M41T94: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 (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”.

Key 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
Product Specifications
DescriptionVersionSize
DS2166: Serial real-time clock with 44 bytes NVRAM and reset7.0555 KB
Application Notes
DescriptionVersionSize
AN3060: Applications guide for serial real-time clocks (RTCs)3.0878 KB
AN1011: Battery technology used in NVRAM and real-time clock (RTC) products from ST4.0248 KB
AN934: How to use the digital calibration feature in TIMEKEEPER® and serial real-time clock (RTC) products4.1123 KB
AN1216: Implementing a periodic alarm with TIMEKEEPER® and serial real-time clocks (RTCs)2.0192 KB
AN4641: Integrating TIMEKEEPER® and real-time clock supervisor functions1.0479 KB
AN923: Managing century information using serial real-time clocks and TIMEKEEPER® NVRAMs4.0142 KB
AN1572: Power-down time-stamp function in serial real-time clocks (RTCs)2.0171 KB
AN1336: Power-fail comparator for NVRAM supervisory devices2.0127 KB
AN1012: Predicting the battery life and data retention period of NVRAMs and serial RTCs4.1439 KB
AN922: Using a Super Cap to back up the M41T56, M41T00, M41T11, M41T81, M41T94, and M41ST84W (16-pin)2.184 KB
User Manuals
DescriptionVersionSize
UM0402: Single-phase multi tariff energy meter1.3587 KB
HW Model & CAD Libraries
DescriptionVersionSize
Ibis model1.022 KB
Brochures
DescriptionVersionSize
Serial real-time clock ICs1.0827 KB
Product Certifications
DescriptionVersionSize
Products Underwriter Laboratories (UL) Information2.1543 KB
Clocks and Timers Software
Part NumberManufacturerDescription
STSW-SRTC001STI2C code for Serial RTC
STSW-SRTC002STSPI code -Serial RTC
Sample & Buy
Part NumberPackagePacking TypeOperating Temperature (°C) (min)Operating Temperature (°C) (max)Unit Price (US$) *QuantityNVRAM size (B)ECCN (EU)ECCN (US)Country of Origin
M41T94MH6FSO-28Tape And Reel-40852.823100044NECEAR99MALAYSIA
M41T94MQ6FSO-16Tape And Reel-40851.705100044NECEAR99MOROCCO
Quality & Reliability
Part NumberPackageGradeRoHS Compliance GradeMaterial Declaration**
M41T94MH6FSO-28IndustrialEcopack1md_ab-wspc-so-wspc-28-wspc-battery_hzmhb6aa94h-wspc-(m41t94mh6f)-wspc-ver2_signed.pdf
md_ab-wspc-so-wspc-28-wspc-battery_hzmhb6aa94h-wspc-(m41t94mh6f)-wspc-wcp-wspc-ver2.xml
M41T94MQ6FSO-16IndustrialEcopack1md_so-wspc-16-wspc-.15-wspc-to-wspc-jedec-wspc-ms-012_bzmq-wspc-b6aa94q_vers2_sdm_signed.pdf
md_so-wspc-16-wspc-.15-wspc-to-wspc-jedec-wspc-ms-012_bzmq-wspc-b6aa94q_vers2.xml
Serial real-time clock with 44 bytes NVRAM and reset M41T94
circuit_diagram_7564_thumbnail.png M41T94
串行实时时钟(RTC)应用指南 M41T60
ST NVRAM 和实时时钟(RTC)产品中使用的电池技术 M4Z28-BR00SH
How to use the digital calibration feature in TIMEKEEPER® and serial real-time clock (RTC) products M41T60
Implementing a periodic alarm with TIMEKEEPER® and serial real-time clocks (RTCs) M41T94
集成TIMEKEEPER® 与实时时钟监控器功能 M41T60
Managing century information using serial real-time clocks and TIMEKEEPER® NVRAMs M41T60
串行实时时钟(RTC)的掉电时间戳功能 M41T60
Power-fail comparator for NVRAM supervisory devices M41T60
预测NVRAM 和串行RTC 的电池寿命和数据保存期限 M4Z28-BR00SH
使用Super Cap 为M41T56、M41T00、M41T11、M41T81、M41T94 和M41ST84W (16 引脚)提供备用电源 M41T94
Single-phase multi tariff energy meter ST72264G1
Single-phase multi tariff energy meter M41T94
Predicting the battery life and data retention period of NVRAMs and serial RTCs M4T28-BR12SH
Predicting the battery life and data retention period of NVRAMs and serial RTCs M4Z28-BR00SH
md_ab-wspc-so-wspc-28-wspc-battery_hzmhb6aa94h-wspc-(m41t94mh6f)-wspc-ver2_signed.pdf M41T94
md_ab-wspc-so-wspc-28-wspc-battery_hzmhb6aa94h-wspc-(m41t94mh6f)-wspc-wcp-wspc-ver2.xml M41T94
md_so-wspc-16-wspc-.15-wspc-to-wspc-jedec-wspc-ms-012_bzmq-wspc-b6aa94q_vers2_sdm_signed.pdf M41T94
md_so-wspc-16-wspc-.15-wspc-to-wspc-jedec-wspc-ms-012_bzmq-wspc-b6aa94q_vers2.xml M41T94