LS7220

LSI/CSI LS7220 U® L LSI Computer Systems, Inc. 1235 Walt Whitman Road, Melville, NY 11747 (631) 271-0400 FAX (631) 271-0405 A3800 DIGITAL LOCK FOR AUTOMOTIVE IGNITIONS January 2003 FEATURES: 5040 Four-Digit Combinations (for a 10 digit Keypad) Combinations are Hard-Wire Programmed Sense Input Enables Operation Save Memory Feature for Valet Parking Convenience Delay Controlled by External Capacitor Static or Momentary Lock Control Output Save Memory and Lock Status Outputs +5V to +18V Operation (Vss - VDD) LS7220 (DIP), LS7220-S (SOIC) - See Figure 1 DESCRIPTION: 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 (See Figure 5). These features include Sense input which enables the IC, Save Memory for Valet Parking, Convenience Delay to maintain Unlock condition for short term interruptions of the Sense input and Save Status and Lock Status outputs which can be used for direct drive of LED indicators. LS 7220 LSI PIN ASSIGNMENT - TOP VIEW SENSE IN 1 14 V SS (+V) UNSELECTED KEYS 2 (RESET) I1 3 13 LOCK OUT 12 CONVENIENCE DELAY SELECTED KEYS (IN SEQUENCE) I2 4 I3 5 I4 6 11 SAVE IN 10 SAVE STATUS OUT 9 VDD (-V) LOCK IN 7 FIGURE 1. 8 LOCK STATUS OUT UNSELECTED KEYS (RESET) INPUT (Pin 2) A high at this input resets the Sequential De...