LSI/CSI
UL
®
LS7338
(631) 271-0400 FAX (631) 271-0405
LSI Computer Systems, Inc. 1235 Walt Whitman Road, Melville, NY 11747
A3800
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 monolithic MOS integrated circuit designed to turn a
triac On and Off in a Power Switch for Incandescent Lighting. Ac-
tivation 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.
(See Figures 2 and 3)
OPERATING MODE
PHASE ANGLE, ø
% LOAD POWER
(1)
TABLE 1
STATE 0
STATE 1
OFF
No Output
0
Timed-On
159˚
99
STATE 2
Delayed -Off
107˚ to 41˚
68 to 7
PIN ASSIGNMENT - TOP VIEW
June 2001
SENSE
1
8
SYNC
LSI
SLAVE
2
7
CAP
LS7338
V
DD
(-V)
3
6
OSC
TRIG
4
5
V
SS
(+V)
FIGURE 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 ø 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.
During the STATE 2 Time-out, the TRIG phase angle ø (See
Figure 2) is ramped down from 107˚ to 41˚ in decrements of
1.4˚. When
ø
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.
7338-062001-1
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 33µs. Table 1 in the General
Description shows values of the TRIG phase angle for the differ-
ent states. (See Figure 2 and Figure 3.)
ABSOLUTE MAXIMUM RATINGS:
PARAMETER
DC supply voltage
Any input voltage
Operating temperature
Storage temperature
SYMBOL
V
SS
- V
DD
V
IN
T
A
T
STG
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.)
VALUE
+20
V
SS
-20 to V
SS
+ .5
0 to +85
-65 to +150
UNIT
V
V
°C
°C
DC ELECTRICAL CHARACTERISTICS:
(TA = 25°C, all voltages referenced to V
DD
)
PARAMETER
Supply Voltage
Supply Current
SYMBOL
V
SS
I
SS
MIN
+12
-
TYP
-
1.6
MAX
+18
2.2
UNIT
V
mA
CONDITIONS
-
V
SS
= +15V,
Output off
Input Voltages
SYNC Lo
SYNC Hi
SENSE Lo
SENSE Hi
SLAVE Lo
SLAVE Hi
Input Current
SYNC, SENSE &
SLAVE Hi
SYNC, SENSE &
SLAVE Lo
TRIG Hi Voltage
TRIG Lo Voltage
TRIG Sink Current
V
IRL
V
IRH
V
IOL
V
IOH
V
IVL
V
IVH
0
V
SS
-5.5
0
V
SS
-2
0
V
SS
-2
-
-
-
-
-
-
V
SS
-9.5
V
SS
V
SS
-8
V
SS
V
SS
-8
V
SS
V
V
V
V
V
V
-
-
-
-
-
-
I
IH
-
-
110
uA
With Series 1.5MΩ
Resistor to 115VAC
I
IL
V
OH
V
OL
I
OS
-
-
-
25
-
V
SS
V
SS
-8
-
100
-
-
-
nA
V
V
mA
-
-
V
SS
= +15V
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
SYNC Frequency
SENSE/SLAVE Sense Time
TRIG Pulse Width
STATE 1 Time-out period
STATE 2 Time-out period
SYMBOL
Fs
T
s1
Tw
T
D1
T
D2
MIN
40
50
-
-
-
TYP
-
-
33
255RC
209
MAX
70
Infinite
-
-
-
UNIT
Hz
ms
µs
s
s
7338-112497-2
FIGURE 5. A TYPICAL LIGHT SWITCH APPLICATION
SEE NOTE 2
P
G
MT1
P
R10
EXTN
R6
+
Z1
C7
R9
T1
MT2
-
C3
SEE NOTE
3
R4
4
R7
3
2
1
OUT V
DD
SLV S E N S E
LS7338
V
SS
OSC CAP SYNC
5
6
7
8
C3
C4
R5
R3
ELECTRONIC
EXTENSION
(Figure 6)
AC
MAINS
L1
C1
D1
C2
SENSOR
PLATE
R1
R2
A
B
LOAD
N
SEE NOTE 1
R8
-
C6
+
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 Mechanical Switch.
3.
Connection between Pin 2 and Pin 3 is removed when SLAVE input is used.
4.
See Table 2 for Component Functional Description
(1)
R1
(2)
R1
R2
R3
R4
(3)
R5
R6
R7
R8
R9
R10
C1
115VAC
270Ω, 1W
82Ω
1.5MΩ
2.7MΩ
2.7MΩ
1MΩ to 5MΩ
100Ω
(4)
(4)
1.5MΩ
150kΩ
0.15µF, 200V
220VAC
1kΩ, 2W
(1)
82Ω
(2)
1.5MΩ
4.7MΩ
4.7MΩ
1MΩ to 5MΩ
100Ω
(4)
(4)
1.5MΩ
150kΩ
(6)
0.15µF, 400V
C2
C2
C3
C4
C5
C6
C7
Z1
D1
L1
T1
115VAC
0.33µF,200V
0.22µF,200V
47µF
470pF
.047µF
(5)
0.1µF,200V
15V, 1/2W
1N4148
100µH
Q4008L4
220VAC
0.22µF,400V
0.1µF,400V
47µF
470pF
.047µF
(5)
0.1µF,400V
15V, 1/2W
1N4148
200µH
Q5004L4
TABLE 2 . FIGURE 5 COMPONENT FUNCTIONAL DESCRIPTION
COMPONENTS
Z1, D1, R1, C2, C3
R2, C4
C1, L1
C5
R3, R4, R5
FUNCTIONAL DESCRIPTION
DC Power Supply.
Current limit and filter AC for SYNC input.
RFI filtering for AC Mains.
PLL filter capacitor.
Network sets the Touch Sensitivity
for the SENSE input.
Current limiting and isolation between
IC output and Triac Gate.
Oscillator R-C network.
Potentiometer R6 required only if providing
user adjustment of Time-out, TD1.
Filter for the Electronic Extension
Current limiting resistor for
the Mechanical Switch Extension.
(1)
Connection A
(2)
Connection B
(3)
Select for desired touch sensitivity
(4)
100kΩ
≤
(R7 + R8)
≤
10MΩ
(5)
(R7 + R8)C6
≥
5ms
(6)
Typical
All Resistors 1/4W, all Capacitors 25V unless otherwise specified
R6
R7, R8, C6
R9, C7
R10
Microcontroller MCU
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