memory products - Al Kossow's Bitsavers

MK48C02AI12A(K,N)-15/20/25TRUTH TABLE (MK48C02AI12A)Vec" E ~ W MODE DQVIH X X Deselect High-Z." Vee (Min) VIL VIL VIH Read DourVIL VIH VIH Read High-ZVsoDeselectsVso X X X Battery High-ZBack-upDESCRIPTIONThe MK48C02N12A is a CMOS RAM with internalpower fail support circuitry for battery backup ap-plications. The fully static RAM uses an HCMQSsix transistor cell and is organized 2K x 8. Includedin the device is a feature to conserve batteryenergy and a method of providing data security duringVee transients. A precision voltage detectorwrite-protects the RAM to prevent inadvertent lossof data when Vee falls out of toleranc~. In thl! way,all input and output pins (including E and W) become"don't care". The device permits full functionalability of the RAM for Vee above 4.7SV(MK48C02A) and 4.SV (MK48C12A). Data protectionis provided for Vee below 4.SV (MK48C02A) and4.2V (MK48C12A),and maintains data in the absenceofVee with no addi.tional support circuitryother than a primary cell. The current supplied bythe battery during data retention is for junction leakageonly (typically less thanSna) because all powerconsumingcircuitry is turned off. The low batterydrain allows use of a long life Lithium primary cell.FIGURE 2. BLOCK DIAGRAMr------------,IIIIIIII2Kx8~~--~~----_, POWERRAMI VOLTAGE SENSECMOSINT~-----I AND i>oR CELL IISWITCHINGCIRCUITRY BOK IL _______________ ...1IDQO-DQ7EViiG2110290