Datasheet

AD7626 Data Sheet
Rev. B | Page 20 of 28
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
A 1 1 Power-up
Internal reference and internal
reference buffer in use
B 0 1 External 1.2 V reference applied to
REFIN pin required
C 1 0 External 4.096 V reference applied to
REF pin required.
0 0 Power-down mode
AD7626
IN+
IN–
REF
REFIN
10µF
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.
A
07648-131
Figure 35. Powered Up, Internal Reference and Internal Reference Buffer
AD7626
IN+
IN–
REF REFIN
10µF 10µF
EN1 = 0 AND EN0 = 1
EXTERNAL 1.2V REFERENCE CONNECTED TO REFIN PIN IS REQUIRED.
B
ADR280
V–
V
OUT
V+
0.1µF
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
07648-132
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.
C
CONNECT BUFFERED 4.096V SIGNAL TO REF PIN.
DECOUPLE THE REF PIN EXTERNALLY.
REFIN IS A NO CONNECT.
NO CONNECT
10µF
10µF
ADR434/
ADR444
GND
V
IN
V
OUT
0.1µF
0.1µF
(6.1V ≤ V
IN
≥ 18V) 4.096V
VIN
AD8031
V+
07648-133
Figure 37. External 4.096 V Reference Applied to REF Pin