Dallas Semiconductor DS1225Y-200-IND, DS1225Y-200, DS1225Y-170, DS1225Y-150-IND, DS1225Y-150 Datasheet

DS1225Y

64K Nonvolatile SRAM

DS1225Y

021998 1/8

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 EE-

PROM

• Unlimited write cycles

• Low-power CMOS

• JEDEC standard 28–pin DIP package

• Read and write access times as fast as 150 ns

• Full ±10% operating range

• 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

25

26

27

28NC

A12

A7
A6
A5
A4
A3
A2

A1

A0
DQ0
DQ1
DQ2

GND

VCC

NC
A8
A9
A11

A10

DQ7
DQ6
DQ5
DQ4
DQ3

WE

OE

CE

28–PIN ENCAPSULATED PACKAGE

720 MIL EXTENDED

PIN DESCRIPTION

A0–A12 – Address Inputs
DQ0–DQ7 – Data In/Data Out
CE

– Chip Enable
WE – Write Enable
OE – Output Enable
V

CC

– Power (+5V)
GND – Ground
NC – No Connect

DESCRIPTION

The DS1225Y 64K Nonvolatile SRAM is a 65,536–bit,
fully static, nonvolatile RAM 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
SRAM can be used in place of existing 8K x 8 SRAMs

directly conforming to the popular bytewide 28–pin DIP
standard. The DS1225Y also matches the pinout of the
2764 EPROM or 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.

DS1225Y

021998 2/8

READ MODE

The DS1225Y executes a read cycle whenever WE
(Write Enable) is inactive (high) and CE (Chip Enable)
and OE (Output Enable) are active (low). The unique
address specified by the 13 address inputs (A

0–A12

) de­fines which of the 8192 bytes of data is to be accessed.
Valid data will be available to the eight data output driv­ers within t

ACC

(Access Time) after the last address in­put signal is stable, providing that CE and OE access
times are also satisfied. If CE and OE access times are
not satisfied, then data access must be measured from
the later occurring signal and the limiting parameter is
either t

CO

for CE or tOE for OE rather than address ac-

cess.

WRITE MODE

The DS1225Y executes a write cycle whenever the WE
and CE signals are active (low) after address inputs are
stable. The latter occurring falling edge of CE or WE will
determine the start of the write cycle. The write cycle is
terminated by the earlier rising edge of CE

or WE. All
address inputs must be kept valid throughout the write
cycle. WE must return to the high state for a minimum

recovery time (t

WR

) before another cycle can be initi-

ated. The OE

control signal should be kept inactive
(high) during write cycles to avoid bus contention. How­ever, if the output drivers are enabled (CE and OE ac­tive) then WE will disable the outputs in t

ODW

from its

falling edge.

DATA RETENTION MODE

The DS1225Y provides full functional capability for V

CC

greater than 4.5 volts and write protects at 4.25 nominal.
Data is maintained in the absence of V

CC

without any
additional support circuitry. The DS1225Y constantly
monitors VCC. Should the supply voltage decay, the NV
SRAM automatically write protects itself, all inputs be­come “don’t care,” and all outputs become high imped­ance. As VCC falls below approximately 3.0 volts, a
power switching circuit connects the lithium energy
source to RAM to retain data. During power–up, when
V

CC

rises above approximately 3.0 volts, the power
switching circuit connects external VCC to RAM and dis­connects the lithium energy source. Normal RAM oper­ation can resume after V

CC

exceeds 4.5 volts.

DS1225Y

021998 3/8

ABSOLUTE MAXIMUM RATINGS*

Voltage on Any Pin Relative to Ground –0.3V to +7.0V
Operating Temperature 0°C to 70°C; –40°C to +85°C for IND parts
Storage Temperature –40°C to +70°C; –40°C to +85°C for IND parts
Soldering T emperature 260°C for 10 seconds

* 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.

RECOMMENDED DC OPERATING CONDITIONS (tA: See Note 10)

PARAMETER SYM MIN TYP MAX UNITS NOTES

Power Supply Voltage V

CC

4.5 5.0 5.5 V

Input Logic 1 V

IH

2.2 V

CC

V

Input Logic 0 V

IL

0.0 +0.8 V

DC ELECTRICAL CHARACTERISTICS (tA: See Note 10; VCC = 5V ± 10%)

PARAMETER SYMBOL MIN TYP MAX UNITS NOTES

Input Leakage Current I

IL

–1.0 +1.0 µA

I/O Leakage Current
CE

> VIH < V

CC

I

IO

–1.0 +1.0 µA

Output Current @ 2.4V I

OH

–1.0 mA

Output Current @ 0.4V I

OL

2.0 mA

Standby Current CE = 2.2V I

CCS1

5 10 mA

Standby Current CE = VCC–0.5V I

CCS2

3 5 mA

Operating Current t

CYC

=200 ns

(Commercial)

I

CCO1

75 mA

Operating Current t

CYC

=200 ns

(Industrial)

I

CCO1

85 mA

Write Protection Voltage V

TP

4.25 V 10