《智能非易失性存储器ds1213b》由会员分享，可在线阅读，更多相关《智能非易失性存储器ds1213b（7页珍藏版）》请在金锄头文库上搜索。
1、 1 of 7040601FEATURES ? Accepts standard 2K x 8 or 8K x 8 CMOS static RAMs ? Embedded lithium energy cell retains RAM data ? Self-contained circuitry safeguards data ? Data retention time is greater than 10 years with proper RAM selection ? IC socket permits upgrading from 2K x 8 to 8K RAM ? Proven
2、gas-tight socket contacts ? Operating temperature range 0C to 70CPIN ASSIGNMENTPIN DESCRIPTIONCE- Conditioned Chip Enable VCC - Switched VCC GND - Ground All pins pass through except 20, 26 and 28.DESCRIPTION The DS1213B SmartSocket is a 28-pin, 600 mil DIP socket with a built-in CMOS controller cir
3、cuit and an embedded lithium energy source. It accepts either 24-pin 2K x 8 (lower-justified) or 28-pin 8K x 8 JEDEC bytewide CMOS static RAM. When the socket is mated with a CMOS RAM, it provides a complete solution to problems associated with memory volatility. The Smart-Socket monitors incoming V
4、CC for an out-of-tolerance condition. When such a condition occurs, the internal lithium energy source is automatically switched on and write protection is unconditionally enabled to prevent data corruption.Using the SmartSocket saves printed circuit board space since the SRAM/SmartSocket combinatio
5、n occupies no more area than the SRAM alone. The SmartSocket modifies only pins 20, 26 and 28, to nonvolatize the RAM. All other pins are passed straight through.DS1213B SmartSocket 16k/28-Pin Intelligent Socket26 VCC31 279864 51012111328 VCC 272220 CE212325 241917181615GND 14DS1213B2 of 7OPERATION
6、The DS1213B SmartSocket performs five circuit functions required to battery back up a CMOS memory. The first function involves switching between the battery and the VCC supply, depending on which is greater. The switch has a voltage drop of less than 0.2 volts.The second function is power-fail detec
7、tion. The DS1213B constantly monitors the VCC supply. When VCC falls below 4.75 volts, a precision comparator detects the condition and inhibits the RAM chip enable.The third function, write protection, is accomplished by holding the RAM chip enable signal to within 0.2 volts of VCC or the battery s
8、upply whichever is greater. If the incoming chip enable signal is active at the time power fail detection occurs, write protection is delayed until after the current memory cycle is complete to avoid corruption of data. Power fail detection occurs in the range of 4.75 to 4.5 volts. During nominal po
9、wer supply conditions the chip enable signal will be passed through from the socket pin to the socket contact with a maximum propagation delay of 20 ns.The fourth function the DS1213B performs is to check battery status to warn of potential data loss. Each time that VCC power is restored to the Smar
10、tSocket the battery voltage is checked with a precision comparator. If the battery supply is less than 2.0 volts, the second memory access to the SmartSocket is inhibited. Battery status can, therefore, be determined by a three-step process. First, a read cycle is performed to any location in the me
11、mory, in order to save the contents of that location. A subsequent write cycle can then be executed to the same memory location, altering the data. If the next read cycle fails to verify the written data, then the battery voltage is less than 2.0V and data is in danger of being corrupted.The fifth f
12、unction the SmartSocket provides is battery redundancy. In many applications, data integrity is paramount. In these applications it is desirable to use two batteries to ensure reliability. The DS1213B SmartSocket provides two batteries and an internal isolation switch to select between them. During
13、battery back up, the battery with the highest voltage is selected for use. If one battery fails, the other automatically takes over. The switch between batteries is transparent to the user. A battery status warning will occur if both batteries are less than 2.0 volts. Each of the two internal lithiu
14、m cells has a 45 mAh capacity.NOTE: As shipped from Dallas Semiconductor, battery voltage cannot be measured on the VCC socket contact. Only after VCC has been applied to the device for the first time and then removed will the battery voltage be present on socket contacts 28, 26 and 20.DS1213B3 of 7
15、ABSOLUTE MAXIMUM RATINGS* Voltage on Any Pin Relative to Ground -0.3V to +7.0V Operating Temperature 0C to 70C Storage Temperature -40C to +70C Soldering Temperature See J-STD-020A Specification This is a stress rating only and functional operation of the device at these or any other conditions abov
16、e 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 (0 C to 70 C) PARAMETERSYMBOLMINTYPMAXUNITSNOTES PIN 26 L, PIN 28 L Supply VoltageVCC4.755.05.5V1,3Logic 1 PIN 20 LVIH2.2VCC +0.3V1,3 Logic 0 PIN 20 LVIL-0.3+0.8V1,3DC ELECTRICAL CHARACTERISTICS (0 C to 70 C; V
