AD7245A/AD7248A
AD7245A ORDERING GUIDE
DAC GAIN ERROR
Model
l
AD7245AAN
AD7245ABN
AD7245AAQ
AD7245ATQ
3
AD7245AAP
AD7245AAR
AD7245ABR
AD7245ATE
3
Temperature
Range
–40°C to +85°C
–40°C to +85°C
–40°C to +85°C
–55°C to +125°C
–40°C to +85°C
–40°C to +85°C
–40°C to +85°C
–55°C to +125°C
Relative
Accuracy
±
3/4 LSB
±
1/2 LSB
±
3/4 LSB
±
3/4 LSB
±
3/4 LSB
±
3/4 LSB
±
1/2 LSB
±
3/4 LSB
Package
Option
2
N-24
N-24
Q-24
Q-24
P-28A
R-24
R-24
E-28A
DAC Gain Error is a measure of the output error between an
ideal DAC and the actual device output with all 1s loaded after
offset error has been allowed for. It is, therefore defined as:
Measured Value—Offset—Ideal Value
where the ideal value is calculated relative to the actual refer-
ence value.
UNIPOLAR OFFSET ERROR
Unipolar Offset Error is a combination of the offset errors of the
voltage mode DAC and the output amplifier and is measured
when the part is configured for unipolar outputs. It is present
for all codes and is measured with all 0s in the DAC register.
BIPOLAR ZERO OFFSET ERROR
NOTES
1
To order MIL-STD-883, Class B. processed parts, add /883B to part number.
Contact our local sales office for military data sheet and availability.
2
E = Leadless Ceramic Chip Carrier; N = Plastic DIP; P = Plastic Leaded Chip
Carrier; Q = Cerdip; R = SOIC.
3
This grade will be available to /883B processing only.
Bipolar Zero Offset Error is measured when the part is config-
ured for bipolar output and is a combination of errors from the
DAC and output amplifier. It is present for all codes and is
measured with a code of 2048 (decimal) in the DAC register.
SINGLE SUPPLY LINEARITY AND GAIN ERROR
AD7248A ORDERING GUIDE
Model
l
AD7248AAN
AD7248ABN
AD7248AAQ
AD7248ATQ
3
AD7248AAP
AD7248AAR
AD7248ABR
Temperature
Range
–40°C to +85°C
–40°C to +85°C
–40°C to +85°C
–55°C to +125°C
–40°C to +85°C
–40°C to +85°C
–40°C to +85°C
Relative
Accuracy
±
3/4 LSB
±
1/2 LSB
±
3/4 LSB
±
3/4 LSB
±
3/4 LSB
±
3/4 LSB
±
1/2 LSB
Package
Option
2
N-20
N-20
Q-20
Q-20
P-20A
R-20
R-20
NOTES
1
To order MIL-STD-883, Class B, processed parts, add /883B to part number.
Contact our local sales office for military data sheet and availability.
2
N = Plastic DIP; P = Plastic Leaded Chip Carrier; Q = Cerdip; R = SOIC.
3
This grade will be available to /883B processing only.
TERMINOLOGY
RELATIVE ACCURACY
The output amplifier of the AD7245A/AD7248A can have a
true negative offset even when the part is operated from a single
positive power supply. However, because the lower supply rail
to the part is 0 V, the output voltage cannot actually go nega-
tive. Instead the output voltage sits on the lower rail and this re-
sults in the transfer function shown. This is an offset effect and
the transfer function would have followed the dotted line if the
output voltage could have gone negative. Normally, linearity is
measured after offset and full scale have been adjusted or al-
lowed for. On the AD7245A/AD7248A the negative offset is al-
lowed for by calculating the linearity from the code which the
amplifier comes off the lower rail. This code is given by the
negative offset specification. For example, the single supply lin-
earity specification applies between Code 3 and Code 4095 for
the 25°C specification and between Code 5 and Code 4095 over
the T
MIN
to T
MAX
temperature range. Since gain error is also
measured after offset has been allowed for, it is calculated between
the same codes as the linearity error. Bipolar linearity and gain er-
ror are measured between Code 0 and Code 4095.
Relative Accuracy, or end-point nonlinearity, is a measure of the
actual deviation from a straight line passing through the end-
points of the DAC transfer function. It is measured after allow-
ing for zero and full scale and is normally expressed in LSBs or
as a percentage of full-scale reading.
DIFFERENTIAL NONLINEARITY
OUTPUT
VOLTAGE
Differential Nonlinearity is the difference between the measured
change and the ideal 1 LSB change between any two adjacent
codes. A specified differential nonlinearity of
±
1 LSB max over
the operating temperature range ensures monotonicity.
DIGITAL FEEDTHROUGH
0V
NEGATIVE
OFFSET
{
DAC CODE
Digital Feedthrough is the glitch impulse injected from the digi-
tal inputs to the analog output when the inputs change state. It
is measured with
LDAC
high and is specified in nV-s.
–4–
REV. A
AD [ ANALOG DEVICES ]
