Datasheet
Table Of Contents
- FEATURES
- APPLICATIONS
- GENERAL DESCRIPTION
- FUNCTIONAL BLOCK DIAGRAM
- TABLE OF CONTENTS
- REVISION HISTORY
- SPECIFICATIONS
- ABSOLUTE MAXIMUM RATINGS
- TIMING SPECIFICATIONS
- PIN CONFIGURATION AND FUNCTION DESCRIPTIONS
- TERMINOLOGY
- TYPICAL PERFORMANCE CHARACTERISTICS
- APPLICATIONS INFORMATION
- TYPICAL CONNECTION DIAGRAM
- INTERFACES
- APPLICATION HINTS
- OUTLINE DIMENSIONS
AD7622
Rev. 0 | Page 16 of 28
TRANSFER FUNCTIONS
Using the OB/
2C
digital input, the AD7622 offers two output
codings: straight binary and twos complement. The LSB size
with V
REF
= 2.048 V is 2 × V
REF
/ 65536 which is 62.5 μV. Refer to
Figure 23 and Table 7 for the ideal transfer characteristic.
000...000
000...001
000...010
111. ..101
111...110
111. ..111
ADC CODE (Straight Binary)
ANALOG INPUT
+FSR – 1.5 LSB
+FSR – 1 LSB–FSR + 1 LSB
–FSR
–FSR + 0.5 LSB
06023-022
Figure 23. ADC Ideal Transfer Function
Table 7. Output Codes and Ideal Input Voltages
Digital Output Code (Hex)
Description
Analog Input
V
REF
= 2.048 V
Straight
Binary
Twos
Complement
FSR −1 LSB +2.047938 V 0xFFFF
1
0x7FFF
1
FSR − 2 LSB +2.047875 V 0xFFFE 0x7FFE
Midscale + 1 LSB +62.5 μV 0x8001 0x0001
Midscale 0 V 0x8000 0x0000
Midscale − 1 LSB −62.5 μV 0x7FFF 0xFFFF
−FSR + 1 LSB −2.047938 V 0x0001 0x8001
−FSR −2.048 V 0x0000
2
0x8000
2
1
This is also the code for overrange analog input (V
IN+
− V
IN−
above
+V
REF
− V
REFGND
).
2
This is also the code for underrange analog input (V
IN+
− V
IN−
below
−V
REF
+ V
REFGND
).
06023-023
RD
CS
100nF 100nF
AVDD
10µF
100nF
AGND DGND DVDD OVDD OGND
CNVST
BUSY
SDOUT
SCLK
RESET
PD
REFBUFIN
10Ω
D
CLOCK
AD7622
MICROCONVERTER/
MICROPROCESSOR/
DSP
SERIAL
PORT
DIGITAL
INTERFACE
SUPPLY
(2.5V OR 3.3V)
ANALOG
SUPPLY (2.5V)
OVDD
WARP
DIGITAL
SUPPLY (2.5V)
IN+
IN–
U2
15Ω
NOTE 5
50Ω
50pF
NOTE 1
ANALOG
INPUT +
C
C
C
C
2.7nF
2.7nF
U1
15Ω
NOTE 1
SER/PAR
OB/2C
REFGND
REF
PDBUF
PDREF
100nF
ANALOG
INPUT –
NOTE 2
NOTE 2
NOTE 3
NOTE 4
NOTE 3
NOTE 7
NOTE 6
NORMAL
10µF
10µF
C
REF
10µF
10kΩ
50pF
1. SEE ANALOG INPUTS 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 (FOR EXAMPLE, PANASONIC ECJ3YB0J106M).
SEE VOLTAGE REFERENCE INPUT SECTION.
5. OPTION, SEE POWER SUPPLY SECTION.
6. OPTION, SEE POWER-UP SECTION.
7. OPTIONAL LOW JITTER CNVST, SEE CONVERSION CONTROL SECTION.
Figure 24. Typical Connection Diagram