F1206A0R20FSTR datasheet(21/23 Pages) AVX

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Fig. 6b. Choice of 0.75A fuse, example #6.

Pre-arcing I2t

Maximum I2t design rule

I2t for sample switch-on pulse

Fig. 5b. Choice of fuse, example #5.

Pre-arcing I2t

Maximum I2t design rule

I2t for sample switch-on pulse

Accu-Guard®

SMD Thin-Film Fuse

6. Switch-on pulse and steady-state current

In Figure 6a, the switch-on pulse is a triangle pulse with a

5.1 x 10-3 A2sec Joule integral of 5 msec duration; the 0.75A

fuse will meet this requirement, see Figure 6b.

5. Complex current pulse

If the pulse consists of several waveforms, all of them should

be evaluated separately, and then the total Joule integral

should be calculated as well.

2 msec/div

0.5A/div

Fig. 6a. Switch-on pulse and steady-state current,

example #6.

200

μsec/div

2A/div

Fig. 5a. Complex pulse, example #5.

0.75A

PRE-ARCING TIME l2t, A2 sec

PRE-ARCING TIME, sec

100

10-1

10-2

10-3

10-4

10-5

10-7

10-6

10-5

10-4

10-3

10-2

10-1

110

x x

FUSE PRE-ARCING JOULE INTEGRALS

vs. PRE-ARCING TIME

The

Joule

integral

for

the

second

triangle

[(5.33A)2 x 269 x 10-6sec]/3 = 2.55 x 10-3 A2sec, and

0.75A fuse is suitable for this case also, see Figure 5b.

However, for the whole pulse, the Joule integral is

4.7 x 10-3 A2sec, and the total duration is 563 μsec. For the

0.75A fuse, the Joule integral is only 8.6 x 10-3 A2sec for this

pulse duration, so the 1A fuse should be chosen for this

application, see Figure 5b.

In Figure 5a, the Joule integral for the first triangle is

[(4.67A)2 x 294 x 10-6sec]/3=2.14 x 10-3 A2sec

and 0.75A fuse should meet this condition, see Figure 5b.

FUSE PRE-ARCING JOULE INTEGRALS

vs. PRE-ARCING TIME

0.75A

PRE-ARCING TIME l2t, A2 sec

PRE-ARCING TIME, sec

100

10-1

10-2

10-3

10-4

10-5

10-7

10-6

10-5

10-4

10-3

10-2

10-1

110

The steady-state current is 0.5A, and 1A fuse is typically rec-

ommended to meet the steady-state condition. Based on

steady-state current, the 1A fuse should be chosen for this

application.

DESIGNING FOR CURRENT PULSE SITUATIONS (CONT.)

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