Datasheet

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 Options
1
Option EN1 EN0 Reference Mode
A 1 1 Use internal reference and internal
reference buffer (both are enabled).
B 0 1 Use external 1.2 V reference with
internal reference buffer enabled.
The internal reference is disabled.
C 1 0 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–
B
C
A
07652-026
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