Littelfuse 494 User Manual

Surface Mount Fuses

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®

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Thin Film > 0603 Size > Fast-Acting > 494 Series

494 Series Fuse, NRA Special Series Integrated Circuit Protector

Description

The 494 Series Fast-Acting SMF is an ultra small (0603
size) thin-film device designed for secondary protection
of circuits used in space constrained applications such
as hand-held portable electronic devices. This series is
100% lead-free and meets the requirements of the RoHS
directive. New Halide-Free 494 Series fuses are available
to order using the “HF” suffix. See Part Numbering section
for additional information.

Features

Agency Approvals

AGENCY AGENCY FILE NUMBER AMPERE RANGE

E10480 250mA - 5A

LR29862 250mA - 5A

Electrical Characteristics for Series

% of Ampere

Rating

100% 4 hours, Minimum

200% 5 sec., Maximum

300% 0.2 sec., Maximum

Opening Time at 25

O

C

Additional Information

Datasheet

Resources

Samples

• Compatiblewithlead-

free solders and higher
temperature profiles

• Highperformance

materials provide
improved performance
in elevated ambient
temperature applications

• Markedontopsurface

with code to allow ampere
rating identification
without testing

• Lowproleforheight

sensitive applications

• Flattopsurfaceforpick-

and-place operations

Applications

Secondary protection for space constrained applications:

• Cellphones

• Batterypacks

• Element-coveringmaterial

is resistant to industry
standard cleaning
operations

• Mountingpadand

electrical performance are
identical to Littelfuse 431
and 434 Series products

• Alloy-basedelement

construction provides
superior inrush withstand
characteristics (I
ceramic or glass-based
0603 fuse products

• Digitalcameras

• DVDplayers

2

t) over

• Harddisk
drives

Electrical Specifications by Item

Ampere

Rating

(A)

0.250 .250 32

0.375 .375 32 0.2900 0.0053 128.03 0.0480 x x

0.500 .500 32 0.1870 0.0087 115.71 0.0579 x x

0.750 .750 32 0.1170 0.0171 107.33 0.0805 x x

1. 0 0 0 01. 32 0.0710 0.0212 89.10 0.0891 x x

1.25 1.25 32

1.50 01.5 32 0.0410 0.0766 81.14 0.1217 x x

1.75 1.75 32 0.0320 0.0903 78.75 0.1378 x x

2.00 002. 32 0.0300 0.1103 78.22 0.1564 x x

2.50 02.5 32 0.0220 0.1440 76.10 0.1903 x x

3.00 003. 32 0.0180 0.2403 75.04 0.2251 x x

3.50 03.5 32 0.0150 0.4306 74.25 0.2599 x x

4.00 004. 32 0.0130 0.5760 73.72 0.2949 x x

5.00 005. 32 0.0090 0.9000 72.71 0.3635 x x

1. Measured at 10% of rated current, 25ºC. 2. Measured at rated voltage.

Amp

Code

Max

Voltage

Rating

(V)

Interrupting

Rating

50A @32V AC/DC

35A @32V AC/DC

Nominal Cold

Resistance

(Ohms)

0.5450 0.0030 158.56 0.0396 x x

0.0530 0.0518 84.32 0.1054 x x

Nominal

Melting

2

t (A2sec)

I

Nom

Voltage

Drop

(mV)

Nom

Power

Dissipation

(W)

Specifications are subject to change without notice.

Agency Approvals

© 2013 Littelfuse, Inc.

Revised: 12/19/13

Surface Mount Fuses

0

0.00

A

A

A

A

Thin Film > 0603 Size > Fast-Acting > 494 Series

Temperature Rerating Curve

Average Time Current Curves

1.50 A

1.25 A

0.500

0.375

100

10

TIME IN SECONDS

0.1

0.01

0.250

1

1

0.1

1.00 A

0.750

1

CURRENT IN AMPERES

3.50 A

3.00 A

2.50 A

2.00 A

1.75 A

10 10

5.00 A

4.00 A

Soldering Parameters

Reflow Condition Pb – free assembly

- Temperature Min (T

Pre Heat

- Temperature Max (T

- Time (Min to Max) (ts) 60 – 180 seconds

Average Ramp-up Rate (Liquidus Temp
(T

) to peak)

L

to TL - Ramp-up Rate 5°C/second max.

T

S(max)

Reflow

- Temperature (TL) (Liquidus) 217°C

- Temperature (tL) 60 – 150 seconds

Peak Temperature (TP) 250

Time within 5°C of actual peak
Temperature (t

)

p

) 150°C

s(min)

) 200°C

s(max)

5°C/second max.

+0/-5

°C

20 – 40 seconds

T

Temperature

S(max)

T

S(min)

T

P

T

L

25

time to peak temperature

Preheat

t

S

(t 25ºC to peak)

Ramp-up

Ramp-down Rate 5°C/second max.

Time 25°C to peak Temperature (T

) 8 minutes max.

P

Do not exceed 260°C

t

P

Critical Zone

T

to T

L

P

t

L

Ramp-down

Time

© 2013 Littelfuse, Inc.
Specifications are subject to change without notice.
Revised: 12/19/13