Application information

ACST1235-8FP

8/13

DocID026033 Rev 1

2.2

AC line transient voltage ruggedness

In comparison with standard Triac, which need additional protection components against

surge voltage, the ACST1235-8FP is self-protected against overvoltage, 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 ACST1235-8FP 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 limits 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 ACST1235-8FP folds back safely to the on state as shown in

Figure 20

. The ACST1235-8FP 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

Filtering unit

Model of the load

ACST

2 kV surge

R = 11

L = 3 µH V

= 2 kV

Ω,

,

PP

Rg = 62

Ω

Rg

R

L

Rgene