EVAL-AD7675CB Ver la hoja de datos (PDF) - Analog Devices

Número de pieza

componentes Descripción

Fabricante

EVAL-AD7675CB

16-Bit, 100 kSPS, Differential ADC

Analog Devices 

ANALOG

SUPPLY

(5V)

+ 10␮F 100nF

100⍀

NOTE 6

+ 10␮F

DVDD

100nF

AD7675

100nF + 10␮F

DIGITAL SUPPLY

(3.3V OR 5V)

ADR421

2.5V REF

NOTE 1

1M⍀

100nF

50k⍀ + CREF

NOTE 2

1␮F

NOTE 3

50⍀

AVDD AGND

REF

REFGND

–

15⍀

NOTE 4 U1

IN+

ANALOG INPUT+

+

AD8021

CC

2.7nF

NOTE 5

50⍀

–

15⍀

NOTE 4 U2

IN–

ANALOG INPUT–

+

AD8021

CC

2.7nF

NOTE 5

DGND DVDD OVDD

OGND

SCLK

SDOUT

BUSY

CNVST

AD7675

OB/2C

SER/PAR

SERIAL PORT

50⍀

D

NOTE 7

DVDD

␮C/␮P/DSP

CS

RD

BYTESWAP

RESET

PD

CLOCK

NOTES

1. SEE VOLTAGE REFERENCE INPUT SECTION.

2. WITH THE RECOMMENDED VOLTAGE REFERENCES, CREF IS 47␮F. SEE CHAPTER VOLTAGE REFERENCE INPUT SECTION

3. OPTIONAL CIRCUITRY FOR HARDWARE GAIN CALIBRATION.

4. THE AD8021 IS RECOMMENDED. SEE DRIVER AMPLIFIER CHOICE SECTION.

5. SEE ANALOG INPUT SECTION.

6. OPTION, SEE POWER SUPPLY SECTION

7. OPTIONAL LOW JITTER CNVST, SEE CONVERSION CONTROL SECTION.

Figure 5. Typical Connection Diagram. (±2.5 V Range Shown)

TYPICAL CONNECTION DIAGRAM

Figure 5 shows a typical connection diagram for the AD7675.

the input buffer’s (U1) or (U2) supplies are different from

AVDD. In such a case, an input buffer with a short-circuit

Different circuitry shown on this diagram is optional and is

discussed below.

Analog Inputs

Figure 6 shows a simplified analog input section of the AD7675.

current limitation can be used to protect the part.

This analog input structure is a true differential structure. By

using these differential inputs, signals common to both inputs

are rejected, as shown in Figure 7, which represents the typical

CMRR over frequency.

AVDD

85

80

IN+

R+ = 684⍀

75

CS

70

CS

IN–

65

R– = 684⍀

60

AGND

Figure 6. Simplified Analog Input

The diodes shown in Figure 6 provide ESD protection for the

inputs. Care must be taken to ensure that the analog input sig-

nal never exceeds the absolute ratings on these inputs. This will

cause these diodes to become forward-biased and start conducting

current. These diodes can handle a forward-biased current of

120 mA maximum. This condition could eventually occur when

55

50

45

40

1k

10k

100k

1M

10M

FREQUENCY – Hz

Figure 7. Analog Input CMRR vs. Frequency

REV. A

–11–

Share Link: