MB3790 Fujitsu Media Devices, MB3790 Datasheet - Page 7

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

DataSheet4U.com
www.DataSheet4U.com
DataSheet
4
(4) Momentary power failure or voltage dip
When the power supply voltage drops less than or equal to V
voltage dips momentarily, the RESET pin outputs a High level and the RESET pin outputs a low level. The devices
such as SRAM or a microprocessor are thereby placed in the standby mode and powered from the battery. When
in this mode, the primary battery voltage detection and the secondary battery recharging operations are stopped.
Note: To guarantee backup operation in case of momentary power failure, make sure the 5 V-to-0 V fall time on V
2. Alarm Operation
If the primary battery voltage decreases while the power supply voltage (V
Typ), alarm signals are output as described below. At this time, if the V
alarm pin becomes indeterminate.
(1) Primary battery replacement alarm (alarm-1 output)
If the primary battery voltage drops to V
indicating that it’s time to replace the primary battery.
(2) Primary battery minimum voltage alarm (alarm-2 output)
If the primary battery voltage further drops to V
an alarm indicating that the primary battery power has dropped below the voltage necessary to retain the SRAM
data (approx. 2.0 V).
U
.com
is 50 s or more by using, for example, a capacitor.
ALARM1
ALARM2
V
BAT1
(1)
BAT1
(2)
(2.65 V Typ), the ALARM1 pin is forced to a Low level to issue an alarm
DataSheet4U.com
BAT2
(2.37 V Typ), the ALARM2 pin is forced to a Low level to issue
INL
. (4.2 V Typ) as the power supply goes down or its
(1)
BAT1
(2)
pin is released open, the output from the
IN
DV
) is greater than or equal to V
BAT2
DV
BAT1
MB3790
V
V
V
V
BATH1
BATL1
BATH2
BATL2
INH
(4.3 V
IN
7