Application information

ACST1635-8FP

8/13

Doc ID 023630 Rev 1

2.2

AC line transient voltage ruggedness

In comparison with standard Triacs, which needs additional protection components against

surge voltage, the ACST1635-8FP is self-protected against over-voltage, specified by the

voltages either by clamping the low energy spikes, such as the inductive spikes at switch off,

or by switching to the on state (for less than 10 ms) to dissipate higher energy shocks

through the load. This safety feature works even with high turn-on current ramp-up.

The test circuit of Figure 19 represents the ACST1635-8FP application, and is used to

stress the ACST switch according to the IEC 61000-4-5 standard conditions. With the

additional effect of the load which is limiting the current, the ACST switch withstands the

voltage spikes up to 2 kV on top of the peak line voltage. The protection is based on an

overvoltage crowbar technology. The ACST1635-8FP folds back safely to the on state as

shown in Figure 20. The ACST1635-8FP recovers its blocking voltage capability after the

surge and the next zero crossing current. Such a non repetitive test can be done at least 10

times on each AC line voltage polarity.

Figure 19.

Overvoltage ruggedness test circuit for resistive and inductive loads for

IEC 61000-4-5 standards

AC mains

R

Filtering unit

Rg

Model of the load

Rgene

Surge generator

ACST

2kV surge

L

R =

, L =

µH, V

= 2 kV

R = 62

62

Ω

sur ge

g

Ω