DS1746-70

DS1746/DS1746P Y2K-Compliant, Nonvolatile Timekeeping RAMs 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. Century Byte Register (i.e., Y2K Compliant) Totally Nonvolatile with Over 10 Years of Operation in the Absence of Power BCD-Coded Century, Year, Month, Date, Day, Hours, Minutes, and Seconds with Automatic Leap Year Compensation Valid Up to the Year 2100 Battery Voltage-Level Indicator Flag Power-Fail Write Protection Allows for ±10% VCC Power Supply Tolerance Lithium Energy Source is Electrically Disconnected to Retain Freshness Until Power is Applied for the First Time DIP Module Only Standard JEDEC Byte-Wide 128k x 8 Static RAM Pinout PowerCap Module Board Only Surface Mountable Package for Direct Connection to PowerCap Containing Battery and Crystal Replaceable Battery (PowerCap) Power-On Reset Output Pin-for-Pin Compatible with Other Densities of DS174xP Timekeeping RAM Also Available in Industrial Temperature Range: -40°C to +85°C Underwriters Laboratories (UL) Recognized PIN CONFIGURATIONS 1 of 16 TOP VIEW N.C. A16 A14 A12 A7 A6 A5 A4 A3 A2 A1 1 Maxim 2 DS1746 3 4 5 6 7 8 9 10 11 12 32 31 30 29 28 27 26 25 24 23 22 21 VCC A15 N.C. WE A13 A8 A9 A11 OE A10 CE DQ0 13 20 DQ6 DQ1 DQ2 14 19 DQ5 15 18 DQ4 GND 16 17 DQ3 A0 DQ7 Encapsulated DIP N.C. A15 A16 RST VCC WE OE CE DQ7 DQ6 DQ5 DQ4 DQ3 DQ2 DQ1 DQ0 GND 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 Maxim DS1746P X1 GND VBAT X2 34 33 32 31 30 29 28 27 26 25 24 23 22 21 20 19 18 N.C. N.C. A14 A13 A12 A11 A10 A9 A8 A7 A6 A5 A4 A3 A2 A1 A0 PowerCap Module Board (Uses DS9034PCX+ or DS9034I-PCX+ PowerCap) 19-5503; Rev 6/13 DS1746/DS1746P Y2K-Compliant, Nonvolatile Timekeeping RAMs PIN DESCRIPTION PDIP 1, 30 2 3 4 5 6 7 8 9 10 11 12 23 25 26 27 28 31 13 14 15 17 18 19 20 21 16 22 24 29 32 PIN PowerCap 1, 33, 34 3 32 30 25 24 23 22 21 20 19 18 28 29 27 26 31 2 16 15 14 13 12 11 10 9 17 8 7 6 5 — 4 — FUNCTION NAME N.C. A16 A14 A12 A7 A6 A5 A4 A3 A2 A1 A0 A10 A11 A9 A8 A13 A15 DQ0 DQ1 DQ2 DQ3 DQ4 DQ5 DQ6 DQ7 GND CE OE WE VCC RST X1, X2, VBAT No Connection Address Input Data Input/Output Ground Active-Low Chip Enable Input Active-Low Output Enable Input Active-Low Write-Enable Input Power-Supply Input Active-Low Power-Fail Output, Open Drain. Requires a pullup resistor for proper operation. Crystal Connection, VBAT Battery Connection. UL recognized to ensure against reverse charging when used with a lithium battery (www.maximintegrated.com/qa/info/ul/) 2 of 16 DS1746/DS1746P Y2K-Compliant, Nonvolatile Timekeeping RAMs ORDERING INFORMATION PART DS1746-70+ DS1746-70IND+ DS1746P-70+ DS1746P-70IND+ DS1746W-120+ DS1746W-120IND+ DS1746WP-120+ DS1746WP-120IND+ VOLTAGE RANGE (V) 5.0 5.0 5.0 5.0 3.3 3.3 3.3 3.3 TEMP RANGE PIN-PACKAGE TOP MARK† 0°C to +70°C -40°C to +85°C 0°C to +70°C -40°C to +85°C 0°C to +70°C -40°C to +85°C 0°C to +70°C -40°C to +85°C 32 EDIP (0.740a) 32 EDIP (0.740a) 34 PowerCap* 34 PowerCap* 32 EDIP (0.740a) 32 EDIP (0.740a) 34 PowerCap* 34 PowerCap* DS1746+070 DS1746+070 IND DS1746P+70 DS1746P+070 IND DS1746W+120 DS1746W+120 IND DS1746WP+120 DS1746WP+120 IND +Denotes a lead(Pb)-free/RoHS-compliant package. The top mark will include a “+” symbol on lead-free devices. *DS9034-PCX+ or DS9034I-PCX+ required (must be ordered separately). † An “IND” anywhere on the top mark denotes an industrial temperature grade device. DESCRIPTION The DS1746 is a full-function, year-2000-compliant (Y2KC), real-time clock/calendar (RTC) and 128k x 8 nonvolatile static RAM. User access to all registers within the DS1746 is accomplished with a byte-wide interface as shown in Figure 1. The RTC information and control bits reside in the eight uppermost RAM locations. The RTC registers contain century, year, month, date, day, hours, minutes, and seconds data in 24-hour binary-coded decimal (BCD) format. Corrections for the date of each 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 DS1746 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. 3 of 16 DS1746/DS1746P Y2K-Compliant, Nonvolatile Timekeeping RAMs Figure 1. Block Diagram PACKAGES The DS1746 is available in two packages (32-pin DIP and 34-pin PowerCap module). The 32-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 DS1746P 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. CLOCK OPERATIONS—READING THE CLOCK While the double-buffered register structure reduces the chance of reading incorrect data, internal updates to the DS1746 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 one is written into the read bit, bit 6 of the century register (see Table 2). As long as a one 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 current 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 DS1746 registers are updated simultaneously after the internal clock register updating process has been re-enabled. Updating is within a second after the read bit is written to zero. The READ bit must be a zero for a minimum of 500µs to ensure the external registers will be updated. 4 of 16 DS1746/DS1746P Y2K-Compliant, Nonvolatile Timekeeping RAMs Table 1. Truth Table VCC VCC>VPF VSO