Datasheet

UNISONIC TECHNOLOGIES CO., LTD
US203
Preliminary
CMOS IC
HIGH-SIDE POWER SWITCHES
WITH FLAG

4
5
DESCRIPTION
The UTC US203 are low voltage cost-effective high-side power
switches with flag function. These devices are particularly suitable for
self-powered and bus-powered USB applications. The build-in
N-MOSFET’s RDS(ON) which meets the requirements of USB voltage drop
is as low as 80mΩ.
The UTC US203 contains a charge pump circuitry to drive the internal
MOSFET switch and also incorporate such protection circuits: soft-start
circuit protect these devices from being damaged by limiting inrush
current during plug-in; thermal shutdown circuit is used to prevent
catastrophic switch failure from high-current loads. UVLO is used to
ensure that the device remains off unless there is a valid input voltage
present.
A flag output is designed to indicate fault conditions to the local USB
controller. lower quiescent current as 25μA making this device ideal for
portable battery-operated equipment.
The UTC US203 are applied in USB Bus/Self powered hubs, USB
peripherals, NB, PCs, PC card hot swap, battery-powered equipment,
hot-plug power supplies, battery-charger circuits, ACPI power
distribution.

3
SOT-25
1
SOP-8
FEATURES
* Input Voltage Varies From 3.5V to 5.5V
* Built-in N-MOSFET
* Output Can Be Forced Higher Than Input (Off-State)
* Typical Low Supply Current:
- Switch On: 25μA (TYP)
- Switch Off: 0.1μA (TYP)
* Open-Drain Fault Flag Output To Indicate Fault
Conditions

2
1
* Protection Circuits:
- Soft-start( Hot plug-in application)
- UVLO 1.7V (TYP.)
- Current Limiting Protection
- Thermal Shutdown Protection
* Reverse Current Flow Blocking (No Body Diode)
ORDERING INFORMATION
Ordering Number
US203XXG-AF5-R
US203XXG-S08-R
www.unisonic.com.tw
Copyright © 2015 Unisonic Technologies Co., Ltd
Package
SOT-25
SOP-8
Packing
Tape Reel
Tape Reel
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US203
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Preliminary
CMOS IC
MARKING
SOT-25

SOP-8
PIN CONFIGURATION
SOT-25

PIN DESCRIPTION
SOP-8
6,7,8
1
4
2,3
PIN NO.
SOT-25
5
2
3
4
5

SOP-8
PIN NAME
1
DESCRIPTION
VOUT
GND
EN
VIN
Output Voltage
Ground
Enable. Never let this pin floating.
Power Input Voltage
FLG
Open-Drain Fault Flag Output
BLOCK DIAGRAM
VIN
Current
Limiting
UVLO
EN
Gate
Control
Bias
Oscillator
Thermal
Protection
Charge
Pump
Output
Voltage
Detection
Delay
VOUT
FLG
GND
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US203
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Preliminary
CMOS IC
ABSOLUTE MAXIMUM RATING (TA = 25°C, unless otherwise specified)
PARAMETER
SYMBOL
RATINGS
UNIT
Supply Voltage
VIN
6.5
V
Enable Input Voltage
VEN
-0.3 ~ +6.5
V
Flag Voltage
VFLG
6.5
V
Power Dissipation (TA = 25°C)
PD
0.4
W
Junction Temperature
TJ
150
°C
Storage Temperature
TSTG
-65~150
°C
Notes: Absolute maximum ratings are those values beyond which the device could be permanently damaged.
Absolute maximum ratings are stress ratings only and functional device operation is not implied.

THERMAL DATA
PARAMETER
SYMBOL
SOT-25
SOP-8
Junction to Ambient

θJA
UNIT
RATINGS
3.5 ~ 5.5
0 ~ 5.5
-40 ~ +125
-40 ~ +85
UNIT
V
V
°C
°C
°C/W
RECOMMENDED OPERATING CONDITIONS
PARAMETER
Supply Input Voltage
Enable Input Voltage
Junction Temperature
Ambient Operating Temperature

RATINGS
250
190
SYMBOL
VIN
VI(EN)
TJ
TOPR
ELECTRICAL CHARACTERISTICS (VIN=5V, CIN=COUT=1μF, TA=25°C, unless otherwise specified)
PARAMETER
Switch On Resistance
(US203A, US203B)
Switch On Resistance
(US203C, US203D)
Supply Current
EN Threshold Voltage
EN Input Current
Output Leakage Current
Output Turn-On Rise Time
Current Limit
Short Circuit Fold-Back
Current
FLAG Output Resistance
FLAG Off Current
SYMBOL
SOT-25
SOP-8
SOT-25
SOP-8
IOUT= 1A, VIN= 5V
IOUT= 0.5A, VIN= 5V
tD
switch on, RLOAD Open
switch off, RLOAD Open
VIN = 3.5V ~ 5.5V
VIN = 3.5V ~ 5.5V
VEN/EN = 0V ~ 5.5V
VEN=0V, RLOAD= 0Ω
10% to 90% of VOUT rising
2.0
Current Ramp (< 0.1A/ms) on
VOUT
2.1
1.6
1.1
0.6
VOUT = 0V, measured prior to
thermal shutdown
ISINK= 1mA
V FLG = 5V
From fault condition to FLG
assertion
VEN=0V, VEN
VIN increasing
VIN decreasing
Shutdown Pull-Low Resistance
RDS
Under-Voltage Lockout
VUVLO
Under-Voltage Hysteresis
∆VUVLO
Thermal Shutdown Protection
TSD
Thermal Shutdown Hysteresis
∆TSD
Note: The device is not guaranteed to function outside its operating conditions.
UNISONIC TECHNOLOGIES CO., LTD
www.unisonic.com.tw
MIN
RDS(ON)
ISW_ON
ISW_OFF
Logic-Low
VIL
Logic-High
VIH
IEN
IO(LEAK)
TON(RISE)
US203Ax
US203Bx
ILIMIT
US203Cx
US203Dx
US203Ax
US203Bx
ISC(FB)
US203Cx
US203Dx
R FLG
I FLG _OFF
FLAG Delay Time
TEST CONDITIONS
5
1.3
TYP
80
90
80
90
25
0.1
0.01
0.5
400
2.5
2.0
1.5
0.8
1
1
1
1
20
0.01
MAX UNIT
100
mΩ
110
100
mΩ
110
45
μA
1
0.8
V
V
μA
10
μA
μs
3.2
A
2.5
A
1.8
A
1.1
A
A
A
A
A
400
Ω
1
μA
12
20
ms
75
1.7
0.1
130
20
150
Ω
V
V
°C
°C
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Preliminary
CMOS IC
APPLICATION INFORMATION
Input and Output
VIN (input) is the power source connection to the internal circuitry and the drain of the MOSFET. VOUT (output) is
the source of the MOSFET. In a typical application, current flows through the switch from VIN to VOUT toward the load.
Because the MOSFET is bidirectional when on, if VOUT is greater than VIN, current will flow from VOUT to VIN
There is no a parasitic body diode of N-MOSFET between the drain and source compared to a normal MOSFET,.
The US203 can protect damage from reverse current flow if VOUT being externally forced to a higher voltage than VIN
when the output disabled (VEN > 2V).
Enable Input
The switch will be disabled when the EN pin is in a logic low/high condition. During this condition, the internal
circuitry and MOSFET are turned off, reducing the supply current to 0.1μA typical. Floating the EN may cause
unpredictable operation. EN should not be allowed to go negative with respect to GND. The EN pin may be directly
tied to VIN (GND) to keep the part on.
Soft Start for Hot Plug-In Applications
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.
Fault Flag
The fault flag is an open-drained output of an N-channel MOSFET. The flag drops low to indicate fault conditions:
current limit, thermal shutdown or VOUT < VIN − 1V. In order to reduce energy drain, a large pull-up resistor is required.
100kΩ pull-up resistor is recommended for most applications.
In the case of over current condition, the fault flag is active only if the flag response delay time (tD) has elapsed.
This ensures that FLG is asserted only upon valid over-current conditions and that erroneous error reporting is
eliminated. For example, false over-current conditions may occur during hot-plug events when extremely large
capacitive loads are connected and causes a high transient inrush current that exceeds the current limit threshold.
The FLG response delay time tD is typically 10ms.
Under-Voltage Lockout
UVLO (Under-voltage Lockout) turns off the MOSFET switch once the input voltage falls below 1.3V, and the
FLG is in active. If the input voltage exceeds approximately 1.7V, the switch will be turned on. Under-voltage
detection functions only when the switch is enabled.
Current Limiting and Short-Circuit Protection
The current limit circuit protects the MOSFET switch and the hub downstream port from damage. This circuit can
deliver load current up to the current limit threshold of typically 2.5A through the switch of US203AH/AL, 2A for
US203BH/BL, 1.5A for US203CH/CL and 0.8A for US203DH/DL. When an enabled switch applies a heavy load or
short circuit, a large-desired transient current occurs which can cause the current limit circuit response. If this current
becomes higher than the current limit threshold, the devices enter constant current mode until thermal shutdown
occurs or the fault is removed.
Thermal Shutdown
The thermal shutdown circuit is used to prevent damage occurs when the die temperature becomes higher than
approximately 130°C. After 20°C of hysteresis, the switch will automatically restart if it enabled. When these devices
are disabled or the fault is removed, the output and FLG signal will continue to cycle on and off.
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www.unisonic.com.tw
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Preliminary
CMOS IC
APPLICATION INFORMATION(Cont.)
Power Dissipation
The UTC US203’s junction temperature varies depending the several factors such as the load, PCB layout,
ambient temperature and package type. The output pin of UTC US203 can deliver the current of up to
2.5A(US203AH/AL) , 2A(US203BH/BL), 1.5A(US203CH/CL) and 0.8A(US203DH/DL) over the full operating junction
temperature range. However, at higher ambient temperature the maximum output current must be derated to ensure
the junction temperature does not exceed 100°C. With all possible conditions, the junction temperature must be
within the range specified under operating conditions. Power dissipation is determined by the output current and the
RDS(ON) of switch, the relationship between them is as seen is the following:
PD = RDS(ON) x IOUT
2
Although the devices are rated for 2.5A, 2A, 1.5A and 0.8A of output current, but the application may limit the
amount of output current based on the total power dissipation and the ambient temperature. The final operating
junction temperature for any set of conditions is calculated as follows:
PD (MAX) = ( TJ (MAX) - TA ) / θJA
Universal Serial Bus (USB) & Power Distribution
The USB’s goal is to be enabled device from different vendors to interoperate in an open architecture. The USB
is characterized incorporating ease of use for the end user, a wide range of workloads and applications, robustness,
synergy with the PC industry, and low-cost implementation. In addition, the benefits of the USB contain
self-identifying peripherals, dynamically attachable and reconfigurable peripherals, multiple connections (support for
concurrent operation of many devices), support physical devices up to 127, and compatibility with PC Plug-and-Play
architecture.
Each USB system has one USB host, and the USB connects USB devices with a USB host. USB devices can be
classified either as hubs, which provide additional attachment points to the USB, or as functions, which provide
capabilities to the system (for example, a digital joystick). Then the hub devices are classified as either bus-power
hubs or self-powered Hubs.
Self-powered hub power for the internal functions and downstream ports does not come from the USB, although
the USB interface may draw up to 100mA from its upstream connect, to allow the interface to function when the
remainder of the hub is powered down. The hub must be able to supply up to 500mA on all of its external
downstream ports. Over-current protection devices such as fuses and PTC resistors (also called poly fuse or
polyswitch) have slow trip times, high on-resistance, and lack the necessary circuitry for USB-required fault reporting.
A bus-powered hub draws all of the power to any internal functions and downstream ports from the USB connector
power pins. The hub may draw current as high as 500mA from the upstream device. External ports in a bus-powered
hub can supply up to 100mA per port, with a maximum of four external ports.
In order to protect the hubs to operating on the faults conditions, the faster trip time of the UTC US203 power
distribution can make it. For meeting voltage regulation and fault notification requirements, low on-resistance and
internal fault-reporting circuitry are required.
Furthermore, because the devices are power switches, they provide the designer of self-powered hubs flexibility
to turn off power to output ports. The devices have controlled rise and fall times to provide the needed inrush current
limiting required for the bus-powered hub power switch compared to a normal MOSFFT.
Supply Filter/Bypass Capacitor
To prevent input voltage droop occurs during hot-plug condition, a 1uF low-ESR ceramic capacitor located
between VIN and GND is strongly desired. However, higher capacitor values will further reduce the voltage droop on
the input. Furthermore, without the bypass capacitor, an output short may cause sufficient ringing on the input (from
source lead inductance) to destroy the internal control circuitry. The input transient’s value must be not higher than
the absolute maximum supply voltage ( 6.5V) even for a short duration.
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Preliminary
CMOS IC
APPLICATION INFORMATION(Cont.)
Output Filter Capacitor
To meet the requirement of the maximum droop (330mV) in the hub VBUS, a 150μF low-ESR electrolytic or
tantalum located from VOUT and GND is strongly desired. Standard bypass methods should be used to minimize
inductance and resistance between the bypass capacitor and the downstream connector to reduce EMI and
decouple voltage droop caused when downstream cables are hot-insertion transients. For EMI and ESD protection
consideration , ferrite beads in US203 with VBUS, the ground line and the 0.1μF bypass capacitors at the power
connector pins are needed. The bypass capacitor itself should have a low dissipation factor to allow decoupling at
higher frequencies.
Voltage Drop
A minimum port-output voltage in two locations on the bus is shown in the USB specification, in which, 4.75V out
of a self- powered hub port and 4.40V out of a bus-powered hub port. As with the self-powered hub, all resistive
voltage drops for the bus-powered hub must be accounted for to guarantee voltage regulation. VOUT (MIN) for multiple
ports (NPORTS) ganged together through one switch (if using one switch per port, NPORTS is equal to 1) can be
established by the following equation:
VOUT (MIN) = 4.75V − [ II x ( 4 x RCONN + 2 x RCABLE ) ] − (0.1A x NPORTS x RSWITCH ) − VPCB
Where,
RCONN = Resistance of connector contacts (two contacts per connector)
RCABLE = Resistance of upstream cable wires (one 5V and one GND)
RSWITCH = Resistance of power switch (80mΩ typical for UTC US203)
VPCB = PCB voltage drop
The USB specification defines the maximum resistance per contact (RCONN) of the USB connector to be 30mΩ
and the drop across the PCB and switch to be 100mV. This basically leaves two variables in the equation: the
resistance of the switch and the resistance of the cable. If the hub consumes the maximum current (II) of 500mA, the
maximum resistance of the cable is 90mΩ. The following equation determines the resistance of the switch:
RSWITCH= { 4.75V − 4.4V − [ 0.5A x ( 4 x 30mΩ + 2 x 90mΩ) ] − VPCB } ÷ ( 0.1A x NPORTS )
= (200mV − VPCB ) ÷ ( 0.1A x NPORTS )
If the voltage drop across the PCB is limited to 100mV, the maximum resistance for the switch is 250mΩ for four
ports ganged together. The UTC US203, with its maximum 100mΩ on-resistance over temperature, easily meets this
requirement.
PCB Layout Guide
Careful PCB layout should be taken into consideration for meeting the requirements of the voltage drop, droop,
and EMI.
The following guidelines must be paid attention.
 Output capacitor and ferrite beads should be placed as close to the USB connectors as possible to lower
impedance (mainly inductance) between the port and the capacitor and improve transient load performance.
 The UTC US203 should be placed as close as possible to the output port to limit switching noise.
 Ceramic bypass capacitors should be placed as close as possible to the VIN pins of the UTC US203
 Keep all VBUS traces as short as possible and use at least 50-mil, 2 ounce copper for all VBUS traces.
 Avoid VIAS as much as possible. If VIAS are necessary, make them as large as feasible.
 Place a ground plane under all circuitry to lower both resistance and inductance and improve DC and
transient performance (Use a separate ground and power plans if possible).
 Place cuts in the ground plane between ports to help reduce the coupling of transients between ports.
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Preliminary
CMOS IC
TYPICAL APPLICATION CIRCUIT
Note: A low-ESR 150µF aluminum electrolytic or tantalum between VOUT and GND is strongly recommended to meet
the 330mV maximum droop requirement in the hub VBUS. (see Application Information Section for further
details)
UTC assumes no responsibility for equipment failures that result from using products at values that
exceed, even momentarily, rated values (such as maximum ratings, operating condition ranges, or
other parameters) listed in products specifications of any and all UTC products described or contained
herein. UTC products are not designed for use in life support appliances, devices or systems where
malfunction of these products can be reasonably expected to result in personal injury. Reproduction in
whole or in part is prohibited without the prior written consent of the copyright owner. The information
presented in this document does not form part of any quotation or contract, is believed to be accurate
and reliable and may be changed without notice.
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www.unisonic.com.tw
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