TOUCH CONTROL LAMP STEP DIMMER

DESCRIPTION:

LS7237 is a monolithic, MOS integrated circuit designed

to control the brightness of an incandescent lamp. The

output of the LS7237 triggers a triac connected in series

with a lamp(See Figure 5). The lamp brightness is de-

termined by controlling the output conduction angle (triac

triggering angle) in relation to the AC line frequency (See

Figure 2).

The output conduction angle can be varied by applying a

low level pulse at the SENS input or a high level pulse at

the EXT input. When implemented as shown in Figure 5,

this is accomplished by touching the Touch Plate which

causes the lamp brightness to change in specified steps

as follows:

LEVEL

BRIGHTNESS (% Rated Wattage)

Off

0

Night Light

9

Mood Light

29

Medium

66

Maximum

99

The LS7237 can operate in one of three different modes

selected by the MODE input. The Brightness Sequences

produced by the different modes are as follows:

MODE

BRIGHTNESS SEQUENCE

0

Off-Max-Off

1

Off-Mood-Med-Max-Off

2

Off-Night-Mood-Med-Max-Off

After AC power-up, the output comes up in the OFF state.

Following that, every time the Touch Plate is touched, the

output steps to the next level of brightness. The next step

following the maximum brightness is the OFF state, in-

itiating a new sequence.

1

2

3

4

8

7

6

5

MODE

CAP

SYNC

TRIG

EXT

SENS

FIGURE 1

PIN ASSIGNMENT - TOP VIEW

7237-041100-1

April 1995

INPUT/OUTPUT DESCRIPTION:

Supply voltage positive terminal.

MODE (Pin 2)

The operating mode for the circuit is selected by con-

necting this input as follows:

MODE INPUT

SELECTED MODE

Mode 0

Mode 1

Float

Mode 2

CAP (Pin 3)

PLL filter input capacitor. A 0.047µF capacitor should be

connected to this input.

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 pulse applied to this input causes the TRIG out-

put to step to the next conduction angle in the sequence

selected by the MODE input. The change in conduction an-

gle takes place with the trailing edge of the SENS input

pulse.

FEATURES:

• PLL synchronization allows use as a Wall Switch

• Provides brightness control of an incandescent lamp

with a touch plate or mechanical switch

• Can control speed of shaded pole and universal AC motors

• Controls the "duty cycle" from 23% to 88% (conduction

angles for AC half-cycles between 45˚ and 158˚, respectively)

• Operates at 50Hz/60Hz line frequency

• Extension input for remote activation

• 8-Pin Plastic DIP , 8-Pin SOIC-See Figure 1

LSI/CSI

LSI Computer Systems, Inc. 1235 Walt Whitman Road, Melville, NY 11747

(631) 271-0400 FAX (631) 271-0405

LS7237

UL

®

A3800