Strap Battery
PolySwitch Strap Battery
Resettable Devices
Raychem Circuit Protection, pio-
neer of polymeric PTC resettable
devices, has developed several
material platforms specifically tai-
lored to help protect battery
applications. Each of these mate-
rial platforms offers different per-
formance characteristics,
allowing the engineer greater
design flexibility. Raychem Circuit
Protection’s battery protection
family includes SRP, LTP, LR4,
VTP, VLP, and VLR series, disc,
and special application strap
devices.
4
Benefits:
• Many material platforms and
device form factors give engi-
neers more design flexibility
• Compatible with high-volume
electronics assembly
• Assists in meeting regulatory
requirements
• Low resistance devices
increase battery operating time
Features:
• Broad range of resettable
devices available
• Current ratings from 0.7A to
9.0A
• Voltage ratings from 12V to 30V
• Agency recognition, UL, CSA,
TÜV
• Fast time-to-trip
• Low resistance
Applications:
•
•
•
•
•
•
Mobile phone battery packs
Cordless phone battery packs
Mobile radio packs
Computer battery packs
Camcorder battery packs
PDA battery packs
Devices in this section are grouped by:
Activation Temperature, Device Series, Hold Current
Raychem Circuit Protection
PolySwitch Strap Battery Resettable Devices
259
Selection Guide for Strap Battery Devices
Step 1.
Determine the circuit’s operating parameters.
Fill in the following information about the circuit:
Maximum ambient operating temperature
Normal operating current
Maximum operating voltage
(i.e., VTP210G is 16V max.)
Maximum interrupt current
Step 2.
Select the PolySwitch device that will accommodate the
circuit’s maximum ambient temperature and
normal operating current.
Look across the top of Table B2 to find the temperature that most
closely matches the circuit’s maximum operating temperature. Look
down the column to find the value equal to or greater than the circuit's
normal operating current. Now look to the far left of that row to find the
part number for the PolySwitch strap device that will best accommo-
date the circuit. Devices in this section are grouped by typical activa-
tion temperature; therefore, your operating current requirement may be
found in more than one grouping.
The thermal derating curves located in Figure B3 are the normalized
representations of the data in Table B2.
Step 3.
Compare the selected device’s electrical ratings with the
circuit’s maximum operating voltage and maximum inter-
rupt current.
Look down the first column of Table B3 to find the part number you
selected in Step 2. Look to the right in that row to find the device’s
maximum operating voltage (V
MAX
) and maximum interrupt current
(I
MAX
). Ensure that V
MAX
and I
MAX
are greater than or equal to the cir-
cuits maximum operating voltage and maximum interrupt current.
Step 4.
Determine time-to-trip.
Time-to-trip is the amount of time it takes for a device to switch to a
high-resistance state once a fault current has been applied across the
device. Identifying the PolySwitch device’s time-to-trip is important in
order to provide the desired protection capabilities. If the device you
choose trips too fast, undesired or nuisance tripping will occur. If the
device trips too slowly, the components being protected may be
damaged before the device switches to a high resistance state.
260
PolySwitch Strap Battery Resettable Devices
Raychem Circuit Protection
4
Strap Battery
Selection Guide for Strap Battery Devices
Figures B19-25 show the typical time-to-trip at 20°C for each of the
PolySwitch devices.
If the PolySwitch device time-to-trip is too fast or too slow for the circuit, go
back to Step 2 and choose an alternate device.
Step 5.
Match Thermal Cut-Off to Cell Chemistry.
Thermal cut-off is the temperature at which a PolySwitch device will trip when
sourced with a specific current. Figure B1 demonstrates how the resistance-
versus-temperature characteristics of various PolySwitch strap device series
differ by use of different material platforms. Figure B2 shows the thermal cut-
off behavior for each strap battery series device. Actual device performance
can vary depending on the application environment, and users should inde-
pendently test and evaluate each product in their application. Thermally sen-
sitive cell chemistries such as Li-ion and NiMH typically use devices with
lower thermal cut-off, which can provide enhanced thermal protection (VLR,
VLP, and VTP series). Less sensitive chemistries, like NiCd, typically use
devices with higher thermal cut-off temperatures (LR4, SRP series).
Step 6.
Verify ambient operating conditions.
Ensure that your application’s minimum and maximum ambient tempera-
tures are within the operating temperature range of -40°C to 85°C (except
for VLR series, which is -40°C to 70°C).
4
Step 7.
Verify the PolySwitch device dimensions.
Using dimensions in Table B4, compare the dimensions of the PolySwitch
device you selected with the application’s space considerations.
Figure B1. Resistance vs. Temperature
1000000
180
Figure B2. Typical Thermal Cut-Off at 1 A
A = VLR
B = VTP
C = VLP
D = LTP
E = SRP
F = LR4
F
C D
B
A
C
A
D
B
E
C
100000
10000
Resistance (Ω)
1000
100
10
1
0.1
0.01
0.001
0
20
40
60
80
100
120
140
E
B
D
A
Thermal Cut-off Temperature (°C)
F
A = VLR
B = VLP
C = VTP
D = LTP
E = SRP
F = LR4
160
140
120
100
80
60
40
20
0
F
E
DE
F
C
BA
160
0
0.02
0.04
0.06
0.08
0.1
0.12
0.14
0.16
Temperature (°C)
Resistance at 20
°C
(Ω)
Raychem Circuit Protection
PolySwitch Strap Battery Resettable Devices
261
Protection Application Selection Guide for Strap Battery Devices
The guide below lists PolySwitch
devices which are typically used in
these applications. The following
pages contain the specifications for
the part numbers recommended
below. Once a device is selected,
the user should evaluate and test
each product for its intended
application.
PolySwitch Resettable Devices—Key Device Selection Criteria
Protection Application
Mobile phone battery packs
Additional Comments
NiCd
Installation Method
Cylindrical
(diameter greater
than AAA)
Lowest Resistance
LR4-17OU
LR4-190
LR4-260
SRP200
SRP420
TAC100-09
TAC170-09
TAC210
VTP170
LR4-190
LR4-260
SRP120
SRP175
VLP270
VTP210G
LR4-190
LR4-260
—
—
—
VLP210
VTP170
TAC100-09
TAC170-09
TAC210
miniSMDE190
VLP220
VLP270
VTP210G
LR4-190
LR4-260
LR4-380
VLP220
VLP270
VTP210G
LR4-190
LR4-260
miniSMDE190
VLP220
VLP270
VTP210G
PSR-23096 (single cell)
PSR-22631 (single cell)
Lowest Thermal Cut-off
LTP070
LTP190
LTP260
LTP340
—
VTP170
VTP210G
—
—
—
—
—
—
VLR170
VLR230
VLP270
VTP210G
LTP180
LTP190
LTP260
VLP210
VTP170
VTP210G
LTP180L (4 cells)
—
miniSMDE190
VLR170
VLR230
VLP220
VLP270
VTP210G
LTP180
VLR170
VLR230
VLP220
VLP270
VTP210G
miniSMDE190
VLR170
VLR230
VLP270
VTP210G
VTP175
Cylindrical
(AAA cell)
Prismatic
NiMH
Cylindrical
(diameter greater
than AAA)
4
Cylindrical
(AAA cell)
Flexprint
Prismatic
Li-ion
Cylindrical
(diameter greater
than AAA)
Flexprint
Prismatic
262
PolySwitch Strap Battery Resettable Devices
Raychem Circuit Protection
Strap Battery
Protection Application Selection Guide for Strap Battery Devices
continued
PolySwitch Resettable Devices—Key Device Selection Criteria
Protection Application
Cordless phone battery packs
Additional Comments
NiCd
Installation Method
Cylindrical
Lowest Resistance
SRP120
SRP175
VTP210G
NiMH
Cylindrical
LTP070
LTP100
VTP210G
Mobile radio packs
NiCd
Cylindrical
LR4-380
LR4-730
SRP350
NiMH
Cylindrical
LR4-380
LR4-730
SRP350
Computer battery packs
NiMH
Cylindrical
LR4-380
LR4-450
LR4-550
LR4-600
LR4-730
SRP420
SRP350
Li-ion
Cylindrical
LR4-380
LR4-450
LR4-550
LR4-600
LR4-730
SRP350
SRP420
Prismatic
Camcorder battery packs
NiCd or Li-Ion
Cylindrical
Consult Local Rep
LR4-450
LR4-550
LR4-600
LR4-730
PDA
Li-Ion
Prismatic
VLP220
VLP270
—
—
—
—
—
—
Lowest Thermal Cut-off
LTP070
LTP100
VTP210G
LTP070
LTP100
VTP210G
LTP260
LTP300
LTP340
LTP260
LTP300
LTP340
LTP260
LTP340
—
—
—
—
—
—
—
—
—
—
—
—
Consult Local Rep
VTP210G
—
—
—
VLR170
VLR230
VTP110
VTP170
VTP210G
LTP070
LTP100
LTP180
4
Raychem Circuit Protection
PolySwitch Strap Battery Resettable Devices
263
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