MAX532
Output Amplifiers
The output amplifiers are stable with any combination
of resistive loads ≥ 2kΩ and capacitive loads ≤ 100pF.
They are internally compensated, and settle to ±0.01%
FSR (1/2LSB) in 2.5µs.
Unipolar Configuration
Figure 9 shows DACA connected for unipolar binary
operation. Similar connections apply for DACB. When
V
IN
is an AC signal, the circuit performs two-quadrant
multiplication. Table 2 shows the codes for this circuit.
Bipolar Operation
Figure 10 shows the MAX532 connected for bipolar
operation. The coding is offset binary, as shown in
Table 3. When V
IN
is an AC signal, the circuit performs
four-quadrant multiplication. To maintain gain error
specifications, resistors R1, R2, and R3 should be ratio-
matched to 0.01%.
__________Applications Information
Layout, Grounding, and Bypassing
For best system performance, use printed circuit boards
with separate analog and digital ground planes. Wire-
wrap boards are not recommended. The two ground
planes should be tied together at the low-impedance
power-supply source, as shown in Figure 11.
The board layout should ensure that digital and analog
signal lines are kept separate from each other as much
as possible. Do not run analog and digital lines parallel
to one another.
The output amplifiers are sensitive to high-frequency
noise in the V
DD
and V
SS
power supplies. Bypass
these supplies to the analog ground plane with 0.1µF
and 10µF bypass capacitors. Minimize capacitor lead
lengths for best noise rejection.
Dual, Serial-Input,
Voltage-Output, 12-Bit MDAC
12 ______________________________________________________________________________________
1111 1111 1111
-V
IN
x (4095/4096)
1000 0000 0000
-V
IN
x (2048/4096) = -1/2V
IN
0000 0000 0001
-V
IN
x (1/4096)
0000 0000 0000 0V
DAC Latch Contents
Table 2. Unipolar Code Table
1LSB = V
IN
/4096
DAC_
AGND_
V
SS
DGND
RFB_
VOUT_
V
IN
-12V to -15V
V
DD
VREF_
+12V to +15V
MAX532
V
OUT
R1
20k
R2
20k
R3
10k
Figure 10. Bipolar Operation
V
DD
V
SS
AGNDA AGNDB DGND
MAX532
+15V -15V AGND +5V DGND
ANALOG
SUPPLY
DIGITAL
SUPPLY
DIGITAL
CIRCUITRY
+5V DGND
Figure 11. Power-Supply Grounding
Table 3. Bipolar Code Table
DAC Latch Contents
1111 1111 1111
+V
IN
x (2047/2048)
1000 0000 0001
+V
IN
x (1/2048)
1000 0000 0000 0V
0111 1111 1111
-V
IN
x (1/2048)
1LSB = V
IN
/2048
0000 0000 0000
-V
IN
+ (2048/2048) = -V
IN
MSB LSB
Analog Output, V
OUT
MSB LSB
Analog Output, V
OUT
