DS1244Y

256K NV SRAM with Phantom Clock

FEATURES

• Real time clock keeps track of hundredths of seconds, minutes, hours, days,

date of the month, months, and years

• 32K x 8 NV SRAM directly replaces volatile static RAM or EEPROM

• Embedded lithium energy cell maintains calendar operation and retains RAM data

• Watch function is transparent to RAM operation

• Month and year determine the number of days in each month; volid up to 1200

• Standard 28–pin JEDEC pinout

• Full 10% operating range

• Operating temperature range 0°C to 70°C

• Accuracy is better than ±1 minute/month @ 25°C

• Over 10 years of data retention in the absence of power

• Available in 120, 150 and 200 ns access time

DESCRIPTION

The DS1244Y 256K NV SRAM with Phantom Clock is a fully static nonvolatile RAM (organized as 32,768 words by 8 bits) with a built–in real time clock. The DS1244Y 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 garbled data in both the memory and real time clock.

The Phantom Clock provides timekeeping information including hundredths of seconds, seconds, minutes, hours, day, date, month, and year information. The date at the end of the month is automatically adjusted for months with less than 31 days, including correction for leap years. The Phantom Clock operates in either 24–hour or 12–hour format with an AM/PM indicator.

PIN ASSIGNMENT

PIN DESCRIPTION

ABSOLUTE MAXIMUM RATINGS*

Voltage on Any Pin Relative to Ground –0.3V to +7.0V

Operating Temperature 0°C to 70°C

Storage Temperature –40°C to +70°C

Soldering Temperature 260°C for 10 seconds (See Note 13)

* 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.

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