DS1251Y Datasheet, PDF (1/12 Pages) Dallas Semiconductor – 4096K NV SRAM with Phantom Clock

DS1251Y
DS1251Y
4096K 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
• 512K x 8 NV SRAM directly replaces volatile static
RAM or EEPROM
• Embedded lithium energy cell maintains calendar op-
eration and retains RAM data
• Watch function is transparent to RAM operation
• Month and year determine the number of days in each
month; valid up to 2100
• Standard 32–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 ns and 150 ns access time
ORDERING INFORMATION
DS1251Y–120 120 ns access
DS1251Y–150 150 ns access
PIN ASSIGNMENT
A18/RST 1
A16 2
A14 3
A12 4
A7 5
A6 6
A5 7
A4 8
A3 9
A2 10
A1 11
A0 12
DQ0 13
DQ1 14
DQ2 15
GND 16
32 V_CC
31 A15
30 A17
29 WE
28 A13
27 A8
26 A9
25 A11
24 OE
23 A10
22 CE
21 DQ7
20 DQ6
19 DQ5
18 DQ4
17 DQ3
32–PIN ENCAPSULATED PACKAGE
740 MIL FLUSH
PIN DESCRIPTION
A₀–A₁₈
CE
GND
DQ₀–DQ₇
V_CC
WE
OE
RST
– Address Inputs
– Chip Enable
– Ground
– Data In/Data Out
– Power (+5V)
– Write Enable
– Output Enable
– Reset
DESCRIPTION
The DS1251Y 4096K NV SRAM with Phantom Clock is
a fully static nonvolatile RAM (organized as 512K words
by 8 bits) with a built–in real time clock. The DS1251Y
has a self–contained lithium energy source and control
circuitry which constantly monitors V_CC 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.
ECopyright 1997 by Dallas Semiconductor Corporation.
All Rights Reserved. For important information regarding
patents and other intellectual property rights, please refer to
Dallas Semiconductor data books.
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