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M41ST85WMH6TR 数据表(PDF) 4 Page - STMicroelectronics |
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M41ST85WMH6TR 数据表(HTML) 4 Page - STMicroelectronics |
4 / 34 page M41ST85W 4/34 SUMMARY DESCRIPTION The M41ST85W is a combination Serial Real- Time Clock, Microprocessor Supervisor, and NVRAM Supervisor. It is built in a low power CMOS SRAM process and has a 64-byte memory space with 44 bytes of NVRAM and 20 memory- mapped RTC registers (see Table 2., page 14). The RTC registers are configured in binary coded decimal (BCD) format. The M41ST85W combines a 400kHz I2C Serial RTC with an Automatic Back-up Battery Switcho- ver circuit for powering an external LPSRAM as well as the internal RTC. When power begins to fail, the switchover automatically connects to the back-up battery to keep the RTC and external LPSRAM alive in the absence of system power. Access to the LPSRAM is also cut off via a chip- enable gate function, thereby write-protecting the memory. A programmable Watchdog and Power- on Reset/Low Voltage Detect function are the key elements in the Microprocessor Supervisor sec- tion. The Real-Time Clock includes a built-in 32.768kHz oscillator (crystal-controlled), which provides the time base for the timekeeping and calendar functions. Eight of the 20 clock registers provide the basic clock/calendar functions while the other 12 bytes provide status/control for the Alarm, Watchdog, and Squarewave functions. RTC addresses and data are transferred serially via the two-line, bi-directional I2C interface. The built-in address register is incremented automati- cally after each WRITE or READ data byte. The M41ST85W has a built-in power sense circuit which detects power failures and automatically switches to the back-up battery when a power fail- ure occurs. During an outage, the power to sustain the SRAM and clock operations is typically sup- plied by a small lithium button-cell battery as is the case when using the SNAPHAT® package option. Functions available to the user include a non-vol- atile, time-of-day clock/calendar, Alarm interrupts, Watchdog Timer, and programmable Squarewave generator. Other features include a Power-on Re- set as well as two additional debounce reset inputs (RSTIN1 and RSTIN2) which can also generate an output Reset (RST). The eight registers for basic clock/calendar func- tions contain the century, year, month, date, day, hour, minute, second, and tenths/hundredths of a second in 24 hour BCD format. Corrections for 28, 29 (leap year - valid until year 2100), 30 and 31 day months are made automatically. The M41ST85W is offered in two 28-lead SOIC packages. The 300mil SOH28 SNAPHAT IC pack- age mates with ST’s SNAPHAT Battery/Crystal top (ordered separately). SNAPHAT battery op- tions include 48mAh and 120mAh. ST’s 300mil SOX28 Embedded Crystal IC includes the 32KHz crystal and is perfect for applications where a low profile is a must. The SOH28 SNAPHAT SOIC includes sockets with gold plated contacts at both ends for direct connection to the SNAPHAT top. The SNAPHAT battery/crystal top is inserted atop the IC package after the completion of the surface mount assem- bly process which avoids potential battery and crystal damage due to the high temperatures re- quired for device surface-mounting. The unique design allows the battery to be replaced, thus ex- tending the life of the RTC and NVRAM indefinite- ly. The SNAPHAT top is keyed to prevent reverse in- sertion. The SNAPHAT IC and SNAPHAT tops are shipped separately. The ICs are available in plas- tic anti-static tubes or in Tape & Reel form. The SNAPHAT tops are shipped in plastic anti-static tubes. The part numbers are M4T28-BR12SH1 (48mAh) and M4T32-BR12SH1 (120mAh). For the extended temperature requirement, the 120mAh M4T32-BR12SH6 is available. For more information, see Table 19., page 32. Caution: Do not place the SNAPHAT battery/crys- tal top in conductive foam, as this will drain the lith- ium button-cell battery. The 300mil SOX embedded crystal SOIC typically requires a user-supplied battery for non-volatile operation. Capacitor back-up can also be imple- mented with this package. |
类似零件编号 - M41ST85WMH6TR |
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类似说明 - M41ST85WMH6TR |
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