Datasheet

AD7983
Rev. A | Page 13 of 24
Transfer Functions
The ideal transfer characteristic for the AD7983 is shown in
Figure 22 and Table 7.
000 ... 000
000 ... 001
000 ... 010
111 ... 101
111 ... 110
111 ... 111
–FSR –FSR + 1LSB
–FSR + 0.5LSB
+FSR – 1 LSB
+FSR – 1.5 LSB
ANALOG INPUT
ADC CODE (STRAIGHT BINARY)
0
6974-007
Figure 22. ADC Ideal Transfer Function
Table 7. Output Codes and Ideal Input Voltages
Analog Input
Description V
REF
= 5 V Digital Output Code (Hex)
FSR − 1 LSB 4.999924 V FFFF
1
Midscale + 1 LSB 2.500076 V 8001
Midscale 2.5 V 8000
Midscale − 1 LSB 2.499924 V 7FFF
−FSR + 1 LSB 76.3 μV 0001
−FSR 0 V 0000
2
1
This is also the code for an overranged analog input (V
IN+
− V
IN−
above V
REF
− V
GND
).
2
This is also the code for an underranged analog input (V
IN+
− V
IN−
below V
GND
).
TYPICAL CONNECTION DIAGRAM
Figure 23 shows an example of the recommended connection
diagram for the AD7983 when multiple supplies are available.
AD7983
3- OR 4-WIRE INTERFACE
2.5VV+
20Ω
V+
V–
0 TO VRE
F
1.8V TO 5V
100nF
10µF
2
2.7nF
4
100nF
REF
IN+
IN–
VDD VIO
SDI
CNV
SCK
SDO
GND
REF
1
1
SEE THE VOLTAGE REFERENCE INPUT SECTION FOR REFERENCE SELECTION.
2
C
REF
IS USUALLY A 10µF CERAMIC CAPACITOR (X5R).
3
SEE THE DRIVER AMPLIFIER CHOICE SECTION.
4
OPTIONAL FILTER. SEE THE ANALOG INPUTS SECTION.
5
SEE THE DIGITAL INTERFACE SECTION FOR THE MOST CONVENIENT INTERFACE MODE.
06974-008
Figure 23. Typical Application Diagram with Multiple Supplies