VISHAY INTERTECHNOLOGY, INC.
Corporate Headquarters
: 63 Lincoln Highway, Malvern
,
PA 19355-2120, U.S.A.
Phone
: 610- 644-1300
Fax
: 610-296-0657
www.vishay.com
ONE OF THE WORLD’S LARGEST MANUFACTURERS OF DISCRETE SEMICONDUCTORS AND PASSIVE COMPONENTS
VISHAY Load Dump TVS Series for 24 V Powertrains
By Soo Man (Sweetman) Kim
As more trucks and buses are built with complex electrical systems, load dump protection is an
important safety feature for vehicles with 24 V powertrains. This article describes the changes to
the load dump test condition and defines the maximum surge suppressing capability for Vishay
load dump TVS series in these conditions.
The New ISO Standard ISO-16750-2 (2010) vs. the Old ISO Standard ISO-7637-2 (2004)
The most significant difference between the new and old load dump tests is that the new
standard (ISO-16750-2, 2010) requires 10 pulses in 10 minutes with a one-minute interval per
pulse, as shown in Table 1. The old standard (ISO-7637-2, 2004) required only a single pulse.
Table 1: Pulse requirements for ISO-16750-2
Parameter
Type of system
Minimum
test requirements
UA = 12 V
UA = 24 V
US (V)
79 to 101
151 to 202
10 pulses
at intervals of 1 min.
Ri (Ohm)
0.5 to 4
1 to 8
td (ms)
40 to 400
100 to 350
tr (ms)
10 / +0 / -5
10 / +0 / -5
The test condition of the 10 pulses in 10 minutes shows the reliability of the load dump
protection device, which assists the circuit designer in selecting the best device based on surge
capability in high-temperature conditions.
Load Dump Protection for 24 V Systems Using an AEC-Q101-Qualified TVS Series Device
Figure 1 illustrates the load dump protection device clamping in the specified voltage range,
which is different from the standard waveform. The active voltage range of the clamping device
in the load dump pulse is the reason for this difference, as shown in Figure 1. The device in
Figure 2 is clamping at 202 V U
S
, 3.5 Ω Ri, and a 350 ms pulse width.
Figure 1: Input waveform of an ISO-16750-2 pulse: 5 A, 201 V U
s
, 350 ms pulse width condition
Figure 2: Clamped waveform of the SM8S36A at an ISO-16750-2 pulse: 5 A, 202 V U
S
, 3.5 Ω
Ri, 350 ms pulse input condition
VISHAY INTERTECHNOLOGY, INC.
Corporate Headquarters
: 63 Lincoln Highway, Malvern
,
PA 19355-2120, U.S.A.
Phone
: 610- 644-1300
Fax
: 610-296-0657
www.vishay.com
ONE OF THE WORLD’S LARGEST MANUFACTURERS OF DISCRETE SEMICONDUCTORS AND PASSIVE COMPONENTS