LSI/CSI
UL
廬
LS7237
(631) 271-0400 FAX (631) 271-0405
April 1995
LSI Computer Systems, Inc. 1235 Walt Whitman Road, Melville, NY 11747
A3800
TOUCH CONTROL LAMP STEP DIMMER
FEATURES:
鈥?PLL synchronization allows use as a Wall Switch
鈥?Provides brightness control of an incandescent lamp
with a touch plate or mechanical switch
鈥?Can control speed of shaded pole and universal AC motors
鈥?Controls the "duty cycle" from 23% to 88% (conduction
angles for AC half-cycles between 45藲 and 158藲, respectively)
鈥?Operates at 50Hz/60Hz line frequency
鈥?Extension input for remote activation
鈥?+12V to +18V DC Power Supply (V
SS -
V
DD
)
鈥?8-Pin Plastic DIP , 8-Pin SOIC-See Figure 1
PIN ASSIGNMENT - TOP VIEW
V
SS
(+V)
1
8
TRIG
LSI
MODE
2
7
V
DD
(-V)
LS7237
CAP
3
6
EXT
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
Off
Night Light
Mood Light
Medium
Maximum
BRIGHTNESS (% Rated Wattage)
0
9
29
66
99
SYNC
4
5
SENS
FIGURE 1
INPUT/OUTPUT DESCRIPTION:
V
SS
(Pin 1)
Supply voltage positive terminal.
MODE (Pin 2)
The operating mode for the circuit is selected by con-
necting this input as follows:
MODE INPUT
V
SS
V
DD
Float
SELECTED MODE
Mode 0
Mode 1
Mode 2
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
0
1
2
BRIGHTNESS SEQUENCE
Off-Max-Off
Off-Mood-Med-Max-Off
Off-Night-Mood-Med-Max-Off
CAP (Pin 3)
PLL filter input capacitor. A 0.047碌F 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.
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.
7237-041100-1
1
2
3
4
