
11
LTC1821
Figure 2. Bipolar Operation (4-Quadrant Multiplication) VOUT = – VREF to VREF
Bipolar Mode
(4-Quadrant Multiplying, VOUT = – VREF to VREF)
The LTC1821 contains on chip all the 4-quadrant resistors
necessary for bipolar operation. 4-quadrant multiplying
APPLICATIONS INFORMATION
WU
U
operation can be achieved with a minimum of external
components—a capacitor and a single op amp, as shown
in Figure 2. With a fixed 10V reference, the circuit shown
gives a precision bipolar – 10V to 10V output swing.
VCC
LTC1821
RFB
ROFS
5V
LD
10
9
24
23
718
2
13
15
20
117
16
R1
RCOM
8
6
3
2
REF
11
12
0.1
F
0.1
F
15V
–15V
14
IOUT
VOUT
22pF
VOUT =
–VREF
TO VREF
1821 F02
AGNDF AGNDS
DGND
WR
25 TO 36,
3 TO 6
WR
CLR DNC* DNC*
CLR
VREF
–
+
16-BIT DAC
R1
R2
16
DATA
INPUTS
0.1
F
19
DNC*
21
NC
22
V–
V+
–
+
LT1001
Bipolar Offset Binary Code Table
DIGITAL INPUT
BINARY NUMBER
IN DAC REGISTER
VREF (32,767/32,768)
VREF (1/32,768)
0V
–VREF (1/32,768)
–VREF
LSB
1111 1111
1111
0000 0000
0001
0000 0000
0000
1111 1111
1111
0000 0000
0000
ANALOG OUTPUT
VOUT
MSB
1111
1000
0111
0000
*DO NOT CONNECT