TABLE 1

TOUCH TYPE

PRE-TOUCH

POST-TOUCH

PRE-TOUCH

POST-TOUCH

Ø

Ø

Ø

Ø

Off

Max

Off

Starts varying at Min

Max

Off

Max

Starts varying at Max

Intermediate

Off

Intermediate

Starts varying at

Pre-Touch brightness

Off

Memory

Off

Starts varying at

(Note 1)

Memory (Note 2)

Max

Off

Max

Starts varying at Max

Intermediate

Off

Intermediate

Starts varying at

Pre-Touch brightness

Off

Max

Off

Starts varying at Min

Max

Off

Max

Starts varying at Max

Intermediate

Off

Intermediate

Starts varying at

Pre-Touch brightness

Off

Memory

Off

Starts varying at

(Note 1)

Memory (Note 2)

Max

Off

Max

Starts varying at Max

Intermediate

Off

Intermediate

Starts varying at

Pre-Touch brightness

SYNC (Pin 4)

The AC Line Frequency is applied to this input through an

external RC circuit (See Figure 5). The Phase-Lock Loop

in the IC synchronizes all internal timings to the AC signal

at the SYNC input.

SENS (Pin 5)

A low level activates this input (See Table 1) which con-

trols the turn-on, turn-off and conduction angle Ø (See-

Figure 3) of the TRIG signal with respect to the SYNC in-

put.

EXT (Pin 6)

The EXT input is functionally identical to the SENS input

except that a high level activates this input. It is rec-

ommended that the EXT input be used instead of the

SENS input when long extension wires are employed be-

tween the IC and the Sensing Circuitry (See Figure 5 and

Figure 6) because the EXT input is less susceptible to

“Noise”.

Supply voltage negative terminal.

TRIG (Pin 8)

The TRIG output is a low level pulse occurring once every

half-cycle of the SYNC input. The conduction angle, Ø, of the

output in relation to the SYNC signal controls the lamp bright-

ness.

In continuous dimming operation (i.e. when the SENS input is

continuously held low) the TRIG conduction angle, Ø, sweeps

up and down between 41˚ and 158˚ continuously. The time vs

Ø curve is not linear (See Figure 2). Between two maxima on

this curve, there are 4 discontinuous points labeled A1, B1,

B2, A2. The discontinuities are as follows:

1. From maximum to A1. In this region, Ø is changed by

equal increments (

∆ø) for every 2 SYNC clocks.

2. From A1 to B1. In this region, the increments (

∆ø) take

place for every 4 SYNC clocks.

3. From B1 to B2. In this region Ø is held at a constant

level (

∆ø = 0).

4. From B2 to A2. Same as 2.

5. From A2 to Max. Same as 1.

The slower rate of change in ø over A1B1B2A2 region is to

accommodate for eye adjustment at lower light intensity.

The functional differences of different versions of the light dimmer ICs are explained in Table 1 and the TRIG

output conduction angle diagrams in Figure 2.

PART

NUMBER

LS7231

LS7232

LS7233

LS7234

DIMMING

DIRECTION

REVERSAL

(Note 3)

N/A

N/A

NO

YES

N/A

YES

N/A

N/A

YES

NO

N/A

NO

NOTE 1: "Memory" refers to the conduction angle, Ø which existed prior to the current off-state. First time after power-up,

the Memory value defaults to maximum conduction angle.

NOTE 2: First time after power-up, LONG touch causes intensity to vary starting at minimum conduction angle.

NOTE 3: NO = Dimming direction does not reverse from prior dimming direction.

YES = Dimming direction does reverse from prior dimming direction.

N/A = Does not apply

7231-34-033195-2