Meaning of Snubberless Triac

In ST's website (https://www.st.com/internet/analog/subclass/124.jsp) BTA24 is stated as Snubberless Triac where BTA40 is marked as standard Triac. Why?

As per the datasheet -
BTA24: dV/dt=500V/us, dI/dt=13A/us
BTA40: dV/dt=500V/us, dI/dt=20A/us

So, it seems that BTA40 is slightly stronger than BTA24 in terms of dI/dt sustain capability.

This application note on the ST web site describes their Snubberless Triacs:

Thomson Semiconductors were the first to market a three-quadrant TRIAC as the Alternators, later after the consolidation of Thomson Semiconductors into STMicroelectronics, the Alternators were marketed under the trademark Snubberless.

The term Snubberless when used in conjunction with TRAIC was trademarked by STMicroelectronics and therefore limited its use in reference to Alternators/TRIACs to STMicroelectronics manufactured Alternistors (three-quadrant TRIACs).

While there are now other manufacturers of three-quadrant TRIAC and although they cannot be marketed as Snubberless TRIACs, their common design enhancements do offer many of the features which reduce the need of a Snubber Circuit in some applications.

For example, NXP Semiconductors refers to these three-quadrant devices as High commutation or Hi-Com TRIACs, some other manufacturers still use the term Alternistors.

However, stating categorically they don't require a Snubber Circuit would be incorrect as pointed in the appnote provide in the above reply:

Reference: , Section: IS IT ALWAYS POSSIBLE TO REMOVE THE SNUBBER CIRCUIT?, Page 4

IS IT ALWAYS POSSIBLE TO REMOVE THE
SNUBBER CIRCUIT ?

The answer is not in the affirmative because
sometimes it has other functions :

improvement of the triac immunity against transients
in the off state ;

compensation of latching current at turn on (not
dealt in this paper).

Switching on and voltage perturbations can
provoke overvoltages and fast voltage variations
across the triac :

this one could break over when the overvoltages
are higher than its repetitive peak off state voltage,
VDRM;

due to the junction capacitance fast voltage variations
create a gate current and could trigger the
triac; the device limit is the rate of rise of the offstate
voltage, dV/dt.


The snubber circuit can improve the triac behavior
in off-state. But its efficiency is linked to the values
of series inductance L at the oscillation frequency
of perturbations (typically higher than 100 kHz).

We could add a saturable inductor in series with
the triac when L is too low: particularly this is the
case of resistive load.

Click to expand...

A three-quadrant TRIAC simply reduces the requirement for the implementation of a Snubber Circuit, however they do not alleviate the requirement of a Snubber Circuit in all applications.


BigDog

As per the datasheet

BTA24 is Snubberless TRIAC. As per the datasheet, BTA40 is also be snumberless. Am I correct? or any other rating (other than dV/dt and dI/dt) is required to snuberless considerstion?

BTA24: dV/dt=500V/us, dI/dt=13A/us
BTA40: dV/dt=500V/us, dI/dt=20A/us