Application information ACST1635-8FP
8/13 DocID023630 Rev 2
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 overvoltage, specified by the
new parameter V
CL
. The ACST1635-8FP 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 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
62Ω
sur ge
g
Ω
