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
new parameter V
CL
. The ACST1235-8FP switch can safely withstand AC line transient
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 kVΩ, ,
PP
Rg = 62 Ω
Rg
R
L
Rgene
