AD7690 Analog Devices, AD7690 Datasheet - Page 13

• Manufacturer Part Number: AD7690
• Manufacturer: Analog Devices

Specifications of AD7690

• Resolution (bits): 18bit
• # Chan: 1
• Sample Rate: 400kSPS
• Interface: Ser,SPI
• Analog Input Type: Diff-Uni
• Ain Range: (2Vref) p-p
• Adc Architecture: SAR
• Pkg Type: CSP,SOP

Transfer Functions
The ideal transfer characteristic for the AD7690 is shown in
Figure 25 and Table 7.
011...111
011...110
011...101
100...010
100...001
100...000
–FSR + 0.5LSB
–FSR
Figure 25. ADC Ideal Transfer Function
–FSR + 1LSB
0 TO V
V
REF
ADA4841-2
ADA4841-2
TO 0
REF
ANALOG INPUT
1
2
3
4
5
SEE VOLTAGE REFERENCE INPUT SECTION FOR REFERENCE SELECTION.
C
SEE TABLE 8 FOR ADDITIONAL RECOMMENDED AMPLIFIERS.
OPTIONAL FILTER. SEE ANALOG INPUT SECTION.
SEE THE DIGITAL INTERFACE SECTION FOR MOST CONVENIENT INTERFACE MODE.
3
3
REF
V+
V–
V+
V–
V+
IS USUALLY A 10µF CERAMIC CAPACITOR (X5R).
+FSR – 1.5LSB
Figure 26. Typical Application Diagram with Multiple Supplies
REF
4
4
2.7nF
2.7nF
15Ω
15Ω
1
+FSR – 1LSB
10µF
2
IN+
IN–
Rev. B | Page 13 of 24
GND
REF
AD7690
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 26 shows an example of the recommended connection
diagram for the AD7690 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- OR 4-WIRE INTERFACE
5V
1.8V TO VDD
Analog Input
V
+4.999962 V
−4.999962 V
−5 V
+38.15 μV
0 V
−38.15 μV
REF
= 5 V
5
IN+
Digital Output
Code (Hex)
0x1FFFF
0x00001
0x00000
0x3FFFF
0x20001
0x20000
− V
IN+
IN−
− V
above V
AD7690
IN−
1
2
below V
REF
− V
GND
GND
).
).