M41T80 Serial access real-time clock with alarm 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 interface supports I2C bus (400 kHz) ■ 2.0 to 5.
Contents M41T80 Contents 1 Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 2 Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 2.1 3 2-Wire bus characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 2.1.1 Bus not busy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 2.1.2 Start data transfer .
M41T80 List of tables List of tables Table 1. Table 2. Table 3. Table 4. Table 5. Table 6. Table 7. Table 8. Table 9. Table 10. Table 11. Table 12. Table 13. Table 14. Table 15. Table 16. Signal names . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 AC characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 Clock register map . . . . . . . . . . . . . . . . .
List of figures M41T80 List of figures Figure 1. Figure 2. Figure 3. Figure 4. Figure 5. Figure 6. Figure 7. Figure 8. Figure 9. Figure 10. Figure 11. Figure 12. Figure 13. Figure 14. Figure 15. 4/27 Logic diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 8-pin SOIC connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Block diagram . . . . . . . . . . . . . . .
M41T80 1 Description Description The M41T80 is a low power serial RTC with a built-in 32.768 kHz oscillator (external crystal controlled). Eight registers (see Table 3: Clock register map on page 14) are used for the clock/calendar function and are configured in binary coded decimal (BCD) format. An additional 12 registers provide status/control of alarm, 32 KHz output, and square wave functions. Addresses and data are transferred serially via a two line, bi-directional I2C interface.
Description M41T80 Figure 2. 8-pin SOIC connections XI XO F32K(1) VSS 1 2 3 4 M41T80 8 7 6 5 VCC IRQ/OUT/SQW(1) SCL SDA AI07006 1. Open drain output Figure 3. Block diagram REAL TIME CLOCK CALENDAR CRYSTAL 32KHz OSCILLATOR RTC W/ALARM AF IRQ/OUT/SQW(1) SDA I2C INTERFACE SQUARE WAVE SCL F32K(1) AI07007 1.
M41T80 2 Operation Operation The M41T80 clock operates as a slave device on the serial bus. Access is obtained by implementing a start condition followed by the correct slave address (D0h). The 20 bytes contained in the device can then be accessed sequentially in the following order: 2.
Operation 2.1.4 M41T80 Data valid The state of the data line represents valid data when after a start condition, the data line is stable for the duration of the high period of the clock signal. The data on the line may be changed during the Low period of the clock signal. There is one clock pulse per bit of data. Each data transfer is initiated with a start condition and terminated with a stop condition. The number of data bytes transferred between the start and stop conditions is not limited.
M41T80 Figure 5. Operation Acknowledgement sequence CLOCK PULSE FOR ACKNOWLEDGEMENT START SCL FROM MASTER 1 DATA OUTPUT BY TRANSMITTER 2 8 MSB 9 LSB DATA OUTPUT BY RECEIVER AI00601 Figure 6.
Operation M41T80 Table 2. AC characteristics Parameter(1) Sym Min Typ Max Units 400 kHz fSCL SCL clock frequency tLOW Clock low period 1.
M41T80 Operation Figure 7. Slave address location R/W START A 1 LSB MSB SLAVE ADDRESS 1 0 1 0 0 0 AI00602 R/W SLAVE ADDRESS DATA n+1 ACK DATA n ACK BUS ACTIVITY: S ACK WORD ADDRESS (An) ACK S R/W SDA LINE ACK BUS ACTIVITY: MASTER START READ mode sequence START Figure 8.
Operation 2.3 M41T80 WRITE mode In this mode the master transmitter transmits to the M41T80 slave receiver. Bus protocol is shown in Figure 10: WRITE mode sequence on page 12. Following the START condition and slave address, a logic '0' (R/W=0) is placed on the bus and indicates to the addressed device that word address “An” will follow and is to be written to the on-chip address pointer.
M41T80 3 Clock operation Clock operation The M41T80 is driven by a quartz-controlled oscillator with a nominal frequency of 32,768 Hz. The accuracy of the real-time clock depends on the frequency of the quartz crystal that is used as the time-base for the RTC. The 20-byte register map (see Table 3: Clock register map on page 14) is used to both set the clock and to read the date and time from the clock, in a binary coded decimal format.
Clock operation M41T80 Clock register map(1) Table 3. Addr D7 00h D6 D5 D4 D3 0.1 seconds D2 D0 0.
M41T80 3.2 Clock operation Setting alarm clock registers Address locations 0Ah-0Eh contain the alarm settings. The alarm can be configured to go off at a prescribed time on a specific month, date, hour, minute, or second or repeat every year, month, day, hour, minute, or second. Bits RPT5-RPT1 put the alarm in the repeat mode of operation. Table 4: Alarm repeat modes shows the possible configurations.
Clock operation M41T80 Table 5. Square wave output frequency Square wave bits 3.3 Square wave RS3 RS2 RS1 RS0 Frequency Units 0 0 0 0 None - 0 0 0 1 32.768 kHz 0 0 1 0 8.192 kHz 0 0 1 1 4.096 kHz 0 1 0 0 2.048 kHz 0 1 0 1 1.
M41T80 3.5 Clock operation Output driver pin When the AFE bit and SQWE bit are not set, the IRQ/OUT/SQW pin becomes an output driver that reflects the contents of D7 of the control register. In other words, when D7 (OUT bit) of address location 08h is a '0,' then the IRQ/OUT/SQW pin will be driven low. Note: The IRQ/OUT/SQW pin is an open drain which requires an external pull-up resistor. 3.
Maximum rating 4 M41T80 Maximum rating Stressing the device above the rating listed in the “absolute maximum ratings” table may cause permanent damage to the device. These are stress ratings only and operation of the device at these or any other conditions above those indicated in the operating sections of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.
M41T80 5 DC and AC parameters DC and AC parameters This section summarizes the operating and measurement conditions, as well as the DC and AC characteristics of the device. The parameters in the following DC and AC Characteristic tables are derived from tests performed under the measurement conditions listed in the relevant tables. Designers should check that the operating conditions in their projects match the measurement conditions when using the quoted parameters.
DC and AC parameters Table 10. DC characteristics Symbol Test condition(1) Parameter ILI Input leakage current ILO Output leakage current ICC1 Supply current Min Typ Max Unit 0 V ≤ VIN ≤ VCC ±1 µA 0 V ≤ VOUT ≤ VCC ±1 µA 3.0 V 30 µA 5.5 V 200 µA 3.0 µA 35 µA 2.4 µA 31 µA Switch freq (SCL) = 400 kHz All inputs = VCC – 0.2 V Switch freq (SCL) = 0 Hz Supply current (standby) ICC2(2) M41T80 32KE = 1 3.0 V or SQWE = 1 5.5 V 1.8 32KE = 0 3.0 V and SQWE = 0 5.5 V 1.
M41T80 6 Package mechanical data Package mechanical data In order to meet environmental requirements, ST offers these devices in different grades of ECOPACK® packages, depending on their level of environmental compliance. ECOPACK® specifications, grade definitions and product status are available at: www.st.com. ECOPACK® is an ST trademark.
Package mechanical data M41T80 Figure 13. SO8 – 8-lead plastic small outline, 150 mils body width, package mechanical drawing h x 45° A2 A c ccc b e 0.25 mm GAUGE PLANE D k 8 E1 E 1 A1 L L1 SO-A 1. Drawing is not to scale. Table 12. SO8 – 8-lead plastic small outline, 150 mils body width, package mechanical data millimeters inches Symbol Typ Min A Typ Min 1.75 Max 0.069 A1 0.10 A2 1.25 b 0.28 0.48 0.011 0.019 c 0.17 0.23 0.007 0.009 ccc 0.25 0.004 0.010 0.049 0.
M41T80 Package mechanical data Figure 14. Carrier tape for SO8 package P0 E P2 D T A0 F TOP COVER TAPE W B0 P1 CENTER LINES OF CAVITY K0 USER DIRECTION OF FEED AM03073v1 Table 13. Carrier tape dimensions for SO8 package Package W D SO8 12.00 ±0.30 1.50 +0.10/ –0.00 E P0 P2 F 1.75 4.00 2.00 5.50 ±0.10 ±0.10 ±0.10 ±0.05 A0 B0 K0 P1 T 6.50 ±0.10 5.30 ±0.10 2.20 ±0.10 8.00 ±0.10 0.30 ±0.
Package mechanical data M41T80 Figure 15. Reel schematic T 40mm min. Access hole At slot location B D C N A G measured Tape slot In core for Full radius Tape start 2.5mm min.width At hub AM04928v1 Table 14. Reel dimensions for 12 mm carrier tape - SO8 package (150 mils body width) A B (max) (min) 330 mm (13-inch) 1.5 mm Note: 24/27 C 13 mm ± 0.2 mm D N (min) (min) 20.2 mm 60 mm G 12.4 mm + 2/–0 mm T (max) 18.
M41T80 7 Part numbering Part numbering Table 15. Ordering information scheme Example: M41T 80 M 6 E Device type M41T Supply voltage and write protect voltage 80 = VCC = 2.0 to 5.5 V Package M = SO8 Temperature range 6 = –40 °C to 85 °C Shipping method E = ECOPACK® package, tubes (1) F = ECOPACK® package, tape & reel 1. Shipping in tubes is not recommended for new design. Contact local ST sales office for availability.
Revision history 8 M41T80 Revision history Table 16. 26/27 Revision history Date Revision Changes Oct-2002 1 First issue 15-Jun-2004 2 Reformatted; add lead-free information; update characteristics (Table 7, Table 10, Table 15) 29-Aug-2006 3 Changed document to new template; added new features in Features on page 1; updated package mechanical data in Section 6: Package mechanical data; small text changes for entire document, ECOPACK® compliant.
M41T80 Please Read Carefully: Information in this document is provided solely in connection with ST products. STMicroelectronics NV and its subsidiaries (“ST”) reserve the right to make changes, corrections, modifications or improvements, to this document, and the products and services described herein at any time, without notice. All ST products are sold pursuant to ST’s terms and conditions of sale.
