AD7661 Analog Devices, AD7661 Datasheet - Page 17

• Manufacturer Part Number: AD7661
• Manufacturer: Analog Devices

Specifications of AD7661

• Resolution (bits): 16bit
• # Chan: 1
• Sample Rate: 100kSPS
• Interface: Par,Ser,SPI
• Analog Input Type: Diff-Uni
• Ain Range: (Vref) p-p,2.5V p-p,Uni (Vref),Uni 2.5V
• Adc Architecture: SAR
• Pkg Type: CSP,QFP

Transfer Functions
Using the OB/ 2C digital input, the AD7661 offers two output
codings: straight binary and twos complement. The LSB size is
V
transfer characteristic is shown in Figure 25 and Table 7.
REF
/65536, which is about 38.15 µV. The AD7661’s ideal
111...111
111...110
111...101
000...010
000...001
000...000
ANALOG INPUT
(0V TO 2.5V)
0.5 LSB
0V
ANALOG
SUPPLY
Figure 25. ADC Ideal Transfer Function
(5V)
1 LSB = V
1 LSB
REF
NOTES
1
2
3
4
U1
C
SEE VOLTAGE REFERENCE INPUT SECTION.
THE CONFIGURATION SHOWN IS USING THE INTERNAL REFERENCE AND INTERNAL BUFFER.
THE AD8021 IS RECOMMENDED. SEE DRIVER AMPLIFIER CHOICE SECTION.
OPTIONAL LOW JITTER.
A 10 µ F CERAMIC CAPACITOR (X5R, 1206 SIZE) IS RECOMMENDED (e.g., PANASONIC ECJ3YB0J106M).
R
2
4
/65536
ANALOG INPUT
C
+
C
10
100nF
µ
F
V
REF
100nF
– 1.5 LSB
PDREF
REF
REFBUFIN
REFGND
IN
INGND
AVDD
V
REF
– 1 LSB
PD
20
Figure 26. Typical Connection Diagram
1
AGND
Ω
PDBUF
+
Rev. 0 | Page 17 of 28
10
µ
F
AD7661
RESET
DGND
100nF
DVDD
Table 7. Output Codes and Ideal Input Voltages
Description
FSR –1 LSB
FSR – 2 LSB
Midscale + 1 LSB
Midscale
Midscale – 1 LSB
–FSR + 1 LSB
–FSR
1
2
CS
This is also the code for overrange analog input (V
This is also the code for underrange analog input (V
V
REF
– V
OVDD
REFGND
RD
BYTESWAP
).
SER/PAR
CNVST
OGND
SDOUT
OB/2C
BUSY
SCLK
100nF
Analog
Input
2.499962 V
2.499923 V
1.250038 V
1.25 V
1.249962 V
38 µV
0 V
+
D
DVDD
10
3
µ
SERIAL
PORT
F
CLOCK
DIGITAL SUPPLY
(3.3V OR 5V)
Digital Output Code (Hex)
Straight
Binary
FFFF
FFFE
8001
8000
7FFF
0001
0000
1
2
µC/µP/DSP
IN
IN
– V
below V
INGND
Twos
Complement
7FFF1
7FFE
0001
0000
FFFF
8001
8000
above
INGND
AD7661
2
).