AD7845SQ/883B Просмотр технического описания (PDF) - Analog Devices
Номер в каталоге
Компоненты Описание
производитель
AD7845SQ/883B Datasheet PDF : 12 Pages
| |||
AD7845
UNIPOLAR BINARY OPERATION
Figure 13 shows the AD7845 connected for unipolar binary
operation. When VIN is an ac signal, the circuit performs
2-quadrant multiplication. The code table for Figure 13 is given
in Table I.
BIPOLAR OPERATION
(4-QUADRANT MULTIPLICATION)
The recommended circuit for bipolar operation is shown in
Figure 14. Offset binary coding is used.
The offset specification of this circuit is determined by the
matching of internal resistors RB and RC and by the zero code
offset error of the device. Gain error may be adjusted by varying
the ratio of R1 and R2.
To use this circuit without trimming and keep within the gain
error specifications, resistors R1 and R2 should be ratio
matched to 0.01%.
The code table for Figure 14 is given in Table II.
Figure 13. Unipolar Binary Operation
Table I. Unipolar Binary Code Table for AD7845
Binary Number In
DAC Register
MSB
1111
1111
LSB
1111
Analog Output, VOUT
4095
–VIN 4096
1000
0000
0000
2048
–VIN 4096 = –1/2 VIN
0000
0000
0000
0000
0001
0000
1
–VIN 4096
0V
OFFSET AND GAIN ADJUSTMENT FOR FIGURE 13
Zero Offset Adjustment
1. Load DAC with all 0s.
2. Trim R3 until VOUT = 0 V.
Gain Adjustment
1. Load DAC with all 1s.
2.
Trim R1 so that VOUT = –VIN
4095 .
4096
In fixed reference applications, full scale can also be adjusted by
omitting R1 and R2 and trimming the reference voltage magni-
tude. For high temperature applications, resistors and potenti-
ometers should have a low temperature coefficient.
Figure 14. Bipolar Offset Binary Operation
Table II. Bipolar Code Table for Offset Binary Circuit of
Figure 14
Binary Number In
DAC Register
MSB
1111
1111
LSB
1111
Analog Output, VOUT
2047
+VIN 2048
1000
1000
0111
0000
0000
1111
0001
0000
1111
1
+VIN 2048
0V
1
–VIN 2048
0000
0000
0000
2048
–VIN 2048 = –VIN
REV. B
–7–
Share Link: 