AD7982 Analog Devices, AD7982 Datasheet - Page 13

• Manufacturer Part Number: AD7982
• Manufacturer: Analog Devices

Specifications of AD7982

• Resolution (bits): 18bit
• # Chan: 1
• Sample Rate: 1MSPS
• Interface: Ser,SPI
• Analog Input Type: Diff-Uni
• Ain Range: (2Vref) p-p
• Adc Architecture: SAR
• Pkg Type: SOP

Transfer Functions
The ideal transfer characteristic for the AD7982 is shown in
Figure 22 and Table 7.
100...010
100...001
100...000
011...110
011...101
011...111
–FSR + 0.5 LSB
–FSR
Figure 22. ADC Ideal Transfer Function
–FSR + 1 LSB
0 TO VREF
VREF TO 0
ADA4841
ANALOG INPUT
2, 3
+FSR – 1.5 LSB
V+
V–
V+
V–
V+
Figure 23. Typical Application Diagram with Multiple Supplies
NOTES
1
2
3
4
SEE VOLTAGE REFERENCE INPUT SECTION FOR REFERENCE SELECTION.
C
SEE DRIVER AMPLIFIER CHOICE SECTION.
OPTIONAL FILTER. SEE ANALOG INPUT SECTION.
SEE RECOMMENDED LAYOUT FIGURE 41 AND FIGURE 42.
+FSR – 1 LSB
REF
2.7nF
2.7nF
REF
4
4
20Ω
20Ω
IS USUALLY A 10µF CERAMIC CAPACITOR (X5R).
1
10µF
2
Rev. A | Page 13 of 24
IN+
IN–
GND
REF
AD7982
VDD
Table 7. Output Codes and Ideal Input Voltages
Description
FSR – 1 LSB
Midscale + 1 LSB
Midscale
Midscale – 1 LSB
–FSR + 1 LSB
–FSR
1
2
TYPICAL CONNECTION DIAGRAM
Figure 23 shows an example of the recommended connection
diagram for the AD7982 when multiple supplies are available.
This is also the code for an overranged analog input (V
This is also the code for an underranged analog input (V
VIO
SCK
SDO
CNV
SDI
100nF
100nF
3-WIRE INTERFACE
Analog Input
V
+4.999962 V
+38.15 μV
0 V
−38.15 μV
−4.999962 V
−5 V
REF
2.5V
1.8V TO 5V
= 5 V
IN+
Digital Output
Code (Hex)
0x1FFFF
0x00001
0x00000
0x3FFFF
0x20001
0x20000
− V
IN+
IN−
− V
above V
AD7982
IN−
1
2
below V
REF
− V
GND
GND
).
).