DS1644/DS1644P
Nonvolatile Timekeeping RAM
www.maxim-ic.com
FEATURES
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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% V
CC
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
A12
A7
A6
A5
A4
A3
A2
A1
A0
DQ0
DQ1
DQ2
GND
1
2
3
4
5
6
7
8
9
10
11
12
13
14
28
27
26
25
24
23
22
21
20
19
18
17
16
15
V
CC
WE
A13
A8
A9
A11
OE
A10
CE
DQ7
DQ6
DQ5
DQ4
DQ3
28-Pin Encapsulated Package
(720-mil Extended)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
34
33
32
31
30
29
28
27
26
25
24
23
22
21
20
19
18
NC
NC
A14
A13
A12
A11
A10
A9
A8
A7
A6
A5
A4
A3
A2
A1
A0
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NC
NC
NC
PFO
V
CC
WE
OE
CE
DQ7
DQ6
DQ5
DQ4
DQ3
DQ2
DQ1
DQ0
GND
X1
GND V
BAT
X2
34-Pin PowerCap Module Board
(Uses DS9034PCX PowerCap)
PowerCap is a registered trademark of Dallas Semiconductor.
ORDERING INFORMATION
PART
DS16440120+
DS16440-120
DS1644P120+
DS1644P-120
VOLTAGE
RANGE (V)
5.0
5.0
5.0
5.0
TEMP RANGE PIN-PACKAGE
0°C to +70°C
0°C to +70°C
0°C to +70°C
0°C to +70°C
32 EDIP (0.740a)
32 EDIP (0.740a)
34 PowerCap*
34 PowerCap*
TOP MARK
DS1644+120
DS1644-120
DS1644P+120
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.
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REV: 040805
DALLAS [ DALLAS SEMICONDUCTOR ]
