OUTPUT

DRIVER

DIGITAL

COMPARATOR

Ø

MEMORY

Ø

POINTER

PHASE

LOCK

LOOP

CONTROL

LOGIC

BUF

BUF

BUF

BUF

SYNC

CAP

DOZE

EXT

SENS

FIGURE 4

LS7231-4 BLOCK DIAGRAM

4

3

2

6

5

1

7

TRIG

(+V)

(-V)

8

APPLICATION EXAMPLE:

A typical implementation of a lamp dimmer circuit is shown in Fig. 5. Here the brightness of the lamp is set by touch-

ing the Touch Plate . The functions of different components are as follows:

•

The 15V DC supply for the chip is provided by Z, D1, R1, C2 and C5.

•

R2 and C4 generate the filtered signal for the SYNC input for synchronizing the internal PLL with the line

frequency.

•

R3 and C7 act as a filter circuit for the electronic extension. If extensions are not used, the EXT input (Pin 6)

•

R4, R5, R6 set up the sensitivity of the SENS input. C6 provides noise filtering.

•

C3 is the filter capacitor for the internal PLL.

•

R8 provides current limiting and isolation between the chip output and the triac gate.

•

C1 and L are RF filter circuits.

In the case of momentary power failure, the circuit state remains unchanged for a period of up to 1 sec. For longer

power interruptions, the output is shut off.

ø

TRIG

SYNC

FIGURE 3. TRIG OUTPUT CONDUCTION ANGLE, Ø

7231-4 040695-5