Datasheet

AD5512A/AD5542A
Rev. A | Page 16 of 24
Assuming a perfect reference, the unipolar worst-case output
voltage can be calculated from the following equation:
( )
INLVVV
D
V
ZSE
GE
REF
N
UNIOUT
+++×=
−
2
where:
V
OUT−UNI
is the unipolar mode worst-case output.
D is the code loaded to DAC.
N is the resolution of the DAC.
V
REF
is the reference voltage applied to the part.
V
GE
is the gain error in volts.
V
ZSE
is the zero-scale error in volts.
INL is the integral nonlinearity in volts.
BIPOLAR OUTPUT OPERATION
With the aid of an external op amp, the AD5512A/AD5542A
can be configured to provide a bipolar voltage output. A typical
circuit is shown in Figure 32. The matched bipolar offset resistors,
R
FB
and R
INV
, are connected to an external op amp to achieve
this bipolar output swing, typically R
FB
= R
INV
= 28 kΩ. Table 10
shows the transfer function for this output operating mode.
Also provided on the AD5542A are a set of Kelvin connections
to the analog ground inputs. The example includes the ADR421
2.5 V reference and the AD8628 low offset and zero-drift
reference buffer.
Table 10. AD5542A Bipolar Code Table
DAC Latch Contents
MSB LSB Analog Output
1111 1111 1111 1111 +V
REF
× (32,767/32,768)
1000 0000 0000 0001 +V
REF
× (1/32,768)
1000 0000 0000 0000 0 V
0111 1111 1111 1111 −V
REF
× (1/32,768)
0000 0000 0000 0000 −V
REF
× (32,768/32,768) = −V
REF
Assuming a perfect reference, the worst-case bipolar output
voltage can be calculated from the following equation:
A
RD
RDVRDVV
V
REF
OS
UNI
OUT
BIPOUT
)2(1
)]1()2)([(
++
+−+
+
=
−
−
where:
V
OUT−BIP
is the bipolar mode worst-case output
V
OUT−UNI
is the unipolar mode worst-case output.
V
OS
is the external op amp input offset voltage.
RD is the R
FB
and R
INV
resistor matching error.
A is the op amp open-loop gain.
V
OUT
REFSREFF
INV
R
FB
R
INV
DGND AGNDF
V
DD
DIN
SCLK
LDAC
CS
AD5512A/
AD5542A
AGNDS
+
0.1µF0.1µF
10µF
BIPOLAR
OUTPUT
EXTERNAL
OP AMP
+2.5V
+5V
+5V
–5V
SERIAL
INTERFACE
R
FB
09199-024
Figure 32. Bipolar Output