MAXIM DS1220Y Technical data

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www.maxim-ic.com

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

§ Full ±10% operating range

§ Optional industrial temperature range of

-40°C to +85°C, designated IND

Not Recommended for New Design

DS1220

16k Nonvolatile SRAM

PIN ASSIGNMENT

PIN DESCRIPTION

A0-A10 - Address Inputs
DQ0-DQ7 - Data In/Data Out

A7
A6
A5
A4
A3

A2
A1

A0
DQ0

DQ1

DQ2

GND

1

2
3
4

5
6

7
8

9
10

11
12

24
23

22
21

20
19

18
17

16

15

14

13

VCC

8
9

OE

10
CE
DQ7
DQ6

DQ5

DQ4

DQ3

24-Pin ENCAPSULATED PACKAGE

720-mil EXTENDED

CE - Chip Enable

WE - Write Enable

OE - Output Enable

V

- Power (+5V)

CC

GND - Ground

DESCRIPTION

The DS1220Y 16k Nonvolatile SRAM is a 16,384-bit, fully static, nonvolatile RAM organized as 2048
words by 8 bits. Each NV SRAM has a self-contained lithium energy source and control circuitry which
constantly monitors V
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 2k x 8 SRAMs directly conforming to
the popular bytewide 24-pin DIP standard. The DS1220Y also matches the pinout of the 2716 EPROM or
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 additional support circuitry is required for
microprocessor interfacing.

for an out-of-tolerance condition. When such a condition occurs, the lithium

CC

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DS1220Y

READ MODE

The DS1220Y 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 11 address inputs
(A0-A10) defines which of the 2048 bytes of data is to be accessed. Valid data will be available to the
eight data output drivers within t

CE and OE access times are also satisfied. If CE and OE access times are not satisfied, then data

that

access must be measured from the later-occurring signal and the limiting parameter is either t

for OE rather than address access.

t

OE

(Access Time) after the last address input signal is stable, providing

ACC

for CE or

CO

WRITE MODE

The DS1220Y executes a write cycle whenever the WE and CE signals are active (low) after address

inputs are stable. The later-occurring falling edge of

cycle. The write cycle is terminated by the earlier rising edge of

kept valid throughout the write cycle.

) before another cycle can be initiated. The OE control signal should be kept inactive (high) during

(t

WR

WE must return to the high state for a minimum recovery time

write cycles to avoid bus contention. However, if the output drivers are enabled (

then

WE will disable the outputs in t

from its falling edge.

ODW

CE or WE will determine the start of the write

CE or WE . All address inputs must be

CE and OE active)

DATA RETENTION MODE

The DS1220Y provides full-functional capability for VCC greater than 4.5 volts and write protects at 4.25
nominal. Data is maintained in the absence of V
DS1220Y constantly monitors V

. Should the supply voltage decay, the NV SRAM automatically write

CC

protects itself, all inputs become “don’t care,” and all outputs become high-impedance. As V
below approximately 3.0 volts, a power switching circuit connects the lithium energy source to RAM to
retain data. During power-up, when V
connects external V
resume after V

CC

to RAM and disconnects the lithium energy source. Normal RAM operation can

CC

exceeds 4.5 volts.

rises above approximately 3.0 volts, the power switching circuit

CC

without any additional support circuitry. The

CC

falls

CC

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DS1220Y

ABSOLUTE MAXIMUM RATINGS*

Voltage on Any Pin Relative to Ground -0.3V to +7.0V
Operating Temperature 0
Storage Temperature -40

°C to 70°C; -40°C to +85°C for IND parts

°C to +70°C; -40°C to +85°C for IND parts

Soldering Temperature +260°C for 10 seconds
Caution: Do Not Reflow (Wave or Hand Solder Only)

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 SYMBOL MIN TYP MAX UNITS NOTES

Power Supply Voltage VCC 4.5 5.0 5.5 V
Input Logic 1 VIH 2.2 VCC V
Input Logic 0 VIL 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 IIL -1.0 +1.0
I/O Leakage Current

CE ³ V

IH

£ V

CC

I

-1.0 +1.0

IO

mA
mA

Output Current @ 2.4V IOH -1.0 mA
Output Current @ 0.4V IOL 2.0 mA

I

3.0 7.0 mA

Standby Current CE =2.2V

Standby Current CE =VCC -0.5V
Operating Current t

= 200ns

CYC

CCS1

I

2.0 4.0 mA

CCS2

I

75 mA

CCO1

(Commercial)
Operating Current t

CYC

=200ns

I

85 mA

CCO1

(Industrial)
Write Protection Voltage VTP 4.25 V

CAPACITANCE (T

A

PARAMETER SYMBOL MIN TYP MAX UNITS NOTES

Input Capacitance CIN 5 10 pF
Input/Output Capacitance C

5 12 pF

I/O

= 25°C)

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