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| DS1218 Nonvolatile Controller www.dalsemi.com FEATURES Converts CMOS RAM into nonvolatile memories Unconditionally write protects when VCC is out of tolerance Automatically switches to battery when power fail occurs Space saving 8-pin mini-DIP/8-pin 150 mil SOIC Consumes less than 100 na of battery current PIN ASSIGNMENT VCCO NC NC GND 1 2 3 4 8 7 6 5 VCCI VBAT CEO CEI PIN DESCRIPTION VCCI VCCO CEI NC CEO VBAT GND - Input +5 Volt Supply - RAM Power (VCC) Supply - Chip Enable Input - No Connection - Chip Enable Output - + Battery - Ground DESCRIPTION The DS1218 is a CMOS circuit which solves the application problems of converting CMOS RAM into nonvolatile memory. Incoming power is monitored for an out-of-tolerance condition. When such a condition is detected, the chip enable output is inhibited to accomplish write protection and the battery is switched on to supply RAM with uninterrupted power. Special circuitry uses a low-leakage CMOS process which affords precise voltage detection at extremely low battery consumption. The 8-pin miniDIP package keeps PC board real estate requirements to a minimum. By combining the DS1218 nonvolatile controller chip with a full CMOS memory and lithium batteries, 10 years of nonvolatile RAM operation can be achieved. OPERATION The DS1218 Nonvolatile Controller performs the circuit functions required to battery back-up a RAM. First, a switch is provided to direct power from the battery or VCCI supply, depending on which is greater. This switch has a voltage drop of less than 0.2V. The second function which the nonvolatile controller provides is power-fail detection. The DS1218 constantly monitors the VCC supply. When VCCI falls to 1.26 times the battery voltage, a precision comparator outputs a power-fail detect signal to the chip enable logic. The third function of write protection is accomplished by holding the chip enable output signal to within 0.2V of the VCCI or battery supply, when a power-fail condition is detected. During nominal supply conditions, the chip enable output will follow chip enable input with a maximum propagation delay of 10 ns. 1 of 4 111899 DS1218 ABSOLUTE MAXIMUM RATINGS* Voltage on Any Pin Relative to Ground Operating Temperature Storage Temperature Soldering Temperature * -0.5V to +7.0V 0C to 70C -55C to +125C 260C for 10 seconds This is a stress rating only and functional operation of the device at these or any other conditions above those indicated in the operation sections of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods of time may affect reliability. RECOMMENDED DC OPERATING CONDITIONS PARAMETER Supply Logic 1 Logic 0 Battery Supply SYMBOL VCCI VIH VIL VBAT MIN 4.5 2.0 -0.3 2.5 TYP 5.0 MAX 5.5 5.5 0.8 3.5 (0C to 70C) UNITS V V V V NOTES 1 1 1 1 3.0 DC ELECTRICAL CHARACTERISTICS PARAMETER Active Current Battery Current RAM Current (VCCO1 VCCI -0.3V) RAM Current (VCCO VCCI -0.2V) Input Leakage CEO Output @ 2.4V CEO Output @ 0.4V VCC Trip Point SYMBOL ICCI IBAT ICCO ICCO IIL IOH IOL VCCTP -1.0 -1.0 MIN (0C to 70C; VCCI = 5V 10%) TYP 2 MAX 5 100 80 UNITS mA nA mA mA +1.0 4.0 1.26XVBAT A mA mA NOTES 3 3, 4 5 70 CAPACITANCE PARAMETER Input Capacitance Output Capacitance SYMBOL CIN COUT MIN TYP MAX 5 7 (tA = 25C) UNITS pF pF NOTES AC ELECTRICAL CHARACTERISTICS PARAMETER CE Propagation Delay Recovery at Power-up VCC Slew Rate CE Pulse Width SYMBOL tPD tREC tF tCE MIN 0.2 500 (0C to 70C; VCC = 5.0V 10%) TYP 4 MAX 10 2 1.5 UNITS ns ms s s NOTES 2 6, 7 2 of 4 DS1218 TIMING DIAGRAM: POWER-UP TIMING DIAGRAM: POWER-DOWN 3 of 4 DS1218 NOTES: 1. All voltages referenced to ground. 2. Measured with a load as shown in Figure 1. 3. Outputs open. 4. Drain from battery when VCC < VBAT. 5. Maximum amount of current which can be drawn through pin 1 of the controller. 6. tCE max must be met to ensure data integrity on power loss. 7. CEO can only sustain leakage current in the battery backup mode. OUTPUT LOAD Figure 1 4 of 4 |
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