Fast transient immunity tests

AN1379

6/10

Doc ID 8317 Rev 5

The high voltage output of the burst generator is connected:

–

In the case of the “plug test”: to a 33 nF capacitor with its other terminal connected

to L, N, ground, or several of these terminals (as required in the IEC 61000-4-4

standard).

–

In the case of the “I/O test”: to six 100 pF discrete capacitors with their other

terminal connected to the four A2 (or OUT), L and N terminals (in order to simulate

the coupling aluminum sheet).

A test is carried out for each coupling mode. The minimum burst level which causes a

spurious firing, of one of the four devices, is measured. Figure 8 gives the results of these

tests.

Sensitive Triacs and ACSs with identical gate currents were compared. For a 5 mA

maximum gate current, Z0107MA Triacs and ACS102-5TA devices were used. For a 10 mA

maximum gate current, Z0109MA Triacs and ACS108-5SA / ACS402-5SB4 devices were

used. All these components are in TO92 packages except the ACS402-5SB4 which is in

DIL20 package. One can see that using one ACS array instead of several devices is an

advantage in terms of noise immunity. Indeed, the board including four ACS108 in TO92 can

sustain up to 3.7 kV and the other, including ACS402 in DIL20, can sustain up to 4 kV.

It can be noticed that the generator used can only delivers bursts up to 4.5 kV. For some

ACS108 and ACS402 devices, this has not reached the level above which they turn on.

The different capability of these devices depends on the dV/dt characteristics. The device

can switch on due to excessive dV/dt rates. For example, Figure 9 shows, that a Z0109MA

turns on after a 17 kV/µs rate, due to a 2 kV burst coupled to the line in the “plug test”

configuration. As for the maximum junction temperature, 5 mA and 10 mA sensitivity ACSs

can sustain up to 300 V/µs and 500 V/µs respectively, whereas Triacs of similar sensitivities

only withstands 20 and 50 V/µs respectively, it is obvious that choosing ACSs will improve

the burst immunity of the electronic board.

“I/O tests” have also been carried out. The difference between Triacs and ACSs is more

difficult to prove as most of the devices sustain bursts higher than the maximum capacity of

the used generator (4.5 kV). Table 1 shows the results of these trials. In fact, the higher

immunity of ACSs could be demonstrated by removing the mains filter. In this case, the

board using ACS402-5SB4 will sustain bursts in the range of 4 kV, but for Z0109MA, the

capability drops to around 3 kV.