LSI/CSI
UL
®
LS7231-7234
(631) 271-0400 FAX (631) 271-0405
December 2000
LSI Computer Systems, Inc. 1235 Walt Whitman Road, Melville, NY 11747
A3800
TOUCH CONTROL LAMP DIMMER
FEATURES:
• Phase-lock loop synchronization allows use in Wall
Switch applications.
• Provides brightness control of incandescent lamps
with touch plates or mechanical switches.
• Controls the "duty cycle" from 23% to 88%
(conduction angles for AC half-cycles between 41˚
and 158˚, respectively.)
• Operates at 50Hz/60Hz line frequency.
• Extension input for remote activation.
• Input for slow dimming.
• +12V to +18V DC Power Supply voltage. (V
SS
- V
DD
)
• LS7231 to LS7234 (DIP) - See Figure 1
LS7231-S to LS7234-S (SOIC)
DESCRIPTION:
LS7231 through LS7234 are a series of monolithic, MOS
integrated circuits designed for the control of brightness of
incandescent lamps. The outputs of these ICs control the
brightness of a lamp by controlling the firing angle of a
triac connected in series with the lamp. All internal timings
are synchronized with the line frequency by means of a
built-in phase-lock loop circuit. The output occurs once
every half-cycle of the line frequency. Within the half-
cycle, the output can be positioned anywhere between
158˚conduction angle for maximum brightness and 41˚
conduction angle for minimum brightness in relation to the
AC line frequency. The positioning of the output is con-
trolled by applying a low level at the SENS input or a high
level at the EXT input.
These functions may be implemented with very few inter-
face components, as shown in Figure 5. When imple-
mented in this manner, touching of the Touch Plate caus-
es the lamp brightness to change as follows:
1. If the Touch Plate is touched momentarily (42ms to
333ms), the lamp is:
a) turned off if it was on,
b) turned on if it was off.
The brightness resulting is either full brightness or
depending on the circuit type, a previous brightness
stored in the IC memory.
2. If the Touch Plate is touched for a prolonged time
(more than 342ms) the light intensity changes slowly.
As long as the touch is maintained, the change con-
tinues; the direction of change reverses whenever the
maximum or minimum brightness is reached.
PIN ASSIGNMENT - TOP VIEW
LSI
V
SS
(+V)
DOZE
1
2
8
TRIG
V
DD
(-V)
7
LS7231-34
CAP
SYNC
3
4
6
5
EXT
SENS
FIGURE 1
The IC also provides an input for slow dimming. By
applying a slow clock to this input, the lamp can be
dimmed slowly until total turn off occurs. This fea-
ture can be useful at bedtime in a child’s room.
INPUT/OUTPUT DESCRIPTION:
V
SS
(Pin 1)
Supply voltage positive terminal.
DOZE
(Pin 2)
A clock applied to this input causes the brightness to de-
crease in equal increments with each negative transition
of the clock. Eventually, when the lamp turns off, this in-
put has no further effect. The lamp can be turned on
again by activating either the SENS input or the EXT in-
put. For the transition from maximum brightness to off, a
total of 83 clock pulses are needed at the DOZE input.
When either the SENS or the EXT input is active, the
DOZE input is disabled. (See Figure 7)
CAP
(Pin 3)
The CAP input is for the PLL filter capacitor. A 0.047µF
capacitor should be connected to this input.
7231-4-120100-1
LSI [ LSI COMPUTER SYSTEMS ]
