Transient Voltage Suppressors (TVS) for

Automotive Electronic Protection

Application Note

Vishay General Semiconductor

Document Number: 88490

For technical questions within your region, please contact one of the following:

www.vishay.com

Revision: 09-Aug-10

3

Ω to 4 Ω

Some vehicle manufactures apply different conditions for

the load dump test based on ISO-7637-2 pulse 5. The peak

clamped current of the load dump TVS will be estimated by

the following equation:

Calculation for peak clamping current

Figure 6a shows the current and voltage waveforms of

Fig. 6a - Clamped Voltage and Current of SM5A24A

in ISO 7637-2 Test

Figure 6b shows the clamped voltage and current of load

voltage drops to near zero, and the current passed through

the device is increased to the maximum allowed by the line

impedance.

Fig. 6b - Clamped Voltage and Current of Load Dump TVS

Failures in ISO7637-2 Test

Maximum clamping capability of Vishay load dump TVS of

400 ms pulse width is as Figure 6c.

Fig. 6c - Maximum Clamping Capability of Vishay Load Dump TVS

in ISO7637-2 Test

0

100

200

400

50

(ms)

300

Line Impedance and Pulse Duration

JASO A-1:

0.8

Ω, 200 ms

ISO-7637:

0.5

Ω min. (0.5 Ω to 4 Ω),

400 ms max. (40 ms to 400 ms)

(V)

ISO 7637

V

JASO A-1

36.8 % of V

P

V

P

V

S

V

r

100

0

I

PP

V

in

V

c

–

() R

i

⁄

=

I

V

V

R