AD7626 datasheet(20/28 Pages) AD

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AD7626

Rev. A | Page 20 of 2

VOLTAGE REFERENCE OPTIONS

The AD7626 allows flexible options for creating and buffering

the reference voltage. The AD7626 conversions refer to 4.096 V

only. The various options creating this 4.096 V reference are

controlled by the EN1 and EN0 pins (see Table 8).

Table 8. Voltage Reference Options

Option

EN1

EN0

Reference Mode

Power-up

Internal reference and internal

reference buffer in use

External 1.2 V reference applied to

REFIN pin required

External 4.096 V reference applied to

REF pin required.

Power-down mode

AD7626

IN+

IN–

REF

REFIN

10µF

DECOUPLE THE REF AND

REFIN PINS EXTERNALLY.

EN1 = 1 AND EN0 = 1

POWER-UP—INTERNAL REFERENCE AND REFERENCE BUFFER IN USE.

NO EXTERNAL REFERENCE CIRCUITRY REQUIRED.

Figure 35. Powered Up, Internal Reference and Internal Reference Buffer

AD7626

IN+

IN–

REF

REFIN

10µF

EN1 = 0 AND EN0 = 1

EXTERNAL 1.2V REFERENCE CONNECTED TO REFIN PIN IS REQUIRED.

ADR280

V–

VOUT

V+

0.1µF

1.2V

(2.4V

≤ V+ ≥ 5.5V)

V+

CONNECT 1.2V EXTERNAL REFERENCE TO REFIN PIN.

1.2V REFIN INPUT IS BUFFERED INTERNALLY.

IT CREATES A 4.096V REFERENCE FOR THE ADC.

DECOUPLE THE REF AND REFIN PINS EXTERNALLY

Figure 36. External 1.2 V Reference Using Internal Reference Buffer

AD7626

IN+

IN–

REF

REFIN

EN1 = 1 AND EN0 = 0

EXTERNAL 4.096V REFERENCE CONNECTED TO REF PIN IS REQUIRED.

CONNECT BUFFERED 4.096V SIGNAL TO REF PIN.

DECOUPLE THE REF PIN EXTERNALLY.

REFIN IS A NO CONNECT.

NO CONNECT

10µF

ADR434/

ADR444

GND

VIN

VOUT

0.1µF

(6.1V

≤ VIN ≥ 18V)

4.096V

VIN

AD8031

V+

Figure 37. External 4.096 V Reference Applied to REF Pin

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