AN3361 Datasheet, PDF (1/15 Pages) STMicroelectronics – Schottky diode avalanche performance in automotive applications

AN3361
Application note
Schottky diode avalanche performance in automotive applications
Introduction
Electronic modules connected to automotive power rails may be affected by polarity
inversion due to poor battery handling and load-dump surges when the battery is
disconnected while the alternator is still charging. To protect against these phenomena,
module manufacturers add reverse-battery protection, usually using diodes.
Schottky diodes are preferred over bipolar ones because of their higher performance in
direct conduction. Schottky diodes feature a low forward voltage drop, and are able to
withstand the pulses defined in ISO 7637-2.
However, the diode needs a breakdown voltage higher than 150 V in order to pass the tests
for negative pulses 1 and 3a, whereas this tends to lower the forward performances. For
Schottky diodes, the intrinsic trade-off obeys the rule: the higher the breakdown voltage, the
higher the forward voltage drop.
There is a way to reconcile these conditions. Some Schottky diodes (depends on the
technology) have the ability to dissipate some power in reverse condition. This concerns the
P_ARM parameter (Repetitive Peak Avalanche Power). For instance a 100 V breakdown
voltage Schottky diode may on the one hand support the negative pulse 1 and pulse 3a of
the ISO 7637-2 standard and on the other hand offer a very good performance in forward
voltage drop.
This Application note explains how to choose the best Schottky diode trade off in automotive
applications in order to preserve the low forward voltage drop performance and the ability to
pass the ISO 7637-2 pulses.
September 2011
Doc ID 018589 Rev 1
1/15
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