UNISONIC TECHNOLOGIES CO., LTD
US202
Preliminary
CMOS IC
100mΩ POWER DISTRIBUTION
SWITCHES
DESCRIPTION
The
US202
is a power distribution switch. It is particularly suitable
for self-powered and bus-powered USB (Universal Series bus)
applications. It has 23μA low quiescent supply current that meets the
requirements of battery-powered portable equipments.
A built-in charge pump is used to drive the N-channel N-MOSFET
that is free of parasitic body diode to eliminate any reversed current
flow across the switch when it is powered off.
The
US202
incorporates some protection circuits such as current
limit and short protection circuits, soft start circuit, thermal shutdown
and UVLO (Under-voltage Lockout) protection circuits. The thermal
shutdown circuits protect this device from damage when over current
occurs, and the soft start circuits are used to prevent inrush current
when plug-in event occurs.
The
US202
can be used in such applications such as
battery-powered equipments, motherboard USB power switchs, USB
device power switchs, hot-plug power supplies, battery-charger
circuits and so on.
FEATURES
* Input Voltage Varies From 2.2V to 6V
* Guaranteed Continuous Current: 1.1A
* High-Side NMOSFET: 100mΩ (TYP)
* Soft Start
* Current Limit:1.5A
* Thermal Protection
* Low Supply Current: 23μA
ORDERING INFORMATION
Ordering Number
Lead Free
US202XL-AF5-R
Halogen Free
US202XG-AF5-R
Package
SOT-25
Packing
Tape Reel
www.unisonic.com.tw
Copyright © 2011 Unisonic Technologies Co., Ltd
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US202
APPLICATION INFORMATION
Preliminary
CMOS IC
The UTC
US202
is a high-side single N-Channel
MOSFET
switch with active-high enable input.
Input and Output
V
IN
pin (input) is the power supply connection
to the circuitry and the drain of the output MOSFET. V
OUT
pin (output)
is the source of the output MOSFET. In a typical circuit, current flows through the switch from V
IN
to V
OUT
toward the
load. Both V
OUT
pins must be short on the board and connected to the load and so do both V
IN
pins but connected to
the power source.
Thermal Shutdown
Thermal shutdown is used to turn off the output MOSFET when the if the temperature is higher than130°C, 20°C
of hysteresis prevents the switch turn on until the die temperature drops to 110°C.
Soft Start
When hot-plug events occur, the soft start is used to eliminate the upstream voltage droop due to the inrush
current. The soft-start protects power supplies from damage caused by highly capacitive loads.
Under-Voltage Lockout
UVLO (Under voltage Lockout) turn off the MOSFET switch once the input voltage falls below 1.8V (TYP.) and if
the input voltage exceeds 1.8V, the switch will be turned on.
Current Limiting and Short Protection
The current limit threshold is preset internally. The minimum value is 1.1A. The current limit circuit protects this
device from damage resulting from undesired excess inrush current, which is encountered during hot plug-in events.
The output current is limited to approximately 1.5A (TYP). When the output is short to ground, it will limit to a
constant current 1A until thermal shutdown or short condition removed.
V
IN
C
IN
1µF
V
CE
V
IN
CE
GND
On
Off
V
OUT
V
OUT
C
OUT
1µF
V
OUT
Figure 1. High Side Power Switch with Chip Enable Control
Filtering
During the hot-plug events, in order to limit the input voltage drop, a 1μF ceramic capacitor is recommended to
be placed between V
IN
to GND. However special care must be taken to the values of the capacitor, because higher
capacitor values will further reduce the voltage drop at the input.
In order to prevent inductive parasitic from pulling V
OUT
negative during turn-off or EMI damage to other
components during the hot detachment, it’s better to connect a sufficient capacitor from V
OUT
to GND. This capacitor
is also necessary for meeting the USB specification during hot plug-in operation.
If the UTC
US202
is implanted in device and application, minimum 1μF capacitor from V
OUT
to GND is
recommended and higher capacitor values are also preferred.
Choosing these capacitors properly is critical. A lower ESR on the capacitor can get a lower IR drop during the
operation, so the Effective Series Resistance (ESR) of the capacitors must be considered.
For ferrite beads, if they are in series with all power and ground lines, the EMI will be eliminated or reduced. The
DC resistance of the wire kept to a minimum to reduce the voltage drop should be considered in choosing ferrite
beads.
Reverse Current Preventing
Since the UTC
US202’s
MOSFET is bi-directional, it allows the voltage on V
OUT
pin is higher than that on V
IN
pin.
In order to avoid reverse current occur, turn off this switch or connect V
IN
to a fixed voltage less than 1.3V.
UNISONIC TECHNOLOGIES CO., LTD
www.unisonic.com.tw
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