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 VCC supply is in an out-of-tolerance
condition. This feature prevents loss of data from unpredictable system operation brought on by
low VCC as errant access and update cycles are avoided.
Key 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
Notes: **This pricing is BUDGETARY, for comparing similar parts. Prices are in
U.S. dollars and subject to change. Quantity pricing may vary
substantially and international prices may differ due to local
duties, taxes, fees, and exchange rates. For volume-specific prices
and delivery, please see the price and availability page
or contact an authorized distributor.
*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.
* Some packages have variations, listed on the drawing. "PkgCode/Variation" tells which variation the product uses. Note that "+", "#", "-" in the part number suffix describes RoHS status. Package drawings may show a different suffix character.
Devices:
1-4
of
4
DS1644
Notes
Free Sample
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Package:
TYPE PINS FOOTPRINT
DRAWING CODE/VAR *
Temp
RoHS/Lead-Free? Materials Analysis
DS1644-120
120ns
MOD;28 pin;
Dwg: 56-G0002-001
Use pkgcode/variation: MDF28-5*
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