MB3790 Datasheet, PDF (15/21 Pages) Fujitsu Component Limited. – Battery Backup IC

MB3790
s APPLICATION
1. Method of Using the CONTROL Pin
It is possible to control the operation of analog switch 1 by entering a High or Low level to the CONTROL pin while
being powered by the battery. The Table below shows how the analog switch operates when its operation is controlled
from the CONTROL pin.
When using the primary and the secondary batteries in combination as in the case of memory cards, be sure to
set the CONTROL pin High to prevent the primary battery from being recharged by the secondary battery current
flowing from analog switch 1.
• Control Conditions of CONTROL Pin
Operating state
Standby/active state
Backup state
Control conditions
Input voltage (VIN) CONTROL pin*¹
VIN > VINL
High/Low
VINL > VIN
High (= VOUT)
VINL > VIN
Low (= GND)
ON/OFF State of analog switch*²
Analog switch 1 Analog switch 2
OFF
OFF
OFF
ON
ON
ON
*1: If the CONTROL pin is released open, the logic state of the CMOS circuit may become instable letting current
flow into the circuit. Therefore, the CONTROL pin must always have a High or Low level input.
*2: The ON-resistance of the analog switch is approximately 10 K ohms.
Analog Switch connection Diagram
V OUT
Analog Switch 1
SBD
Analog Switch 2
V BAT1
Connection to the
primary battery
V BAT2
Connection to the
secondary battery
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