AD7985 Analog Devices, AD7985 Datasheet - Page 14

• Manufacturer Part Number: AD7985
• Description: 16-Bit, 2.5 MSPS PulSAR 11 mW ADC in QFN
• Manufacturer: Analog Devices

Specifications of AD7985

• Resolution (bits): 16bit
• # Chan: 1
• Sample Rate: 2.5MSPS
• Interface: Ser,SPI
• Analog Input Type: SE-Uni
• Ain Range: (Vref) p-p,Uni (Vref)
• Adc Architecture: SAR
• Pkg Type: CSP

AD7985
Transfer Functions
The ideal transfer characteristic for the AD7985 is shown in
Figure 22 and Table 7.
000 ... 010
000 ... 001
000 ... 000
111 ... 111
111 ... 110
111 ... 101
–FSR + 0.5 LSB
–FSR
Figure 22. ADC Ideal Transfer Function
–FSR + 1 LSB
0V TO V
NOTES
1. GND REFERS TO REFGND, AGND, AND DGND.
ANALOG INPUT
REF
+FSR – 1.5 LSB
Figure 23. Typical Application Diagram with Multiple Supplies
V+
V–
+FSR – 1 LSB
15Ω
2.7nF
Rev. A | Page 14 of 28
IN+
IN–
10µF
BVDD
REF
5V
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 AD7985 when multiple supplies are available.
AD7985
This is also the code for an overranged analog input (V
This is also the code for an underranged analog input (V
REFGND).
AVDD,
DVDD
GND
2.5V
1.8V
2.7V
VIO
TO
TURBO
SCK
SDO
CNV
SDI
Analog Input,
V
4.095938 V
2.048063 V
2.048 V
2.047938 V
62.5 µV
0 V
REF
3- OR 4-WIRE
INTERFACE:
SPI, CS,
DAISY CHAIN
(TURBO = LOW)
VIO
= 4.096 V
IN+
Digital Output
Code (Hex)
0xFFFF
0x8001
0x8000
0x7FFF
0x0001
0x0000
IN+
− V
− V
IN−
below REFGND).
IN−
1
2
above V
REF
−