LS7220-S, LS7220

The LS7220 is a MOS digital lock circuit. When wired to a ten-digit keypad, the circuit will recognize one four-digit combination out of a possible 5040 combinations. The LS7220 is configured with the features required for an automotive ignition anti-theft digital lock. These features include SENSE input which enables the IC, Save Memory for valet parking, Convenience Delay to maintain the unlock condition for short term interruptions of the SENSE input and the SAVE STATUS and LOCK STATUS outputs which can be used for direct drive of LED indicators.

When the SENSE input goes high, the LS7220 is enabled. The LOCK STATUS output turns on and the SAVE STATUS and LOCK outputs remain off. When the programmed four-digit combination is entered from the keypad, in proper sequence, LOCK turns on and LOCK STATUS turns off. If the SENSE input is interrupted for a period of time less than the Convenience Delay, the operation of the LS7220 is unaffected. A momentary high at the SAVE input sets the Save Memory and causes the LS7220 to save an unlock condition (Sequential Memory is set) for any time duration interruption of the SENSE input (i.e., valet parking). The SAVE STATUS output turns on when the Save Memory is set. The LOCK input is used to reset the Save Memory and return the LS7220 to normal operation.