PolySwitch Resettable Fuses
New RUSB products provide lower resistance and faster trip times
PolySwitch RUSB devices designed to meet
all USB overcurrent requirements
New PolySwitch RUSB devices
are designed to meet USB and
safety agency requirements.
The RUSB family of leaded
resettable fuses offers
overcurrent protection for
USB applications.
The low resistance, fast trip
times, and tight trip-to-hold ratio
of these devices provide flexibility
for designers. The RUSB product
family is available in a range of
currents, from 0.75 to 2.5 amps
and has a 6-volt/40-amp rating.
Features
• Low resistance
• Fast trip times
• Tighter trip-to-hold ratio
Benefits
• Meets voltage droop requirements
• Meets voltage-output limits
• Suitable in low- and high-wattage
power supplies
• Suitable for self-powered and bus-
powered hub port protection.
ISO
9 0 0 1
USB requirements
Overcurrent protection
The USB Specification 1.0 states
that overcurrent protection is required to
prevent damage in the event of:
• catastrophic device failure
• software error
• user action, such as shorting of pins
Section 7.2.1 of the specification
delineates the following USB
overcurrent protection requirements:
• The host and all self-powered hubs
must implement overcurrent protection
for safety reasons.
• The overcurrent value cannot exceed 5 A.
• The host and all self-powered hubs must
have a way to detect an overcurrent
condition and report it to the hub controller.
Voltage output
The USB Specification requires a minimum
port output voltage (V
OUT
) in two locations on
the bus: 4.75 V out of a self-powered hub port
and 4.40 V out of a bus-powered hub port.
The two following tables show how typical
designs meet USB voltage-drop requirements.
Self-Powered Hub
(individual port protection)
Power supply
5.000 V
Trace
20 mΩ x 0.5 A = 0.010
Ferrite bead
5 mΩ x 0.5 A = 0.003
RUSB120
80 mΩ x 0.5 A = 0.040
V
OUT
4.947 V
Bus-Powered Hub
(individual port protection)
Upstream V
MIN
Cable/connectors
500 mΩ x 0.5 A
Trace
5 mΩ x (0.5 A & 0.1 A)
Ferrite bead
5 mΩ x 0.1 A
FET
80 mΩ x 0.4 A
RUSB075
150 mΩ x 0.1 A
V
OUT
=
=
=
=
=
4.750 V
0.250
0.002
0.001
0.032
0.015
4.450 V
Voltage droop
Voltage droop occurs during a hot-plug
event resulting from the connection of a
peripheral and its uncharged input bulk
capacitance to a USB port. Test results
(shown below) on a range of devices
demonstrate that PolySwitch devices
meet the USB Specification’s voltage
droop requirement of 0.330 V maximum
for host/self-powered hubs and bus-
powered hubs.
Vdroop
(V)
0.116
0.140
0.196
Powered
hub
Self or bus
Self
Self
Port
protection
Individual
Individual
Ganged
Device
RUSB075
RUSB120
RUSB250
PolySwitch Resettable Fuses
P l S i hR
bl F
2
PolySwitch RUSB family advantages
• Conformity with USB Specification 1.0
• Compliance with:
—UL1950/IEC950 safety requirements
—Windows 95 and PC98 standards
• Resettable protection
• UL recognized safety device
• Highest reliability
• Lowest-cost solution
Hub designs using PolySwitch devices
Self-powered hub design
5V
Power Supply
F1
PolySwitch
RUSB120
PFAIL1-
L1
Bead
C1
0.1
+
J1
1
2
3
4
USB-A
C2
150 uF 6-V Lo-ESR
J2
As above
1
2
3
4
USB-A
J3
PF
1
2
3
4
PFAIL1-
PFAIL2-
Control Logic
PFAIL3-
PFAIL4-
Note 1
As above
1
2
3
4
USB-A
J4
As above
1
2
3
4
USB-B
Note 1: Ground is common power/signal ground, not host chassis ground.
Ground is referred to host Vbus cable ground only.
Note 2: Only Vbus power connections shown.
C1, C2, C5, C7
C2, C4, C6, C8
F1, F2, F3, F4
L1, L2, L3, L4
Panasonic ECUS1J104MEA or equivalent.
150- F Lo-ESR Panasonic EEUFA1V151 or equivalent.
Raychem RUSB120 PolySwitch device.
Ferrite bead >50 ohms at 100-MHz Steward 28L0138-20R or equivalent.
USB-A
Bus-powered hub design
Vbus
Q1
P-Channel MOSFET
F1
PolySwitch
RUSB075
Control Logic
R1
100 K
PWR ON-
R2
47K C1
0.1
PFAIL1-
PFAIL2-
PFAIL3-
PFAIL4-
As above
As above
PFAIL1-
L1
Bead
C2
0.1
+
C3
J1
1
2
3
4
PF
1
2
3
4
Note 1
USB-A
150-uF 6-V Lo-ESR
USB-B
J2
1
2
3
4
USB-A
J3
1
2
3
4
R1
100 K 1/8 W 10%
R2
47K 1/8 W 10%
C1, C2, C4, C6, C8 0.1 F Panasonic ECUS1J104MEA or equivalent.
C3, C5, C7, C9
150- F Lo-ESR Panasonic EEUFA1V151 or equivalent.
F1, F2, F3, F4
Raychem RUSB075 PolySwitch device.
L1, L2, L3, L4
Ferrite bead >50 ohms at 100-MHz Steward 28L0138-20R or equivalent.
Q1
P-channel logic MOSFET Temic Si9434DY or equivalent.
PolySwitch Resettable Fuses
USB-A
J4
As above
1
2
3
4
USB-A
3
RUSB product data
This section provides the following
product data for RUSB devices:
• Thermal derating curve
• Product dimensions
• Electrical characteristics
• Time-to-trip curve
• Physical characteristics
• Environmental characteristics
• Ordering information
• Part numbering system
• Part marking system
RUSB thermal derating curve
160
Percent of rated hold and trip current
140
120
100
80
60
40
20
0
–40 –30
–20
–10
0
10
20
30
40
50
60
70
80
Device ambient temperature (°C)
Product dimensions
(millimeters/inches)
Operating/storage temperature range: –40°C to 85°C
Device surface temperature in the tripped state: 125°C
Figure 1
A
E
Figure 2
A
E
Marking
Marking
B
B
D
D
C
C
L
C
L
C
C
L
C
L
RUSB075
RUSB090
RUSB110
RUSB120
RUSB135
RUSB160
RUSB185
RUSB250
A
max.
6.9
(0.27)
7.4
(0.29)
7.4
(0.29)
6.9
(0.27)
8.9
(0.35)
8.9
(0.35)
10.2
(0.40)
11.4
(0.45)
B
max.
11.4
(0.45)
12.2
(0.48)
14.2
(0.56)
11.7
(0.46)
13.5
(0.53)
15.2
(0.60)
15.7
(0.62)
18.3
(0.72)
C
min.
4.3
(0.17)
4.3
(0.17)
4.3
(0.17)
4.3
(0.17)
4.3
(0.17)
4.3
(0.17)
4.3
(0.17)
4.3
(0.17)
max.
5.9
(0.23)
5.9
(0.23)
5.9
(0.23)
5.9
(0.23)
5.9
(0.23)
5.9
(0.23)
5.9
(0.23)
5.9
(0.23)
D
min.
7.6
(0.30)
7.6
(0.30)
7.6
(0.30)
7.6
(0.30)
7.6
(0.30)
7.6
(0.30)
7.6
(0.30)
7.6
(0.30)
E
max.
3.1 (
0.12)
3.1 (
0.12)
3.1 (
0.12)
3.1 (
0.12)
3.1 (
0.12)
3.1 (
0.12)
3.1 (
0.12)
3.1 (
0.12)
Fig.
2
1
1
2
1
1
1
1
PolySwitch Resettable Fuses
P l S i hR
bl F
4
Electrical characteristics (20°C)
Part number
RUSB075
RUSB090
RUSB110
RUSB120
RUSB135
RUSB160
RUSB185
RUSB250
I
H
(A)
0.75
0.90
1.10
1.20
1.35
1.60
1.85
2.50
I
T
(A)
1.30
1.80
2.20
2.00
2.70
3.20
3.70
5.00
Initial resistance
R typ.
R max.
(Ω)
(Ω)
0.14
0.23
0.10
0.18
0.08
0.14
0.08
0.14
0.06
0.12
0.05
0.11
0.05
0.09
0.03
0.06
Max. time
2A
6.0
–
–
30.0
–
–
–
–
to trip (s)
3A
2.3
–
–
4.0
–
–
–
–
8A
0.4
1.2
2.3
0.5
4.5
9.0
10.0
40.0
P
d
(W)
0.3
0.6
0.7
0.6
0.8
0.9
1.0
1.2
I
H
= Hold current—maximum current at which the device will not trip at 20°C still air.
I
T
= Trip current—minimum current at which the device will always trip at 20°C still air.
P
d
= Typical power dissipation—typical amount of power dissipated by the device when in tripped state in 20°C still air environment.
Typical time-to-trip curve (20°C)
A
=
B
=
C
=
D
=
E
=
F
=
G
=
H
=
RUSB075
RUSB120
RUSB090
RUSB110
RUSB135
RUSB160
RUSB185
RUSB250
100
B
10
A
C DE F GH
Time to trip (s)
1
0.1
0.01
0.001
1
10
Fault current (A)
100
Physical characteristics
Lead material
Soldering characteristics
RUSB075: Tin/lead-plated nickel/copper alloy
RUSB090-250: Tin/lead-plated copper-clad steel
Solderability per ANSI/J-STD 002
Solder heat withstand per IEC 68-2-20
RUSB120: Test Tb, Method 1a, condition a; can withstand 5 seconds at 260˚C ±5˚C
All others: Test Tb, Method 1a, condition b; can withstand 10 seconds at 260˚C ±5˚C
Cured, flame-retardant epoxy polymer; meets UL94V-0 requirements
Insulating material
PolySwitch Resettable Fuses
5
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