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DS1644-120+

P1-P3P4-P6P7-P9P10-P12P13-P14
1 of 14
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% 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
ORDERING INFORMATION
PART VOLTAGE (V) TEMP RANGE PIN-PACKAGE TOP MARK
DS1644-120+ 5.0 0°C to +70°C 32 EDIP (0.740a) DS1644+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).
+Denotes a lead(Pb)-free/RoHS-compliant package. The top mark includes a “+” symbol on lead(Pb)-free devices.
1
NC
2
3
NC
NC
P
FO
V
CC
W
E
O
E
C
E
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
X1 GND V
BAT
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
V
CC
W
E
A13
A8
A9
A11
O
E
A10
C
E
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
A
6
A4
A14
DS1644/DS1644P
Nonvolatile Timekeeping RAM
www.maxim-ic.com
19-5203; Rev 4/10
DS1644/DS1644P
2 of 14
PIN DESCRIPTION
PIN
PDIP PowerCap
NAME FUNCTION
1 32 A14
2 30 A12
3 25 A7
4 24 A6
5 23 A5
6 22 A4
7 21 A3
8 20 A2
9 19 A1
10 18 A0
Address Input
11 16 DQ0
12 15 DQ1
13 14 DQ2
Data Input/Output
14 17 GND Ground
15 13 DQ3
16 12 DQ4
17 11 DQ5
18 10 DQ6
19 9 DQ7
Data Input/Output
20 8 CE Active Low Chip-Enable Input
21 28 A10 Address Input
22 7 OE Active Low Output-Enable Input
23 29 A11
24 27 A9
25 26 A8
26 31 A13
Address Input
27 6
WE
Active-Low Write-Enable Input
28 5 V
CC
Power-Supply Input
- 4
RST
Active-Low Reset Output, Open Drain. Requires a pull-up resistor for
proper operation.
- 1-3,33,34 NC No Connection
- X1, X2,
V
BAT
Crystal Connection V
BAT
Battery Connection
DESCRIPTION
The DS1644 is a 32k x 8 nonvolatile static RAM with a full function real time clock, which are both
accessible in a byte-wide format. The nonvolatile timekeeping RAM is functionally equivalent to any
JEDEC standard 32k x 8 SRAM. The device can also be easily substituted for ROM, EPROM and
EEPROM, providing read/write nonvolatility and the addition of the real time clock function. The real
time clock information resides in the eight uppermost RAM locations. The RTC registers contain year,
month, date, day, hours, minutes, and seconds data in 24-hour BCD format. Corrections for the day of the
month and leap year are made automatically. The RTC clock registers are double-buffered to avoid access
of incorrect data that can occur during clock update cycles. The double-buffered system also prevents
time loss as the timekeeping countdown continues unabated by access to time register data. The DS1644
also contains its own power-fail circuitry, which deselects the device when the V
CC
supply is in an out-of-
tolerance condition. This feature prevents loss of data from unpredictable system operation brought on by
low V
CC
as errant access and update cycles are avoided.
DS1644/DS1644P
3 of 14
PACKAGES
The DS1644 is available in two packages (28-pin DIP and 34-pin PowerCap module). The 28-pin DIP
style module integrates the crystal, lithium energy source, and silicon all in one package. The 34-pin
PowerCap Module Board is designed with contacts for connection to a separate PowerCap (DS9034PCX)
that contains the crystal and battery. This design allows the PowerCap to be mounted on top of the
DS1644P after the completion of the surface-mount process. Mounting the PowerCap after the surface
mount process prevents damage to the crystal and battery due to the high temperatures required for solder
reflow. The PowerCap is keyed to prevent reverse insertion. The PowerCap Module Board and PowerCap
are ordered separately and shipped in separate containers. The part number for the PowerCap is
DS9034PCX.
CLOCK OPERATIONS—READING THE CLOCK
While the double-buffered register structure reduces the chance of reading incorrect data, internal updates
to the DS1644 clock registers should be halted before clock data is read to prevent reading of data in
transition. However, halting the internal clock register updating process does not affect clock accuracy.
Updating is halted when a 1 is written into the read bit, the 7th most significant bit in the control register.
As long as a 1 remains in that position, updating is halted. After a halt is issued, the registers reflect the
count, that is day, date, and time that was present at the moment the halt command was issued. However,
the internal clock registers of the double-buffered system continue to update so that the clock accuracy is
not affected by the access of data. All of the DS1644 registers are updated simultaneously after the clock
status is reset. Updating is within a second after the read bit is written to 0.
DS1644 BLOCK DIAGRAM Figure 1
DS1644 TRUTH TABLE Table 1
V
CC
CE OE WE
MODE DQ POWER
V
IH
X X DESELECT HIGH-Z STANDBY
X X X DESELECT HIGH-Z STANDBY
V
IL
X V
IL
WRITE DATA IN ACTIVE
V
IL
V
IL
V
IH
READ DATA OUT ACTIVE
5V 10%
V
IL
V
IH
V
IH
READ HIGH-Z ACTIVE
<4.5V >V
BAT
X X X DESELECT HIGH-Z CMOS STANDBY
<V
BAT
X X X DESELECT HIGH-Z DATA RETENTION
MODE
P1-P3P4-P6P7-P9P10-P12P13-P14

DS1644-120+

Mfr. #:
Buy DS1644-120+
Manufacturer:
Maxim Integrated
Description:
Real Time Clock NV Timekeeping RAM
Lifecycle:
New from this manufacturer.
Delivery:
DHL FedEx Ups TNT EMS
Payment:
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