EVAL-AD7678CB Analog Devices Inc, EVAL-AD7678CB Datasheet - Page 16

• Manufacturer Part Number: EVAL-AD7678CB
• Description: BOARD EVALUATION FOR AD7678
• Manufacturer: Analog Devices Inc
• Series: PulSAR®r

Specifications of EVAL-AD7678CB

• Number Of Adc's: 1
• Number Of Bits: 18
• Sampling Rate (per Second): 100k
• Data Interface: Serial, Parallel
• Inputs Per Adc: 1 Differential
• Input Range: ±VREF
• Power (typ) @ Conditions: 31mW @ 100kSPS
• Voltage Supply Source: Analog and Digital
• Operating Temperature: -40°C ~ 85°C
• Utilized Ic / Part: AD7678
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

AD7678
Transfer Functions
Except in 18-bit interface mode, the AD7678 offers straight
binary and twos complement output coding when using OB/ 2C .
See Figure 20 and Table 8 for the ideal transfer characteristic.
ANALOG INPUT+
ANALOG INPUT–
111...111
111...110
111...101
000...010
000...001
000...000
ADR421
2.5V REF
NOTE 1
–FS + 0.5 LSB
–FS
ANALOG
Figure 20. ADC Ideal Transfer Function
SUPPLY
NOTE 4
NOTE 4
100nF
(5V)
AD8021
1M
AD8021
NOTES
1. SEE VOLTAGE REFERENCE SECTION.
2. C
3. OPTIONAL CIRCUITRY FOR HARDWARE GAIN CALIBRATION.
4.THE AD8021 IS RECOMMENDED. SEE DRIVER AMPLIFIER CHOICE SECTION.
5. OPTION, SEE POWER SUPPLY SECTION.
–FS + 1 LSB
1206 PANASONIC ECJ-3xB0J106 IS RECOMMENDED. SEE VOLTAGE REFERENCE SECTION.
NOTE 3
REF
–
+
–
+
U1
U2
50
50
is 10F CERAMIC CAPACITOR OR LOW ESR TANTALUM. CERAMIC SIZE
ANALOG INPUT
50k
C
C
C
C
100nF
+
Figure 21. Typical Connection Diagram (Internal Reference Buffer, Serial Interface)
NOTE 2
10F
C
10F
REF
+FS – 1.5 LSB
100nF
REFBUFIN
IN+
IN–
+FS – 1 LSB
REF
REFGND
AVDD
03084-0-026
NOTE 5
20
AGND
Rev. A | Page 16 of 28
+
10 F
AD7678
DGND
100nF
Table 8. 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
above V
This is also the code for underrange analog input (V
below –V
DVDD
DVDD
REF
REF
– V
OVDD
+ V
REFGND
REFGND
).
MODE1
MODE0
PDBUF
).
SDOUT
CNVST
RESET
4.095962 V
4.095924 V
-4.095962 V
-4.096 V
OGND
Analog Input
V
31.25 μV
0 V
–31.25 μV
OB/2C
SCLK
BUSY
REF
CS
RD
PD
100nF
= 4.096 V
+
DVDD
10 F
SERIAL PORT
Straight
Binary
(Hex)
3FFFF
3FFFE
20001
20000
1FFFF
00001
00000
DIGITAL SUPPLY
(3.3V OR 5V)
CLOCK
IN+
1
2
IN+
– V
– V
IN–
IN–
Twos
Complement
(Hex)
1FFFF
1FFFE
00001
00000
3FFFF
20001
20000
C/P/DSP
03084-0-027
1
2