Littelfuse ST User Manual

ST Series

POLYFUSE® Resettable PTCs

POLYFUSE® Resettable PTCs

Axial Lead Battery Strap Type > ST Series

Description

The new ST Series device provides reliable, noncycling
protection against overcharging and short circuits events
for rechargeable battery cells where resettable protection
is desired.

Features

• RoHS compliant and
lead–free

• Weldable Nickel terminals

• Low resistance

• Provides overcurrent
protection at 125°C trip
temperature

Agency Approvals

AGENCY AGENCY FILE NUMBER

E183209

R50119583

Applications

• Rechargeable battery cell
protection

Electrical Characteristics

Part Number

I

hold

(A)

I
(A)

V

trip

(Vdc)

max

I

(A)

max

P

max.

(W)

Maximum Time

d

Current

(A)

To Trip

Time

(Sec.)

R

(Ω)

min

Resistance

R

typ

(Ω)

R

1max

(Ω)

15ST120 1.2 2.7 15 100 1.2 6.00 5.00 0.085 0.160 0.220

15ST120S 1.2 2.7 15 100 1.2 6.00 5.00 0.085 0.160 0.220

15ST175 1.75 3.8 15 100 2.5 8.75 5.00 0.050 0.090 0.120

15ST175S 1.75 3.8 15 100 2.5 8.75 5.00 0.050 0.090 0.120

30ST200 2.00 4.4 30 100 1.9 10.00 4.00 0.030 0.060 0.100

30ST350 3.50 6.3 30 100 2.5 20.00 3.00 0.017 0.031 0.050

30ST420 4.20 7.6 30 100 2.9 20.00 6.00 0.012 0.024 0.040

Items with S at end of part number identify items with slit lead option. See Dimension Drawing and Part Ordering Number System sections of this document for more information.

I

= Hold current: maximum current device will pass without tripping in 20°C still air.

hold

= Trip current: minimum current at which the device will trip in 20°C still air.

I

trip

= Maximum voltage device can withstand without damage at rated current (I max)

V

max

= Maximum fault current device can withstand without damage at rated voltage (V

I

max

= Power dissipated from device when in the tripped state at 20°C still air.

P

d

= Minimum resistance of device in initial (un-soldered) state.

R

min

)

max

= Typical resistance of device in initial (un-soldered) state.

R

typ

= Maximum resistance of device at 20°C measured one hour after tripping or reflow

R

1max

soldering of 260°C for 20 sec.

Caution: Operation beyond the specified rating may result in damage and possible arcing
and flame.

Agency

Approvals

XX

XX

XX

XX

XX

XX

XX

ST Series

© 2010 Littelfuse, Inc

Specifications are subject to change without notice.
Please refer to www.littelfuse.com/series/ST.html for current information.

121

Revised: June 4, 2010

ST Series

POLYFUSE® Resettable PTCs

Axial Lead Battery Strap Type > ST Series

Temperature Rerating

Ambient Operation Temperature

-40°C -20°C 0°C 23°C 40°C 50°C 60°C 70°C 85°C

Part Number Hold Current (A)

15ST120 1.90 1.70 1.50 1.20 1.00 0.90 0.80 0.70 0.50

15ST120S 1.90 1.70 1.50 1.20 1.00 0.90 0.80 0.70 0.50

15ST175 2.50 2.30 2.00 1.75 1.50 1.30 1.20 1.10 0.90

15ST175S 2.50 2.30 2.00 1.75 1.50 1.30 1.20 1.10 0.90

30ST200 3.20 2.80 2.50 2.00 1.70 1.60 1.40 1.20 0.90

30ST350 5.40 4.80 4.30 3.50 3.00 2.80 2.50 2.20 1.70

30ST420 6.40 5.70 5.10 4.20 3.60 3.30 3.00 2.60 2.10

Average Time Current Curves

1.20 A

1.75 A

2.00 A

3.50 A

10

1

Time in Seconds

0.1

0.01
1 10 100 1000

4.20 A

Current in Amperes

ST

Temperature Rerating Curve

170%

150%

130%

110%

90%

70%

50%

Percentage of Rated Current

30%

10%

-40 -30 -20 -10 0 10 20 30 40 50 60 70 80

Temperature (°C)

The average time current curves and Temperature Rerating curve performance is affected
by a number or variables, and these curves provided as guidance only. Customer must
verify the performance in their application.

ST Series

Revised: June 4, 2010

122

© 2010 Littelfuse, Inc.

Please refer to www.littelfuse.com/series/ST.html for current information.

Specifications are subject to change without notice.