DS1644-120+ Datasheet PDF - Maxim Integrated

●The DS1644-120+ is a non-volatile Static RAM with a full function real time clock, which are both accessible in a byte-wide format. The non-volatile timekeeping RAM is functionally equivalent to any JEDEC standard 32k x 8 SRAM. The device can also be easily substituted for ROM, EPROM and EEPROM, providing read/write non-volatility and the addition of the real time clock function. The real time clock information resides in the eight uppermost RAM locations. The RTC registers contain year, month, date, day, hours, minutes and seconds data in 24-hour BCD format. Corrections for the day of the month and leap year are made automatically. The RTC clock registers are double-buffered to avoid access of incorrect data that can occur during clock update cycles. The double-buffered system also prevents time loss as the timekeeping countdown continues unabated by access to time register data.

● Integrated NV SRAM, real-time clock, crystal, power-fail control circuit and Lithium energy source

● Clock registers are accessed identically to the static RAM

● Totally non-volatile with over 10 years of operation in the absence of power

● Leap year compensation valid up to 2100

● Power-fail write protection allows for ±10% VCC power supply tolerance