19-5500 Rev 9/10 DS1556 1M, Nonvolatile, Y2K-Compliant Timekeeping RAM www.maxim-ic.com FEATURES PIN CONFIGURATIONS Integrated NV SRAM, Real-Time Clock (RTC), Crystal, Power-Fail Control Circuit, TOP VIEW and Lithium Energy Source RST 1 32 V CC Maxim Clock Registers are Accessed Identically to A16 31 A15 2 DS1556 A14 the Static RAM These Registers Reside in 3 30 IRQ/FT A12 4 29 WE the 16 Top RAM Locations A13 A7 5 28 A6 6 27 A8 Century Byte Register (i.e., Y2K Compliant) A5 A9 7 26 Totally Nonvolatile with Over 10 Years of A4 8 25 A11 A3 OE 9 24 Operation in the Absence of Power A2 10 23 A10 Precision Power-On Reset CE A1 11 22 12 21 A0 DQ7 Programmable Watchdog Timer and RTC 13 20 DQ0 DQ6 Alarm 14 19 DQ1 DQ5 DQ2 BCD-Coded Year, Month, Date, Day, Hours, 15 18 DQ4 GND 16 17 DQ3 Minutes, and seconds with Automatic Leap- Year Compensation Valid Up to the Year Encapsulated DIP 2100 Battery Voltage-Level Indicator Flag Power-Fail Write Protection Allows for 10% 34 N.C. V Power-Supply Tolerance IRQ/FT 1 CC Maxim A15 2 33 N.C. DS1556 32 A14 A16 3 Lithium Energy Source is Electrically 31 RST 4 A13 30 5 A12 V CC Disconnected to Retain Freshness Until 6 29 A11 WE 7 28 A10 Power is Applied for the First Time OE 27 A9 8 CE 26 A8 9 DQ7 Also Available in Industrial Temperature 25 10 A7 DQ6 24 A6 11 DQ5 Range: -40C to +85C 23 12 A5 DQ4 22 A4 13 DQ3 14 21 A3 DQ2 20 A2 15 DQ1 19 A1 16 DQ0 X1 GND V X2 BAT 18 17 A0 GND PowerCap Module Board (Uses DS9034PCX PowerCap) Note: Some revisions of this device may incorporate deviations from published specifications known as errata. Multiple revisions of any device may be simultaneously available through various sales channels. For information about device errata, click here: www.maxim-ic.com/errata. 1 of 18 DS1556 1M, Nonvolatile, Y2K-Compliant Timekeeping RAM PIN DESCRIPTION A0A16 - Address Input DQ0DQ7 - Data Input/Outputs IRQ/FT - Interrupt, Frequency Test Output (Open Drain) RST - Power-On Reset Output (Open Drain) CE - Chip Enable OE - Output Enable WE - Write Enable V - Power Supply Input CC GND - Ground N.C. - No Connection X1, X2 - Crystal Connection V - Battery Connection BAT ORDERING INFORMATION VOLTAGE PART TEMP RANGE PIN-PACKAGE TOP MARK** (V) DS1556-70+ 0C to +70C 5.0 32 EDIP (0.740a) DS1556+070 DS1556-70IND+ -40C to +85C 5.0 32 EDIP (0.740a) DS1556+070 IND DS1556P-70+ 0C to +70C 5.0 34 PowerCap* DS1556P+70 DS1556P-70IND+ -40C to +85C 5.0 34 PowerCap* DS1556P+70 IND DS1556W-120+ 0C to +70C 3.3 32 EDIP (0.740a) DS1556W+120 DS1556W-120IND+ -40C to +85C 3.3 32 EDIP (0.740a) DS1556W+120 IND DS1556WP-120+ 0C to +70C 3.3 34 PowerCap* DS1556WP+120 DS1556WP-120IND+ -40C to +85C 3.3 34 PowerCap* DS1556WP+120 IND +Denotes a lead(Pb)-free/RoHS-compliant package. *DS9034-PCX+ or DS9034I-PCX+ required (must be ordered separately). **A + in top mark denotes a lead(Pb)-free device. An IND anywhere on the top mark indicates an industrial temperature grade device. 2 of 18