UL
®
LSI/CSI
LS7339-7340
(631) 271-0400 FAX (631) 271-0405
June 2001
LSI Computer Systems, Inc. 1235 Walt Whitman Road, Melville, NY 11747
A3800
AUTO SHUT-OFF AC POWER SWITCH
WITH PROGRAMMABLE TIMER
FEATURES:
• Phase-Lock Loop Synchronization allows use in
Wall Switch Applications.
• PLL accuracy delivers Pure AC Power.
• Timer programmable with external R-C.
• ON input switches AC Power On and starts Timer.
• OFF input switches AC Power Off.
• 50/60Hz Line Frequency.
• +12V to +18V Operation (V
SS
- V
DD
).
• LS7339, LS7340 ( DIP) - See Figure 1
LS7339-S, LS7340-S (SOIC)
APPLICATIONS:
• AUTO SHUT-OFF TIMER for appliances such as coffee pots,
curling irons, hair curlers, electric blankets, hand dryers.
• TIMED-ON WALL SWITCH for incandescent lighting and
heat lamps.
DESCRIPTION:
The LS7339 and LS7340 are monolithic MOS integrated circuits de-
signed to turn a triac On and Off in a Power Switch for AC loads. Ac-
tivation of the ON input will always turn the triac On and start 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. Activation
of the OFF input will always turn the triac Off. The two ICs differ only
in the width of the TRIG pulse used to trigger the triac. (See I/O De-
scription, Pin 4.)
In a typical application (Figure 5), the output of the LS7339 drives the
gate of a triac in series with the load. Because the LS7339 is ac-
curately synchronized to the line frequency with a phase-lock loop, the
power delivered by the triac to the load is pure AC, allowing use with
inductive loads such as motors and transformers.
There are two states through which the LS7339 can be stepped. The
states and their corresponding operating modes, phase angles, and
delivered power levels are shown in Table 1.
TABLE 1
(See Figures 2 and 3)
OPERATING MODE
PHASE ANGLE, ø
% LOAD POWER
(1)
STATE 0
OFF
No Output
0
STATE 1
Timed-On
159˚
99
PIN ASSIGNMENT - TOP VIEW
ON
1
8
SYNC
LSI
LS7339/7340
OFF
2
7
CAP
V
DD
(-V)
3
6
OSC
TRIG
4
5
V
SS
(+V)
FIGURE 1
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 circuit automatically steps to STATE 0. If the ON input tran-
sitions to logic 0 before completion of the time-out period in
STATE 1, the Timer is restarted, beginning a new time-out
INPUT/OUTPUT DESCRIPTION:
ON (Pin 1) -
See NOTE 1
A logic 0 applied to this input for a minimum of three SYNC cy-
cles, T
S1
(50ms for 60Hz, 60ms for 50Hz), turns TRIG On and
starts a Timer. Upon completion of the Time-out, T
D1
, TRIG
turns Off. While the Time-out is in progress a new transition to
logic 0 at this input for a minimum of three SYNC Cycles, T
S1
,
restarts the Timer. This input is designed for Touch or Switch
control. (See Figure 5.)
OFF (Pin 2) -
See NOTE 2
A logic 0 applied to this input for a minimum of three SYNC cy-
cles, T
S1
, turns TRIG Off. This input is designed for Switch con-
trol only. (See Figure 5.)
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 1ms (LS7339) or 33µs
(LS7340). The LS7339 wide pulse width may be required for in-
ductive loads. The LS7340 narrow pulse width allows use of a
smaller value of C2 power supply capacitor. (See Figure 5.)
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.)
(1)
The percentage of full power delivered to a resistive load by the
triac switch.
OPERATING DESCRIPTION:
Upon power up, internal power-on-reset starts the LS7339 in STATE 0.
When the ON input transitions to logic 0, the circuit steps to STATE 1.
When the OFF input transitions to logic 0, the circuit steps to STATE 0.
When implemented as shown in the application example (Figure 5),
this is accomplished by the momentary switching of the appropriate in-
put to V
DD
through S1. STATE 1 is a quasi-stable state.
7339/40-032499-1
LSI [ LSI COMPUTER SYSTEMS ]
