AD7631

Rev. A | Page 19 of 32

RD

CS

100nF

100nF

AVDD

10µF

100nF

10Ω

AGND

DGND

DVDD

OVDD

OGND

CNVST

BUSY

SDOUT

SDCLK

RESET

PD

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+

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

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

2.7nF

U1

NOTE 2

15Ω

15Ω

33Ω

AGND

DGND

NOTE 8

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

D2

IN+ OR IN–

VEE

VCC

AGND

D3

D4

AVDD

0V TO 5V

RANGE ONLY

Figure 28. Simplified Analog Input