Littelfuse 437 User Manual

Surface Mount Fuses

Ceramic Fuse > 437 Series

437 Series – 1206 Fast-Acting Fuse

Description

This 100% Lead-free, RoHS compliant and Halogen-free
fuse series has been designed specifically to provide over
current protection to circuits that see high working ambient
temperatures (up to 150ºC).

The general design ensures excellent temperature stability
and performance reliability.

In addition to this, the high I²t values typical of the
Littelfuse Ceramic Fuse family ensure high inrush current
withstand capability.

Features

Agency Approvals

AGENCY AGENCY FILE NUMBER AMPERE RANGE

E10480 0.250A ~ 8A

LR29862 0.250A ~ 8A

Electrical Characteristics for Series

• OperatingTemperature

from -55ºC to +150ºC

• 100%Lead-freeand

RoHS compliant

Applications

• LCDDisplays

• Servers

• Suitableforbothleaded

and lead-free reflow /
wave soldering

• Scanners

• DataModems

• Printers

% of Ampere

Rating

100% 250mA - 8A 4 hours, Minimum
250% 750mA - 8A 5 seconds, Maximum
350% 250mA -500mA 5 seconds, Maximum
350% 750mA - 8A 1 second, Maximum

Ampere Rating Opening Time at 25ºC

Additional Information

Datasheet

Resources

Samples

Electrical Specifications by Item

Ampere

Rating

250mA .250 125
375mA .375 125 1.330 0.010 0.60 0.225 x x
500mA .500 63
750mA .750 63 0.665 0.064 0.45 0.335 x x

1.25A 1.25 63 0.318 0.256 0.40 0.496 x x

1.75A 1.75 63 0.0703 0.075 0.27 0.474 x x

Notes:

1. AC Interrupting Rating tested at rated voltage with unity power factor. DC Interrupting
Rating tested at rated voltage with time constant < 0.8 msec.

2. Nominal Resistance measured with < 10% rated current.

3. Nominal Melting I²t measured at 1 msecs. opening time.

4. Nominal Voltage Drop measured at rated current after temperature has stabilized.

Amp

Code

(A)

1A 001. 63 0.360 0.100 0.41 0.415 x x

1.5A 01. 5 63 0.209 0.324 0.39 0.579 x x

2A 002. 63 0.058 0.144 0.17 0.345 x x

2.5A 02.5 32
3A 003. 32 0.033 0.400 0.15 0.462 x x

3.5A 03.5 32 0.027 0.576 0.16 0.560 x x
4A 004. 32 0.022 1.024 0.16 0.618 x x
5A 005. 32 0.016 1.936 0.09 0.484 x x
7A 0 0 7. 32 0 .010 4.900 0.11 0.760 x x
8A 008. 32 0.0084 6.400 0.067 0.539 x x

Max.

Voltage

Rating (V)

Interrupting Rating

50 A @ 125 V AC/DC

50 A @ 63 V AC/DC

50 A @ 32 V AC/35 V DC

Nominal

Resistance

(Ohms)

2.290 0.003 0.78 0.195 x x

0.908 0.018 0.52 0.260 x x

0.043 0.225 0.14 0.363 x x

Nominal

Melting I2t

2

(A2Sec.)

Nominal Voltage

Drop At Rated

3

Current (V)

Devices designed to carry rated current for 4 hours minimum. It is recommended that
devices be operated continuously at no more than 80% rated current. See “Temperature
Rerating Curve”for additional rerating information.

Devices designed to be mounted with marking code facing up.

Nominal Power

Dissipation At

4

Rated Current (W)

Agency Approvals

Specifications are subject to change without notice.

© 2013 Littelfuse, Inc.

Revised: 12/19/13

Surface Mount Fuses

Ceramic Fuse > 437 Series

Temperature Rerating Curve

140

120

100

80

PERCENT OF RATING

60

40

-65 -45 -25 -5 15 35 55 75 95 115 135 155

TEMPERATURE (°C)

Note:

1. Rerating depicted in this curve is in addition to the standard rerating of 20% for
continuous operation.

Example:
For continuous operation at 75 degrees celsius, the fuse should be rerated as follows:

I = (0.80)(0.85)I

RAT

= (0.68)I

RAT

Average Time Current Curves

.375A

.500A

.750A1A2A

100

10

1

0.1

TIME IN SECONDS

0.01

0.001

0.1

.250A

1

CURRENT IN AMPERES

1.25

1.5A

1.75

7A

2.5A3A3.5A4A5A

8A

10 100

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) 260

Time within 5°C of actual peak
Temperature (t

)

p

Ramp-down Rate 6°C/second max.

Time 25°C to peak Temperature (T
Do not exceed 260°C

Wave Soldering 260°C, 10 seconds max.

) 150°C

s(min)

) 200°C

s(max)

3°C/second max.

+0/-5

°C

10 – 30 seconds

) 8 minutes max.

P

Temperature

T

T

T

T

S(max)

S(min)

25

P

L

time to peak temperature

(t 25ºC to peak)

Preheat

t

S

Ramp-up

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