mb3802pf-g-bnd Fujitsu Microelectronics, Inc., mb3802pf-g-bnd Datasheet - Page 3

• Manufacturer Part Number: mb3802pf-g-bnd
• Description: Power Management Switch
• Manufacturer: Fujitsu Microelectronics, Inc.

MB3802
BLOCK DIAGRAM AND EXTERNAL CONNECTIONS
C
D
Extemal capacitor
DLY
Power supply
SW
IN
Switch-ON
Comp
V
IN
circuit
DC/DC converter
SW
OUT
Switch-OFF
(+)
circuit
Switch control
DDG
Load
Load discharge
circuit
GND
Note : The MB3802 incorporates two switch blocks as shown above. However, GND is common to both blocks.
BLOCK DESCRIPTION
The MB3802 is a one-way switching IC with the SWIN and SWOUT pins serving respectively for input and output.
When V
exceeds 2.2 V, the Comp. starts driving the DC/DC converter to switch the N-ch MOS and applies the
IN
optimum voltage for the switch gate.
The DC/DC converter boosts the V
voltage.
IN
When VIN is below 2.1 V, the Comp. stops the DC/DC converter, starts the switch-OFF circuit, and discharges
the voltage from the switch gate to GND. The switch-OFF circuit is powered from the SW
and consumes 0.4 A
IN
at 5 V.
Since the N-ch MOS back gate is connected to GND, switch-OFF reverse current is prevented irrespective of
the High level state between SW
and SW
. Note, however, that turning the VIN pin on/off with 1.5 V or less
IN
OUT
applied to the SWIN pin may cause reverse current to flow because the switch-off circuit does not work then.
For the method of compensating for the operation of the switch-off circuit, see section “ APPLICATIONS 7.Low-
side Switch.”
The load discharge circuit installed between SW
and GND is powered by the DCG pin, and discharges the
OUT
load-side capacitor at switch OFF. When it is not necessary to discharge the load, connect the DCG pin to GND.
The DLY pins are for connection to an external capacitor to delay the switch-ON/OFF time. The surge current
at the load side is cut at power-on by controlling the switch-ON time. The switch-ON time depends on the boot
time of the DC/DC converter. Consequently, when the VIN level is high and the SW
level is low, the switch-ON
IN
time is small; when the SW
level is high, the switch-OFF time is small.
IN
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