Application information

ACST2

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DocID13304 Rev 4

2

Application information

2.1

Typical application description

The ACST2 device has been designed to switch on and off highly inductive or resistive

loads such as pump, valve, fan, or bulb lamp. Thanks to its high sensitivity

resistor as shown on the typical application diagram. Thanks to its thermal and turn-off

commutation performances, the ACST2 switch can drive, without any additional snubber, an

inductive load up to 2 A.

Figure 16. AC induction motor control – typical diagram

2.2

AC line transient voltage ruggedness

In comparison with standard Triacs, which are not robust against surge voltage, the ACST2

fast transients. The ACST2 switch can safely withstand AC line transient voltages either by

clamping the low energy spikes, such as 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 17 represents the ACST2 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 ACST2 folds back safely to the on state as shown in Figure 18. The ACST2

recovers its blocking voltage capability after the surge and the next zero current crossing.

Such a non repetitive test can be done at least 10 times on each AC line voltage polarity.

AC LOAD

MCU

Line

Power supply

L

AC Mains

R

Rg

ACST2