AD7621 Analog Devices, AD7621 Datasheet - Page 16

• Manufacturer Part Number: AD7621
• Description: 16-Bit, 2 LSB INL, 3 MSPS PulSAR® ADC
• Manufacturer: Analog Devices

Specifications of AD7621

• Resolution (bits): 16bit
• # Chan: 1
• Sample Rate: 3MSPS
• Interface: Byte,Par,Ser,SPI
• Analog Input Type: Diff-Uni
• Ain Range: (2Vref) p-p
• Adc Architecture: SAR
• Pkg Type: CSP,QFP

AD7621
TRANSFER FUNCTIONS
Using the OB/ 2C digital input, the AD7621 offers two output
codings: straight binary and twos complement. The LSB size
with V
Figure 22 and Table 7 for the ideal transfer characteristic.
1. SEE ANALOG INPUT SECTION.
2. THE AD8021 IS RECOMMENDED. SEE DRIVER AMPLIFIER CHOICE SECTION.
3. THE CONFIGURATION SHOWN IS USING THE INTERNAL REFERENCE. SEE VOLTAGE REFERENCE INPUT SECTION.
4. A 10μF CERAMIC CAPACITOR (X5R, 1206 SIZE) IS RECOMMENDED (e.g., PANASONIC ECJ3YB0J106M).
5. OPTION, SEE POWER SUPPLY SECTION.
6. OPTION, SEE POWER UP SECTION.
7. OPTIONAL LOW JITTER CNVST, SEE CONVERSION CONTROL SECTION.
ANALOG
ANALOG
SUPPLY (2.5V)
INPUT +
INPUT –
SEE VOLTAGE REFERENCE INPUT SECTION.
ANALOG
REF
111...111
111...110
111...101
000...010
000...001
000...000
= 2.048 V is 2 × V
–FSR+0.5 LSB
–FSR
Figure 22. ADC Ideal Transfer Function
NOTE 2
C
NOTE 2
C
U1
U2
C
C
–FSR+1 LSB
C
10μF
10μF
REF
NOTE 1
10Ω
NOTE 1
10Ω
1nF
1nF
100nF
REF
100nF
NOTE 4
ANALOG INPUT
/65536, which is 62.5 μV. Refer to
REF
REFBUFIN
REFGND
IN+
IN–
AVDD
+FSR–1.5 LSB
NOTE 3
NOTE 5
AGND
10Ω
+FSR–1 LSB
10μF
Figure 23. Typical Connection Diagram
DGND
PD
100nF
AD7621
Rev. 0 | Page 16 of 32
PDREF
SUPPLY (2.5V)
NOTE 3
DIGITAL
PDBUF
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
This is also the code for overrange analog input (V
This is also the code for underrange analog input (V
V
−V
OVDD
REF
REF
− V
+ V
100nF
REFGND
SER/PAR
IMPULSE
REFGND
SDOUT
CNVST
RESET
OGND
OB/2C
WARP
BUSY
SCLK
).
RD
CS
).
10μF
Analog Input
V
+2.047938 V
+2.047875 V
+62.5 μV
0 V
−62.5 μV
−2.047938 V
−2.048 V
REF
10kΩ
NOTE 6
50pF
= 2.048 V
50pF
50Ω
SERIAL
PORT
OVDD
(2.5V OR 3.3V)
NOTE 7
INTERFACE
DIGITAL
SUPPLY
D
CLOCK
Straight
Binary
0xFFFF
0xFFFE
0x8001
0x8000
0x7FFF
0x0001
0x0000
Digital Output Code
IN+
IN+
MICROPROCESSOR/
1
MICROCONVERTER/
2
− V
− V
IN−
IN−
Twos
Complement
0x7FFF
0x7FFE
0x0001
0x0000
0xFFFF
0x8001
0x8000
above
DSP
below
1
2