
CALIFORNIA MICRO DEVICES
Preliminary
CM3512
2003 California Micro Devices Corp. All rights reserved.
11/10/03
430 N. McCarthy Blvd, Milpitas, California 95035 Tel: (408) 263-3214 Fax: (408) 263-7846 www.calmicro.com
C0970500
1
Dual USB Overcurrent 1.2A Switches with Independent Controls
Features
Dual switches, each with independent over-current
protection and flag indicator, for 4 USB ports
Two active low Enable controls, one per output
Up to 1.2A continuous current each output
Over-current limits at 1.2A min
10msec min fault blanking delay on OC# outputs
prevents false overcurrent alarms
Prevents backdrive current when host powered off
Low operating current (95
μ
A typ.)
Low quiescent current when disabled (<1
μ
A max)
Small 8-Lead SOIC package
Applications
PC’s, Notebooks, STBs
The CM3512 also prevents backdrive current
flowing into the host from the connected peripheral.
This can occur when V
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.
Pin Diagram
Product Description
California Micro Devices CM3512 is a dual channel
USB overcurrent power switch that provides 5V
power to four independent USB ports. The device
has two power switches that provide the V
BUS
voltage at each USB output port with minimal
voltage drop.
When either of the EN# inputs is at logic low, the
corresponding power switch is ON and V
CC
is
connected to the corresponding output through the
switch. When either of the EN# inputs is at logic
high, the corresponding power switch is OFF, and
no power is available at the output.
Both of the power switches have full over-current
protection. Whenever the current limit out of either
switch is exceeded, the device enters a constant-
current
mode,
and
the
progressively reduced to prevent the current from
increasing further. Each switch is independent of the
other, so if a switch is on but is not in overcurrent
mode then it will remain switched on. The OC#
output becomes active low only if the overcurrent
condition exceeds a minimum continuous duration of
10ms. This fault blanking delay prevents false
alarms 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 that
switch will be turned off and the device temperature
cools down. At T
MIN
the switch then turns on again,
and the device heats up again to T
MAX
, and so on,
until the fault is removed.
output
voltage
is
Typical Application Circuit
Simplified Electrical Schematic
OC1#
V
OUT1
OC2#
V
OUT2
V
CC
EN2#
GND
EN1#
SOIC-8
TOP
V
BUS
V
BUS
V
CC
EN2#
GND
EN1#
OC1#
V
OUT1
OC2#
V
OUT2
V
CC
2 USB Ports
2 USB Ports
EN2#
EN1#
OC1#
V
OUT1
OC2#
V
OUT2
V
CC
Over
current
protect
Over
current
protect
Charge
Pump
Charge
Pump