SEE NOTE 2

(CONVENIENCE DELAY)

FROM

IGNITION

SWITCH

C (See Note 1)

+12V

SENSE IN

VSS

UNSELECTED

KEYS (RESET)

LOCK IN

LOCK

CONVENIENCE

DELAY

SAVE IN

SAVE

STATUS

LOCK

STATUS

GREEN LED (SAVE INDICATIOR)

RED LED (LOCK INDICATOR)

C1 (See Note 2)

RELAY

COIL

(UNLOCK RELAY)

+12V

.05

µF,25V

+12V

FIGURE 5. TYPICAL ANTI-THEFT DIGITAL LOCK

LS7220

.05

µF

250V

KEYPAD

1

2

3

4

5

6

7

8

9

10

11

12

13

14

Note 1: C is optional. It may be required to prevent ignition noise from

generating a false reset. (Typical values range from 0.1µF to 0.47µF)

Note 2: See Figure 2 to select C1 value for desired Convenience Delay Time.

If Convenience Delay is not desired, wire Keypad to +12V instead of

CONVENIENCE DELAY and eliminate C1.

To

Starter

Solenoid

or

Starter

Motor

or

Hood Lock

NC

NO

+12V

-

+

A typical automotive anti-theft digital lock circuit is shown in Figure 5.

When the Ignition Switch is turned on the SENSE input (Pin 1) goes high

and the circuit is ready to accept the unlocking input sequence at I1, I2, I3

and I4 (Pins 3, 4, 5 and 6, respectively). If the keys associated with these

inputs are depressed exactly in sequence, the LOCK output (Pin 13) turns

ON and the Unlock Relay is energized. This state is indicated by the OFF

condition of the LOCK STATUS output (Pin 8) which turns the red LED

OFF (indicates unlock condition). If the keys are depressed in any se-

quence other than as described above, the internal sequential detector re-

sets and the entire sequence must be repeated (See Figure 4).

UNSELECTED

KEYS

CONVENIENCE

DELAY

+12V

-

+

C1 (See Note 1)

LS7220

1

2

3

4

5

6

7

8

9

10

11

12

13

14

TO

LOCK CONTROL

CIRCUIT

NOTE 1:

C1 value determines the

Combination Entry Time and

duration of Momentary LOCK

Output (See Figure 4). Select

C1 value from Figure 2. Code

shown is 4179.

See Note 1

See

Note 1

0

1

2

3

4

5

6

7

8

9

FIGURE 6. DIGITAL LOCK WITH MOMENTARY OUTPUT

LOCK

KEYPAD

+12V

In order to save the ON condition of the LOCK output before the ignition switch

is turned Off (i.e., when the SENSE input becomes low) the key associated with

the SAVE input (Pin 11) has to be depressed. The "SAVE" status is indicated

by a high at the SAVE STATUS output (Pin 10), which turns the green LED On.

If the ignition switch is turned Off when the green LED is On, all the output stat-

us are preserved in the internal memory, so that when the ignition switch is

turned on again there is no need to go through the input sequence again. This

feature could be used for valet parking and garage service.

Status saving may be cancelled by depressing the LOCK input key followed by

turning the ignition switch Off for a time greater than the CONVENIENCE

DELAY (See Figure 2). This also turns OFF the LOCK output.

7220-012703-4