1 of 13

REV: 040805

FEATURES

§ Integrated NV SRAM, Real-Time Clock,

Crystal, Power-Fail Control Circuit and

Lithium Energy Source

§ Clock Registers are Accessed Identically to

the Static RAM. These Registers are

Resident in the Eight Top RAM Locations.

§ Totally Nonvolatile with Over 10 Years of

Operation in the Absence of Power

§ BCD-Coded Year, Month, Date, Day, Hours,

Minutes, and Seconds with Leap Year

Compensation Valid Up to 2100

§ Power-Fail Write Protection Allows for

§ DS1644 Only (DIP Module)

Upward Compatible with the DS1643

Timekeeping RAM to Achieve Higher

RAM Density

Standard JEDEC Bytewide 32k x 8 Static

RAM Pinout

§ DS1644P Only (PowerCap

Surface Mountable Package for Direct

Connection to PowerCap Containing

Battery and crystal

Replaceable Battery (PowerCap)

Power-Fail Output

Pin-for-Pin Compatible with Other Densities

of DS164XP Timekeeping RAM

Underwriters Laboratory (UL) Recognized

PIN CONFIGURATIONS

ORDERING INFORMATION

PART

VOLTAGE

RANGE (V)

TEMP RANGE PIN-PACKAGE

TOP MARK

DS16440120+

5.0

0°C to +70°C

32 EDIP (0.740a)

DS1644+120

DS16440-120

5.0

0°C to +70°C

32 EDIP (0.740a)

DS1644-120

DS1644P120+

5.0

0°C to +70°C

34 PowerCap*

DS1644P+120

DS1644P-120

5.0

0°C to +70°C

34 PowerCap*

DS1644P-120

*DS9034-PCX, DS9034I-PCX, DS9034-PCX+ required (must be ordered separately).

A “+" indicates a lead-free product. The top mark will include a “+" symbol on lead-free devices.

1

NC

2

3

NC

NC

PFO

WE

OE

CE

DQ7

DQ6

DQ5

DQ4

DQ3

DQ2

DQ1

DQ0

GND

4

5

6

7

8

9

10

11

12

13

14

15

16

17

NC

A14

33

32

31

30

29

28

27

26

25

24

23

22

21

20

19

18

A13

A12

A11

A10

A9

A8

A7

A6

A5

A4

A3

A2

A1

A0

34

NC

X2

34-Pin PowerCap Module Board

(Uses DS9034PCX PowerCap)

15

13

27

28-Pin Encapsulated Package

(720-mil Extended)

A7

A5

A3

A2

A1

A0

DQ0

DQ1

GND

DQ2

WE

A13

A8

A9

A11

OE

A10

CE

DQ7

DQ6

DQ5

DQ3

DQ4

1

2

3

4

5

6

7

8

9

10

11

12

14

28

26

25

24

23

22

21

20

19

18

17

16

A12

A6

A4

A14

DS1644/DS1644P

Nonvolatile Timekeeping RAM

www.maxim-ic.com

PowerCap is a registered trademark of Dallas Semiconductor.