DS1225AB Datasheet, PDF (1/10 Pages) Dallas Semiconductor – 64k Nonvolatile SRAM

DS1225AB/AD
64k Nonvolatile SRAM
www.dalsemi.com
FEATURES
10 years minimum data retention in the
absence of external power
Data is automatically protected during power
loss
Directly replaces 8k x 8 volatile static RAM
or EEPROM
Unlimited write cycles
Low-power CMOS
JEDEC standard 28-pin DIP package
Read and write access times as fast as 70 ns
Lithium energy source is electrically
disconnected to retain freshness until power
is applied for the first time
Full ±10% V_CC operating range (DS1225AD)
Optional ±5% V_CC operating range
(DS1225AB)
Optional industrial temperature range of
-40°C to +85°C, designated IND
PIN ASSIGNMENT
NC 1
A12 ₂
A7 3
A6 4
A5 5
A4 6
A3 7
A2 8
A1 9
A0 10
DQ0 11
DQ1 ¹²
DQ2 ¹³
GND 14
28
VCC
27 WE
26 NC
25 A8
24
A9
23 A11
22
OE
21 A10
20
CE
19 DQ7
18
DQ6
17
DQ5
16
DQ4
15
DQ3
28-Pin ENCAPSULATED PACKAGE
720-mil EXTENDED
PIN DESCRIPTION
A0-A12
DQ0-DQ7
- Address Inputs
- Data In/Data Out
CE
- Chip Enable
WE
- Write Enable
OE
V_CC
GND
NC
- Output Enable
- Power (+5V)
- Ground
- No Connect
DESCRIPTION
The DS1225AB and DS1225AD are 65,536-bit, fully static, nonvolatile SRAMs organized as 8192 words
by 8 bits. Each NV SRAM 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
data corruption. The NV SRAMs can be used in place of existing 8k x 8 SRAMs directly conforming to
the popular bytewide 28-pin DIP standard. The devices also match the pinout of the 2764 EPROM and
the 2864 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.
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