MAXIM DS1220AB, DS1220AD User Manual

CE

WE

OE

DS1220AB/AD

19-5580; Rev 10/10

www.maxim-ic.com

14

VCC

1 2 3 4 5 6 7

8 9 10

11

12

13

24

15

23

22

21

20

19

18

17

16

A7 A5 A3

A2

A1

A0

DQ0

DQ1

GND

DQ2 A6

A4

A8

A9

OE

A10

CE

DQ7

DQ6

DQ5

DQ3

DQ4

FEATURES

 10 years minimum data r etent ion in the

absence of external power

 Data is automatically pro tected during power

loss

 Directly replaces 2k x 8 volatile static RAM

or EE P R O M

 Unlimited write c ycles
 Low-power CMOS
 JEDEC standard 24-pin DIP packag e
 Read and write access times of 100 ns
 Lithium energy sour ce is electrically

disconnected to retain freshness until power
is applied for the first time

 Full ±10% VCC operating range (DS1220AD)
 Optional ±5% VCC operating range

(DS1220AB)

 Optional industrial temperature range of

-40°C to +85°C, designated IND

16k Nonvolatile SRAM

PIN ASSIGNMENT

24-Pin ENCAPSULATED PACKAGE

720-mil EXTENDED

PIN DESCRIPTION

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

- Chip Enable

- Write Enable

- Output Enable

V

- Power (+5V)

CC

GND - Ground

DESCRIPTION

The DS1220AB and DS1220AD 16k Nonvolatile SRAMs are 16,384-bit, fully st atic, nonvolatile SRAMs
organized as 2048 words by 8 bits. Each NV SRAM has a self-contained lithium energy source and
cont r ol c ircuit ry w h i ch c onsta n tly mon ito r s VCC fo r a n o ut-of-to ler a nc e c o nditio n. Whe n s uc h a c o nd ition
occurs, the lithium energy source is automatically switched on and write prot ection is uncond itionally
enabled to prevent data corruption. The NV SRAMs can be used in place of existing 2k x 8 SRAMs
directly conforming 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 o n t he number of write cycles that can be execut ed and no additional support circuitry is
required for microp ro cessor interfacing.

1 of 8

2 of 8

READ MODE

WE

CE

OE

OE

WE

WE

WE

WE

OE

OE

WE

DS1220AB/AD

The DS1220AB and DS1220AD execute a read cycle whenever

(Write Enable) is inact ive (high) and

(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 o f data is to be accessed. Valid data w ill be
available to the eight data output drivers within t

stable, providing that the CEand

access t imes are also sat isfied. If CEand

(Access T ime) after the last address input signal is

ACC

access times are not

satisfied, then data access must be measured fro m the later-oc cu rr ing s ig na l a nd t he li miting p ar a meter is
either tCO for CEor tOE for OE rather than address access.

WRITE MODE

The DS1220AB and DS1220AD execute a write cycle whenever the
after address inputs are stable. T he latt er occurring falling edge of CEor
the write cycle. Th e write cycle is terminated b y the earlier r ising edge o f CEor
must be kept va lid t hro ug ho ut the wr it e c ycle.
time ( tWR ) before a not her cycle can be in itiated. The

must return to the high state for a minimum recovery

co ntrol sig nal s hould be kept inact ive (hig h)
during write cycles to avoid bus contention. However, if the output drivers are enabled (CEand
active) then

will disable the o utputs in t

from its falling edge.

ODW

and CE signals are act ive (low)

will de ter mine t he start of

. All address inputs

DATA RETENTION MODE

The DS1220AB provides full functional capability for V

4.5V. The DS1220AD provides full functional capability for VCC greater than 4.5 volts and write protects
by 4.25V. Data is maintained in the absence of VCC without any additional support circuitry. The
nonvolatile static RAMs constantly monitor VCC. Should the supply voltage decay, the NV SRAMs
automatically write protect themselves, all inputs become “don’t care,” and all outputs become high
impedance. As VCC falls below approximately 3.0 volts, a power sw itching circu it co nnects the lithiu m
energy source to RAM to r etain data. During power-up , when VCC rises above approximately 3.0 volts,
the power sw itching c ircuit connect s external VCC to RAM and disconnects the lithium energy source.
Normal RAM operat ion can resu me after VCC exceeds 4.75 volts for the DS1220AB and 4.5 volts for the
DS1220AD.

greater t han 4.75 volts and wr ite protect s by

CC

FRESHNESS SEAL

Each DS1220 device is shipped from Dallas Semiconductor with its lithium energy source disconnected,
guaranteeing fu ll energ y capac it y. When VCC is first app lied at a level o f greater t han VTP, t he lithi um
energy source is enabled for battery backup operation.

DS1220AB/AD

3 of 8

DS1220AB Power Supply Voltage

VCC

4.75

5.0

5.25

V

DS1220AD Power Supply Voltage

VCC

4.50

5.0

5.50

V

Log ic 1

VIH

2.2 VCC

V

Log ic 0

VIL

0.0 +0.8

V

Input Leakage Current

IIL

-1.0

+1.0

µA

I/O Leakage Current

CE

-1.0

Output Current @ 2.4V

IOH

-1.0

mA

Output Current @ 0.4V

IOL

2.0

mA

CE

Standby Current

CE

VCC-0.5V

Operating Current
(Commercial)

Operating Current
(Industrial)

Write Protection Voltage
(DS1220AB)

Write Protection Voltage
Input Capacitance

CIN

5 10

pF

Input/O utput Capacitanc e

C

I/O

5 12

pF

ABSOLUTE MAXIMUM RATINGS

Voltage on Any Pin Relative to Ground -0.3V to +6.0V
Operating Temperat ur e Range
Commercial: 0°C to +70°C
Industrial: -40°C to +85°C
Storage Temperatu r e -40°C to +85°C
Lead Temperature (soldering, 10s) +260°C
Note: EDIP is wave or hand soldered 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 i mplied. Exposure to absolute m ax imum rating condition s for extended periods of tim e may affect reliability.

RECOMMENDED DC OPERATING CONDITIONS (TA: See Note 10)

PARAMETER SYMBOL MIN TYP MAX UNITS NOTES

DC ELECTRICAL CHARACTERISTICS (TA: See Note 10)

(V

= 5V ± 5% for DS1220AB)

CC

(V

= 5V ± 10% for DS1220AD)

CC

PARAMETER SYMBOL MIN TYP MAX UNITS NOTES

≥ V

≤ VCC

IH

Standby Current

= 2.2V
=

I

CCS1

I

CCS2

I

CC01

I

CCO1

IO

+1.0

µA

5.0 10.0 mA

3.0 5.0 mA
75 mA

85 mA

I

VTP 4.5 4.62 4.75 V

(DS1220AD)

VTP 4.25 4.37 4.5 V

CAPACITANCE (TA = +25°C)

PARAMETER SYMBOL MIN TYP MAX UNITS NOTES