EVAL-AD7980SDZ View Datasheet(PDF) - Analog Devices
Part Name
Description
MFG CO.
'EVAL-AD7980SDZ' PDF : 29 Pages View PDF
Data Sheet
Transfer Functions
The ideal transfer characteristic for the AD7980 is shown in
Figure 26 and Table 8.
111 ... 111
111 ... 110
111 ... 101
000 ... 010
000 ... 001
000 ... 000
–FSR –FSR + 1LSB
+FSR – 1 LSB
–FSR + 0.5LSB
+FSR – 1.5 LSB
ANALOG INPUT
Figure 26. ADC Ideal Transfer Function
AD7980
Table 8. Output Codes and Ideal Input Voltages
Analog Input
Description
VREF = 5 V Digital Output Code (Hex)
FSR − 1 LSB
4.999924 V FFFF1
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
0V
00002
1 This is also the code for an overranged analog input (VIN+ − VIN− above VREF − VGND).
2This is also the code for an underranged analog input (VIN+ − VIN− below VGND).
TYPICAL APPLICATION CIRCUIT WITH MULTIPLE
SUPPLIES
Figure 27 shows an example of a typical application circuit for
the AD7980 when multiple supplies are available.
0 TO VREF
V+
V+
REF1
10µF2
20Ω
2.7nF
V–
4
REF
IN+
VDD
VIO SDI
SCK
AD7980
SDO
IN–
GND
CNV
2.5V
100nF
1.8V TO 5V
100nF
3- OR 4-WIRE INTERFACE
1SEE THE VOLTAGE REFERENCE INPUT SECTION FOR REFERENCE SELECTION.
2CREF IS USUALLY A 10µF CERAMIC CAPACITOR (X5R).
3SEE THE DRIVER AMPLIFIER CHOICE SECTION.
4OPTIONAL FILTER. SEE THE ANALOG INPUT SECTION.
5SEE THE DIGITAL INTERFACE FOR THE MOST CONVENIENT INTERFACE MODE.
Figure 27. Typical Application Circuit with Multiple Supplies
Rev. F | Page 15 of 26
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