Manual

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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%

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

PIN ASSIGNMENT

PIN DESCRIPTION

A0-A14 - Address Input

CE - Chip Enable

OE - Output Enable

WE - Write Enable

- +5V

GND - Ground

DQ0-DQ7 - Data Input/Output

NC - No Connection

PFO - Power-fail Output

(DS1644P only)

X1, X2 - Crystal Connection

BAT

- Battery Connection

DS1644/DS1644P

Nonvolatile Timekeeping RAM

www.dalsemi.com

28-Pin Encapsulated Package (720-mil

Extended)

DQ0

DQ1

GND

DQ2

VCC

DQ7

DQ6

DQ5

DQ3

DQ4

A12

A14

PFO

DQ7

DQ6

DQ5

DQ4

DQ3

DQ2

DQ1

DQ0

GND

X1 GND V

BAT

34-Pin PowerCap Module Board

(Uses DS9034PCX PowerCap)

A12

Summary of content (11 pages)

PAGE 1
DS1644/DS1644P Nonvolatile Timekeeping RAM www.dalsemi.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.
PAGE 2
DS1644/DS1644P ORDERING INFORMATION DS1644 28-pin DIP module *DS1644P 34-pin PowerCap Module Board *DS9034PCX (Power Cap) Required; must be ordered separately 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 function equivalent to any JEDEC standard 32k x 8 SRAM.
PAGE 3
DS1644/DS1644P DS1644 BLOCK DIAGRAM Figure 1 DS1644 TRUTH TABLE Table 1 VCC 5V ± 10% <4.5V >VBAT
PAGE 4
DS1644/DS1644P CLOCK ACCURACY (DIP MODULE) The DS1644 is guaranteed to keep time accuracy to within ±1 minute per month at 25°C. The RTC is calibrated at the factory by Dallas Semiconductor using nonvolatile tuning elements, and does not require additional calibration. For this reason, methods of field clock calibration are not available and not necessary.
PAGE 5
DS1644/DS1644P RETRIEVING DATA FROM RAM OR CLOCK The DS1644 is in the read mode whenever WE (write enable) is high, and CE (chip enable) is low. The device architecture allows ripple-through access to any of the address locations in the NV SRAM. Valid data will be available at the DQ pins within tAA after the last address input is stable, providing that the CE and OE access times and states are satisfied.
PAGE 6
DS1644/DS1644P ABSOLUTE MAXIMUM RATINGS* Voltage on Any Pin Relative to Ground Storage Temperature Soldering Temperature -0.3V to +7.0V -40°C to +85°C 260°C for 10 seconds (DIP Package) (See Note 7) See IPC/JEDEC Standard J-STD-020A for Surface Mount Devices *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 implied.
PAGE 7
DS1644/DS1644P AC ELECTRICAL CHARACTERISTICS PARAMETER Read Cycle Time Address Access Time CE Access Time CE Data Off Time Output Enable Access Time Output Enable Data Off Time Output Enable to DQ Low-Z CE to DQ Low-Z Output Hold from Address Write Cycle Time Address Setup Time CE Pulse Width Address Hold from End of Write Write Pulse Width WE Data Off Time WE or CE Inactive Time Data Setup Time Data Hold Time High (Over the Operating Range) SYMBOL tRC tAA tCEA tCEZ tOEA tOEZ tOEL tCEL tOH tWC tAS tCEW t
PAGE 8
DS1644/DS1644P DS1644 READ CYCLE TIMING DS1644 WRITE CYCLE TIMING 8 of 11
PAGE 9
DS1644/DS1644P POWER-DOWN/POWER-UP TIMING NOTES: OUTPUT LOAD 1. All voltages are referenced to ground. 2. Typical values are at 25°C and nominal supplies. 3. Outputs are open. 4. Data retention time is at 25°C and is calculated from the date code on the device package. The date code XXYY is the year followed by the week of the year in which the device was manufactured. For example, 9225 would mean the 25th week of 1992. 5. tAH1, tDH1 are measured from WE going high. 6.
PAGE 10
DS1644/DS1644P DS1644 28-PIN PACKAGE PKG DIM A IN. MM B IN. MM C IN. MM D IN. MM E IN. MM F IN. MM G IN. MM H IN. MM J IN. MM K IN. MM 28-PIN MIN 1.470 37.34 0.715 18.16 0.335 8.51 0.075 1.91 0.015 0.38 0.140 3.56 0.090 2.29 0.590 14.99 0.010 0.25 0.015 0.38 MAX 1.490 37.85 0.740 18.80 0.365 9.27 0.105 2.67 0.030 0.76 0.180 4.57 0.110 2.79 0.630 16.00 0.018 0.45 0.025 0.64 DS1644P PKG DIM A B C D E F G INCHES MIN 0.920 0.980 0.052 0.048 0.015 0.025 NOM 0.925 0.985 0.055 0.050 0.020 0.027 MAX 0.930 0.
PAGE 11
DS1644/DS1644P DS1644P WITH DS9034PCX ATTACHED PKG DIM A B C D E F G INCHES MIN 0.920 0.955 0.240 0.052 0.048 0.015 0.020 NOM 0.925 0.960 0.245 0.055 0.050 0.020 0.025 MAX 0.930 0.965 0.250 0.058 0.052 0.025 0.030 NOM 1.050 0.826 0.050 0.030 0.