M41T94

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

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Product overview

Description

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 (RSTIN1and 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”.

  • All 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
    • 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

Circuit Diagram

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Quality and Reliability

Part Number Marketing Status Package Grade RoHS Compliance Grade Material Declaration**
M41T94MH6F
Active
SOH28 Industrial Ecopack2 (**)
M41T94MQ6F
Active
SO-16 Industrial Ecopack2

M41T94MH6F

Package:

SOH28

Material Declaration**:

PDF

Marketing Status

Active

Package

SOH28

Grade

Industrial

RoHS Compliance Grade

Ecopack2 (**)

M41T94MQ6F

Package:

SO-16

Material Declaration**:

PDF XML

Marketing Status

Active

Package

SO-16

Grade

Industrial

RoHS Compliance Grade

Ecopack2

(**) The Material Declaration forms available on st.com may be generic documents based on the most commonly used package within a package family. For this reason, they may not be 100% accurate for a specific device. Please contact our sales support for information on specific devices.

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M41T94MQ6F
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M41T94MH6F Active

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Part Number:

M41T94MH6F

Operating Temperature (°C)

Min:

Max:

NVRAM size (B):

44

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M41T94MQ6F Active

Budgetary Price (US$)*/Qty:
-
Package:
Packing Type:
RoHS:
Country of Origin:
ECCN (US):
ECCN (EU):

Part Number:

M41T94MQ6F

Operating Temperature (°C)

Min:

Max:

NVRAM size (B):

44

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(*) Suggested Resale Price (USD) per defined quantity for BUDGETARY USE ONLY. For quotes, prices in local currency, please contact your local ST Sales Office or our Distributors