MB3790 Fujitsu Media Devices, MB3790 Datasheet - Page 15

• Manufacturer Part Number: MB3790
• Description: Battery Backup IC
• Manufacturer: Fujitsu Media Devices

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DataSheet
4
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.
*1: If the CONTROL pin is released open, the logic state of the CMOS circuit may become instable letting current
*2: The ON-resistance of the analog switch is approximately 10 k .
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APPLICATION
Analog Switch connection Diagram
• Control Conditions of CONTROL Pin
Standby/active state
flow into the circuit. Therefore, the CONTROL pin must always have a High or Low level input.
Operating state
Backup state
Analog Switch 1
Input voltage (V
Connection to the
primary battery
V
V
V
IN
INL
INL
> V
> V
> V
V
Control conditions
BAT1
INL
IN
IN
SBD
IN
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)
CONTROL pin*
Low (= GND)
High (= V
Analog Switch 2
High/Low
Connection to the
secondary battery
OUT
)
1
V
BAT2
Analog switch 1
ON/OFF State of analog switch*
OFF
OFF
ON
V
OUT
Analog switch 2
MB3790
OFF
ON
ON
2
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