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DS1644

Nonvolatile Timekeeping RAM

Maxim Integrated 

19-5203; Rev 4/10

DS1644/DS1644P

Nonvolatile Timekeeping RAM

www.maxim-ic.com

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

±10% VCC Power Supply Tolerance

 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 Module Board)

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

A14 1

A12 2

A7 3

A6 4

A5 5

A4 6

A3 7

A2 8

A1 9

A0 10

DQ0 11

DQ1 12

DQ2 13

GND 14

28

VCC

27

WE

26 A13

25 A8

24

A9

23 A11

22

OE

21 A10

20

CE

19 DQ7

18

DQ6

17

DQ5

16

DQ4

15

DQ3

28-Pin Encapsulated Package

(720-mil Extended)

NC

1

34

NC

NC

2

NC

3

PFO

4

VCC

WE

5

6

33

NC

32

A14

31

A13

30

A12

29

A11

OE

7

CE

DQ7

8

9

28

A10

27

A9

26

A8

DQ6

10

25

A7

DQ5

11

DQ4

12

24

A6

23

A5

DQ3

13

22

A4

DQ2

DQ1

DQ0

14

21

15

16

X1

GND

VBAT

X2

20

19

A3

A2

A1

GND

17

18

A0

34-Pin PowerCap Module Board

(Uses DS9034PCX PowerCap)

ORDERING INFORMATION

PART

VOLTAGE (V)

DS1644-120+

5.0

DS1644P-120+

5.0

TEMP RANGE

0°C to +70°C

0°C to +70°C

PIN-PACKAGE

32 EDIP (0.740a)

34 PowerCap*

TOP MARK

DS1644+120

DS1644P+120

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

+Denotes a lead(Pb)-free/RoHS-compliant package. The top mark includes a “+” symbol on lead(Pb)-free devices.

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