AN442 APPLICATION NOTE

2/5

Due to the low output current of the microcontroller, the triac had to be very sensitive and consequently

was not able to withstand for example the static dv/dt, and the commutation.

NEW ST SOLUTION

Two parameters have been improved:

– The sensitivity of the triacs.

– The output capability of the microcontrollers in terms of sunk current.

A microcontroller is now able to drive one standard triac or several sensitive triacs, without buffer transis-

tors (see Figure 3).

Figure 3. An easy connection!

Table 1 shows the output capability of a range of controllers and the sensitivity of the triacs.

Table 1. Triac and microcontroller characteristics

MICROCONTROLLERS &

OUTPUT CAPABILITIES

TRIAC

SENSITIVITY

GATE

PARAMETERS

CONNECTION

ST621x SERIES

ST622x SERIES

at

T & TW SERIES

Tx05 SERIES

at

1 PORT/TRIAC

S & SW SERIES

Tx10 SERIES

at

1 PORT/TRIAC

C SERIES

at

2 PORTS

IN PARALLEL/TRIAC

CW SERIES

at

3 PORTS

IN PARALLEL/TRIAC

B & BW SERIES

at

4 PORTS

IN PARALLEL/TRIAC

LINE

G

A2

A1

0V

ST

µC

ST

TRIAC