AD7653 datasheet(17/24 Pages) AD

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Data Sheet

AD7625

Rev. A | Page 17 of 24

VOLTAGE REFERENCE OPTIONS

The AD7625 allows flexible options for creating and buffering

the reference voltage. The AD7625 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 Options1

Option

EN1

EN0

Reference Mode

Use internal reference and internal

reference buffer (both are enabled).

Use external 1.2 V reference with

internal reference buffer enabled.

The internal reference is disabled.

Use external 4.096 V reference with

an external reference buffer. The

internal reference and reference

buffer are disabled.

1 EN1 = 0 and EN0 = 0 is an illegal state.

10µF

ADR434

ADR444

REF

IN+

AD7625

V+

REFIN

10µF

ADR280

V+

V–

V+

SETTING EN1 = 1 AND EN0 = 0

DISABLES THE INTERNAL REFERENCE

AND REFERENCE BUFFER. CONNECT THE

BUFFERED 4.096V SIGNAL TO

THE REF PIN.

SETTING EN1 = 1 AND EN0 = 1 ENABLES THE INTERNAL

REFERENCE AND REFERENCE BUFFER. DECOUPLE

THE REF AND REFIN PINS EXTERNALLY.

IN–

SETTING EN1 = 0 AND EN0 = 1

DISABLES THE INTERNAL REFERENCE

AND ENABLES THE INTERNAL REFERENCE BUFFER.

CONNECT A 1.2V REFERENCE TO THE REFIN PIN. THE 1.2V

APPLIED TO THE REFIN PIN IS BUFFERED INTERNALLY

TO CREATE A 4.096V REFERENCE FOR THE ADC.

Figure 25. Voltage Reference Options

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