||This product is Not Recommended for New Designs. Some versions may be
No Longer Available or being discontinued and subject to Last Time
Buy, after which new orders can not be placed. See Ordering
Information for details.
|Replacement units for existing systems are still available. Do not substitute product types.
1) Write protection voltage (VTP) on the DS1220Y and DS1225Y are determined by an internal voltage-divider circuit (~1.26 x VBAT). As the internal battery in the module degrades, the corresponding VTP also degrades, resulting in a change in the response of the module to system power loss. The AB/AD versions have a precision band-gap reference voltage that is independent of the battery.
2) Storage and handling of battery-backed products can be critical to achieve the expected 10 years of potential data retention from a new module. The DS1220Y and DS1225Y do not contain the Freshness Seal circuitry, which means the 10 year warranty begins with date of manufacture, as opposed to the date of customer's first use on AB/AD versions.
The DS1220Y 16k Nonvolatile SRAM is a 16,384-bit, fully static, nonvolatile RAM organized as 2048 words by 8 bits. Each NV SRAM has a self-contained lithium energy source and control circuitry which constantly monitors VCC for an out-of-tolerance condition. When such a condition occurs, the lithium energy source is automatically switched on and write protection is unconditionally enabled to prevent data corruption. The NV SRAM can be used in place of existing 2k x 8 SRAMs directly conforming to the popular bytewide 24-pin DIP standard. The DS1220Y also matches the pinout of the 2716 EPROM or the 2816 EEPROM, allowing direct substitution while enhancing performance. There is no limit on the number of write cycles that can be executed and no additional support circuitry is required for microprocessor interfacing.