AD7685 Analog Devices, AD7685 Datasheet - Page 14

• Manufacturer Part Number: AD7685
• Manufacturer: Analog Devices

Specifications of AD7685

• Resolution (bits): 16bit
• # Chan: 1
• Sample Rate: 250kSPS
• Interface: Ser,SPI
• Analog Input Type: Diff-Uni
• Ain Range: (Vref) p-p
• Adc Architecture: SAR
• Pkg Type: CSP,SOP

AD7685
Transfer Functions
The ideal transfer characteristic for the AD7685 is shown in
Figure 26 and Table 8.
Table 8. Output Codes and Ideal Input Voltages
Description
FSR – 1 LSB
Midscale + 1 LSB
Midscale
Midscale – 1 LSB
–FSR + 1 LSB
–FSR
1
2
This is also the code for an overranged analog input (V
This is also the code for an underranged analog input (V
000...010
000...001
000...000
111...101
111...110
111...111
–FS + 0.5 LSB
–FS
Figure 26. ADC Ideal Transfer Function
–FS + 1 LSB
0 TO VREF
NOTES
1. SEE VOLTAGE REFERENCE INPUT SECTION FOR REFERENCE SELECTION.
2. C
3. SEE DRIVER AMPLIFIER CHOICE SECTION.
4. OPTIONAL FILTER. SEE ANALOG INPUT SECTION.
5. SEE DIGITAL INTERFACE FOR MOST CONVENIENT INTERFACE MODE.
3
ANALOG INPUT
REF
≤–2V
≥7V
≥7V
IS USUALLY A 10µF CERAMIC CAPACITOR (X5R).
+FS – 1.5 LSB
Analog Input V
4.999924 V
76.3 μV
0 V
REF
2.500076 V
2.5 V
2.499924 V
4
2.7nF
IN+
Figure 27. Typical Application Diagram with Multiple Supplies
33Ω
1
− V
+FS – 1 LSB
IN+
IN−
− V
10µF
above V
IN−
2
below V
REF
IN+
IN–
REF
− V
= 5 V
GND
GND
Rev. C | Page 14 of 28
REF
GND
).
).
AD7685
VDD
VIO
TYPICAL CONNECTION DIAGRAM
Figure 27 shows an example of the recommended connection
diagram for the AD7685 when multiple supplies are available.
SCK
SDO
CNV
SDI
Digital Output Code Hexa
FFFF
8001
7FFF
0001
0000
8000
1
2
100nF
100nF
3- OR 4-WIRE INTERFACE
5V
1.8V TO VDD
5