output (0 V) and the actual output of a DAC
when the input code is loaded with the MSB = “1” and the rest
of the bits = “0” and the MODE is bipolar.
MONOTONICITY: A DAC is said to be monotonic if the out-
put either increases or remains constant for increasing digital
inputs such that the output will always be a nondecreasing func-
tion of input. All versions of the AD664 are monotonic over
their full operating temperature range.
SETTLING TIME: Settling time is the time required for the
output to reach and remain within a specified error band about
its final value, measured from the digital input transition.
CROSSTALK: Crosstalk is the change in an output caused by
a change in one or more of the other outputs. It is due to
capacitive and thermal coupling between outputs.
DIFFERENTIAL LINEARITY: Monotonic behavior requires
that the differential linearity error be less than 1 LSB both at
25°C as well as over the temperature range of interest. Differen-
tial nonlinearity is the measure of the variation in analog value,
normalized to full scale, associated with a 1 LSB change in digi-
tal input code. For example, for a 10 V full-scale output, a
change of 1 LSB in digital input code should result in a
2.44 mV change in the analog output (VREF = 10 V, Gain = 1,
1 LSB = 10 V × 1/4096 = 2.44 mV). If in actual use, however, a
1 LSB change in the input code results in a change of only
0.61 mV (1/4 LSB) in analog output, the differential non-
linearity error would be –1.83 mV, or –3/4 LSB.
REFERENCE FEEDTHROUGH: The portion of an ac refer-
ence signal that appears at an output when all input bits are low.
Feedthrough is due to capacitive coupling between the reference
input and the output. It is specified in decibels at a particular
frequency.
REFERENCE 3 dB BANDWIDTH: The frequency of the ac
reference input signal at which the amplitude of the full-scale
output response falls 3 dB from the ideal response.
GLITCH IMPULSE: Glitch impulse is an undesired output
voltage transient caused by asymmetrical switching times in the
switches of a DAC. These transients are specified by their net
area (in nV-sec) of the voltage vs. time characteristic.
GAIN ERROR: DAC gain error is a measure of the difference
between the output span of an ideal DAC and an actual device.
PIN CONFIGURATIONS
28-Pin DIP Package
44-Pin Package
D
REV.
–5–
ADI [ ADI ]
