M41T0
Serial real-time clock
Features
■ Counters for seconds, minutes, hours, day,
date, month, years, and century
■ 32 KHz crystal oscillator integrating load
capacitance (12.5 pF) providing exceptional
oscillator stability and high crystal series
resistance operation
■ Oscillator stop detection monitors clock
operation
■ Serial interface supports I
(400 kHz protocol)
■ Low standby current 0.9 µA (typ at 3 V)
■ 2.0 to 5.5 V clock operating voltage
■ Special software programmable output
■ Operating temperature of –40 to 85 °C
2
C bus
8
1
SO8
June 2011 Doc ID 9105 Rev 7 1/23
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1
Contents M41T0
Contents
1 Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
2 Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
2.1 2-wire bus characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
2.1.1 Bus not busy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
2.1.2 Start data transfer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
2.1.3 Stop data transfer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
2.1.4 Data valid . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
2.1.5 Acknowledge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
2.2 READ mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
2.3 WRITE mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
3 Clock operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
3.1 Output driver pin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
3.2 Oscillator stop detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
3.3 Initial power-on defaults . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
4 Maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
5 DC and AC parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
6 Package mechanical information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
7 Part numbering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
8 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
2/23 Doc ID 9105 Rev 7
M41T0 List of tables
List of tables
Table 1. Signal names . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Table 2. AC characteristics. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Table 3. Register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Table 4. Absolute maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Table 5. Operating and AC measurement conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Table 6. Capacitance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Table 7. DC characteristics. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Table 8. Crystal electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Table 9. SO8 – 8-lead plastic small outline, 150 mils body width, package mechanical data . . . . . 18
Table 10. Carrier tape dimensions for SO8 package (150 mils body width) . . . . . . . . . . . . . . . . . . . . 19
Table 11. Reel dimensions for 12 mm carrier tape - SO8 package (150 mils body width) . . . . . . . . . 20
Table 12. Ordering information scheme . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Table 13. Document revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Doc ID 9105 Rev 7 3/23
List of figures M41T0
List of figures
Figure 1. Logic diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Figure 2. SOIC connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Figure 3. Block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Figure 4. Serial bus data transfer sequence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Figure 5. Acknowledgement sequence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Figure 6. Bus timing requirements sequence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Figure 7. Slave address location . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Figure 8. READ mode sequence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Figure 9. Alternate READ mode sequence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Figure 10. WRITE mode sequence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Figure 11. AC testing input/output waveform . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Figure 12. SO8 – 8-lead plastic small outline, 150 mils body width, package mechanical drawing. . . 18
Figure 13. Carrier tape for SO8 package (150 mils body width) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Figure 14. Reel schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
4/23 Doc ID 9105 Rev 7
M41T0 Description
1 Description
The M41T0 real-time clock is a low power serial real-time clock with a built-in 32.768 kHz
oscillator (external crystal controlled). Eight registers are used for the clock/calendar
function and are configured in binary coded decimal (BCD) format. Addresses and data are
transferred serially via a two-line bidirectional bus. The built-in address register is
incremented automatically after each WRITE or READ data byte.
The M41T0 is supplied in 8-lead plastic small outline package.
Figure 1. Logic diagram
V
CC
OSCI
SCL
Figure 2. SOIC connections
OSCI V
(1)
NF
SS
1. NF pin must be tied to VSS.
Table 1. Signal names
OSCI Oscillator input
OCSO Oscillator output
M41T0
V
SS
1
2
3
4
M41T0
8
7
6
5
AI07029
OSCO
SDA
OUT
AI07028
CC
OUTOSCO
SCL
SDAV
OUT Output driver (open drain)
SDA Serial data address input / output
SCL Serial clock
(1)
NF
V
CC
V
SS
1. NF pin must be tied to VSS.
No function
Supply voltage
Ground
Doc ID 9105 Rev 7 5/23
Description M41T0
Figure 3. Block diagram
OSCI
OSCO
OSCILLATOR
32.768 kHz
DIVIDER
1 Hz
SECONDS
MINUTES
OUT
V
CC
V
SS
SCL
SDA
SERIAL
BUS
INTERFACE
CONTROL
LOGIC
ADDRESS
REGISTER
CENTURY/HOURS
DAY
DATE
MONTH
YEAR
CONTROL
AI07030
6/23 Doc ID 9105 Rev 7
M41T0 Operation
2 Operation
The M41T0 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 8 bytes
contained in the device can then be accessed sequentially in the following order:
1. Seconds register
2. Minutes register
3. Century/hours register
4. Day register
5. Date register
6. Month register
7. Years register
8. Control register
2.1 2-wire bus characteristics
This bus is intended for communication between different ICs. It consists of two lines: one
bidirectional for data signals (SDA) and one for clock signals (SCL). Both the SDA and the
SCL lines must be connected to a positive supply voltage via a pull-up resistor.
The following protocol has been defined:
● Data transfer may be initiated only when the bus is not busy.
● During data transfer, the data line must remain stable whenever the clock line is high.
Changes in the data line while the clock line is high will be interpreted as control
signals.
Accordingly, the following bus conditions have been defined:
2.1.1 Bus not busy
Both data and clock lines remain high.
2.1.2 Start data transfer
A change in the state of the data line, from high to low, while the clock is high, defines the
START condition.
2.1.3 Stop data transfer
A change in the state of the data line, from low to high, while the clock is high, defines the
STOP condition.
Doc ID 9105 Rev 7 7/23