US202XG-AF5-R(2011) Просмотр технического описания (PDF) - Unisonic Technologies
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US202XG-AF5-R Datasheet PDF : 6 Pages
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US202
Preliminary
CMOS IC
APPLICATION INFORMATION
The UTC US202 is a high-side single N-Channel MOSFET switch with active-high enable input.
Input and Output
VIN pin (input) is the power supply connection to the circuitry and the drain of the output MOSFET. VOUT pin (output)
is the source of the output MOSFET. In a typical circuit, current flows through the switch from VIN to VOUT toward the
load. Both VOUT pins must be short on the board and connected to the load and so do both VIN 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.
VIN
VIN
CIN
1µF
VCE
CE
On
Off
GND
VOUT
VOUT
VOUT
COUT
1µF
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 VIN 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 VOUT negative during turn-off or EMI damage to other
components during the hot detachment, it’s better to connect a sufficient capacitor from VOUT 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 VOUT 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 VOUT pin is higher than that on VIN pin.
In order to avoid reverse current occur, turn off this switch or connect VIN to a fixed voltage less than 1.3V.
UNISONIC TECHNOLOGIES CO., LTD
www.unisonic.com.tw
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