UNISONIC TECHNOLOGIES CO., LTD
US1528
Preliminary
CMOS IC
USB HIGH-SIDE POWER SWITCH
ADVANCE INFORMATION
DESCRIPTION
The UTC
US1528
is an integrated high-side power switch. It is
designed particularly for self-powered and bus-powered USB (Universal
serial bus) applications.
The UTC
US1528
meets the requirements of the USB. The low
on-resistance of the switch meets USB voltage drop requirements.
When the output load becomes higher than the current-limit threshold,
the UTC
US1528
switches into constant- current mode and limits the
output current at 1.4A (TYP).
An open-drain flag, playing a role as the MOSFET output, is included
to indicate error conditions to the local USB controller. A thermal
shutdown circuit protects this device from catastrophic switch failure,
which is caused by increasing power dissipation when continuous heavy
loads or short circuit occurs. In addition, soft start is used to avoid the
momentary voltage drop generated on the upstream port that may occur
when the switch is enabled in bus-powered applications. A UVLO
(under-voltage lockout) circuit is used to keep the device off unless there
is a valid input voltage present, and an enable input that is compatible
with both 3.3V and 5V logic.
The UTC
US1528
can be used for high-side power protection switch,
USB power management, USB host and self-powered hubs, hot plug-in
power supplies and battery-charger circuits.
FEATURES
* Open-Drain Fault Flag
* Low on-Resistance MOSFET: Typical 110mΩ(at 5.0V)
* Operating Voltage Varying From 3.0V to 5.5V
* Output can be Forced Higher than Input when Operating in Off State.
* Slow Turn-On (Soft-Start) and Fast Turn-Off
* On-State Supply Current: 100 µA (TYP)
* Standby Supply Current: 1µA (TYP)
* Current Limit: 1.4A (TYP)
* Thermal Shutdown Protection Circuit
* UVLO (Under-Voltage Lockout): 2.4V (TYP)
* Logic Level Enable Pin, Available with Active-High/Low Version
ORDERING INFORMATION
Ordering Number
US1528XG-S08-R
Package
SOP-8
Packing
Tape Reel
www.unisonic.com.tw
Copyright © 2010 Unisonic Technologies Co., Ltd
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QW-R502-457.b
US1528
PIN CONFIGURATION
Preliminary
CMOS IC
PIN DESCRIPTION
PIN NO.
1
2, 3
4
5
6, 7, 8
PIN NAME
GND
IN
EN
DESCRIPTION
Ground.
Input Supply: Output MOSFET source, which also supplies IC's internal circuitry.
Connect to positive supply.
Active-High switch enable input. A logic low turns on the switch.
Active-Low switch enable input. A logic low turns on the switch.
Open-Drain Fault Flag (Output): Active-low, open-drain output. Indicates overcurrent,
thermal shutdown and UVLO.
Switch Output: Output MOSFET drain. Typically connect to switched side of load.
EN
FLG
OUT
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US1528
BLOCK DIAGRAM
Preliminary
CMOS IC
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US1528
ABSOLUTE MAXIMUM RATING
PARAMETER
Preliminary
CMOS IC
SYMBOL
RATINGS
UNIT
Supply Voltage
V
IN
+6.0
V
Fault Flag Voltage
V
FLG
+6.0
V
Fault Flag Current
I
FLG
50
mA
Output Voltage
V
OUT
+6.0
V
Output Current
I
OUT
Internally Limited
Enable Input
V
EN
-0.3~6
V
Storage Temperature
T
STG
-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.
OPERATING RATINGS
PARAMETER
Supply Voltage
Ambient Operating Temperature
SYMBOL
V
IN
T
OPR
RATINGS
+3~+5.5
-40~85
UNIT
V
°C
THERMAL DATA
PARAMETER
Junction to Ambient
SYMBOL
θ
JA
RATINGS
160
UNIT
°C/W
ELECTRICAL CHARACTERISTICS
(V
IN
=+5V, T
A
=25°C)
UNIT
µA
IN Supply Current (Note)
µA
V
EN/
EN
Enable Threshold
0.8
V
0.01
1
µA
EN/
EN
Input Current
0.01
1
µA
1
pF
EN/
EN
Input Capacitance
V
IN
= 5V, I
OUT
=500mA
110
140
mΩ
Switch Resistance
R
ON
130
180
mΩ
V
IN
= 3.3V, I
OUT
=500mA
OUT Turn-On Delay
t
ON
R
L
=10Ω
0.03
ms
OUT Turn-On Rise Time
t
R
R
L
=10Ω, C
L
=100µF
0.5
ms
OUT Turn-Off Delay
t
OFF
R
L
=10Ω
1
20
µs
OUT Turn-Off Fall Time
t
F
R
L
=10Ω
1
20
µs
OUT Leakage Current
I
O(LEAK)
1
10
µA
Short Circuit Current Limit
I
SHORT
Enable into load
1.0
1.4
2.0
A
Circuit Limit Threshold
Ramped load applied to enabled output
2.0
2.7
3.5
A
Overtemperature Shutdown
T
J
increasing
135
°C
OT
Threshold
Threshold
125
°C
T
J
decreasing
V
IN
=5V, I
L
=10mA
10
25
Ω
FLG Output Resistance
R
ON(FLAG)
V
IN
=3.3V, I
L
=10mA
15
40
Ω
FLG Off Current
I
FLAG
V
FLAG
=5V
0.01
1
µA
V
IN
=increasing
2.5
V
UVLO Threshold
V
UVLO
V
IN
=decreasing
2.3
V
Note:For the UTC
US1528,
off is
≥
2.5V and on is
≤
0.8V. The enable input, EN has approximately 200mV of hysteresis.
PARAMETER
SYMBOL
I
S(OFF)
I
S(ON
)
V
IH
V
IL
I
EN(H)
I
EN(L)
TEST CONDITIONS
switch off, OUT = open
switch on, OUT = open
low to high transition
high to low transition(Note)
V
EN
= V
OH(min)
= 2.5V
V
EN
= V
OL(max)
= 1.0V
MIN
TYP
1
100
MAX
5
160
2.5
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US1528
FUNCTIONAL DESCRIPTION
Preliminary
CMOS IC
The UTC
US1528
is high-side single channel power switch; it has an enable input in active low.
Fault
conditions turn off or inhibit turn-on of the output transistors.
Input and Output
IN pin (input) is the power supply connection to the logic circuitry and the source of the output MOSFET. OUT
pin (output) is the output MOSFET’s drain. Current flows through the switch from IN pin to OUT pin toward the load
in many applications. All OUT pins must be connected together to the load.
The output MOSFET and driving circuit are also designed to allow the MOSFET drain to be externally forced to
a higher voltage than the source (V
OUT
> V
IN
) when the switch is off. This avoids undesirable drain-to-body diode
current flow by connecting the body to the most positive voltage. If V
OUT
>V
IN
when switch is enabled, current will
flow from V
OUT
to V
IN
.
Thermal Shutdown
Thermal shutdown is designed to prevent this device from being damaged due to excessive power dissipation.
It is used to turn off the output MOSFET if the temperature is higher than135°C, 10°C of hysteresis prevents the
switch from turning on until the die temperature drops to 125°C. Thermal shutdown circuit functions only when the
switch is enabled.
Undervoltage Lockout
UVLO (Undervoltage Lockout) turns off the MOSFET switch once the input voltage falls below 2.3V (TYP) and
if the input voltage exceeds 2.5V (TYP), the switch will be turned on. UVLO detection functions only when the switch
is enabled.
Current Sensing and Limiting
The current limit threshold is fixed internally, allowing a 0.5A minimum current to flow through the output
MOSFET. However, the current limit threshold can prevent the output MOSFET and external load from being
damage. A current sense circuit protects the MOSFET switch’s output current. If output current becomes higher than
the current limit threshold, the output MOSFET switch is turned off. The reaction to an overcurrent is measured with
the following scenarios:
Switch Enabled into Heavy Load
If the switch is powered on or enabled into a heavy load or short-circuit, the switch enters a constant-current
mode immediately, reducing the output voltage.
Heavy Load Applied to Enabled Switch
When a heavy load is applied, a large-undesired transient current occurs which may damage the switch. Then
the current limit circuit may turn off the switch, folding back into constant-current mode.
Fault Flag
Fault flag is an open-drained output of an N-channel MOSFET. It drops low to indicate error conditions as
follows: current limiting, UVLO, or thermal shutdown. The flag output MOSFET is capable of sinking a 10mA load to
typically 100mV above ground.
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www.unisonic.com.tw
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QW-R502-457.b
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