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
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
TABLE 1
TOUCH TYPE
SHORT (T
S1
Duration)
PRE-TOUCH
Ø
Off
Max
Intermediate
POST-TOUCH
Ø
Max
Off
Off
LONG (T
S2
Duration)
PRE-TOUCH
Ø
Off
Max
Intermediate
POST-TOUCH
Ø
Starts varying at Min
Starts varying at Max
Starts varying at
Pre-Touch brightness
Starts varying at
Memory (Note 2)
Starts varying at Max
Starts varying at
Pre-Touch brightness
Starts varying at Min
Starts varying at Max
Starts varying at
Pre-Touch brightness
Starts varying at
Memory (Note 2)
Starts varying at Max
Starts varying at
Pre-Touch brightness
DIMMING
DIRECTION
REVERSAL
(Note 3)
LS7231
N/A
N/A
NO
LS7232
Off
Max
Intermediate
Memory
(Note 1)
Off
Off
Off
Max
Intermediate
YES
N/A
YES
LS7233
Off
Max
Intermediate
Max
Off
Off
Off
Max
Intermediate
N/A
N/A
YES
LS7234
Off
Max
Intermediate
Memory
(Note 1)
Off
Off
Off
Max
Intermediate
NO
N/A
NO
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
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 Ø (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.
7231-34-033195-2
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 bright-
ness.
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 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, 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.
ABSOLUTE MAXIMUM RATINGS:
PARAMETER
SYMBOL
DC Supply Voltage
V
SS
Any Input Voltage
V
IN
Operating Temperature
T
A
Storage Temperature
T
STG
DC ELECTRICAL CHARACTERISTICS:
(T
A
= 25˚C, all voltages referenced to V
DD
)
PARAMETER
Supply Voltage
Supply Current
Input Voltages:
DOZE
LO
DOZE
HI
SYNC
LO
SYNC
HI
SENS
LO
SENS
HI
EXT
LO
EXT
HI
Input Current:
SYNC, SENS, EXT
HI
SYMBOL
V
SS
I
SS
VALUE
+20
V
SS
-20 to V
SS
+ 0.5
0 to +80
-65 to +150
UNIT
V
V
˚C
˚C
MIN
+12
–
TYP
–
1.0
MAX
+18
1.4
UNIT
V
mA
CONDITION
-
V
SS
= +15V,
output off
-
-
-
-
-
-
-
-
V
IZL
V
IZH
V
IRL
V
IRH
V
IOL
V
IOH
V
IVL
V
IVH
0
V
SS
-2
0
V
SS
-5.5
0
V
SS
-2
0
V
SS
-2
–
–
–
–
–
–
–
–
V
SS
-6
V
SS
V
SS
-9.5
V
SS
V
SS
-8
V
SS
V
SS
-8
V
SS
V
V
V
V
V
V
V
V
I
IH
–
–
110
µA
SYNC, SENS, EXT
LO
DOZE
HI
DOZE
LO
TRIG
HI Voltage
TRIG
LO Voltage
TRIG
Sink Current
I
IL
I
IH
I
IL
V
OH
V
OL
I
OS
–
–
–
–
–
25
–
–
–
V
SS
V
SS
-8
–
100
100
100
–
–
–
nA
nA
nA
V
V
mA
With Series 1.5MΩ
Resistor to
115VAC Line
-
-
-
-
V
SS
= +15V
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
-
µs
TRIG
Conduction-Angle
Ø
41
-
158
degrees
(Note 1)
Ø
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, Ø with respect to the AC Line by 7° from the values shown above.
7231-34-041195-3
T
S1
SENS
T
S2
LS7231
SHORT
341ms
A
0
LONG
SHORT
LONG
SHORT
LONG
150°
100°
50°
OFF
LS7232
150°
100°
50°
OFF
LS7233
A
0
150°
100°
50°
OFF
S
BA
LS7234
150°
100°
50°
OFF
S
AA
A
0
A
1
A
2
A
0
MEMORY
S
BA
B
1
B
2
S
AA
S
AA
A
1
S
BA
B
1
B
1
B
2
MEMORY
S
BA
A
2
B
2
S
AA
A
1
S
BA
B
1
B
2
A
2
S
AA
REVERSE
S
BA
B
2
S
AA
S
AA
B
1
B
2
A
0
A
1
S
BA
A
2
A
0
MEMORY
MEMORY
S
AA
S
AA
S
AA
B
2
S
BA
A
2
SLOPE = S
AA
A1
SLOPE = S
BA
B
1
B
2
S
AA
A
2
S
AA
B
2
S
BA
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
FIGURE 2. TRIG OUTPUT CONDUCTION ANGLE, Ø, VS SENS INPUT
7231-4-032795-4
SYNC
ø
TRIG
T
W
T
W
FIGURE 3. TRIG OUTPUT CONDUCTION ANGLE, Ø
SYNC
CAP
DOZE
4
3
2
BUF
PHASE
LOCK
LOOP
Ø
MEMORY
BUF
DIGITAL
COMPARATOR
OUTPUT
DRIVER
8
TRIG
EXT
6
BUF
CONTROL
LOGIC
Ø
POINTER
SENS
5
BUF
V
SS
V
DD
1
7
(+V)
(-V)
FIGURE 4
LS7231-4 BLOCK DIAGRAM
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.
7231-4 040695-5
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