POLYSWITCH® Resettable PTCs
Surface Mount > LoRho Series
© 2017 Littelfuse, Inc.
Specifications are subject to change without notice.
Revised: 05/16/17
The Littelfuse LoRho SMD PTC for Charging Cables
provides protection from heat generated due to faults
within the connector such as USB-C, microUSB, and
many others.
As connectors get smaller, their pin-to-pin spacings are
shrinking which increases the opportunity for debris such
as dust, dirt, or water to collect causing a fault. These
faults can generate a tremendous amount of heat which
will damage charging cables, the devices they charge, or
people using them.
Description
Features
Applications
† These charging protocols are the property of their respective owners.
• SMD compatible with
reflow soldering process
• Available in small 1206
and 1210 sizes
• Up to 12Vdc and
4.5A Ihold
• Ultra low internal
resistance
• Reset automatically
• Halogen-free, lead-free
and RoHS compliant
• Over temperature (OT)
protection for USB
connectors and cables
including:
– USB Type-C
– USB Micro-B
– USB-A
• Fast charging standards
and protocols including:
– USB Power Delivery
(PD) †
– Qualcomm Quick
Charge (QC) †
– Mediatek Pump
Express (PE) †
– Samsung Adaptive
Fast Charging (AFC) †
– Huawei/HiSilicon Fast
Charging Protocol
(FCP) †
Electrical Characteristics
Part Number Marking Ihold
1
(A)
Vmax
2
(Vdc)
Thermal Cut Off
(TCO) - ºC @ 2A
Thermal Cut Off
(TCO) - ºC @ 3A Pd
3 typ.
(W)
Resistance Agency
Approvals
Min Max Min Max Rmin
4
(Ω)
R1max
5
(Ω)
nanoSMD350LR-C P 3.50 12 65 85 50 75 1. 0 0.004 0.018 -- --
nanoSMD400LR-C S 4.00 12 70 100 65 90 1. 0 0.004 0.010 -- --
microSMD450LR-C S 4.50 12 90 110 80 100 1. 0 0.002 0.0085 X X
LoRho SMD PTC for Charging Cable Protection
Agency Approvals
AGENCY AGENCY FILE NUMBER AMPERE RANGE
E74889 4.5A
Pending Pending
Notes:
1. I hold = Hold current: maximum current device will pass without tripping in 20°C still air
2. Vmax = Maximum voltage device can withstand without damage at rated current (Imax)
3. Pd = Power dissipated from device when in the tripped state at 20°C still air
4. Rmin = Minimum resistance of device in initial (un-soldered) state
5. R1max = Maximum resistance of device at 20°C measured one hour after tripping or
reflow Soldering of 260°C for 20 seconds
(Values specified were determined using PCBs with 0.115in x 1.0in ounce copper traces)
Caution: Operation beyond the specified rating may result in damage and possible arcing
and flame
TCO and Pd Testing Method:
Thermal Cut-Off Test–
1. Put the device into the thermostatic chamber controlled at room temperature or 25°C.
2. Apply the specified current to the device, and increase the chamber temperature at the
rate of 2°C per minute.
3. Measure the device ambient temperature when the applied current has reduced to less
than 20% of initial value.
Power Dissipation–
1. Conduct thermal cut-off test at rated current/voltage.
2. After device trip, decrease the chamber temperature with keeping trip state.
3. Measure the tripped-state power dissipation when the device ambient temperature has
reduced to 30°C or less.
POLYSWITCH® Resettable PTCs
Surface Mount > LoRho Series
© 2017 Littelfuse, Inc.
Specifications are subject to change without notice.
Revised: 05/16/17
Temperature Rerating
Temperature Derating Curve
Ambient Operating Temperature
Part Number
-20°C 0°C 20°C 60°C 85°C
Hold Current (A)
nanoSMD350LR-C 4.80 4.00 3.50 1.90 1.30
nanoSMD400LR-C 5.20 4.60 4.00 2.82 2.10
microSMD450LR-C 6.20 5.50 4.50 3.30 2.30
Note: The temperature rerating data is for reference only. Please contact Littelfuse technical support for detail temperature rerating information.
Environmental Specifications
Operating Temperature -20°C to +85°C
Maximum Device Surface
Temperature in Tripped State 125°C
Passive Aging
+85°C, 1000 hours
-/+10% typical resistance
change
Humidity Aging
+85°C, 85% R.H.,100 hours
-/+15% typical resistance
change
Thermal Shock
MIL–STD–202, Method 215
No change
Vibration MIL–STD–883, Method 2007,
Condition A No change
Moisture Sensitivity Level Level 2a, J–STD–020
Physical Specifications
Terminal
Materials
Solder-Plated Copper
(Solder Material: Matte Tin (Sn))
Lead
Solderability
Meets EIA Specification RS186-9E, ANSI/J-
STD-002, Category 3
POLYSWITCH® Resettable PTCs
Surface Mount > LoRho Series
© 2017 Littelfuse, Inc.
Specifications are subject to change without notice.
Revised: 05/16/17
Soldering Parameters
Time
Temperature
TP
TL
TS(max)
TS(min)
25
tP
tL
tS
time to peak temperature
Preheat
P
reheat
Ramp-up
R
amp-up
Ramp-down
R
amp-d
o
Profile Feature Pb – Free assembly
Pre Heat
- Temperature Min (Ts(min))150°C
- Temperature Max (Ts(max))200°C
- Time (min to max) (ts)60 – 120 seconds
Average ramp up rate (Liquidus Temp
(TL) to peak 3°C/second max
TS(max) to TL - Ramp-up Rate 3°C/second max
Reflow - Temperature (TL) (Liquidus) 217°C
- Temperature (tL)60 – 150 seconds
Peak Temperature (TP)260°C
Time within 5°C of actual peak
Temperature (tp)30 seconds max
Ramp-down Rate 2°C/second max
Time 25°C to peak Temperature (TP)8 minutes max
Notes:
• All temperature refer to topside of the package, measured on the package body surface.
• If reflow temperature exceeds the recommended profile, devices may not meet the
performance requirements.
• Recommended reflow methods: IR, vapor phase oven, hot air oven, N2 environment
for lead.
• Recommended maximum paste thickness is 0.25 mm (0.010 inch).
• Devices can be cleaned using standard industry methods and solvents.
• Devices can be reworked using the standard industry practices.
Dimensions
P
nanoSMD350LR-C
nanoSMD400LR-C
Marking code varies by device.
See Electrical Characteristics table.
AB B
E
D
C
A
G
CH
DFF
S
microSMD450LR-C Solder Pad Layout
Part Number
Device Dimension Solder Pad
A B C D E F G H
inch mm inch mm inch mm inch mm inch mm
inch mm inch mm inch mm
Min Max Min Max Min Max Min Max Min Max Min Max Min Max Min Max Min Max Min Max
nanoSMD350LR-C 0.12 0.13 3.00 3.43 0.02 0.03 0.60 0.80 0.05 0.07 1.37 1.85 0.01 0.03 0.25 0.75 -- -- -- -- 0.04 1. 10 0.08 2.00 0.07 1.75
nanoSMD400LR-C 0.12 0.13 3.00 3.43 0.02 0.03 0.60 0.80 0.05 0.07 1.37 1.85 0.01 0.03 0.25 0.75 -- -- -- -- 0.04 1. 10 0.08 2.00 0.07 1.75
microSMD450LR-C 0.12 0.13 3.00 3.43 0.02 0.03 0.60 0.80 0.09 0.11 2.35 2.80 0.01 0.03 0.25 0.75 0.003 -- 0.076 -- 0.04 1. 0 0 0.08 2.00 0.10 2.65
POLYSWITCH® Resettable PTCs
Surface Mount > LoRho Series
© 2017 Littelfuse, Inc.
Specifications are subject to change without notice.
Revised: 05/16/17
Packaging
Part Number Ordering IHOLD (A) IHOLD Code Packaging Option Quantity
nanoSMD350LR-C RF4610-000 3.50 350
Tape and Reel
15,000
nanoSMD400LR-C RF4611-000 4.00 400 15,000
microSMD450LR-C RF2515-000 4.50 450 15,000
• Operation of these devices beyond the stated maximum
ratings could result in damage to the devices and lead to
electrical arcing and/or fire.
• These devices are intended to protect against the effects
of temporary over-current or over-temperature conditions
and are not intended to perform as protective devices
where such conditions are expected to be repetitive or
prolonged in duration.
• Exposure to silicon-based oils, solvents, electrolytes,
acids, and similar materials can adversely affect the
performance of these PPTC devices.
• These devices undergo thermal expansion under fault
conditions, and thus shall be provided with adequate
space and be protected against mechanical stresses.
• Circuits with inductance may generate a voltage (L di/dt)
above the rated voltage of the PPTC device.
• Hand-soldering of PTC devices on boards is generally not
recommended. Users shall define and verify this process
if needed.
• Consult Littelfuse when the device is to be applied
with thermal processes other than reflow process on
the circuit board, such as molding, encapsulation. User
should evaluate molding materials used in the charging
cable applications to ensure there are no adverse effect
on the PTC devices.
Installation and Handling Guidelines
Part Numbering System
nano SMD 350 LR -C -2
LoRho
I
HOLD
CURRENT CODE
SIZE
SURFACE MOUNT DEVICE
FOR CHARGING
CABLE APPLICATION
TAPE/REEL
POLYSWITCH® Resettable PTCs
Surface Mount > LoRho Series
© 2017 Littelfuse, Inc.
Specifications are subject to change without notice.
Revised: 05/16/17
Tape and Reel Specifications
W
E2
F
P0
P2
D0
T
T1
K0
A0
P1
Center lines
of Cavity
Cover Tape
B0
E1
Embossment
B1
Cover Tape
Embossed Cavity
Carrier Tape
AN (hub dia.)
W2
(Measured at Hub)
W1
(Measured at Hub)
nanoSMD350LR-C
nanoSMD400LR-C
microSMD450LR-C
W8.0 ± 0.30 8.0 ± 0.30
P04.0 ± 0.10 4.0 ± 0.10
P14.0 ± 0.10 4.0 ± 0.10
P22.0 ± 0.05 2.0 ± 0.05
A01.95 ± 0.10 2.9 ± 0.10
B03.50 + 0.1/-0.08 3.55 ± 0.10
B1 max. 4.35 4.35
D01.55 ± 0.05 1.55 ± 0.05
F 3.50 ± 0.05 3.50 ± 0.05
E11.75 ± 0.10 1.75 ± 0.10
E2 min. 6.25 6.25
T max. 0.3 0.3
T1 max. 0.1 0.1
K00.89 ± 0.10 1.27 ± 0.10
A max. 179 179
N min. 53.5 53.5
W19.5 ± 0.5 9.5 ± 0.5
W2 max. 15 15
Standard Pack Quantity: 3,000 pcs
Minimum Order Quantity: 15,000 pcs
