AD7980 Analog Devices, AD7980 Datasheet - Page 14

• Manufacturer Part Number: AD7980
• Manufacturer: Analog Devices

Specifications of AD7980

• Resolution (bits): 16bit
• # Chan: 1
• Sample Rate: 1MSPS
• Interface: Ser,SPI
• Analog Input Type: Diff-Uni
• Ain Range: Uni (Vref)
• Adc Architecture: SAR
• Pkg Type: CSP,SOP

AD7980
Transfer Functions
The ideal transfer characteristic for the AD7980 is shown in
Figure 26 and Table 7.
000 ... 010
000 ... 001
000 ... 000
111 ... 101
111 ... 110
111 ... 111
–FSR
–FSR + 0.5LSB
0 TO VREF
1
2
3
4
5
SEE THE VOLTAGE REFERENCE INPUT SECTION FOR REFERENCE SELECTION.
C
SEE THE DRIVER AMPLIFIER CHOICE SECTION.
OPTIONAL FILTER. SEE THE ANALOG INPUT SECTION.
SEE THE DIGITAL INTERFACE FOR THE MOST CONVENIENT INTERFACE MODE.
REF
Figure 26. ADC Ideal Transfer Function
–FSR + 1LSB
IS USUALLY A 10µF CERAMIC CAPACITOR (X5R).
V+
V–
ANALOG INPUT
V+
+FSR – 1.5 LSB
4
Figure 27. Typical Application Diagram with Multiple Supplies
20Ω
REF
2.7nF
1
+FSR – 1 LSB
10µF
2
Rev. B | Page 14 of 28
IN–
IN+
GND
REF
AD7980
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 27 shows an example of the recommended connection
diagram for the AD7980 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
VDD
VIO SDI
SCK
SDO
CNV
V
4.999924 V
2.499924 V
76.3 μV
0 V
2.500076 V
2.5 V
REF
100nF
100nF
= 5 V
2.5V
1.8V TO 5V
3- OR 4-WIRE INTERFACE
Analog Input
Digital Output Code
(Hexa)
FFFF
8001
8000
7FFF
0001
0000
1
2
IN+
− V
IN+
IN−
− V
above V
IN−
below V
REF
− V
GND
GND
).
).