Rainbow Electronics DS1220AB_AD User Manual
Rainbow Electronics Storage
E
Copyright 1995 by Dallas Semiconductor Corporation.
All Rights Reserved. For important information regarding
patents and other intellectual property rights, please refer to
Dallas Semiconductor data books.
DS1220AB/AD
16K Nonvolatile SRAM
DS1220AB/AD
100495 1/10
2
FEATURES
•
10 years minimum data retention in the absence of
external power
•
Data is automatically protected during power loss
•
Directly replaces 2K x 8 volatile static RAM or
EEPROM
•
Unlimited write cycles
•
Low-power CMOS
•
JEDEC standard 24–pin DIP package
•
Read and write access times as fast as 100 ns
•
Lithium energy source is electrically disconnected to
retain freshness until power is applied for the first time
•
Full +10% V
CC
operating range (DS1220AD)
•
Optional +5% V
CC
operating range (DS1220AB)
•
Optional industrial temperature range of -40
°
C to
+85
°
C, designated IND
PIN ASSIGNMENT
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
A8
A9
A10
DQ7
DQ6
DQ5
DQ4
DQ3
A7
A6
A5
A4
A3
A2
A1
A0
DQ0
DQ1
DQ2
GND
CE
OE
WE
V
CC
24-PIN ENCAPSULATED PACKAGE
720 MIL EXTENDED
PIN DESCRIPTION
A
0
-A
10
– Address Inputs
DQ
0
-DQ
7
– Data In/Data Out
CE
– Chip Enable
WE
– Write Enable
OE
– Output Enable
V
CC
– Power (+5V)
GND
– Ground
DESCRIPTION
The DS1220AB and DS1220AD are 16,384-bit, fully
static, nonvolatile SRAMs organized as 2048 words by
8 bits. Each NV SRAM has a self-contained lithium en-
ergy source and control circuitry which constantly moni-
tors V
CC
for an out-of-tolerance condition. When such a
condition occurs, the lithium energy source automati-
cally switches on and write protection is unconditionally
enabled to prevent data corruption. The NV SRAMs can
be used in place of existing 2K x 8 SRAMs directly con-
forming to the popular bytewide 24-pin DIP standard.
The devices also match the pinout of the 2716 EPROM
and 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 ad-
ditional support circuitry is required for microprocessor
interfacing.