EVAL-AD421EB Analog Devices Inc, EVAL-AD421EB Datasheet - Page 13

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EVAL-AD421EB

Manufacturer Part Number
EVAL-AD421EB
Description
BOARD EVAL FOR AD421
Manufacturer
Analog Devices Inc
Datasheets

Specifications of EVAL-AD421EB

Rohs Status
RoHS non-compliant
Module/board Type
Evaluation Board
For Use With/related Products
AD421
Lead Free Status / RoHS Status
Not Compliant
AD421
Battery Backup
Figure 19 shows an application circuit for the AD421 where the
DN25D
IN3611
micro and memory sections of the circuitry are protected against
losing data if the loop is broken. The backup circuit switches
IRFF9113
0.1 F
4.7 F
IN3611
from V
to battery voltage without a glitch when V
power is
CC
CC
V
LOOP
V
CC
lost. The IRFF9113 acts as a current source during normal
100k
2.2 F
MICRO/
operation and provides a constant charging current to the supercap
MEMORY
or Nicad. The loss of V
drops the IRFF9113’s gate voltage to
CC
V
SUPERCAP
CC
GND
zero volts, which allows the battery or supercaps current to flow
DRIVE
through the MOSFETs channel and integral body diode to
AD421*
provide power for the micro and memory sections. To calibrate
LOOP
RTN
this circuit, connect an ammeter in series with the battery or
COM
supercap. Then with V
and the load present adjust the 100 kΩ
CC
*ADDITIONAL CIRCUITRY OMITTED FOR CLARITY
potentiometer for the battery charging current recommended by
Figure 19. Battery Backup Circuit
the battery or supercap manufacturer.
Nonrechargeable batteries should not be used in this application
due to danger of explosion.
REV. C
–13–

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