2N2907 LEAD FREE - CENTRAL SEMICONDUCTOR

Not For New Design

This is information on a product still in production but not recommended for new designs.

May 2008 Rev 9 1/25

M41T00

Serial real-time clock

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 I2C bus (100 kHz

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

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

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.

SO8(M)

www.st.com

Contents M41T00
2/25   
Contents
Device overview   . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Device operation  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
1 Wire bus characteristics  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  7
2 Bus not busy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  7
3 Start data transfer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  7
4 Stop data transfer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  8
5 Data valid  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  8
6 Acknowledge   . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  8
7 Characteristics  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  10
8 READ mode  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  10
9 WRITE mode  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  12
10 Data retention mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  12
M41T00 clock operation  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
1 Clock calibration  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  15
2 Output driver pin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  17
3 Initial power-on defaults  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  17
Maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
DC and AC parameters  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Package mechanical data  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Part numbering  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
Revision history   . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

M41T00 List of tables
 3/25
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

List of figures M41T00
4/25   
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

M41T00 Device overview

5/25

1 Device overview

Figure 1. Logic symbol

Figure 2. SOIC connection

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

VBAT Battery supply voltage

VSS Ground

VCC Supply voltage

AI00530

OSCI

VCC

M41T00

VSS

SCL

OSCO

SDA

FT/OUT

VBAT

SDAVSS

SCL

FT/OUTOSCO

OSCI VCC

VBAT

AI00531

M41T00

Device overview M41T00

6/25

Figure 3. Block diagram

AI00603

SECONDS

OSCILLATOR

32.768 kHz

VOLTAGE

SENSE and

SWITCH

CIRCUITRY

SERIAL

BUS

INTERFACE

DIVIDER

CONTROL

LOGIC

ADDRESS

MINUTES

CENTURY/HOURS

DAY

DATE

MONTH

YEAR

CONTROL

OSCI

OSCO

FT/OUT

VCC

VSS

VBAT

SCL

SDA

1 Hz

M41T00 Device operation

7/25

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:

1st byte: seconds register

2nd byte: minutes register

3rd byte: century/hours register

4th byte: day register

5th byte: date register

6th byte: month register

7th byte: years register

8th byte: control register

The M41T00 clock continually monitors VCC for an out of tolerance condition. Should VCC

fall below VSO, the device terminates an access in progress and resets the device address

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 VCC falls below VSO,

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 VCC at VSO and recognizes inputs.

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

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.

Device operation M41T00

8/25

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.

M41T00 Device operation

9/25

Figure 4. Serial bus data transfer sequence

Figure 5. Acknowledge sequences

Figure 6. Bus timing requirements sequence

1. P = STOP and S = START

AI00587

DATA

CLOCK

DATA LINE

STABLE

DATA VALID

START

CONDITION

CHANGE OF

DATA ALLOWED

STOP

CONDITION

AI00601

DATA OUTPUT

BY RECEIVER

DATA OUTPUT

BY TRANSMITTER

SCLK FROM

MASTER

START

CLOCK PULSE FOR

ACKNOWLEDGEMENT

12 89

MSB LSB

AI00589

SDA

tSU:STOtSU:STA

tHD:STA

SCL

tSU:DAT

tHD:DAT

tHIGH

tLOW

tHD:STAtBUF

Device operation M41T00

10/25

2.7 Characteristics

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.

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.

Table 2. AC characteristics

Symbol Parameter(1)

1. Valid for ambient operating temperature: TA = –40 to 85°C; VCC = 2.0 to 5.5 V (except where noted).

Min Typ Max Units

fSCL SCL clock frequency 0 100 kHz

tLOW Clock low period 4.7 µs

tHIGH Clock high period 4µs

tR SDA and SCL rise time 1µs

tF SDA and SCL fall time 300 ns

tHD:STA START condition hold time

(after this period the first clock pulse is generated) 4µs

tSU:STA START condition setup time

(only relevant for a repeated start condition) 4.7 µs

tHD:DAT(2)

2. Transmitter must internally provide a hold time to bridge the undefined region (300 ns max) of the falling

edge of SCL.

Data hold time 0 ns

tSU:DAT Data setup time 250 ns

tSU:STO STOP condition setup time 4.7 µs

tBUF Time the bus must be free before a new

transmission can start 4.7 µs

M41T00 Device operation

11/25

Figure 7. Slave address location

Figure 8. READ mode sequence

Figure 9. Alternate READ mode sequence

AI00602

R/W

SLAVE ADDRESS

START A

0100011

MSB

LSB

AI00899

BUS ACTIVITY:

ACK

NO ACK STOP

START

SDA LINE

BUS ACTIVITY:

MASTER

R/W

DATA n DATA n+1

DATA n+X

WORD

ADDRESS (An)

SLAVE

ADDRESS

START

R/W

SLAVE

ADDRESS

ACK

AI00895

BUS ACTIVITY:

ACK

NO ACK STOP

START

PSDA LINE

BUS ACTIVITY:

MASTER

R/W

DATA n DATA n+1 DATA n+X

SLAVE

ADDRESS

Device operation M41T00

12/25

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

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 VCC falls (see Figure 11).

Figure 11. Power down/up mode AC waveforms

AI00591

BUS ACTIVITY:

ACK

ACK STOP

START

PSDA LINE

BUS ACTIVITY:

MASTER

R/W

DATA n DATA n+1 DATA n+X

WORD

ADDRESS (An)

SLAVE

ADDRESS

AI00596

VCC

tREC

tPD

VSO

SDA

SCL DON'T CARE

Table 3. RTC power down/up ac characteristics

Symbol Parameter(1)(2) Min Typ Max Unit

tPD SCL and SDA at VIH before power down 0 ns

trec SCL and SDA at VIH after power up 10 µs

1. Valid for ambient operating temperature: TA = -40 to 85°C; VCC = 2.0 to 5.5 V (except where otherwise noted).

2. VCC fall time should not exceed 5 mV/µs.

M41T00 Device operation

13/25

Table 4. RTC power down/up trip points dc characteristics

Symbol Parameter(1)(2)

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 VSS.

Min Typ Max(3)

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 VCC -10 %

operation.

Unit

VSO(4)

4. Switchover and deselect point.

Backup switchover voltage VBAT -0.80 VBAT -0.50 VBAT -0.30 V

M41T00 clock operation M41T00

14/25

3 M41T00 clock operation

The eight byte clock register (see Ta b l 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

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.

M41T00 M41T00 clock operation

15/25

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.

Table 5. Register map(1)

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

Address Data Function/range

BCD format

D7 D6 D5 D4 D3 D2 D1 D0

0 ST 10 seconds Seconds Seconds 00-59

1 X 10 minutes Minutes Minutes 00-59

2CEB(2)

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.

CB 10 hours Hours Century/hours 0-1/00-23

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

M41T00 clock operation M41T00

16/25

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

AI00999b

–160

0 10203040506070

Frequency (ppm)

Temperature °C

80–10–20–30–40

–100

–120

–140

–40

–60

–80

–20

ΔF= K x (T –TO)2

K = –0.036 ppm/°C2 ± 0.006 ppm/°C2

TO = 25°C ± 5°C

M41T00 M41T00 clock operation

17/25

Figure 13. Clock calibration

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.

AI00594B

NORMAL

POSITIVE

CALIBRATION

NEGATIVE

CALIBRATION

Maximum ratings M41T00

18/25

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.

Caution: Negative undershoots below -0.3 V are not allowed on any pin while in the backup mode.

Table 6. Absolute maximum ratings

Symbol Parameter Value Unit

TSTG Storage temperature (VCC off, oscillator off) –55 to 125 °C

TAAmbient operating temperature -40 to 85 °C

VIO Input or output voltages –0.3 to 7 V

TSLD(1)

1. Reflow at peak temperature of 260°C (total thermal budget not to exceed 245°C for greater than 30

seconds).

Lead solder temperature for 10 seconds 260 °C

VCC Supply voltage –0.3 to 7 V

IO Output current 20 mA

PD Power dissipation 0.25 W

M41T00 DC and AC parameters

19/25

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.

Figure 14. AC testing input/output waveform

Table 7. Operating and AC measurement conditions(1)

1. Output Hi-Z is defined as the point where data is no longer driven.

Parameter M41T00

Supply voltage (VCC) 2.0 to 5.5 V

Ambient operating temperature (TA) -40 to 85 °C

Load capacitance (CL) 100 pF

Input rise and fall times ≤ 5 ns

Input pulse voltages 0.2 VCC to 0.8 VCC

Input and output timing reference voltages 0.3 VCC to 0.7 VCC

Table 8. Capacitance

Symbol Parameter (1)(2)

1. Effective capacitance measured with power supply at 3.3 V; sampled only, not 100% tested

2. At 25°C, f = 1 MHz

Min Max Unit

CIN Input capacitance (SCL) 7 pF

COUT(3)

3. Output deselected.

Output capacitance (SDA,FT/OUT) 10 pF

tLP Low-pass filter input time constant (SDA and SCL) 250 1000 ns

AI02568

0.8VCC

0.2VCC

0.7VCC

0.3VCC

DC and AC parameters M41T00

20/25

Table 9. DC characteristics

Symbol Parameter Test condition(1) Min Typ Max Unit

ILI Input leakage current 0 V = VIN = VCC ±1 µA

ILO Output leakage current 0 V = VOUT = VCC ±1 µA

ICC1 Supply current Switch frequency = 100 kHz 300 µA

ICC2 RTC supply current (standby) SCL, SDA = VCC – 0.3 V 70 µA

VIL Input low voltage –0.3 0.3VCC V

VIH Input high voltage 0.7 VCC VCC + 0.5 V

VOL Output low voltage IOL = 3.0 mA 0.4 V

Output low voltage (open drain) FT/OUT 5.5 V

VBAT(2) Battery supply voltage 2.5(3) 3.5(4) V

IBAT Battery supply current TA = 25 °C, VCC = 0 V

oscillator ON, VBAT = 3 V 0.8 1 µA

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 (VSO), VBAT(min) can be 2.0 V for crystal with RS = 40 KΩ.

4. For rechargeable backup, VBAT(max) may be considered VCC.

Table 10. Crystal electrical characteristics

Symbol Parameter (1)(2) Min Typ Max Units

fO Resonant frequency 32.768 kHz

RS Series resistance 60 KΩ

CLLoad capacitance 12.5 pF

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.

M41T00 Package mechanical data

21/25

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.

Package mechanical data M41T00

22/25

Figure 15. SO8 – 8-lead plastic small outline, 150 mils body width, package mechanical data

1. Drawing is not to scale.

SO-A

ccc

h x 45

0.25 mm

GAUGE PLANE

Table 11. SO8 – 8-lead plastic small outline, 150 mils body width, package mechanical data

Symbol

millimeters inches

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

M41T00 Part numbering

23/25

7 Part numbering

Table 12. Ordering information scheme

Example: M41T 00 M 6 E

Device type

M41T

Supply voltage and WRITE protect voltage

00 = VCC = 2.0 to 5.5 V

Package

M = SO8 (150 mils width)

Temperature range

6 = –40 to 85 °C

Shipping method

E = ECOPACK® package, tubes

F = ECOPACK® package, tape & reel

Revision history M41T00
24/25   
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: RS Max changed (Ta b l e 1 0 )
12-Dec-2000 1.3 Edit VSO (Ta b l e 3 )
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 le 9 , Ta bl e 2 ); added 
temp./voltage info. to tables
27-Nov-2001 3.2 Features, (page 1); DC Characteristics (Ta bl e 9 ); Crystal Electrical 
(Tab le 1 0); Power Down/Up Trip Points (Ta bl e 3 ) changes; add table 
footnote (Ta b l e 1 0 )
21-Jan-2002 3.3 Fix table footnotes (Ta b l e 9 , Tab le 1 0)
13-May-2002 3.4 Modify reflow time and temperature footnote (Tab le 6 )
05-Jun-2002 3.5 Corrected operating voltage
03-Jul-2002 3.6 Modify “Clock Operation” text, Crystal Electrical Characteristics table 
footnote (Ta b l 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; Table 6 , Tab l e 9 )
28-Jun-2004 6 New features summary
08-Dec-2006 7 Updated Inside Cover to new template; AIN pin removed from Ta ble 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 l e 6 .

M41T00

25/25

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