Datasheet

REV. B
AD7663
–12–
SW
A
COMP
SW
B
IND
4R
REF
REFGND
LSB
MSB
32,768C
INGND
16,384C
4C
2C
CC
CONTROL
LOGIC
SWITCHES
CONTROL
BUSY
OUTPUT
CODE
INC
4R
INA
R
INB
2R
CNVST
65,536C
Figure 3. ADC Simplified Schematic
Table III. Output Codes and Ideal Input Voltages
Digital Output
Code (Hexa)
Straight Twos
Description Analog Input Binary Complement
Full-Scale Range
1
±10 V ±5 V ±2.5 V 0 V to 10 V 0 V to 5 V 0 V to 2.5 V
Least Significant Bit 305.2 µV 152.6 µV 76.3 µV 152.6 µV 76.3 µV 38.15 µV
FSR – 1 LSB 9.999695 V 4.999847 V 2.499924 V 9.999847 V 4.999924 V 2.499962 V FFFF
2
7FFF
2
Midscale + 1 LSB 305.2 µV 152.6 µV 76.3 µV 5.000153 V 2.570076 V 1.257038 V 8001 0001
Midscale 0 V 0 V 0 V 5 V 2.5 V 1.25 V 8000 0000
Midscale – 1 LSB –305.2 µV –152.6 µV –76.3 µV 4.999847 V 2.499924 V 1.249962 V 7FFF FFFF
–FSR + 1 LSB –9.999695 V –4.999847 V –2.499924 V 152.6 µV 76.3 µV 38.15 µV 0001 8001
–FSR –10 V –5 V –2.5 V 0 V 0 V 0 V 0000
3
8000
3
NOTES
1
Values with REF = 2.5 V, with REF = 3 V, all values will scale linearly.
2
This is also the code for an overrange analog input.
3
This is also the code for an underrange analog input.
000...000
000...001
000...010
111...101
111...110
111...111
ADC CODE – Straight Binary
ANALOG INPUT
+FS – 1.5 LSB
+FS – 1 LSB
–FS + 1 LSB–FS
–FS + 0.5 LSB
Figure 4. ADC Ideal Transfer Function
Transfer Functions
Using the OB/2C digital input, the AD7663 offers two output
codings: straight binary and twos complement. The ideal transfer
characteristic for the AD7663 is shown in Figure 4 and Table III.
TYPICAL CONNECTION DIAGRAM
Figure 5 shows a typical connection diagram for the AD7663.
Different circuitry shown on this diagram is optional and is
discussed in the figure’s notes.
Analog Inputs
The AD7663 is specified to operate with six full-scale analog
input ranges. Connections required for each of the four analog
inputs, IND, INC, INB, and INA, and the resulting full-scale
ranges are shown in Table I. The typical input impedance for
each analog input range is also shown.