EVAL-CED1Z View Datasheet(PDF) - Analog Devices
Part Name
Description
MFG CO.
'EVAL-CED1Z' PDF : 28 Pages View PDF
AD7679
Transfer Functions
Except in 18-bit interface mode, the AD7679 offers straight
binary and twos complement output coding when using OB/2C.
See Figure 24 and Table 8 for the ideal transfer characteristic.
111...111
111...110
111...101
000...010
000...001
000...000
–FS –FS + 1 LSB
+FS – 1 LSB
–FS + 0.5 LSB
+FS – 1.5 LSB
ANALOG INPUT
Figure 24. ADC Ideal Transfer Function
03085-0-026
Table 8. Output Codes and Ideal Input Voltages
Description
Analog Input
VREF = 4.096 V
Straight Twos
Binary Complement
(Hex)
(Hex)
FSR –1 LSB
4.095962 V
3FFFF1 1FFFF1
FSR – 2 LSB
4.095924 V
3FFFE 1FFFE
Midscale +
1 LSB
31.25 μV
20001 00001
Midscale
0V
20000 00000
Midscale –
1 LSB
–31.25 μV
1FFFF 3FFFF
–FSR + 1 LSB -4.095962 V
00001 20001
–FSR
-4.096 V
000002 200002
1 This is also the code for overrange analog input (VIN+ – VIN–
above VREF – VREFGND).
2 This is also the code for underrange analog input (VIN+ – VIN–
below –VREF + VREFGND).
ANALOG
SUPPLY
(5V)
+ 10μF
100nF
20Ω
NOTE 5
+ 10μ F
DVDD
100nF
100nF + 10μ F
DIGITAL SUPPLY
(3.3V OR 5V)
ADR421
2.5V REF
NOTE 1
1MΩ
100nF
50kΩ 100nF
NOTE 2
CREF
47μF
NOTE 1
AVDD AGND
REFBUFIN
REF
REFGND
–
30Ω
NOTE 3 U1
IN+
ANALOG INPUT+
+
AD8021 CC
2.7nF
NOTE 4
–
30Ω
NOTE 3 U2
IN–
ANALOG INPUT–
+
AD8021 CC
2.7nF
NOTE 4
DGND DVDD OVDD
OGND
SCLK
SDOUT
BUSY
CNVST
AD7679
MODE1
MODE0
OB/2C
SERIAL PORT
50Ω
D
NOTE 6
DVDD
μC/μP/DSP
PDBUF
CS
RD
RESET
PD
CLOCK
NOTES
1. SEE VOLTAGE REFERENCE INPUT SECTION.
2. OPTIONAL CIRCUITRY FOR HARDWARE GAIN CALIBRATION.
3.THE AD8021 IS RECOMMENDED. SEE DRIVER AMPLIFIER CHOICE SECTION.
4. SEE ANALOG INPUTS SECTION.
5. OPTION, SEE POWER SUPPLY SECTION.
6. OPTIONAL LOW JITTER CNVST, SEE CONVERSION CONTROL SECTION.
Figure 25. Typical Connection Diagram (Internal Reference Buffer, Serial Interface)
03085-0-027
Rev. A | Page 16 of 28
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