Features
■ For new designs use M41T00S
■ Counters for seconds, minutes, hours, day,
month, years, 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 I
protocol)
■ Ultra low battery supply current of 0.8 µA
(typ at 3 V)
■ 2.0 to 5.5 V clock operating voltage
■ Automatic switchover and deselect circuitry
(for 3 V application select M41T00S datasheet)
■ Software clock calibration to compensate
crystal deviation due to temperature
■ Automatic leap year compensation
■ Operating temperature of -40 to 85 °C
2
C bus (100 kHz
M41T00
Serial real-time clock
Not For New Design
8
1
SO8(M)
Description
The M41T00 is a low power serial real time clock
with a built-in 32.768 kHz oscillator (external
crystal controlled). Eight bytes of the RAM 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 M41T00 clock has a built-in power sense
circuit which detects power failures and
automatically switches to the battery supply
during power failures. The energy needed to
sustain the RAM and clock operations can be
supplied from a small lithium coin cell.
Typical data retention time is in excess of 5 years
with a 50 mA/h 3 V lithium cell (see Section 2.10:
Data retention mode for AC/DC characteristics).
The M41T00 is supplied in 8-lead plastic small
outline package.
May 2008 Rev 9 1/25
This is information on a product still in production but not recommended for new designs.
www.st.com
1
Contents M41T00
Contents
1 Device overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
2 Device operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
2.1 Wire bus characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
2.2 Bus not busy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
2.3 Start data transfer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
2.4 Stop data transfer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
2.5 Data valid . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
2.6 Acknowledge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
2.7 Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
2.8 READ mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
2.9 WRITE mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
2.10 Data retention mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
3 M41T00 clock operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
3.1 Clock calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
3.2 Output driver pin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
3.3 Initial power-on defaults . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
4 Maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
5 DC and AC parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
6 Package mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
7 Part numbering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
8 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
2/25
M41T00 List of tables
List of tables
Table 1. Pin description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Table 2. AC characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Table 3. RTC power down/up ac characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Table 4. RTC power down/up trip points dc characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Table 5. Register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Table 6. Absolute maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Table 7. Operating and AC measurement conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Table 8. Capacitance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Table 9. DC characteristics. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
Table 10. Crystal electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
Table 11. SO8 – 8-lead plastic small outline, 150 mils body width, package mechanical data . . . . . 22
Table 12. Ordering information scheme . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
Table 13. Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
3/25
List of figures M41T00
List of figures
Figure 1. Logic symbol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Figure 2. SOIC connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Figure 3. Block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Figure 4. Serial bus data transfer sequence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Figure 5. Acknowledge sequences . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 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 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Figure 10. WRITE mode sequences . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Figure 11. Power down/up mode AC waveforms. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Figure 12. Crystal accuracy across temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Figure 13. Clock calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Figure 14. AC testing input/output waveform . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Figure 15. SO8 – 8-lead plastic small outline, 150 mils body width, package mechanical data . . . . . 22
4/25
M41T00 Device overview
1 Device overview
Figure 1. Logic symbol
V
V
CC
BAT
OSCI
SCL
Figure 2. SOIC connection
M41T00
V
SS
M41T00
OSCI V
1
2
V
BAT
SS
3
4
8
7
6
5
AI00531
OSCO
SDA
FT/OUT
AI00530
CC
FT/OUTOSCO
SCL
SDAV
Table 1. Pin description
Symbol Name and function
OSCI Oscillator input
OSCO Oscillator output
FT/OUT Frequency test/output driver (open drain)
SCL Serial clock
SDA Serial data address input/output
V
BAT
V
SS
V
CC
Battery supply voltage
Ground
Supply voltage
5/25
Device overview M41T00
Figure 3. Block diagram
OSCI
OSCO
FT/OUT
V
CC
V
SS
V
BAT
SCL
SDA
OSCILLATOR
32.768 kHz
VOLTAGE
SENSE and
SWITCH
CIRCUITRY
SERIAL
BUS
INTERFACE
DIVIDER
CONTROL
LOGIC
ADDRESS
REGISTER
1 Hz
SECONDS
MINUTES
CENTURY/HOURS
DAY
DATE
MONTH
YEAR
CONTROL
AI00603
6/25
M41T00 Device operation
2 Device operation
The M41T00 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:
st
1
byte: seconds register
nd
2
byte: minutes register
rd
3
byte: century/hours register
th
4
byte: day register
th
5
byte: date register
th
6
byte: month register
th
7
byte: years register
th
8
byte: control register
The M41T00 clock continually monitors V
fall below V
, the device terminates an access in progress and resets the device address
SO
counter. Inputs to the device will not be recognized at this time to prevent erroneous data
from being written to the device from an out of tolerance system. When V
the device automatically switches over to the battery and powers down into an ultra low
current mode of operation to conserve battery life. Upon power-up, the device switches from
battery to V
at VSO and recognizes inputs.
CC
2.1 Wire bus characteristics
This bus is intended for communication between different ICs. It consists of two lines: one
bi-directional 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:
2.2 Bus not busy
for an out of tolerance condition. Should VCC
CC
falls below VSO,
CC
Both data and clock lines remain high.
2.3 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.
7/25
Device operation M41T00
2.4 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.
2.5 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.
The information is transmitted byte-wide and each receiver acknowledges with a ninth bit.
By definition, a device that gives out a message is called “transmitter”, the receiving device
that gets the message is called “receiver”. The device that controls the message is called
“master”. The devices that are controlled by the master are called “slaves”.
2.6 Acknowledge
Each byte of eight bits is followed by one acknowledge bit. This acknowledge bit is a low
level put on the bus by the receiver, whereas the master generates an extra acknowledge
related clock pulse.
A slave receiver which is addressed is obliged to generate an acknowledge after the
reception of each byte. Also, a master receiver must generate an acknowledge after the
reception of each byte that has been clocked out of the slave transmitter.
The device that acknowledges has to pull down the SDA line during the acknowledge clock
pulse in such a way that the SDA line is a stable low during the high period of the
acknowledge related clock pulse. Of course, setup and hold times must be taken into
account. A master receiver must signal an end-of-data to the slave transmitter by not
generating an acknowledge on the last byte that has been clocked out of the slave. In this
case, the transmitter must leave the data line high to enable the master to generate the
STOP condition.
8/25
M41T00 Device operation
Figure 4. Serial bus data transfer sequence
DATA LINE
STABLE
DATA VALID
CLOCK
DATA
START
CONDITION
CHANGE OF
DATA ALLOWED
Figure 5. Acknowledge sequences
START
SCLK FROM
MASTER
DATA OUTPUT
BY TRANSMITTER
DATA OUTPUT
BY RECEIVER
12 89
MSB LSB
Figure 6. Bus timing requirements sequence
STOP
CONDITION
AI00587
CLOCK PULSE FOR
ACKNOWLEDGEMENT
AI00601
SDA
SCL
SP
1. P = STOP and S = START
tHD:STAtBUF
tHIGH
tLOW
tF
tSU:DAT
tHD:DAT
SR
tR
tHD:STA
tSU:STOtSU:STA
P
AI00589
9/25
Device operation M41T00
2.7 Characteristics
Table 2. AC characteristics
Symbol
f
SCL clock frequency
SCL
t
Clock low period
LOW
Clock high period
t
HIGH
SDA and SCL rise time
t
R
t
SDA and SCL fall time
F
t
:STA
HD
START condition hold time
(after this period the first clock pulse is generated)
Parameter
(1)
Min Typ Max Units
0 100 kHz
4.7 µs
4µs
1µs
300 ns
4µs
t
:STA
SU
:DAT
t
HD
t
:DAT Data setup time
SU
t
:STO STOP condition setup time 4.7 µs
SU
t
BUF
1. Valid for ambient operating temperature: TA = –40 to 85°C; VCC = 2.0 to 5.5 V (except where noted).
2. Transmitter must internally provide a hold time to bridge the undefined region (300 ns max) of the falling
edge of SCL.
START condition setup time
(only relevant for a repeated start condition)
(2)
Data hold time 0 ns
Time the bus must be free before a new
transmission can start
2.8 READ mode
In this mode, the master reads the M41T00 slave after setting the slave address (see
Figure 7). Following the WRITE mode control bit (R/W = 0) and the acknowledge bit, the
word address An is written to the on-chip address pointer. Next the START condition and
slave address are repeated, followed by the READ mode control bit (R/W = 1). At this point,
the master transmitter becomes the master receiver. The data byte which was addressed
will be transmitted and the master receiver will send an acknowledge bit to the slave
transmitter. The address pointer is only incremented on reception of an acknowledge bit.
The M41T00 slave transmitter will now place the data byte at address An+1 on the bus. The
master receiver reads and acknowledges the new byte and the address pointer is
incremented to An+2.
4.7 µs
250 ns
4.7 µs
This cycle of reading consecutive addresses will continue until the master receiver sends a
STOP condition to the slave transmitter.
An alternate READ mode may also be implemented, whereby the master reads the M41T00
slave without first writing to the (volatile) address pointer. The first address that is read is the
last one stored in the pointer.
10/25
M41T00 Device operation
Figure 7. Slave address location
R/W
START A
Figure 8. READ mode sequence
BUS ACTIVITY:
MASTER
SDA LINE
BUS ACTIVITY:
START
S
SLAVE
ADDRESS
R/W
ADDRESS (An)
ACK
SLAVE ADDRESS
MSB
0100011
WORD
STOP
START
S
ACK
ADDRESS
SLAVE
LSB
AI00602
R/W
DATA n DATA n+1
ACK
ACK
ACK
DATA n+X
P
NO ACK
Figure 9. Alternate READ mode sequence
BUS ACTIVITY:
MASTER
BUS ACTIVITY:
START
S
SLAVE
ADDRESS
R/W
DATA n DATA n+1 DATA n+X
ACK
ACK
ACK
AI00899
STOP
PSDA LINE
ACK
NO ACK
AI00895
11/25
Device operation M41T00
2.9 WRITE mode
In this mode the master transmitter transmits to the M41T00 slave receiver. Bus protocol is
shown in Figure 10. 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. The data word to be written to the
memory is strobed in next and the internal address pointer is incremented to the next
memory location within the RAM on the reception of an acknowledge clock. The M41T00
slave receiver will send an acknowledge clock to the master transmitter after it has received
the slave address and again after it has received the word address and each data byte (see
Figure 7).
Figure 10. WRITE mode sequences
BUS ACTIVITY:
MASTER
BUS ACTIVITY:
START
S
ADDRESS
R/W
WORD
ADDRESS (An)
ACK
SLAVE
2.10 Data retention mode
With valid VCC applied, the M41T00 can be accessed as described above with READ or
WRITE cycles. Should the supply voltage decay, the M41T00 will automatically deselect,
WRITE protecting itself when V
Figure 11. Power down/up mode AC waveforms
V
CC
VSO
SDA
SCL
tPD
falls (see Figure 11).
CC
DON'T CARE
DATA n DATA n+1 DATA n+X
ACK
ACK
ACK
tREC
STOP
PSDA LINE
ACK
AI00591
AI00596
Table 3. RTC power down/up ac characteristics
Symbol
t
PD
t
rec
1. Valid for ambient operating temperature: TA = -40 to 85°C; VCC = 2.0 to 5.5 V (except where otherwise noted).
2. V
CC
Parameter
(1)(2)
Min Typ Max Unit
SCL and SDA at VIH before power down 0 ns
SCL and SDA at VIH after power up 10 µs
fall time should not exceed 5 mV/µs.
12/25
M41T00 Device operation
Table 4. RTC power down/up trip points dc characteristics
Symbol
(4)
V
SO
1. Valid for ambient operating temperature: TA = –40 to 85 °C; VCC = 2.0 to 5.5 V (except where otherwise
noted).
2. All voltages referenced to V
3. In 3.3 V application, if initial battery voltage is > 3.4 V, it may be necessary to reduce battery voltage (i.e.,
through wave soldering the battery) in order to avoid inadvertent switchover/deselection for V
operation.
4. Switchover and deselect point.
Backup switchover voltage
Parameter
.
SS
(1)(2)
Min Typ
V
-0.80 V
BAT
BAT
-0.50 V
Max
BAT
(3)
-0.30
-10 %
CC
Unit
V
13/25
M41T00 clock operation M41T00
3 M41T00 clock operation
The eight byte clock register (see Ta bl e 5 ) is used to both set the clock and to read the date
and time from the clock, in a binary coded decimal format. Seconds, minutes, and hours are
contained within the first three registers. Bits D6 and D7 of clock register 2 (century/hours
register) contain the century enable bit (CEB) and the century bit (CB). Setting CEB to a '1'
will cause CB to toggle, either from '0' to '1' or from '1' to '0' at the turn of the century
(depending upon its initial state). If CEB is set to a '0', CB will not toggle. Bits D0 through D2
of register 3 contain the day (day of week). Registers 4, 5 and 6 contain the date (day of
month), month and years. The final register is the control register (this is described in the
clock calibration section). Bit D7 of register 0 contains the STOP bit (ST). Setting this bit to a
'1' will cause the oscillator to stop. If the device is expected to spend a significant amount of
time on the shelf, the oscillator may be stopped to reduce current drain. When reset to a '0'
the oscillator restarts within one second.
Note: In order to guarantee oscillator start-up after the initial power-up, set the ST bit to a '1,' then
reset this bit to a '0.' This sequence enables a “kick start” circuit which aids the oscillator
start-up during worst case conditions of voltage and temperature.
The seven clock registers may be read one byte at a time, or in a sequential block. The
control register (address location 7) may be accessed independently. Provision has been
made to ensure that a clock update does not occur while any of the seven clock addresses
are being read. If a clock address is being read, an update of the clock registers will be
delayed by 250 ms to allow the read to be completed before the update occurs. This will
prevent a transition of data during the read.
Note: Note: This 250 ms delay affects only the clock register update and does not alter the actual
clock time.
14/25
M41T00 M41T00 clock operation
Table 5. Register map
Address
0 ST 10 seconds Seconds Seconds 00-59
1 X 10 minutes Minutes Minutes 00-59
2
3XXXXX Day Day 01-07
4 X X 10 date Date Date 01-31
5 X X X 10 M. Month Month 01-12
6 10 Years Years Year 00-99
7 OUT FT S Calibration Control
1. Keys:
S = sign bit
FT = frequency test bit
ST = stop bit
OUT = output level
X = don’t care
CEB = century enable bit
CB = century bit
2. When CEB is set to '1', CB will toggle from '0' to '1' or from '1' to '0' at the turn of the century (dependent
upon the initial value set).When CEB is set to '0', CB will not toggle.
D7 D6 D5 D4 D3 D2 D1 D0
(2)
CEB
CB 10 hours Hours Century/hours 0-1/00-23
(1)
Data
Function/range
BCD format
3.1 Clock calibration
The M41T00 is driven by a quartz controlled oscillator with a nominal frequency of
32768 Hz. The devices are tested not to exceed 35 ppm (parts per million) oscillator
frequency error at 25°C, which equates to about ±1.53 minutes per month. With the
calibration bits properly set, the accuracy of each M41T00 improves to better than ±2 ppm
at 25 °C.
The oscillation rate of any crystal changes with temperature (see Figure 12). Most clock
chips compensate for crystal frequency and temperature shift error with cumbersome trim
capacitors. The M41T00 design, however, employs periodic counter correction. The
calibration circuit adds or subtracts counts from the oscillator divider circuit at the divide by
256 stage, as shown in Figure 13. The number of times pulses are blanked (subtracted,
negative calibration) or split (added, positive calibration) depends upon the value loaded into
the five-bit calibration byte found in the control register. Adding counts speeds the clock up,
subtracting counts slows the clock down.
The calibration byte occupies the five lower order bits (D4-D0) in the control register (addr
7). This byte can be set to represent any value between 0 and 31 in binary form. Bit D5 is a
sign bit; '1' indicates positive calibration, '0' indicates negative calibration. Calibration occurs
within a 64minute cycle. The first 62 minutes in the cycle may, once per minute, have one
second either shortened by 128 or lengthened by 256 oscillator cycles. If a binary '1' is
loaded into the register, only the first 2 minutes in the 64 minute cycle will be modified; if a
binary 6 is loaded, the first 12 will be affected, and so on.
15/25
M41T00 clock operation M41T00
Therefore, each calibration step has the effect of adding 512 or subtracting 256 oscillator
cycles for every 125,829,120 actual oscillator cycles, that is +4.068 or –2.034 ppm of
adjustment per calibration step in the calibration register. Assuming that the oscillator is in
fact running at exactly 32768 Hz, each of the 31 increments in the calibration byte would
represent +10.7 or –5.35 seconds per month which corresponds to a total range of +5.5 or
–2.75 minutes per month.
Two methods are available for ascertaining how much calibration a given M41T00 may
require. The first involves simply setting the clock, letting it run for a month and comparing it
to a known accurate reference (like WWV broadcasts). While that may seem crude, it allows
the designer to give the end user the ability to calibrate his clock as his environment may
require, even after the final product is packaged in a non-user serviceable enclosure. All the
designer has to do is provide a simple utility that accessed the calibration byte.
The second approach is better suited to a manufacturing environment, and involves the use
of some test equipment. When the frequency test (FT) bit, the seventh-most significant bit in
the control register, is set to a '1', and the oscillator is running at 32768 Hz, the FT/OUT pin
of the device will toggle at 512 Hz. Any deviation from 512 Hz indicates the degree and
direction of oscillator frequency shift at the test temperature.
For example, a reading of 512.01024 Hz would indicate a +20 ppm oscillator frequency
error, requiring a –10(XX00 1010b) to be loaded into the calibration byte for correction. Note
that setting or changing the calibration byte does not affect the frequency test output
frequency.
Figure 12. Crystal accuracy across temperature
Frequency (ppm)
20
0
–20
–40
–60
–80
ΔF
–100
–120
–140
–160
0 10203040506070
= K x (T –T
F
K = –0.036 ppm/°C2 ± 0.006 ppm/°C
TO = 25°C ± 5°C
Temperature °C
2
)
O
2
80–10–20–30–40
AI00999b
16/25
M41T00 M41T00 clock operation
Figure 13. Clock calibration
NORMAL
POSITIVE
CALIBRATION
NEGATIVE
CALIBRATION
AI00594B
3.2 Output driver pin
When the FT bit is not set, the FT/OUT pin becomes an output driver that reflects the
contents of D7 of the control register. In other words, when D6 of address 7 is a zero and D7
of address 7 is a zero and then the FT/OUT pin will be driven low.
Note: The FT/OUT pin is open drain which requires an external pull-up resistor.
3.3 Initial power-on defaults
Upon initial application of power to the device, the FT bit will be set to a '0' and the OUT bit
will be set to a '1'. All other register bits will initially power on in a random state.
17/25
Maximum ratings M41T00
4 Maximum ratings
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. Refer also to the STMicroelectronics SURE Program and other relevant quality
documents.
Table 6. Absolute maximum ratings
Symbol Parameter Value Unit
T
STG
T
V
IO
T
SLD
V
CC
I
O
P
1. Reflow at peak temperature of 260°C (total thermal budget not to exceed 245°C for greater than 30
seconds).
Storage temperature (VCC off, oscillator off) –55 to 125 °C
Ambient operating temperature -40 to 85 °C
A
Input or output voltages –0.3 to 7 V
(1)
Lead solder temperature for 10 seconds 260 °C
Supply voltage –0.3 to 7 V
Output current 20 mA
Power dissipation 0.25 W
D
Caution: Negative undershoots below -0.3 V are not allowed on any pin while in the backup mode.
18/25
M41T00 DC and AC parameters
5 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.
Table 7. Operating and AC measurement conditions
Parameter M41T00
Supply voltage (V
Ambient operating temperature (T
Load capacitance (C
) 2.0 to 5.5 V
CC
) -40 to 85 °C
A
) 100 pF
L
Input rise and fall times
(1)
5 ns
≤
Input pulse voltages 0.2 VCC to 0.8 V
Input and output timing reference voltages 0.3 VCC to 0.7 V
1. Output Hi-Z is defined as the point where data is no longer driven.
Figure 14. AC testing input/output waveform
0.8V
CC
0.2V
CC
Table 8. Capacitance
Symbol
C
C
OUT
t
1. Effective capacitance measured with power supply at 3.3 V; sampled only, not 100% tested
2. At 25°C, f = 1 MHz
3. Output deselected.
Input capacitance (SCL) 7 pF
IN
(3)
Output capacitance (SDA,FT/OUT) 10 pF
Low-pass filter input time constant (SDA and SCL) 250 1000 ns
LP
Parameter
(1)(2)
0.7V
CC
0.3V
CC
AI02568
Min Max Unit
CC
CC
19/25
DC and AC parameters M41T00
Table 9. DC characteristics
Symbol Parameter
I
LI
ILO
I
CC1
I
CC2
V
IL
V
IH
V
OL
IN
= V
= V
CC
(1)
CC
CC
– 0.3 V
Test condition
Input leakage current
Output leakage current
Supply current Switch frequency = 100 kHz 300 µA
RTC supply current (standby)
Input low voltage –0.3
0 V = V
0 V = V
OUT
SCL, SDA = V
Input high voltage
I
Output low voltage
= 3.0 mA
OL
Min Typ Max Unit
±1 µA
±1 µA
70 µA
0.3V
V
0.7 V
CC
CC
+ 0.5
0.4 V
CC
Output low voltage (open drain) FT/OUT 5.5 V
(2)
V
BAT
I
BAT
1. Valid for ambient operating temperature: TA = –40 to 85 °C; VCC = 2.0 to 5.5 V (except where otherwise noted).
2. STMicroelectronics recommends the RAYOVAC BR1225 or BR1632 (or equivalent)as the battery supply.
3. After switchover (V
4. For rechargeable backup, V
Table 10. Crystal electrical characteristics
Symbol
1. Externally supplied if using the SO8 package. STMicroelectronics recommends the KDS DT-38: 1TA/1TC252E127, Tuning
Fork Type (thru-hole) or the DMX-26S: 1TJS125FH2A212, (SMD) quartz crystal for industrial temperature operations. KDS
can be contacted at kouhou@kdsj.co.jp or http://www.kdsj.co.jp for further information on this crystal type.
2. Load capacitors are integrated within the M41T00. Circuit board layout considerations for the 32.768 kHz crystal of
minimum trace lengths and isolation from RF generating signals should be taken into account.
Battery supply voltage
Battery supply current
), V
SO
(min) can be 2.0 V for crystal with RS = 40 KΩ.
BAT
(max) may be considered VCC.
BAT
Parameter
f
Resonant frequency 32.768 kHz
O
R
Series resistance 60 KΩ
S
C
Load capacitance 12.5 pF
L
TA = 25 °C, VCC = 0 V
oscillator ON, V
(1)(2)
= 3 V
BAT
Min Typ Max Units
2.5
(3)
0.8 1 µA
3.5
(4)
V
V
V
20/25
M41T00 Package mechanical data
6 Package mechanical data
In order to meet environmental requirements, ST offers these devices in ECOPACK®
packages. These packages have a Lead-free second level interconnect . The category of
second level interconnect is marked on the package and on the inner box label, in
compliance with JEDEC Standard JESD97. The maximum ratings related to soldering
conditions are also marked on the inner box label. ECOPACK is an ST trademark.
ECOPACK specifications are available at: www.st.com.
21/25
Package mechanical data M41T00
Figure 15. SO8 – 8-lead plastic small outline, 150 mils body width, package mechanical data
h x 45
A2
b
e
D
8
1
1. Drawing is not to scale.
Table 11. SO8 – 8-lead plastic small outline, 150 mils body width, package mechanical data
E1
A
ccc
E
A1
L
L1
c
0.25 mm
GAUGE PLANE
k
SO-A
millimeters inches
Symbol
Typ Min Max Typ Min Max
A 1.75 0.069
A1 0.10 0.25 0.004 0.010
A2 1.25 0.049
b 0.28 0.48 0.011 0.019
c 0.17 0.23 0.007 0.009
ccc 0.10 0.004
D 4.90 4.80 5.00 0.193 0.189 0.197
E 6.00 5.80 6.20 0.236 0.228 0.244
E1 3.90 3.80 4.00 0.154 0.150 0.157
e1.27––0.050––
h 0.25 0.50 0.010 0.020
k0808
L 0.40 1.27 0.016 0.050
L1 1.04 0.041
22/25
M41T00 Part numbering
7 Part numbering
Table 12. Ordering information scheme
Example: M41T 00 M 6 E
Device type
M41T
Supply voltage and WRITE protect voltage
00 = V
Package
M = SO8 (150 mils width)
Temperature range
6 = –40 to 85 °C
= 2.0 to 5.5 V
CC
Shipping method
E = ECOPACK
F = ECOPACK
®
®
package, tubes
package, tape & reel
23/25
Revision history M41T00
8 Revision history
Table 13. Revision history
Date Revision Changes
Mar-1999 1.0 First Issue
15-May-2000 1.1 AC Characteristic conditions changed (Ta b l e 2 )
25-Jul-2000 1.2 Crystal Electrical Characteristics: R
12-Dec-2000 1.3 Edit V
(Ta bl e 3 )
SO
24-Jan-2001 2.0 Reformatted
27-Feb-2001 3.0 Document Status changed
17-Jul-2001 3.1 Change to DC and AC Characteristics (Ta b l e 9 , Ta b le 2 ); added
temp./voltage info. to tables
27-Nov-2001 3.2 Features, (page 1); DC Characteristics (Ta b le 9 ); Crystal Electrical
(Ta bl e 1 0 ); Power Down/Up Trip Points (Ta bl e 3 ) changes; add table
footnote (Ta bl e 1 0)
21-Jan-2002 3.3 Fix table footnotes (Ta bl e 9 , Ta bl e 1 0 )
13-May-2002 3.4 Modify reflow time and temperature footnote (Ta bl e 6 )
Max changed (Ta bl e 1 0 )
S
05-Jun-2002 3.5 Corrected operating voltage
03-Jul-2002 3.6 Modify “Clock Operation” text, Crystal Electrical Characteristics table
footnote (Ta bl e 1 0)
07-Nov-2002 3.7 Correct figure name on page1
15-Jun-04 5.0 Reformatted; add Lead-free information; update characteristics
(Figure 12; Ta bl e 6 , Tab le 9 )
28-Jun-2004 6 New features summary
08-Dec-2006 7 Updated Inside Cover to new template; AIN pin removed from Ta bl e 1 :
Pin description; small text change in Section 3: M41T00 clock
operation; updated package mechanical data (Section 6: Package
mechanical data).
22-Dec-2006 8 Corrected Table 11: SO8 – 8-lead plastic small outline, 150 mils body
width, package mechanical data.
15-May-2008 9 Datasheet status updated to “not for new design” (updated cover page),
updated Ta b le 6 .
24/25
M41T00
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