Datasheet

Data Sheet AD7631
Rev. B | Page 19 of 32
RD CS
100nF 100nF
AVDD
10µF 100nF
10Ω
AGND DGND DVDD OVDD OGND
CNVST
BUSY
SDOUT
SDCLK
RESETPD
REFBUFIN
D
CLOCK
AD7631
DIGITAL
INTERFACE
SUPPLY
(2.5V, 3.3V, OR 5V)
ANALOG
SUPPLY (5V)
OVDD
DIGITAL
SUPPLY (5V)
IN+
IN–
NOTE 5
ANALOG
INPUT+
C
C
2.7nF
U1
NOTE 1
MODE[1:0]
D0/OB/2C
REFGND
REF
PDBUF
PDREF
100nF
NOTE 3
NOTE 4
NOTE 3
NOTE 7
10µF
10µF
C
REF
22µF
NOTES
1. ANALOG INPUTS ARE DIFFERENTIAL (ANTIPHASE). 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/OUTPUT SECTION.
4. A 22µF CERAMIC CAPACITOR (X5R, 1206 SIZE) IS RECOMMENDED (FOR EXAMPLE, PANASONIC ECJ4YB1A226M).
SEE VOLTAGE REFERENCE INPUT/OUTPUT SECTION.
5. OPTIONAL, SEE POWER SUPPLIES SECTION.
6. THE VCC AND VEE SUPPLIES SHOULD BE VCC = [VIN(MAX) + 2V] AND VEE = [VIN(MIN) – 2V] FOR BIPOLAR INPUT RANGES.
FOR UNIPOLAR INPUT RANGES, VEE CAN BE 0V. SEE POWER SUPPLIES SECTION.
7. OPTIONAL LOW JITTER CNVST, SEE CONVERSION CONTROL SECTION.
8. A SEPARATE ANALOG AND DIGITAL GROUND PLANE IS RECOMMENDED, CONNECTED TOGETHER DIRECTLY UNDER THE ADC.
SEE LAYOUT GUIDELINES SECTION.
ANALOG
INPUT–
NOTE 2
VCC
VEE
10µF
100nF
+7V TO +15.75V
SUPPLY
10µF
100nF
–7V TO –15.75V
SUPPLY
NOTE 6
HW/SW
SCCS
SCCLK
SCIN
BIPOLAR
TEN
SERIAL
PORT 1
SERIAL
PORT 2
C
C
2.7nF
U1
NOTE 2
06588-027
15Ω
15Ω
33Ω
AGND
DGND
NOTE 8
MicroConverter
®
/
MICROPROCESSOR/
DSP
Figure 27. Typical Connection Diagram Shown with Serial Interface and Serial Programmable Port
ANALOG INPUTS
Input Range Selection
In parallel mode and serial hardware mode, the input range is
selected by using the BIPOLAR (bipolar) and TEN (10 V range)
inputs. See Table 6 for pin details and the Hardware
Configuration section and the Software Configuration section for
programming the mode selection with either pins or the
configuration register. Note that when using the configuration
register, the BIPOLAR and TEN inputs are don’t cares and
should be tied high or low.
Input Structure
Figure 28 shows an equivalent circuit for the input structure of
the AD7631.
D1
R
IN
C
IN
D2
IN+ OR IN–
VEE
VCC
C
PIN
AGND
D3
D4
AVDD
0
V
TO 5V
RANGE ONLY
0
6588-028
Figure 28. Simplified Analog Input