July 2010

Doc ID 5649 Rev 3

1/13

AN320

Application note

Operation of a Trisil™ crowbar type protection diode

Introduction

In the field of parallel protection, the devices used have two main functions in transient

operation.

If the first function is carried out perfectly by an avalanche junction, confirmed by the

success of the Transil™ series, the second is limited by voltage permanently present across

the diode terminals.

Use of increasingly sophisticated but fragile electronic components and publication of new

standards do not allow the use of Transil diodes in certain applications. This problem is

solved by the use of a semiconductor device with two conducting states such as the thyristor

(or Triac in the bidirectional version).

STMicroelectronics has developed this type of component under the trade name of Trisil.

This Application note describes the operation of the Trisil.

Figure 1.

I / V characteristic of a Trisil

TM: Trisil is a trademark of STMicroelectronics

TM: Transil is a trademark of STMicroelectronics

V

I

0

C

D

A

B

Transient

operation

Standby

operation

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