MB3807A Datasheet, PDF (4/15 Pages) Fujitsu Component Limited. – Power Management Switching IC (with flash memory power switching function)

MB3807A
s BLOCK DIAGRAM
EN1
EN0
DLY
Switch-off circuit
Switch-on circuit
(Charge pump)
(SW1)
Switch-on circuit
(Charge pump)
Switch-off circuit
(SW2)
Note: The MB3807A contains a pair of above circuit blocks.
SWIN1
Power supply
for writing
SWIN2
Power supply
for reading
SWOUT
VPP
Flash
memory
s BLOCK DESCRIPTION
The SWIN1 and SWIN2 pins are connected to the 12-V and 3.5/5.0-V power supplies, respectively. The SWOUT
pin is connected to the VPP power supply pin of the flash memory.
When conditions, EN1 = “H” and EN0 = “L” are established in an attempt to write data to flash memory, the switch-
on circuit (charge pump) on the SW1 side is activated.
The charge pump applies optimum voltage to the SW1 gate to turn the switch on, causing the SWOUT pin to supply
12-V power from the SWIN1 pin to the VPP pin of the flash memory. On the SW2 side, the switch-off circuit discharges
the SW2 gate voltage to the GND to turn the switch off.
Reading data from flash memory assume the conditions EN1 = “L” and EN0 = “H.” When the conditions are
established, the switch-on circuit (charge pump) on the SW2 side and the switch-off circuit on the SW1 side are
activated to cause the SWOUT pin to supply 3.3/5.0-V power from the SWIN2 pin to the VPP pin of the flash memory.
Since the switch-on circuits are powered from the SWIN1 and SWIN2 pins, 80 to 350 µA current flows from the
SWIN1 and SWIN2 pins to the GND when the switch is turned on.
The back gate of the N-channel MOS is connected to the GND. This prevents reverse current from flowing at switch-
off time, regardless of the high potential of SWIN1 or SWIN2 pin and the SWOUT pin.
The DLY pin is an external capacitance connector to delay turning the switch on. Controlling the switch ON time
minimizes surge current flowing to the capacitor connected to the load when the switch is turned on.
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