M41T94MH6F Real-Time Clock (RTC) ICs by STMicroelectronics

Serial real-time clock (RTC) with 44 bytes NVRAM and reset


The M41T94 is a serial real-time clock with 44 bytes of NVRAM and a RESET output. A built-in 32,768 Hz oscillator (external crystal controlled) and 8 bytes of the SRAM (see Table 4 on page 18) are used for the clock/calendar function and are configured in binary coded decimal (BCD) format. An additional 12 bytes of RAM provide status/control of alarm, watchdog and square wave functions. Addresses and data are transferred serially via a serial SPI interface. The built-in address register is incremented automatically after each WRITE or READ data byte. The M41T94 has a built-in power sense circuit which detects power failures and automatically switches to the battery supply when a power failure occurs. The energy needed to sustain the SRAM and clock operations can be supplied by a small lithium button-cell supply when a power failure occurs. Functions available to the user include a non-volatile, time-of-day clock/calendar, alarm interrupts, watchdog timer and programmable square wave output. Other features include a power-on reset as well as two additional debounced inputs ( RSTIN1 and RSTIN2 ) which can also generate an output reset ( RST ). The eight clock address locations 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 ninth clock address location controls user access to the clock information and also stores the clock software calibration setting. The M41T94 is supplied in either a 16-lead plastic SOIC (requiring user supplied crystal and battery) or a 28-lead SOIC SNAPHAT ® package (which integrates both crystal and battery in a single SNAPHAT top). The 28-pin, 330 mil SOIC provides sockets with gold plated contacts at both ends for direct connection to a separate SNAPHAT housing containing the battery and crystal. The unique design allows the SNAPHAT battery/crystal package to be mounted on top of the SOIC package after the completion of the surface mount process. Insertion of the SNAPHAT housing after reflow prevents potential battery and crystal damage due to the high temperatures required for device surface-mounting. The SNAPHAT housing is also keyed to prevent reverse insertion. The SOIC and battery/crystal packages are shipped separately in plastic anti-static tubes or in tape & reel form. For the 28-lead SOIC, the battery/crystal package (e.g., SNAPHAT) part number is “M4TXX-BR12SH”.

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Prices starting from US$3.75

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Features

Counters for tenths/hundredths of seconds, seconds, minutes, hours, day, date, month, year, and century
32 KHz crystal oscillator integrating load capacitance (12.5 pF) providing exceptional oscillator stability and high crystal series resistance operation
Serial peripheral interface (2 MHz SPI)
Ultralow battery supply current of 500 nA (max)
2.7 to 5.5 V operating voltage
2.5 to 5.5 V oscillator operating voltage
Battery low flag
Automatic switchover and deselect circuitry
44 bytes of general purpose RAM
Programmable alarm and interrupt function (valid even during battery backup mode)
Accurate programmable watchdog timer (from 62.5 ms to 128 s)
Microprocessor power-on reset
Choice of power-fail deselect voltages (VCC= 2.7 to 5.5 V): THS = VSS; 2.55 V ≤ VPFD≤ 2.70 V THS = VCC; 4.20 V ≤ VPFD≤ 4.50 V
THS = VSS; 2.55 V ≤ VPFD≤ 2.70 V
THS = VCC; 4.20 V ≤ VPFD≤ 4.50 V
Packaging includes a 28-lead SOIC and SNAPHAT®top (to be ordered separately) or 16-lead SOIC
28-lead SOIC package provides direct connection for a SNAPHAT®top which contains the battery and crystal
RoHS compliant Lead-free second level interconnect
Lead-free second level interconnect

Resources


Application Notes
AN3060 Applications guide for serial real-time clocks (RTCs)
AN1011 Battery technology used in NVRAM and real-time clock (RTC) products from ST
AN934 How to use the digital calibration feature in TIMEKEEPER® and serial real-time clock (RTC) products
AN1216 Implementing a periodic alarm with TIMEKEEPER® and serial real-time clocks (RTCs)
AN4641 Integrating TIMEKEEPER® and real-time clock supervisor functions
AN923 Managing century information using serial real-time clocks and TIMEKEEPER® NVRAMs
AN1572 Power-down time-stamp function in serial real-time clocks (RTCs)
AN1336 Power-fail comparator for NVRAM supervisory devices
AN1012 Predicting the battery life and data retention period of NVRAMs and serial RTCs
AN922 Using a Super Cap to back up the M41T56, M41T00, M41T11, M41T81, M41T94, and M41ST84W (16-pin)




Alternative Descriptions

Real-Time Clock 44B NVRAM Reset SOH28 | RS
Alarm Rtc, 44B, Spi, 5.5V, Soh-28 | Newark Electronics
ALARM RTC, 44B, SPI, 5.5V, SOH-28 | element14
M41T94 Series 2.7 to 5.5 V SPI Serial Real Time Clock Surface Mount - SOIC-28 | Future Electronics
Real Time Clock Serial 64Byte 28-Pin SOH T/R | Avnet America


Frequently Asked Questions

Where can I find additional details, specifications and documents for a M41T94MH6F?

Additional datasheets, footprints and schematics for M41T94MH6F are listed on our Part Details page. You can also find images and similar parts to M41T94MH6F on this page.

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What category does M41T94MH6F fall under?

The M41T94MH6F is listed under Clocks and Timers > Real-Time Clock (RTC) ICs > RTC - Serial Interface.

Can I view similar or alternative parts?

You can view similar parts to M41T94MH6F when available in the RTC - Serial Interface range under the specifications section at the bottom of the details page.

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Is the M41T94MH6F RoHS compliant?

Yes. This part has been flagged as RoHS Compliant by STMicroelectronics.

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Authorised distributors including RS, Newark Electronics, element14, Farnell and Future Electronics have stock available or on a lead time for M41T94MH6F.

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