TOUCH CONTROL LAMP DIMMER
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
158conduction 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.
LSI
1
2
3
4
8
7
6
5
TRIG
V
DD
(-V)
EXT
S E N S
V
SS
(+V)
D O Z E
CAP
SYNC
LS7231-34
FIGURE 1
PIN ASSIGNMENT - TOP VIEW
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 0.047F
capacitor should be connected to this input.
7231-4-120100-1
December 2000
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)
LSI/CSI
LSI Computer Systems, Inc. 1235 Walt Whitman Road, Melville, NY 11747 (631) 271-0400 FAX (631) 271-0405
LS7231-7234
UL
A3800
TABLE 1
TOUCH TYPE
SHORT (T
S1
Duration) LONG (T
S2
Duration)
PRE-TOUCH POST-TOUCH PRE-TOUCH POST-TOUCH
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 (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".
V
DD
(Pin 4)
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, , 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, , sweeps
up and down between 41 and 158 continuously. The time vs
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, is changed by
equal increments (
) for every 2 SYNC clocks.
2. From A1 to B1. In this region, the increments (
) take
place for every 4 SYNC clocks.
3. From B1 to B2. In this region is held at a constant
level (
= 0).
4. From B2 to A2. Same as 2.
5. From A2 to Max. Same as 1.
The slower rate of change in 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, 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
ABSOLUTE MAXIMUM RATINGS:
PARAMETER SYMBOL VALUE UNIT
DC Supply Voltage
V
SS
+20
V
Any Input Voltage
V
IN
V
SS
-20 to V
SS
+ 0.5
V
Operating Temperature
T
A
0 to +80
C
Storage Temperature
T
STG
-65 to +150
C
DC ELECTRICAL CHARACTERISTICS:
(T
A
= 25C, all voltages referenced to V
DD
)
PARAMETER SYMBOL
MIN
TYP MAX UNIT CONDITION
Supply Voltage V
SS
+12
+18
V -
Supply Current
I
SS
1.0
1.4
mA V
SS
= +15V,
output off
Input Voltages:
DOZE LO
V
IZL
0
V
SS
-6
V -
DOZE HI
V
IZH
V
SS
-2
V
SS
V -
SYNC LO
V
IRL
0
V
SS
-9.5
V -
SYNC HI
V
IRH
V
SS
-5.5
V
SS
V -
SENS LO
V
IOL
0
V
SS
-8
V -
SENS HI
V
IOH
V
SS
-2
V
SS
V -
EXT LO
V
IVL
0
V
SS
-8
V -
EXT HI
V
IVH
V
SS
-2
V
SS
V -
Input Current:
SYNC, SENS, EXT HI
I
IH
110
A With Series 1.5M
Resistor to
115VAC Line
SYNC, SENS, EXT LO
I
IL
100
nA -
DOZE HI
I
IH
100
nA -
DOZE LO
I
IL
100
nA -
TRIG HI Voltage
V
OH
V
SS
V -
TRIG LO Voltage
V
OL
V
SS
-8
V V
SS
= +15V
TRIG Sink Current
I
OS
25
mA V
SS
= +15V
V
OL
= V
SS
-4V
TIMING CHARACTERISTICS (See Figures 2 and 3):
All timings are based on fs = 60Hz, unless otherwise specified. 50Hz timings are 1.2 times 60Hz timings.
PARAMETER
SYMBOL
MIN TYP MAX
UNIT
SYNC Frequency
fs
40
-
70
Hz
SHORT TOUCH
T
S1
42
-
333
ms
(ON/OFF Operation)
LONG TOUCH
T
S2
342
-
infinite
ms
(Dimming Operation)
DOZE Frequency
-
-
-
500
Hz
TRIG Pulse Width
T
W
-
33
-
s
TRIG Conduction-Angle
41
-
158
degrees
(Note 1)
Period (Max to Max in
-
-
7.64
-
seconds
continuous dimming)
A1B1 = B2A2 duration
-
-
934
-
ms
B1B2 Min. intensity dwell
-
-
500
-
ms
NOTE 1.
In the circuit schematic shown in Figure 5, the SYNC input signal is delayed in phase with respect to the AC Line by
about 7. This delay reduces the conduction angle, with respect to the AC Line by 7 from the values shown above.
7231-34-041195-3
7231-4-032795-4
OFF
50
100
150
OFF
50
100
150
OFF
50
100
150
OFF
50
100
150
SENS
LS7231
LS7232
LS7233
LS7234
SHORT
LONG
T
S2
T
S1
SHORT
341ms
LONG
SHORT
LONG
S
AA
S
BA
S
AA
S
BA
S
AA
S
BA
SLOPE = S
AA
SLOPE = S
BA
A
0
A1
A
1
A
2
A
2
B
2
B
2
B
1
B
2
B
1
MEMORY
REVERSE
MEMORY
MEMORY
S
BA
= 1.4 per four SYNC CYCLES, 15 steps total for A
1
to B
1
or B
2
to A
2
S
AA
= 1.4 per two SYNC CYCLES, 68 steps total for A
0
to A
1
or A
2
to A
0
A
0
A
0
A
0
S
AA
S
AA
S
AA
S
AA
S
AA
S
AA
A
2
A
2
A
2
S
BA
S
BA
B
2
B
1
B
1
B
2
B
2
B
2
B
1
S
BA
S
BA
S
AA
S
AA
S
BA
S
BA
A
0
B
1
B
2
A
0
S
AA
A
1
A
1
A
2
A
1
B
2
MEMORY
FIGURE 2. TRIG OUTPUT CONDUCTION ANGLE, , VS SENS INPUT
OUTPUT
DRIVER
DIGITAL
COMPARATOR
MEMORY
POINTER
PHASE
LOCK
LOOP
CONTROL
LOGIC
BUF
BUF
BUF
BUF
SYNC
CAP
DOZE
EXT
SENS
V
SS
V
DD
FIGURE 4
LS7231-4 BLOCK DIAGRAM
4
3
2
6
5
1
7
TRIG
(+V)
(-V)
8
APPLICATION EXAMPLE:
A typical implementation of a lamp dimmer circuit is shown in Fig. 5. Here the brightness of the lamp is set by touch-
ing the Touch Plate . The functions of different components are as follows:
The 15V DC supply for the chip is provided by Z, D1, R1, C2 and C5.
R2 and C4 generate the filtered signal for the SYNC input for synchronizing the internal PLL with the line
frequency.
R3 and C7 act as a filter circuit for the electronic extension. If extensions are not used, the EXT input (Pin 6)
should be tied to V
DD
(Pin 7).
R4, R5, R6 set up the sensitivity of the SENS input. C6 provides noise filtering.
C3 is the filter capacitor for the internal PLL.
R8 provides current limiting and isolation between the chip output and the triac gate.
C1 and L are RF filter circuits.
In the case of momentary power failure, the circuit state remains unchanged for a period of up to 1 sec. For longer
power interruptions, the output is shut off.
TRIG
S Y N C
T
W
T
W
FIGURE 3. TRIG OUTPUT CONDUCTION ANGLE,
7231-4 040695-5
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