DELAYED-OFF LIGHT SWITCH
WITH PROGRAMMABLE ON-TIMER
FEATURES:
Phase-Lock Loop Synchronization allows use in
Wall Switch Applications.
Operation automatically sequences from Timed-On
to Delayed-Off to Off.
On-Timer programmable with external R-C.
Transition from Timed-On to Delayed Off indicated
by 31% drop in Delivered Power.
Delayed-Off period denoted by Dim-to-Off operation.
(See Note 1)
Control input initiates Operating Sequence
and can override Automatic Sequencing.
50/60Hz Line Frequency.
+12V to +18V Operation (V
SS
- V
DD
).
LS7338 (DIP); LS7338-S (SOIC) - See Figure 1
NOTE 1: Dim-to-Off time is Mask Programmable. The standard
IC is fixed at 209 seconds for 60Hz. Dim-to-Off time can be pro-
grammed within a range of 6.5 to 836 seconds.
APPLICATIONS:
WALL SWITCH for incandescent lighting in garage, corridor,
staircase, child's bedroom, teenage study area.
IN-LINE SWITCH for table lamps.
DESCRIPTION:
The LS7338 is a MOS integrated circuit designed to turn a triac On
and Off in a Power Switch for Incandescent Lighting. Activation of
SENSE or SLAVE inputs turns the triac On and starts a timer. The
triac remains On for the duration of the Timer which is controlled by
an external R-C connected to the OSCILLATOR input. When Time-
out occurs, the power delivered by the triac is stepped down by 31%
and then slowly reduced to Off over a fixed period of time.
In a typical application (Figure 5), the output of the LS7338 drives
the gate of a triac in series with the load.
There are three states through which the LS7338 can be stepped.
The states and their corresponding operating mode, phase angles
and delivered power levels are shown in Table 1.
OPERATING DESCRIPTION:
Upon power up, internal power-on-reset starts the LS7338 in
STATE 0. When the SENSE input transitions to logic 0, or the
SLAVE input transitions to logic 1, the IC steps to STATE 1.
When implemented as shown in the application example (Fig-
ure 5), this is accomplished by touching the appropriate Sensor
Plate. Subsequent similar transitions at SENSE or SLAVE in-
puts cause the LS7338 to step through the sequence:
STATE 0 --> STATE 1 --> STATE 2 --> STATE 0, etc.
STATE 1 and STATE 2 are quasi-stable states. If left in STATE
1, after a time-out period determined by the frequency set at
the OSC input (See I/O Description, Pin 6), the IC automatically
steps to STATE 2. (If the OSC input is deactivated, STATE 1
becomes stable and its OPERATING MODE is denoted as On).
When the IC steps from STATE 1 to STATE 2, the output
phase angle changes from 159 to 107. This corresponds to
a delivered power reduction of 31%, which causes a reduction
of lamp brightness. This brightness change provides the user
with a positive indication that the transition from STATE 1 to
STATE 2 has occurred. The Time-out period for STATE 2 is
fixed at 209 seconds for 60Hz operation. (See Note 1.)
T
D1
= STATE 1 Time-out period.
T
D2
= STATE 2 Time-out period.
Jnauary 2003
LSI/CSI
LSI Computer Systems, Inc. 1235 Walt Whitman Road, Melville, NY 11747 (631) 271-0400 FAX (631) 271-0405
LS7338
UL
A3800
7338-012703-1
1
2
3
4
5
6
7
LSI
8
PIN ASSIGNMENT - TOP VIEW
FIGURE 1
S E N S E
SLAVE
V
DD
(-V)
TRIG
V
SS
(+V)
S Y N C
CAP
OSC
LS7338
TABLE 1
(See Figures 2 and 3)
STATE 0
STATE 1
STATE 2
OPERATING MODE
OFF
Timed-On
Delayed -Off
PHASE ANGLE,
No Output
159
107 to 41
% LOAD POWER (1)
0
99
68 to 7
During the STATE 2 Time-out, the TRIG phase angle (See
Figure 2) is ramped down from 107 to 41 in decrements of
1.4. When
reaches 41, the IC automatically steps to STATE
0, shutting the TRIG and lamp Off.
The slow Dim-to-Off in STATE 2 gives the user a continuing re-
minder that Delayed-Off is operating and provides the time and
light with which to leave the area or to recycle the Light Switch.
A new operating sequence from STATE 0 can be started only by
transitions at the SENSE and SLAVE inputs.
(1) The percentage of full power delivered to a resistive load
by the triac switch.
INPUT/OUTPUT DESCRIPTION:
SENSE (Pin 1)
A logic 0 applied to this input for a minimum of three SYNC cy-
cles, TS1 (50ms for 60Hz, 60ms for 50Hz), causes the circuit to
step to the next state in the operating sequence.
SLAVE (Pin 2)
Same description as SENSE (Pin 1) except that logic 1 replaces
logic 0. This input is designed to be used with Remote Exten-
sions (See Figure 5 and Figure 6.)
V
DD
(Pin 3)
Supply voltage negative terminal.
TRIG (Pin 4)
TRIG is a negative-going pulse occurring once every half cycle
of the SYNC input. Pulse width is 33s. Table 1 in the General
Description shows values of the TRIG phase angle for the differ-
ent states. (See Figure 2 and Figure 3.)
V
SS
(Pin 5)
Supply voltage positive terminal.
OSC (Pin 6)
An R-C network connected to this input controls the frequency of
oscillation which determines the Time-out, T
D1
, in State 1. T
D1
is
approximately 255RC. The Oscillator is active only in State 1. Chip
to chip Oscillation Tolerance is 10% for fixed value of RC. Tie Pin
6 to V
SS
if a Time-out is not desired. (See Figure 5.)
CAP (Pin 7)
The CAP input is for external component connection for the PLL fil-
ter capacitor. (See Figure 5.)
SYNC (Pin 8)
The AC Line Frequency (50/60Hz) is applied to this input. The
Phase-Lock Loop synchronizes all internal timings to the AC signal
at the SYNC input. (See Figure 5.)
7338-012703-2
ABSOLUTE MAXIMUM RATINGS:
PARAMETER SYMBOL VALUE
UNIT
DC supply voltage V
SS
- V
DD
+20
V
Any input voltage V
IN
V
SS
- 20 to V
SS
+ 0.5
V
Operating temperature
T
A
0 to +85
C
Storage temperature
T
STG
-65 to +150
C
DC ELECTRICAL CHARACTERISTICS:
(TA = 25C, all voltages referenced to V
DD
)
PARAMETER
SYMBOL
MIN
TYP
MAX
UNIT
CONDITIONS
Supply Voltage
V
SS
+12
-
+18
V
-
Supply Current
I
SS
-
1.6
2.2
mA
V
SS
= +15V,
Output off
Input Voltages
SYNC Lo
V
IRL
0
-
V
SS
- 9.5
V
-
SYNC Hi
V
IRH
V
SS
- 5.5
-
V
SS
V
-
SENSE Lo
V
IOL
0
-
V
SS
- 8
V
-
SENSE Hi
V
IOH
V
SS
- 2
-
V
SS
V
-
SLAVE Lo
V
IVL
0
-
V
SS
- 8
V
-
SLAVE Hi
V
IVH
V
SS
- 2
-
V
SS
V
-
Input Current
SYNC, SENSE &
I
IH
-
-
110
uA
With Series 1.5M
SLAVE Hi
Resistor to 115VAC
SYNC, SENSE &
SLAVE 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
TRANSIENT CHARACTERISTICS (See Fig. 2 and 3)
(All timings are based on Fs = 60Hz, unless otherwise specified.)
PARAMETER
SYMBOL
MIN
TYP
MAX
UNIT
SYNC Frequency
Fs
40
-
70
Hz
SENSE/SLAVE Sense Time
T
s1
50
-
Infinite
ms
TRIG Pulse Width
Tw
-
33
-
s
STATE 1 Time-out period
T
D1
-
255RC
-
s
STATE 2 Time-out period
T
D2
- 209
-
s
7338-012703-3
Tw
Tw
FIGURE 2. OUTPUT CONDUCTION ANGLE,
S Y N C
TRIG
S E N S E
S L A V E
T
S1
<T
D1
T
S1
T
S1
T
S1
T
D2
T
D1
<T
D2
OFF/STATE 0
OFF/ STATE 0
159/STATE 1
107/STATE 2
< 41/STATE 2
159/STATE 1
FIGURE 3. OUTPUT PHASE ANGLE
VS
SENSE AND SLAVE
OFF/STATE 0
107/STATE 2
41/STATE 2
DIGITAL
COMPARATOR
DECODE
SYNC
PHASE-ANGLE
POINTER
PHASE-
LOCK
LOOP
CONTROL
LOGIC
BUF
BUF
BUF
SYNC
CAP
S E N S E
S L A V E
V
SS
V
DD
FIGURE 4. LS7338 BLOCK DIAGRAM
TRIG
OSC/TIMER
OSC
(+V)
(-V)
DRIVER
4
8
7
1
2
6
5
3
The information included herein is believed to be
accurate and reliable. However, LSI Computer Systems,
Inc. assumes no responsibilities for inaccuracies, nor for
any infringements of patent rights of others which may
result from its use.
P
AC
MAINS
N
LOAD
C1
T1
L1
C2
R1
R2
A
B
R6
R9
C3
D1
5
6
7
8
4
3
2
1
R5
C3
C4
OUT
V
DD
SLV S E N S E
V
SS
OSC
CAP SYNC
+
L S 7 3 3 8
R4
R3
S E E N O T E 1
FIGURE 5. A TYPICAL LIGHT SWITCH APPLICATION
G
MT2
MT1
Z1
-
ELECTRONIC
EXTENSION
(Figure 6)
EXTN
P
C7
S E E N O T E
3
S E E N O T E 2
R10
S E N S O R
P L A T E
R8
C6
R7
-
+
115VAC
220VAC
115VAC
220VAC
(1) R1
270
, 1W
1k
, 2W
(1) C2
0.33F, 200V 0.22F, 400V
(2) R1
82
82
(2) C2
0.22F, 200V 0.1F, 400V
R2
1.5M
1.5M
C3
47F
47F
R3
2.7M
4.7M
C4
470pF
470pF
R4
2.7M
4.7M
C5
0.047F
0.047F
(3) R5
1M
to 5M
1M
to 5M
C6
(5)
(5)
R6
100
100
C7
0.1F, 200V
0.1F, 400V
R7
(4)
(4)
Z1
15V, 1/2W
15V, 1/2W
R8
(4)
(4)
D1
1N4148
1N4148
R9
1.5M
1.5M
L1
100H
200H
R10
150k
150k
(6) T1
Q4008L4
Q5004L4
C1
0.15F, 200V 0.15F, 400V
(1) Connection A (2) Connection B (3) Select for desired touch sensitivity
(4) 100k
(R7 + R8)
10M
(5) (R7 + R8)C6
5ms (6) Typical
All Resistors 1/4W, all Capacitors 25V unless otherwise specified
TABLE 2 .
FIGURE 5 COMPONENT FUNCTIONAL DESCRIPTION
COMPONENTS FUNCTIONAL DESCRIPTION
Z1, D1, R1, DC Power Supply.
C2, C3
R2, C4 Current limit and filter AC for SYNC input.
C1, L1 RFI filtering for AC Mains.
C5 PLL filter capacitor.
R3, R4, R5 Network sets the Touch Sensitivity
for the SENSE input.
R6 Current limiting and isolation between
I C output and Triac Gate.
R7, R8, C6 Oscillator R-C network.
Potentiometer R6 required only if providing
user adjustment of Time-out, TD1.
R9, C7 Filter for the Electronic Extension
R10 Current limiting resistor for
the Pushbutton Switch Extension.
EXTN
2K
,1/4W
IN914
S E N S O R P L A T E
2M
,1/4W
200K
,1/4W
P
MPS8599
FIGURE 6. ELECTRONIC SWITCH EXTENSION
2M
,1/4W
EXTENSIONS: (See Figure 5 and Figure 6)
All sequence functions can also be inplemented by utilizing the
SLAVE input. This can be done by either a pushbutton switch
or the electronic switch in conjunction with a sensing plate as
shown in Figure 6. When the plate is touched, a logic high level
is generated at the EXTENSION terminal for both half cycles of
the line frequency.
NOTES:
1. Use Connection A when Neutral is not available.
Use Connection B when Neutral is available.
2. C7 is used only with Electronic Extension.
R10 is used only with Pushbutton Switch.
3. Connection between Pin 2 and Pin 3 is removed
when SLAVE input is used.
4. See Table 2 for Component Functional Description
7338-012703-4
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