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

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 brightness.

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 4). 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 the modes of the LS7232ND are explained

in Table 1 and the TRIG output conduction angle diagrams in Figure 4.

MODE

0

(LS7231)

1

(LS7232)

2

(LS7233)

DIMMING

DIRECTION

REVERSAL

(Note 3)

N/A

N/A

NO

YES

N/A

YES

N/A

N/A

YES

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

7232ND-012703-2

OUTPUT

DRIVER

DIGITAL

COMPARATOR

Ø

MEMORY

Ø

POINTER

PHASE

LOCK

LOOP

CONTROL

LOGIC

BUF

BUF

BUF

SYNC

CAP

MODE

EXT

SENS

FIGURE 2

LS7232ND BLOCK DIAGRAM

4

3

2

6

5

1

7

TRIG

(+V)

(-V)

8