SC2041 Semtech Corporation, SC2041 Datasheet - Page 9

• Manufacturer Part Number: SC2041
• Description: HotSwitch USB Power Distribution Switch With Shutdown
• Manufacturer: Semtech Corporation

July 18, 2000
TYPICAL CHARACTERISTICS (Cont.)
Figure 9: Inrush Current, Device Enabled Into
100µF and 10
APPLICATIONS INFORMATION
Theory Of Operation
The SC2041 is a current limited 80m
with error reporting and enable features. The power
switch is an N-channel MOSFET with its gate driven by
an internal charge pump. The switch has been de-
signed to turn on slowly (1.7ms typical) to minimize
inrush currents at turn-on.
The Shutdown pin (SHDN) is compatible with 3V or 5V
logic, and when pulled high, shuts off the power switch,
causing the device to enter a very low power shutdown
mode, where it will draw less than 1µA from the supply.
While enabled, the SC2041 draws only 100µA from the
supply.
The power switch has current limit detection circuitry
which will limit the current through the switch to 0.85A
(typical) and reduce the output voltage accordingly.
When current limit is entered, the open drain Flag pin
(FLG) is asserted low, indicating a fault condition. If an
overcurrent or short condition is continuous, the power
dissipation in the switch will cause the junction temper-
ature to rise, triggering the thermal protection circuitry
© 2000 SEMTECH CORP.
Top Trace: V
Bottom Trace: I
Timebase: 2.5ms/div.
V
IN
= 5V, R
OUT
SHDN
= 10 , C
OUT
, 5V/div.
, 0.2A/div.
OUT
= 100µF
power switch
HotSwitch™ USB Power Distribution
Switch With Shutdown
Figure 10: Inrush Current, Device Enabled Into
470µF and 10
Top Trace: V
Bottom Trace: I
Timebase: 2.5ms/div.
V
to shut the switch down (at T
shut off the output current altogether, and also cause
the Flag pin to be asserted low. Once the junction
temperature has dropped by 20°C (typical), the device
will start up once more in a controlled manner.
The SC2041 will operate from supply voltages as low
as 2.8V, and internal undervoltage lockout circuitry
ensures that the power switch will be turned off at
power-up, even if the device is enabled. Once the
UVLO threshold voltage (2.7V typical) is reached, the
switch will turn on (if enabled) and slowly ramp up the
output.
The SC2041 has been designed for use in USB appli-
cations such as:
1) hosts or self-powered hubs that need to current limit
downstream ports and report overcurrent conditions;
2) bus-powered hubs that need to be able to switch
power to downstream ports, limit inrush currents at
power-up (to less than a 44
10µF capacitor) and power-up and draw less than
100mA;
3) bus-powered functions that need to limit inrush
currents at power-up (to less than a 44
parallel with a 10µF capacitor) and power-up and draw
less than 100mA.
IN
652 MITCHELL ROAD NEWBURY PARK CA 91320
= 5V, R
OUT
SHDN
= 10 , C
OUT
, 5V/div.
, 0.2A/div.
OUT
= 470µF
J
= 150°C typical). This will
resistor in parallel with a
SC2041
resistor in
9