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.

• LS7339, LS7340 (DIP); LS7339-S, LS7340-S - See Figure 1

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 MOS integrated circuits designed to turn

a triac On and Off in a Power Switch for AC loads. Activation of the

ON input will always turn the triac On and start a Timer. The triac re-

mains On for the duration of the Timer which is controlled by an ex-

ternal 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 Description, 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)

STATE 0

STATE 1

OPERATING MODE

OFF

Timed-On

PHASE ANGLE, ø

No Output

159˚

% LOAD POWER (1)

0

99

(1) The percentage of full power delivered to a resistive load

by the triac switch.

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

January 2003

7339-012703-1

1

2

3

4

5

6

7

8

PIN ASSIGNMENT - TOP VIEW

FIGURE 1

ON

OFF

TRIG

SYNC

CAP

OSC

LSI/CSI

LSI Computer Systems, Inc. 1235 Walt Whitman Road, Melville, NY 11747 (631) 271-0400 FAX (631) 271-0405

LS7339-7340

UL

®

A3800

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-

INPUT/OUTPUT DESCRIPTION:

ON (Pin 1) - See NOTE 1

A logic 0 applied to this input for a minimum of three SYNC cy-

turns Off. While the Time-out is in progress a new transition to

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-

trol only. (See Figure 5.)

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.)

Supply voltage positive terminal.

OSC (Pin 6)

An R-C network connected to this input controls the frequency

is approximately 255RC. The Oscillator is active only in State 1.

Chip to chip Oscillation Tolerance is ±10% for fixed value of RC.