bq4287 Real-Time Clock Module With NVRAM Control Features ➤ Direct clock/calendar replacement for IBM® AT-compatible computers and other applications ➤ Functionally compatible with the DS1287/DS1287A and MC146818A ➤ 114 bytes of general nonvolatile storage ➤ Time of day in seconds, minutes, and hours - ➤ Three individually maskable interrupt event flags: ➤ Integral lithium cell and crystal ➤ Intel bus timing ➤ 14 bytes for clock/calendar and control Optional daylight saving adjustment ➤ Programmable square wave output ➤ Automatic backup supply and write-protection to make external SRAM nonvolatile ➤ 160 ns cycle time allows fast bus operation 12- or 24-hour format - Periodic rates from 122 µs to 500 ms - Time-of-day alarm once per second to once per day - End-of-clock update cycle General Description As shipped from Benchmarq, the backup cell is electrically isolated from the memory. Following the first application of VCC, this isolation is broken, and the backup cell provides data retention to the clock, internal RAM, VOUT, and CEOUT on subsequent power-downs. Pin Connections Pin Names 1 2 3 4 5 6 7 8 9 10 11 12 24 23 22 21 20 19 18 17 16 15 14 13 VCC SQW CEOUT CEIN NC INT RST RD NC WR ALE CS 24-Pin DIP Module PN428701.eps The bq4287 uses its integral batterybackup controller and battery to make a standard CMOS SRAM nonvolatile during power-fail conditions. During power-fail, the bq4287 automatically write-protects the external SRAM and provides a VCC output sourced from its internal battery. The bq4287 is a fully compatible real-time clock for IBM AT-compatible computers and other applications. ➤ Calendar in day of the week, day of the month, months, and years with automatic leap-year adjustment VOUT NC NC AD0 AD1 AD2 AD3 AD4 AD5 AD6 AD7 VSS The bq4287 write-protects the clock, calendar, and storage registers during power failure. The integral backup energy source then maintains data and operates the clock and calendar. ➤ Better than one minute per month clock accuracy The CMOS bq4287 is a low-power microprocessor peripheral providing a time-of-day clock and 100-year calendar with alarm features and battery operation. Other features include three maskable interrupt sources, square wave output, and ➤ BCD or binary format for clock and calendar data 114 bytes of general nonvolatile storage. AD0–AD7 Multiplexed address/data input/output CS Chip select input ALE Address strobe input RD Data strobe input WR Read/write input INT Interrupt request output RST Reset input SQW Square wave output CEIN RAM chip enable input CEOUT RAM chip enable output NC No connect VOUT Supply output VCC +5V supply VSS Ground Nov. 1993 C 1 The bq4287 is functionally equivalent to the bq4285, except that the battery (16, 20) and crystal pins (2, 3) are not accessible. These pins are connected internally to a coin cell and quartz crystal. The coin cell provides 130mAh of capacity. For a complete description of features, operating conditions, electrical characteristics, bus timing, and pin descriptions, see the bq4285 data sheet. Caution: Take care to avoid inadvertent discharge through VOUT and CEOUT after battery isolation has been broken. bq4287 Absolute Maximum Ratings Value Unit VCC Symbol DC voltage applied on VCC relative to VSS Parameter -0.3 to 7.0 V VT DC voltage applied on any pin excluding VCC relative to VSS -0.3 to 7.0 V VT ≤ VCC + 0.3 TOPR Operating temperature 0 to +70 °C Commercial TSTG Storage temperature -40 to +70 °C Commercial TBIAS Temperature under bias -10 to +70 °C Commercial TSOLDER Soldering temperature 260 °C For 10 seconds Note: Conditions Permanent device damage may occur if Absolute Maximum Ratings are exceeded. Functional operation should be limited to the Recommended DC Operating Conditions detailed in this data sheet. Exposure to conditions beyond the operational limits for extended periods of time may affect device reliability. Recommended DC Operating Conditions (TA = TOPR) Symbol VCC VSS VIL VIH Note: Parameter Supply voltage Supply voltage Input low voltage Input high voltage Minimum 4.5 0 -0.3 2.2 Typical 5.0 0 - Maximum 5.5 0 0.8 VCC + 0.3 Unit V V V V Typical values indicate operation at TA = 25°C. DC Electrical Characteristics (TA = TOPR, VCC = 5V ± 10%) Symbol Parameter Minimum Typical Maximum C Battery capacity - 130 - ILI Input leakage current - - ±1 ILO Output leakage current - - ±1 VOH VOL Output high voltage Output low voltage 2.4 - - 0.4 ICC Operating supply current - 7 15 ICCB Battery operation current - 0.3 0.5 VSO VPFD Supply switch-over voltage Power-fail-detect voltage 4.0 3.0 4.17 4.35 VBC Backup cell voltage - 3.0 - VOUT1 VOUT2 ICE VOUT voltage VOUT voltage Chip enable input current VCC - 0.3V VBC - 0.3V - - 100 Note: Unit Conditions/Notes Refer to graphs in Typical BatmAh tery Characteristics section µA VIN = VSS to VCC µA AD0–AD7, INT and SQW in high impedance V IOH = -1.0 mA V IOL = 4.0 mA mA Min. cycle, duty = 100%, IOH = 0mA, IOL = 0mA µA VBC = 3V, TA = 25°C, no load on VOUT or CEOUT V V Internal backup cell voltage; V refer to graphs in Typical Battery Characteristics section V IOUT = 100mA, VCC > VBC V IOUT = 100µA, VCC < VBC µA Internal 50K pull-up Typical values indicate operation at TA = 25°C, VCC = 5V. Nov. 1993 C 2 bq4287 Power-Down/Power-Up Timing Symbol Parameter (TA = TOPR) Minimum Typical Maximum Unit Conditions tF VCC slew from 4.5V to 0V 300 - - µs tR VCC slew from 0V to 4.5V 100 - - µs tCSR CS at VIH after power-up 20 - 200 ms Internal write-protection period after VCC passes VPFD on power-up. tDR Data-retention and timekeeping time 10 - - years TA = 25°C, no load on VOUT or CEOUT. tWPT Write-protect time for external RAM 10 16 30 µs Delay after VCC slows down past VPFD before SRAM is write-protected. tCER Chip enable recovery time tCSR - tCSR ms Time during which external SRAM is write-protected after VCC passes VPFD on power-up. tCED Chip enable propagation delay to external SRAM - 7 10 ns Note: Clock accuracy is better than ± 1 minute per month at 25°C for the period of tDR. Caution: Negative undershoots below the absolute maximum rating of -0.3V in battery-backup mode may affect data integrity. Power-Down/Power-Up Timing Nov. 1993 C 3 bq4287 Typical Battery Characteristics (source = Panasonic) CR1632 Load Characteristics 3.50 Temp: 20˚C (68˚F) Voltage (V) 3.00 2.50 2.00 15K (190 A) 100K (29 A) 30K (95 A) 1.50 0 1000 2000 3000 4000 5000 Duration (hours) CR1632 Capacity vs. Load Resistance 150 60˚C (140˚F) 125 20˚C (68˚F) Capacity (mAh) 100 75 50 25 Cut off V: 2.0V 0 Load (K ) 1 ( A) | 2000 | 1000 10 | 300 | 500 | 200 | 100 | 50 100 | 30 Nov. 1993 C 4 bq4287 CR1632 Operating Voltage vs. Load Resistance 3.20 3.00 60˚C (140˚F) Voltage (V) 2.80 2.60 20˚C (68˚F) 2.40 -10˚C (14˚F) 2.20 Load (K ) 1 | 2000 (uA) Voltage at 50% discharge | 1000 10 | 300 | 500 | 200 | 50 100 | 30 700 800 | 100 CR1632 Temperature Characteristics 3.50 Load: 15K (190 A) 60˚C (140˚F) Voltage (V) 3.00 20˚C (68˚F) -10˚C (14˚F) 2.50 2.00 1.50 0 100 200 300 400 Duration (hours) Nov. 1993 C 5 500 600 bq4287 24-Pin MT (T-type module) 24-Pin MT (T-type module) Dimension A A1 B C D E e G L S Minimum 0.360 0.015 0.015 0.008 1.320 0.685 0.590 0.090 0.120 0.100 Maximum 0.375 0.022 0.013 1.335 0.700 0.620 0.110 0.130 0.120 All dimensions are in inches. Nov. 1993 C 6 bq4287 Data Sheet Revision History Change Page No. 1 2 1 Description Nature of Change Power-fail detect voltage VPFD Was 4.1 min, 4.25 max; is 4.0 min, 4.35 max 2 Chip enable input current Additional specification 2 9 Was: “As shipped from Benchmarq, the backup cell is electrically isolated from the memory.” Is: “As shipped from Benchmarq, the backup cell is electrically isolated from the active circuitry.” Clarification 2 14 Deleted specifications for tRWH and tRWS Clarification; these parameters are not supported by the bq4287 Notes: Change 1 = Nov. 1992 B changes from June 1991 A. Change 2 = Nov. 1993 C changes from Nov. 1992 B. Ordering Information bq4287 MT Temperature: blank = Commercial (0 to +70°C) Package Option: MT = T-type module Device: bq4287 Real-Time Clock Module With NVRAM Control Nov. 1993 C 7 IMPORTANT NOTICE Texas Instruments and its subsidiaries (TI) reserve the right to make changes to their products or to discontinue any product or service without notice, and advise customers to obtain the latest version of relevant information to verify, before placing orders, that information being relied on is current and complete. All products are sold subject to the terms and conditions of sale supplied at the time of order acknowledgement, including those pertaining to warranty, patent infringement, and limitation of liability. TI warrants performance of its semiconductor products to the specifications applicable at the time of sale in accordance with TI’s standard warranty. Testing and other quality control techniques are utilized to the extent TI deems necessary to support this warranty. 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