CM3503 Datasheet, PDF (1/6 Pages) California Micro Devices Corp – USB 5V Single 1.4A Overcurrent Switch

CALIFORNIA MICRO DEVICES
PRELIMINARY
CM3503
USB 5V Single 1.4A Overcurrent Switch
Features
• High-side high current switch with active low Enable
• Very low on-resistance switch (0.07? typ.)
• Up to 1.4A continuous current on the output
• Over-current limits at 1.4A min
• 10msec min fault blanking delay on OC# output
prevents false overcurrent alarms
• Prevents backdrive current when host powered off
• Low operating current (95µA typ.)
• Low quiescent current when disabled (<1µA max)
• Small 8-Lead SOIC package
Applications
• 2 USB ports 5V supply overcurrent protection
Pin Diagram
GND
V_CC
V_CC
EN#
SOIC-8
V_OUT
V_OUT
V_OUT
OC#
Product Description
California Micro Devices’ CM3503 is a USB
overcurrent power switch that provides power to two
USB ports. The device has a very low on-resistance
power switch that provides the V_BUS voltage at the
USB output ports with minimal voltage drop. When
the EN# pin is logic low, the power switch is ON,
and V_CC is connected to the output V_OUT. When the
EN# pin is logic high, the power switch is OFF, and
no power is available at the output.
The power switch has full over-current protection.
Whenever the current limit of the switch is
exceeded, the device enters a constant-current
mode, where the output voltage is progressively
reduced to prevent the current from increasing
further. The OC# output becomes active low only if
the overcurrent condition exceeds at least 10ms.
This fault blanking delay prevents false alarms from
being reported to the host USB controller.
If the overcurrent condition is severe enough that
the part heats up to the thermal limit T_MAX, then the
switch will be turned off and the temperature cools
down. At T_MIN the switch then turns on again, and
the device heats up again, and so on, until the fault
is removed.
The CM3503 also prevents backdrive current
flowing into the host from the connected peripheral.
This can occur when V_CC is removed as the host
powers down, and the peripheral still has normal
power applied. The 5V from the peripheral can
therefore be linked to the host’s V_BUS, potentially
causing backdrive current into the host and
overloading the peripheral power supply.
Typical Application Circuit
GND
V_CC
V_CC
V_CC
EN#
V_OUT
V_OUT
V_OUT
OC#
V_BUS
V_BUS
1 USB Port
1 USB Port
Simplified Electrical Schematic
EN#
V_CC
Over
current
protect
V_OUT
OC#
© 2003 California Micro Devices Corp. All rights reserved.
09/10/03 430 N. McCarthy Blvd, Milpitas, California 95035
Tel: [phone]
Fax: [phone]
www.calmicro.com
C0970500
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