19-5203 Rev 4/10 DS1644/DS1644P Nonvolatile Timekeeping RAM www.maxim-ic.com FEATURES PIN CONFIGURATIONS V Integrated NV SRAM, Real-Time Clock, A14 1 28 CC 27 WE 2 A12 Crystal, Power-Fail Control Circuit and A13 A7 3 26 Lithium Energy Source 4 25 A8 A6 A5 A9 5 24 Clock Registers are Accessed Identically to 6 23 A4 A11 the Static RAM. These Registers are A3 7 22 OE Resident in the Eight Top RAM Locations. A2 8 21 A10 A1 9 20 CE Totally Nonvolatile with Over 10 Years of A0 10 19 DQ7 Operation in the Absence of Power DQ6 DQ0 11 18 12 17 DQ1 DQ5 BCD-Coded Year, Month, Date, Day, Hours, 13 16 DQ2 DQ4 Minutes, and Seconds with Leap Year 14 15 GND DQ3 Compensation Valid Up to 2100 28-Pin Encapsulated Package Power-Fail Write Protection Allows for (720-mil Extended) 10% V Power Supply Tolerance CC DS1644 Only (DIP Module) 1 34 NC NC 33 2 NC Upward Compatible with the DS1643 NC 3 32 A14 NC 31 Timekeeping RAM to Achieve Higher A13 4 PFO 30 V 5 A12 CC RAM Density 6 29 A11 WE 28 A10 7 OE Standard JEDEC Bytewide 32k x 8 Static 27 8 A9 CE 26 A8 9 DQ7 RAM Pinout 25 10 A7 DQ6 24 11 A6 DQ5 DS1644P Only (PowerCap Module Board) 23 12 A5 DQ4 22 A4 13 DQ3 Surface Mountable Package for Direct 21 14 A3 DQ2 20 A2 15 DQ1 X1 GND V X2 BAT Connection to PowerCap Containing 19 16 A1 DQ0 18 A0 17 GND Battery and crystal Replaceable Battery (PowerCap) 34-Pin PowerCap Module Board Power-Fail Output (Uses DS9034PCX PowerCap) Pin-for-Pin Compatible with Other Densities of DS164XP Timekeeping RAM Underwriters Laboratory (UL) Recognized ORDERING INFORMATION PART VOLTAGE (V) TEMP RANGE PIN-PACKAGE TOP MARK DS1644-120+ 5.0 0C to +70C 32 EDIP (0.740a) DS1644+120 DS1644P-120+ 5.0 0C to +70C 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 of 14 DS1644/DS1644P PIN DESCRIPTION PIN NAME FUNCTION PDIP PowerCap 1 32 A14 2 30 A12 3 25 A7 4 24 A6 5 23 A5 Address Input 6 22 A4 7 21 A3 8 20 A2 9 19 A1 10 18 A0 11 16 DQ0 Data Input/Output 12 15 DQ1 13 14 DQ2 14 17 GND Ground 15 13 DQ3 16 12 DQ4 17 11 DQ5 Data Input/Output 18 10 DQ6 19 9 DQ7 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 Address Input 25 26 A8 26 31 A13 27 6 WE Active-Low Write-Enable Input 28 5 V Power-Supply Input CC - 4 Active-Low Reset Output, Open Drain. Requires a pull-up resistor for RST proper operation. - 1-3,33,34 NC No Connection - X1, X2, Crystal Connection V Battery Connection BAT V BAT 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 supply is in an out-of- CC tolerance condition. This feature prevents loss of data from unpredictable system operation brought on by low V as errant access and update cycles are avoided. CC 2 of 14