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M41T62, M41T64, M41T65
Low-power serial real-time clocks (RTCs) with alarm
Datasheet - production data
•
•
•
•
•
•
Features
•
•
•
•
•
Serial real-time clock (RTC) with alarm
functions
2
−
400 kHz I C serial interface
−
Memory mapped registers for seconds,
minutes, hours, day, date, month, year,
and century
−
Tenths/hundredths of seconds register
350 nA timekeeping current at 3 V
Timekeeping down to 1.0 V
2
1.3 V to 4.4 V I C bus operating voltage
−
4.4 V max VCC suitable for lithium-ion
battery operation
Low operating current of 35 µA (at 400 kHz
2
I C speed)
October 2015
•
•
•
•
32 KHz square wave output is on at powerup. Suitable for driving a microcontroller in
low-power mode. Can be disabled.
(M41T62/64)
Programmable 1 Hz to 32 KHz square wave
output (M41T62/64)
Programmable alarm with interrupt function
(M41T62/65)
32 KHz crystal oscillator integrates crystal
load capacitors, works with high series
resistance crystals
Oscillator stop detection monitors clock
operation
Accurate programmable watchdog
−
62.5 ms to 31 min timeout
Software clock calibration. Can adjust
timekeeping to within ±2 parts per million (±5
seconds per month)
Automatic leap year compensation
–40 to +85 °C operation
Two package options
−
Very small 3 x 3 mm, lead-free &
®
halogen-free (ECOPACK2 ) 16-lead
QFN
−
Ultra-small 1.5 x 3.2 mm, lead-free &
®
halogen-free (ECOPACK2 ) 8-pin
ceramic leadless chip carrier with
embedded 32 KHz crystal - no external
oscillator components required
(M41T62)
DocID10397 Rev 22
This is information on a product in full production.
1/44
www.st.com
Contents
M41T62, M41T64, M41T65
Contents
1
Description....................................................................................... 6
2
Operation ....................................................................................... 11
2.1
3
2-wire bus characteristics ................................................................ 11
2.1.1
Bus not busy ..................................................................................... 11
2.1.2
Start data transfer ............................................................................. 11
2.1.3
Stop data transfer ............................................................................. 11
2.1.4
Data valid .......................................................................................... 12
2.1.5
Acknowledge .................................................................................... 12
2.2
READ mode .................................................................................... 13
2.3
WRITE mode................................................................................... 14
Clock operation ............................................................................. 15
3.1
RTC registers .................................................................................. 16
3.2
Calibrating the clock ........................................................................ 21
3.3
Setting alarm clock registers ........................................................... 23
3.4
Watchdog timer ............................................................................... 24
3.5
Watchdog output (𝐖𝐖𝐖𝐖𝐖𝐖 - M41T65 only) ......................................... 24
3.6
Square wave output (M41T62/64) ................................................... 25
3.7
Full-time 32 KHz square wave output (M41T64) ............................. 25
3.8
Century bits ..................................................................................... 26
3.9
Leap year ........................................................................................ 26
3.10
Output driver pin (M41T62/65) ........................................................ 27
3.11
Oscillator stop detection .................................................................. 27
3.12
Initial power-on defaults .................................................................. 27
4
Maximum ratings ........................................................................... 28
5
DC and AC parameters ................................................................. 29
6
Package information ..................................................................... 33
7
2/44
6.1
QFN16 package information ........................................................... 34
6.2
LCC8 package information .............................................................. 37
Packing information ...................................................................... 39
7.1
QFN16 carrier tape ......................................................................... 39
7.2
LCC8 carrier tape ............................................................................ 40
7.3
Reel information for QFN16 and LCC8 ........................................... 41
DocID10397 Rev 22
M41T62, M41T64, M41T65
Contents
8
Part numbering .............................................................................. 42
9
Revision history ............................................................................ 43
DocID10397 Rev 22
3/44
List of tables
M41T62, M41T64, M41T65
List of tables
Table 1: Device summary ........................................................................................................................... 6
Table 2: Signal names ................................................................................................................................ 8
Table 3: M41T62 register map.................................................................................................................. 18
Table 4: M41T64 register map.................................................................................................................. 19
Table 5: M41T65 register map.................................................................................................................. 20
Table 6: Alarm repeat modes ................................................................................................................... 23
Table 7: Square wave output frequency ................................................................................................... 25
Table 8: Examples using century bits ....................................................................................................... 26
Table 9: Initial power-up values ................................................................................................................ 27
Table 10: Absolute maximum ratings ....................................................................................................... 28
Table 11: Operating and AC measurement conditions............................................................................. 29
Table 12: Capacitance .............................................................................................................................. 30
Table 13: DC characteristics ..................................................................................................................... 30
Table 14: Crystal electrical characteristics ............................................................................................... 31
Table 15: Crystals suitable for use with M41T6x series RTCs ................................................................. 31
Table 16: Oscillator characteristics ........................................................................................................... 32
Table 17: AC characteristics ..................................................................................................................... 32
Table 18: QFN16 — 16-pin, quad, flat package, no-lead, 3x3 mm, package mechanical data ............... 35
Table 19: LCC8 — 8-pin, 1.5 x 3.2 mm leadless chip carrier package mechanical data ......................... 37
Table 20: Carrier tape dimensions for QFN16 3 x 3 mm package ........................................................... 39
Table 21: Reel dimensions for 12 mm carrier tape - QFN16 and LCC8 packages .................................. 41
Table 22: Ordering information scheme ................................................................................................... 42
Table 23: Document revision history ........................................................................................................ 43
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DocID10397 Rev 22
M41T62, M41T64, M41T65
List of figures
List of figures
Figure 1: M41T62 logic diagram ................................................................................................................. 6
Figure 2: M41T64 logic diagram ................................................................................................................. 7
Figure 3: M41T65 logic diagram ................................................................................................................. 7
Figure 4: M41T62 connections ................................................................................................................... 7
Figure 5: M41T64 connections ................................................................................................................... 8
Figure 6: M41T65 connections ................................................................................................................... 8
Figure 7: M41T62 block diagram ................................................................................................................ 9
Figure 8: M41T64 block diagram ................................................................................................................ 9
Figure 9: M41T65 block diagram ................................................................................................................ 9
Figure 10: Hardware hookup for SuperCap™ backup operation ............................................................. 10
Figure 11: Serial bus data transfer sequence ........................................................................................... 12
Figure 12: Acknowledgement sequence................................................................................................... 13
Figure 13: Slave address location ............................................................................................................ 13
Figure 14: READ mode sequence ............................................................................................................ 14
Figure 15: Alternative READ mode sequence .......................................................................................... 14
Figure 16: WRITE mode sequence .......................................................................................................... 14
Figure 17: Buffer/transfer registers ........................................................................................................... 16
Figure 18: Crystal accuracy across temperature ...................................................................................... 22
Figure 19: Calibration waveform ............................................................................................................... 22
Figure 20: Alarm interrupt reset waveform ............................................................................................... 23
Figure 21: Century bits CB1 and CB0 ...................................................................................................... 26
Figure 22: AC measurement I/O waveform .............................................................................................. 29
Figure 23: Crystal isolation example......................................................................................................... 29
Figure 24: Bus timing requirements sequence ......................................................................................... 32
Figure 25: QFN16 — 16-pin, quad, flat package, no-lead, 3x3 mm, package outline ............................. 34
Figure 26: QFN16 — 16-pin, quad, flat package, no-lead, 3 x 3 mm recommended footprint................. 36
Figure 27: LCC8 — 8-pin, 1.5 x 3.2 mm leadless chip carrier package outline ....................................... 37
Figure 28: LCC8 — 8-pin, 1.5 x 3.2 mm leadless chip carrier recommended footprint ........................... 38
Figure 29: Carrier tape for QFN16 3 x 3 mm package ............................................................................. 39
Figure 30: Carrier tape for LCC8 1.5 x 3.2 mm package.......................................................................... 40
Figure 31: Reel schematic ........................................................................................................................ 41
DocID10397 Rev 22
5/44
Description
1
M41T62, M41T64, M41T65
Description
The M41T6x is a low-power serial real-time clock (RTC) with a built-in 32.768 kHz
oscillator. Eight registers are used for the clock/calendar function and are configured in
binary-coded decimal (BCD) format. An additional eight registers provide status/control of
alarm, 32 KHz output, calibration, and watchdog functions. Addresses and data are
2
transferred serially via a two-line, bidirectional I C interface. The built-in address register is
incremented automatically after each WRITE or READ data byte.
Functions available to the user include a time-of-day clock/calendar, alarm interrupts
(M41T62/65), 32 KHz output (M41T62/64), programmable square wave output
(M41T62/64), and watchdog output (M41T65). 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), 30- and 31-day months
are made automatically.
The M41T6x is supplied in two very small packages: a tiny, 3 x 3 mm 16-pin QFN which
requires a user-supplied 32 KHz crystal, and an ultra-small 1.5 x 3.2 mm LCC with
embedded crystal - no external crystal is required.
Table 1: Device summary
Device
Basic
RTC
Alarms
OSC fail
detect
Watchdog
timer
Calibration
SQW
output
M41T62
✓
✓
✓
✓
✓
✓
M41T64
✓
✓
✓
✓
✓
✓
M41T65
✓
✓
✓
✓
✓
(3)
XI
SCL
(1)
M41T62
SDA
VSS
1.
2.
3.
6/44
Open drain.
Defaults to 32 KHz on power-up.
Not bonded on LCC package.
DocID10397 Rev 22
IRQ/OUT
SQW(2)
✓
✓
F32K
output
✓
VCC
(3)
𝐖𝐖𝐖𝐖𝐖𝐖
output
✓
Figure 1: M41T62 logic diagram
XO
𝐈𝐈𝐑𝐑𝐐𝐐
output
M41T62, M41T64, M41T65
Description
Figure 2: M41T64 logic diagram
VCC
XI
(1)
XO
SQW
M41T64
SCL
(2)
F32K
SDA
VSS
1.
2.
Open drain.
Defaults to 32 KHz on power-up.
Figure 3: M41T65 logic diagram
VCC
XI
WDO(1)
XO
M41T65
SCL
(1)
IRQ/FT/OUT
SDA
VSS
1.
Open drain.
1.
2.
NC
NC
VCC
NC
Figure 4: M41T62 connections
16
15
14
13
VSS
NC
NC
5
VCC
LCC
8
NC
7
4
NC
9
6
IRQ/OUT(2)
SDA
4
5
6
VSS
10
SQW(1)
3
SCL
3
VSS
QFN
NC
2
IRQ/OUT(2)
2
7
SQW(1)
11
XO
SCL
1
NC
1
8
SDA
12
XI
SQW output defaults to 32 KHz upon power-up.
Open drain.
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Description
M41T62, M41T64, M41T65
NC
NC
VCC
NC
Figure 5: M41T64 connections
16
15
14
13
XI
1
12
NC
XO
2
11
SQW(2)
VSS
3
10
SCL
(1)
4
9
SDA
1.
2.
7
8
NC
6
NC
VSS
5
NC
F32K
Enabled on power-up.
Open drain.
1.
NC
NC
VCC
NC
Figure 6: M41T65 connections
16
15
14
13
XO
2
11
IRQ/FT/OUT(1)
VSS
3
10
SCL
WDO(1)
4
9
SDA
5
6
7
8
NC
NC
NC
12
NC
1
VSS
XI
Open drain.
Table 2: Signal names
XI
Oscillator input
XO
Oscillator output
SDA
Serial data input/output
SCL
Serial clock input
IRQ/OUT
IRQ/FT/OUT
8/44
Interrupt or OUT output (open drain)
Interrupt, frequency test, or OUT output (open drain)
SQW
Programmable square wave - defaults to 32 KHz on power-up (open drain for
M41T64 only)
F32K
Dedicated 32 KHz output (M41T64 only)
WDO
Watchdog timer output (open drain)
VCC
Supply voltage
VSS
Ground
DocID10397 Rev 22
M41T62, M41T64, M41T65
Description
Figure 7: M41T62 block diagram
REAL TIME CLOCK
CALENDAR
(3)
XTAL
(3)
SDA
32KHz
OSCILLATOR
I2C
INTERFACE
SCL
1.
2.
3.
OSCILLATOR FAIL
DETECT
OFIE
RTC W/ALARM
AFE
IRQ/OUT(1)
SQWE
SQW(2)
WATCHDOG
SQUARE WAVE
Open drain.
Defaults to 32 KHz on power-up.
Not bonded on embedded crystal (LCC) package.
Figure 8: M41T64 block diagram
32KE
REAL TIME CLOCK
CALENDAR
XTAL
(1)
F32K
OSCILLATOR FAIL
DETECT
32KHz
OSCILLATOR
RTC W/ALARM
SDA
WATCHDOG
I2C
INTERFACE
1.
2.
SQWE
SQUARE WAVE
SCL
(2)
SQW
Defaults enabled on power-up.
Open drain.
Figure 9: M41T65 block diagram
REAL TIME CLOCK
CALENDAR
XTAL
32KHz
OSCILLATOR
OSCILLATOR FAIL OFIE
DETECT
FT
RTC W/ALARM
SDA
I2C
INTERFACE
WATCHDOG
AFE
IRQ/FT/OUT
WDO
(1)
(1)
SCL
1.
Open drain.
DocID10397 Rev 22
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Description
M41T62, M41T64, M41T65
Figure 10: Hardware hookup for SuperCap™ backup operation
POWER SUPPLY
VCC
(1)
D1
+
–
Ro
LEAKAGE�
PATH
M41T6x
VCC
XI
XO
(2)
IRQ/FT/OUT
(3)
WDO
(4)
SQW
VSS
1.
2.
3.
4.
D2
MCU
VCC
Port
Reset Input
SQWIN
SCL
Serial Clock Line
SDA
Serial Data Line
F32K
32KHz CLKIN
Diode D2 required on open drain pin (M41T65 only) when using SuperCap (or battery)
backup. Low threshold BAT42 schottky diode recommended (see note below). D1 and
D2 should be of the same type.
For M41T62 and M41T65 (open drain).
For M41T65 (open drain).
For M41T64 (open drain).
Note: Some power supplies, when shut off, can present a leakage path to ground which will
shorten the backup time provided by the SuperCap (or battery). In such cases, a very low
leakage diode is recommended for D1 (and D2). A non-schottky such as the 1N4148 will
have very low reverse leakage.
10/44
DocID10397 Rev 22
M41T62, M41T64, M41T65
2
Operation
Operation
The M41T6x 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 16 bytes
contained in the device can then be accessed sequentially in the following order:
•
•
•
•
•
•
•
•
•
•
•
•
2.1
st
1 byte: tenths/hundredths of a second register
nd
2 byte: seconds register
rd
3 byte: minutes register
th
4 byte: hours register
th
5 byte: square wave/day register
th
6 byte: date register
th
7 byte: century/month register
th
8 byte: year register
th
9 byte: calibration register
th
10 byte: watchdog register
th
th
11 - 15 bytes: alarm registers
th
16 byte: flags register
2-wire bus characteristics
The bus is intended for communication between different ICs. It consists of two lines: a bidirectional data signal (SDA) and a clock signal (SCL). Both the SDA and 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.
DocID10397 Rev 22
11/44
Operation
2.1.4
M41T62, M41T64, M41T65
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.”
2.1.5
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 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.
Figure 11: Serial bus data transfer sequence
DATA LINE
STABLE
DATA VALID
CLOCK
DATA
START
CONDITION
12/44
CHANGE OF
DATA ALLOWED
DocID10397 Rev 22
STOP
CONDITION
M41T62, M41T64, M41T65
Operation
Figure 12: Acknowledgement sequence
CLOCK PULSE FOR
ACKNOWLEDGEMENT
START
SCL FROM
MASTER
1
DATA OUTPUT
BY TRANSMITTER
2
8
MSB
9
LSB
DATA OUTPUT
BY RECEIVER
READ mode
In this mode the master reads the M41T6x slave after setting the slave address (see Figure
14: "READ mode sequence"). Following the WRITE mode control bit (R/W̅ =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/W̅ =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 clock. The M41T6x 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.
The system-to-user transfer of clock data will be halted whenever the address being read is
a clock address (00h to 07h). The update will resume due to a stop condition or when the
pointer increments to any non-clock address (08h-0Fh).
Note: This is true both in READ mode and WRITE mode.
An alternate READ mode may also be implemented whereby the master reads the M41T6x
slave without first writing to the (volatile) address pointer. The first address that is read is
the last one stored in the pointer (see Figure 15: "Alternative READ mode sequence").
Figure 13: Slave address location
R/W
SLAVE ADDRESS
START
A
1
LSB
MSB
2.2
1
0
1
0
0
DocID10397 Rev 22
0
13/44
Operation
M41T62, M41T64, M41T65
R/W
DATA n
ACK
DATA n+1
ACK
BUS ACTIVIT Y:
S
ACK
ACK
WORD
ADDRESS (An)
ACK
S
START
SDA LINE
R/W
BUS ACTIVIT Y:
MASTER
START
Figure 14: READ mode sequence
SLAVE
ADDRESS
STOP
SLAVE
ADDRESS
P
NO ACK
DATA n+X
P
NO ACK
DATA n+X
ACK
BUS ACTIVIT Y:
DATA n+1
ACK
ACK
DATA n
ACK
S
SD A LINE
STOP
R/W
BUS ACTIVIT Y:
MASTER
START
Figure 15: Alternative READ mode sequence
SL AVE
ADDRESS
2.3
WRITE mode
In this mode the master transmitter transmits to the M41T6x slave receiver. Bus protocol is
shown in Figure 16: "WRITE mode sequence". Following the START condition and slave
address, a logic '0' (R/W̅ =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 address location on the reception of an acknowledge clock. The
M41T6x slave receiver will send an acknowledge clock to the master transmitter after it has
received the slave address see Figure 13: "Slave address location" and again after it has
received the word address and each data byte.
STOP
SL AVE
ADDRESS
14/44
DocID10397 Rev 22
P
DATA n+X
ACK
DATA n+1
ACK
BUS ACTIVIT Y:
DATA n
ACK
WORD
ADDRESS (An)
ACK
S
R/W
SD A LINE
ACK
BUS ACTIVIT Y:
MASTER
START
Figure 16: WRITE mode sequence
M41T62, M41T64, M41T65
3
Clock operation
Clock operation
The M41T6x is driven by a quartz-controlled oscillator with a nominal frequency of
32.768 kHz. 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 eight byte clock register (see Table 3: "M41T62 register map", Table 4: "M41T64
register map", and Table 5: "M41T65 register map") is used to both set the clock and to
read the date and time from the clock, in a binary-coded decimal format.
Tenths/hundredths of seconds, seconds, minutes, and hours are contained within the first
four registers.
A WRITE to any clock register will result in the tenths/hundredths of seconds being reset to
“00,” and tenths/hundredths of seconds cannot be written to any value other than “00.”
Bits D0 through D2 of register 04h contain the day (day of week). Registers 05h, 06h, and
07h contain the date (day of month), month, and years. The ninth clock register is the
calibration register (this is described in the clock calibration section). Bit D7 of register 01h
contains the STOP bit (ST). Setting this bit to a '1' will cause the oscillator to stop. When
reset to a '0' the oscillator restarts within one second (typical).
Upon initial power-up, the user should set the ST bit to a '1,' then immediately reset the ST
bit to '0.' This provides an additional “kick-start” to the oscillator circuit.
Bit D7 of register 02h (minute register) contains the oscillator fail interrupt enable bit
(OFIE). When the user sets this bit to '1,' any condition which sets the oscillator fail bit (OF)
(see Section 3.11: "Oscillator stop detection") will also generate an interrupt output.
Bits D6 and D7 of clock register 06h (century/month register) contain the CENTURY bit 0
(CB0) and CENTURY bit 1 (CB1).
A WRITE to ANY location within the first eight bytes of the clock register (00h-07h),
including the OFIE bit, RS0-RS3 bit, and CB0-CB1 bits will result in an update of the
system clock and a reset of the divider chain. This could result in an inadvertent change of
the current time. These non-clock related bits should be written prior to setting the clock,
and remain unchanged until such time as a new clock time is also written.
The eight clock registers may be read one byte at a time, or in a sequential block. Provision
has been made to assure that a clock update does not occur while any of the eight clock
addresses are being read. If a clock address is being read, an update of the clock registers
will be halted. This will prevent a transition of data during the READ.
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15/44
Clock operation
3.1
M41T62, M41T64, M41T65
RTC registers
The M41T6x user interface is comprised of 16 memory mapped registers which include
clock, calibration, alarm, watchdog, flags, and square wave control. The eight clock
counters are accessed indirectly via a set of buffer/transfer registers while the other eight
registers are directly accessed. Data in the clock and alarm registers is in BCD format.
Figure 17: Buffer/transfer registers
Updates
During normal operation when the user is not accessing the device, the buffer/transfer
2
registers are kept updated with a copy of the RTC counters. At the start of an I C read or
write cycle, the updating is halted and the present time is frozen in the buffer/transfer
registers.
Reads of the clock registers
2
By halting the updates at the start of an I C access, the user is ensured that all the data
transferred out during a read sequence comes from the same instant in time.
16/44
DocID10397 Rev 22
M41T62, M41T64, M41T65
Clock operation
Write timing
2
When writing to the device, the data is shifted into the M41T62's I C interface on the rising
edge of the SCL signal. As shown in Figure 17: "Buffer/transfer registers", on the 8th clock
2
cycle, the data is transferred from the I C block into whichever register is being pointed to
by the address pointer (not shown).
Writes to the clock registers (addresses 0-7)
Data written to the clock registers (addresses 0-7) is held in the buffer registers until the
2
address pointer increments to 8, or an I C stop condition occurs, at which time the data in
the buffer/registers is simultaneously copied into the counters, and then the clock is restarted.
DocID10397 Rev 22
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Clock operation
M41T62, M41T64, M41T65
Table 3: M41T62 register map
Addr
D7
00h
D6
D5
D4
D3
D2
0.1 seconds
D0
Function/range BCD
format
0.01 seconds
10ths/100ths
of seconds
00-99
01h
ST
10 seconds
Seconds
Seconds
00-59
02h
OFIE
10 minutes
Minutes
Minutes
00-59
03h
0
0
Hours (24-hour format)
Hours
00-23
04h
RS3
RS2
Day
01-7
05h
0
0
Date: day of month
Date
01-31
06h
CB1
CB0
Month
Century/
month
0-3/01-12
Year
Year
00-99
07h
10 hours
RS1
RS0
0
Day of week
10 date
0
10M
10 years
08h
OUT
0
S
Calibration
09h
RB2
BMB4
BMB3
BMB2
0Ah
AFE
SQWE
0
Al
10M
0Bh
RPT4
RPT5
0Ch
RPT3
0
0Dh
RPT2
0Eh
RPT1
0Fh
WDF
BMB1
BMB0
Calibration
RB1
RB0
Watchdog
Alarm month
Al month
01-12
AI 10 date
Alarm date
Al date
01-31
AI 10 hour
Alarm hour
Al hour
00-23
Alarm 10 minutes
Alarm minutes
Al min
00-59
Alarm 10 seconds
Alarm seconds
Al sec
00-59
AF
0
0
0
OF
Keys:
0 = must be set to '0'
AF = alarm flag (read only)
AFE = alarm flag enable flag
BMB0 - BMB4 = watchdog multiplier bits
CB0-CB1 = century bits
OF = oscillator fail bit
OFIE = oscillator fail interrupt enable bit
OUT = output level
RB0 - RB2 = watchdog resolution bits
RPT1-RPT5 = alarm repeat mode bits
RS0-RS3 = SQW frequency bits
S = sign bit
SQWE = square wave enable bit
ST = stop bit
WDF = watchdog flag bit (read only)
18/44
D1
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0
0
Flags
M41T62, M41T64, M41T65
Clock operation
Table 4: M41T64 register map
Addr
D7
00h
D6
D5
D4
D3
D2
0.1 seconds
D1
D0
Function/range BCD
format
0.01 seconds
10ths/100ths
of seconds
00-99
01h
ST
10 seconds
Seconds
Seconds
00-59
02h
0
10 minutes
Minutes
Minutes
00-59
03h
0
0
Hours (24-hour format)
Hours
00-23
04h
RS3
RS2
Day
01-7
05h
0
0
Date: day of month
Date
01-31
06h
CB1
CB0
Month
Century/
month
0-3/01-12
Year
Year
00-99
07h
10 hours
RS1
RS0
0
Day of week
10 Date
0
10M
10 years
08h
0
0
S
Calibration
09h
RB2
BMB4
BMB3
BMB2
0Ah
0
SQWE
32KE
Al
10M
0Bh
RPT4
RPT5
0Ch
RPT3
0
0Dh
RPT2
0Eh
RPT1
0Fh
WDF
BMB1
BMB0
Calibration
RB1
RB0
Watchdog
Alarm month
Al month
01-12
AI 10 date
Alarm date
Al date
01-31
AI 10 hour
Alarm hour
Al hour
00-23
Alarm 10 minutes
Alarm minutes
Al min
00-59
Alarm 10 seconds
Alarm seconds
Al sec
00-59
AF
0
0
0
OF
0
0
Flags
Keys:
0 = must be set to '0'
32KE = 32 KHz enable bit
AF = alarm flag (read only)
BMB0 - BMB4 = watchdog multiplier bits
CB0-CB1 = century bits
OF = oscillator fail bit
RB0 - RB2 = watchdog resolution bits
RPT1-RPT5 = alarm repeat mode bits
RS0-RS3 = SQW frequency bits
S = sign bit
SQWE = square wave enable bit
ST = stop bit
WDF = watchdog flag bit (read only)
DocID10397 Rev 22
19/44
Clock operation
M41T62, M41T64, M41T65
Table 5: M41T65 register map
Addr
D7
00h
D6
D5
D4
D3
D2
0.1 seconds
D0
Function/range BCD
format
0.01 seconds
10ths/100ths
of seconds
00-99
01h
ST
10 seconds
Seconds
Seconds
00-59
02h
OFIE
10 minutes
Minutes
Minutes
00-59
03h
0
0
Hours (24-hour format)
Hours
00-23
04h
0
0
Day
01-7
05h
0
0
Date: day of month
Date
01-31
06h
CB1
CB0
Month
Century/
month
0-3/01-12
Year
Year
00-99
07h
10 hours
0
0
0
10 date
0
Day of week
10M
10 years
08h
OUT
FT
S
Calibration
09h
RB2
BMB4
BMB3
BMB2
0Ah
AFE
0
0
Al
10M
0Bh
RPT4
RPT5
0Ch
RPT3
0
0Dh
RPT2
0Eh
RPT1
0Fh
WDF
BMB1
BMB0
Calibration
RB1
RB0
Watchdog
Alarm month
Al month
01-12
AI 10 date
Alarm date
Al date
01-31
AI 10 hour
Alarm hour
Al hour
00-23
Alarm 10 minutes
Alarm minutes
Al min
00-59
Alarm 10 seconds
Alarm seconds
Al sec
00-59
AF
0
0
0
OF
Keys:
0 = must be set to '0'
AF = alarm flag (read only)
AFE = alarm flag enable flag
BMB0 - BMB4 = watchdog multiplier bits
CB0-CB1 = century bits
FT = frequency test bit
OF = oscillator fail bit
OFIE = oscillator fail interrupt enable bit
OUT = output level
RB0 - RB2 = watchdog resolution bits
RPT1-RPT5 = alarm repeat mode bits
S = sign bit
ST = stop bit
WDF = watchdog flag bit (read only)
20/44
D1
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0
Flags
M41T62, M41T64, M41T65
3.2
Clock operation
Calibrating the clock
The M41T6x real-time clock is driven by a quartz controlled oscillator with a nominal
frequency of 32,768 Hz. This provides the time-base for the RTC. The accuracy of the
clock depends on the frequency accuracy of the crystal, and the match between the
capacitive load of the oscillator circuit and the capacitive load for which the crystal was
trimmed. The M41T6x oscillator is designed for use with a 6 - 7 pF crystal load
capacitance. When the calibration circuit is properly employed, accuracy improves to better
than ±2 ppm at 25 °C.
The oscillation rate of crystals changes with temperature (see Figure 18: "Crystal accuracy
across temperature"). Therefore, the M41T6x design 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 19: "Calibration waveform". The number of times
pulses which are blanked (subtracted, negative calibration) or split (added, positive
calibration) depends upon the value loaded into the five calibration bits found in the
calibration register. Adding counts speeds the clock up, subtracting counts slows the clock
down.
The calibration bits occupy the five lower order bits (D4-D0) in the calibration register (08h).
These bits 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 64 minute 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.
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 running at exactly 32,768 Hz, each of the 31 increments in
the calibration byte would represent +10.7 or –5.35 seconds per day which corresponds to
a total range of +5.5 or –2.75 minutes per month (see Figure 19: "Calibration waveform").
Two methods are available for ascertaining how much calibration a given M41T6x may
require:
•
•
The first involves setting the clock, letting it run for a month and comparing it to a
known accurate reference and recording deviation over a fixed period of time.
Calibration values, including the number of seconds lost or gained in a given period,
can be found in application note AN934. This allows the designer to give the end user
the ability to calibrate the clock as the environment requires, even if the final product is
packaged in a non-user serviceable enclosure. The designer could provide a simple
utility that accesses the calibration byte.
The second approach is better suited to a manufacturing environment, and involves
the use of either the SQW pin (M41T62/64) or the IRQ/FT/OUT pin (M41T65). The
SQW pin will toggle at 512 Hz when RS3 = '0,' RS2 = '1,' RS1 = '1,' RS0 = '0,' SQWE
= '1,' and ST = '0.' Alternatively, for the M41T65, the IRQ/FT/OUT pin will toggle at 512
Hz when FT and OUT bits = '1' and ST = '0.'
Any deviation from 512 Hz indicates the degree and direction of oscillator frequency shift at
the test temperature. For example, a reading of 512.010124 Hz would indicate a +20 ppm
oscillator frequency error, requiring a –10 (XX001010) to be loaded into the calibration byte
for correction. Note that setting or changing the calibration byte does not affect the
frequency test or square wave output frequency.
DocID10397 Rev 22
21/44
Clock operation
M41T62, M41T64, M41T65
Figure 18: Crystal accuracy across temperature
Frequency (ppm)
20
0
–20
–40
–60
∆F = K x (T – T )2
O
F
–80
2
2
K = –0.036 ppm/°C ± 0.006 ppm/°C
–100
TO = 25°C ± 5°C
–120
–140
–160
–40
–30
–20
–10
0
10
20
30
40
Temperature °C
Figure 19: Calibration waveform
NORMAL
POSITIVE
CALIBRATION
NEGATIVE
CALIBRATION
22/44
DocID10397 Rev 22
50
60
70
80
M41T62, M41T64, M41T65
3.3
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 6: "Alarm repeat modes" shows the possible configurations.
Codes not listed in the table default to the once per second mode to quickly alert the user
of an incorrect alarm setting.
When the clock information matches the alarm clock settings based on the match criteria
defined by RPT5–RPT1, the AF (alarm flag) is set. If AFE (alarm flag enable) is also set
(M41T62/65), the alarm condition activates the IRQ/OUT or IRQ/FT/OUT pin. To disable the
alarm, write '0' to the alarm date register and to RPT5–RPT1.
Note: If the address pointer is allowed to increment to the flag register address, an alarm
condition will not cause the interrupt/flag to occur until the address pointer is moved to a
different address. It should also be noted that if the last address written is the “Alarm
Seconds,” the address pointer will increment to the flag address, causing this situation to
occur.
The IRQ output is cleared by a READ to the flags register as shown in Figure 20: "Alarm
interrupt reset waveform". A subsequent READ of the flags register is necessary to see
that the value of the alarm flag has been reset to '0.'
Figure 20: Alarm interrupt reset waveform
0Eh
Register address
00h
0Fh
ALARM FLAG BIT (AF)
HIGH-Z
IRQ/OUT or
IRQ/FT/OUT
Table 6: Alarm repeat modes
RPT5
RPT4
RPT3
RPT2
RPT1
Alarm setting
1
1
1
1
1
Once per second
1
1
1
1
0
Once per minute
1
1
1
0
0
Once per hour
1
1
0
0
0
Once per day
1
0
0
0
0
Once per month
0
0
0
0
0
Once per year
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23/44
Clock operation
3.4
M41T62, M41T64, M41T65
Watchdog timer
The watchdog timer can be used to detect an out-of-control microprocessor. The user
programs the watchdog timer by setting the desired amount of time-out into the watchdog
register, address 09h.
Bits BMB4-BMB0 store a binary multiplier and the three bits RB2-RB0 select the resolution
where:
000=1/16 second (16 Hz);
001=1/4 second (4 Hz);
010=1 second (1 Hz);
011=4 seconds (1/4 Hz); and
100 = 1 minute (1/60 Hz).
Note: Invalid combinations (101, 110, and 111) will NOT enable a watchdog time-out.
Setting BMB4-BMB0 = 00000 with any combination of RB2-RB0, other than 000, will result
in an immediate watchdog time-out.
The amount of time-out is then determined to be the multiplication of the five-bit multiplier
value with the resolution. (For example: writing 00001110 in the watchdog register = 3*1 or
3 seconds). If the processor does not reset the timer within the specified period, the
M41T6x sets the WDF (watchdog flag) and generates an interrupt on the IRQ pin
(M41T62), or a watchdog output pulse (M41T65 only) on the WDO pin. The watchdog timer
can only be reset by having the microprocessor perform a WRITE of the watchdog register.
The time-out period then starts over.
Should the watchdog timer time-out, any value may be written to the watchdog register in
order to clear the IRQ pin. A value of 00h will disable the watchdog function until it is again
programmed to a new value. A READ of the flags register will reset the watchdog flag (bit
D7; register 0Fh). The watchdog function is automatically disabled upon power-up, and the
watchdog register is cleared.
Note: A WRITE to any clock register will restart the watchdog timer.
3.5
Watchdog output (𝐖𝐖𝐖𝐖𝐖𝐖 - M41T65 only)
If the processor does not reset the watchdog timer within the specified period, the
watchdog output (WDO) will pulse low for trec (see Table 7: "Square wave output
frequency"). This output may be connected to the reset input of the processor in order to
generate a processor reset. After a watchdog time-out occurs, the timer will remain
disabled until such time as a new countdown value is written into the watchdog register.
Note: The crystal oscillator must be running for the WDO pulse to be available. The WDO
output is an N-channel, open drain output driver (with IOL as specified in Table 13: "DC
characteristics").
24/44
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M41T62, M41T64, M41T65
3.6
Clock operation
Square wave output (M41T62/64)
The M41T62/64 offers the user a programmable square wave function which is output on
the SQW pin. RS3-RS0 bits located in 04h establish the square wave output frequency.
These frequencies are listed in Table 7: "Square wave output frequency". Once the
selection of the SQW frequency has been completed, the SQW pin can be turned on and
off under software control with the square wave enable bit (SQWE) located in register 0Ah.
The SQW output is an N-channel, open drain output driver for the M41T64, and a full
CMOS output driver for the M41T62. The initial power-up default for the SQW output is
32 KHz (except for M41T64, which defaults disabled).
Table 7: Square wave output frequency
Square wave bits
3.7
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
1.024
kHz
0
1
1
0
512
Hz
0
1
1
1
256
Hz
1
0
0
0
128
Hz
1
0
0
1
64
Hz
1
0
1
0
32
Hz
1
0
1
1
16
Hz
1
1
0
0
8
Hz
1
1
0
1
4
Hz
1
1
1
0
2
Hz
1
1
1
1
1
Hz
Full-time 32 KHz square wave output (M41T64)
The M41T64 offers the user a special 32 KHz square wave function which is enabled on
power-up to output on the F32K pin as long as VCC ≥ 1.3 V, and the oscillator is running (ST
bit = '0'). This function is available within one second (typ) of initial power-up and can only
be disabled by setting the 32KE bit to '0' or the ST bit to '1.' If not used, the F32K pin should
be disconnected and allowed to float.
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Clock operation
3.8
M41T62, M41T64, M41T65
Century bits
The two century bits, CB1 and CB0, are bits D7 and D6, respectively, in the century/month
register at address 06h. Together, they comprise a 2-bit counter which increments at the
turn of each century. CB1 is the most significant bit.
The user may arbitrarily assign the meaning of CB1:CB0 to represent any century value,
but the simplest way of using these bits is to extend the year register (07h) by mapping
them directly to bits 9 and 8. (The reader is reminded that the year register is in BCD
format.) Higher order year bits can be maintained in the application software.
Figure 21: Century bits CB1 and CB0
Table 8: Examples using century bits
3.9
CB1
CB0
CENTURY
0
0
2000
0
1
2100
1
0
2200
1
1
2300
Leap year
Leap year occurs every four years, in years which are multiples of 4. For example, 2012
was a leap year. An exception to that is any year which is a multiple of 100. For example,
the year 2100 is not a leap year. A further exception is that years which are multiples of
400 are indeed leap years. Hence, while 2100 is not a leap year, 2400 is.
During any year which is a multiple of 4, the M41T6x RTC will automatically insert leap day,
February 29. Therefore, the application software must correct for this during the exception
years (2100, 2200, etc.) as noted above.
26/44
DocID10397 Rev 22
M41T62, M41T64, M41T65
3.10
Clock operation
Output driver pin (M41T62/65)
When the OFIE bit, AFE bit, and watchdog register are not set to generate an interrupt, the
IRQ/OUT pin becomes an output driver that reflects the contents of D7 of the calibration
register. In other words, when D7 (OUT bit) is a '0,' then the IRQ/OUT pin will be driven low.
3.11
Note: The 𝐼𝐼𝐼𝐼𝐼𝐼/OUT pin is an open drain which requires an external pull-up resistor.
Oscillator stop detection
If the oscillator fail (OF) bit is internally set to a '1,' this indicates that the oscillator has
either stopped, or was stopped for some period of time and can be used to judge the
validity of the clock and date data. This bit will be set to '1' any time the oscillator stops.
In the event the OF bit is found to be set to '1' at any time other than the initial power-up,
the STOP bit (ST) should be written to a '1,' then immediately reset to '0.' This will restart
the oscillator.
The following conditions can cause the OF bit to be set:
•
The first time power is applied (defaults to a '1' on power-up).
Note: If the OF bit cannot be written to '0' four (4) seconds after the initial power-up, the
STOP bit (ST) should be written to a '1,' then immediately reset to '0.'
•
•
•
The voltage present on VCC or battery is insufficient to support oscillation.
The ST bit is set to '1.'
External interference of the crystal
If the oscillator fail interrupt enable bit (OFIE) is set to a '1,' the IRQ pin will also be
activated. The IRQ output is cleared by resetting the OFIE or OF bit to '0' (NOT by reading
the flag register).
The OF bit will remain set to '1' until written to logic '0.' The oscillator must start and have
run for at least 4 seconds before attempting to reset the OF bit to '0.' If the trigger event
occurs during a power-down condition, this bit will be set correctly.
3.12
Initial power-on defaults
Upon application of power to the device, the register bits will initially power-on in the state
indicated in Table 9: "Initial power-up values".
Table 9: Initial power-up values
Condition
Initial
(1)
power-up
Device
ST
OF
OFIE
OUT
FT
AFE
SQWE
32KE
RS3-1
RS0
Watchdog
M41T62
0
1
0
1
N/A
0
1
N/A
0
1
0
M41T64
0
1
N/A
N/A
N/A
N/A
0
1
0
1
0
M41T65
0
1
0
1
0
0
N/A
N/A
N/A
N/A
0
Notes:
(1)
All other control bits power up in an undetermined state.
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Maximum ratings
4
M41T62, M41T64, M41T65
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.
Table 10: Absolute maximum ratings
TSTG
Storage temperature (VCC off, oscillator off)
–55 to 125
Supply voltage
–0.3 to 5.0
V
260
°C
–0.2 to
Vcc+0.3
V
VCC
(3)
Lead solder temperature for 10 seconds
Value
Unit
°C
VIO
Input or output voltages
IO
Output current
20
mA
PD
Power dissipation
1
W
VESD(HBM)
Electro-static discharge voltage
(human body model)
TA = 25 °C
>1500
V
VESD(RCDM)
Electro-static discharge voltage
(robotic charged device model)
TA = 25 °C
>1000
V
Notes:
(1)
(2)
(3)
28/44
(2)
Parameter
TSLD
Condition
(1)
Sym
Test conforms to JEDEC standard.
Data based on characterization results, not tested in production.
Reflow at peak temperature of 260 °C. The time above 255 °C must not exceed 30 seconds.
DocID10397 Rev 22
M41T62, M41T64, M41T65
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.
Table 11: Operating and AC measurement conditions
Parameter
M41T6x
Supply voltage (VCC)
1.3 V to 4.4 V
Ambient operating temperature (TA)
–40 to 85 °C
Load capacitance (CL)
50 pF
Input rise and fall times
≤ 5 ns
Input pulse voltages
0.2 VCC to 0.8 VCC
Input and output timing ref. voltages
0.3 VCC to 0.7 VCC
Note: Output Hi-Z is defined as the point where data is no longer driven.
Figure 22: AC measurement I/O waveform
0.8VCC
0.7VCC
0.3VCC
0.2VCC
Figure 23: Crystal isolation example
Local Grounding Plane
(Layer 2)
Crystal
XI
XO
GND
Note: Substrate pad should be tied to VSS.
DocID10397 Rev 22
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DC and AC parameters
M41T62, M41T64, M41T65
Table 12: Capacitance
Symbol
CIN
COUT
(3)
tLP
Parameter
(1)(2)
Min
Max
Unit
Input capacitance
-
7
pF
Output capacitance
-
10
pF
Low-pass filter input time constant (SDA and SCL)
-
50
ns
Notes:
(1)
(2)
(3)
At 25°C, f = 1 MHz.
Effective capacitance measured with power supply at 3.6 V; sampled only, not 100% tested.
Outputs deselected.
Table 13: DC characteristics
Sym
VCC
(1)
Parameter
Test condition
(2)
Operating voltage
Min
Typ
ICC2
Supply current
1.0
4.4
V
I C bus (400 kHz)
1.3
4.4
V
100
µA
70
µA
Supply current (standby)
SCL = 400 kHz
(no load)
SCL = 0 Hz
all inputs
≥ VCC – 0.2 V
≤ VSS + 0.2 V
Unit
Clock
2
4.4 V
ICC1
Max
3.6 V
50
3.0 V
35
µA
2.5 V
30
µA
2.0 V
20
µA
4.4 V
950
nA
700
nA
3.6 V
375
3.0 V at 25 °C
350
nA
2.0 V at 25 °C
310
nA
SQW off
VIL
Input low voltage
–0.2
0.3 VCC
V
VIH
Input high voltage
0.7 VCC
VCC+0.3
V
0.4
V
0.4
V
VOL
Output low voltage
VOH
VCC = 4.4 V, IOL = 3.0 mA
(SDA)
VCC = 4.4 V, IOL = 1.0 mA
(SQW, WDO, IRQ)
Output high voltage
VCC = 4.4 V, IOH = –1.0 mA (CMOS)
2.4
V
Open drain pull-up
supply voltage
M41T62: IRQ/OUT
(3)
M41T64: SQW
4.4
V
ILI
Input leakage current
M41T65: WDO and IRQ/FT/OUT
0 V ≤ VIN ≤ VCC
±1
µA
ILO
Output leakage current
0 V ≤ VOUT ≤ VCC
±1
µA
Notes:
(1)
Valid for ambient operating temperature: TA = –40 to 85 °C; VCC = 1.3 V to 4.4 V (except where noted).
(2)
Oscillator startup guaranteed at 1.5 V only.
(3)
While the M41T64’s SQW output is open drain, the reader is reminded that the SQW output on the M41T62 is CMOS and hence is not
included in this list.
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DC and AC parameters
Table 14: Crystal electrical characteristics
Sym
fO
Parameter
(1)(2)
Min
Typ
-
32.768
Resonant frequency
RS
Series resistance (TA = –40 to 70 °C, oscillator startup at 2.0 V)
-
CL
Load capacitance
-
Max
Units
kHz
75
(3)(4)
6
kW
pF
Notes:
(1)
Load capacitors are integrated within the M41T6x. 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.
(2)
For the QFN16 package, user-supplied external crystals are required. The 6 and 7 pF crystals listed in Table 15: "Crystals suitable for
use with M41T6x series RTCs" have been evaluated by ST and have been found to be satisfactory for use with the M41T6x series RTC.
(3)
RS (max) = 65 kΩ for TA = –40 to 85 °C and oscillator startup at 1.5 V.
(4)
Guaranteed by design.
Table 15: Crystals suitable for use with M41T6x series RTCs
Manufacturer’s specifications
Vendor
Order number
Citizen
CMJ206T-32.768KDZB-UB
Citizen
CM315-32.768KDZY-UB
max
Temp.
range (°C)
Rated
tolerance
at 25 °C
Rated
load
cap.
8.3 x 2.5 mm
leaded SMT
50 kΩ
–40/+85
±20 ppm
6 pF
3.2 x 1.5 x 0.9 mm SMT
70 kΩ
–40/+85
±20 ppm
7 pF
2.0 x 6.0 mm thru-hole
50 kΩ
–10/+60
±20 ppm
6 pF
7 x 1.5 x 1.4 mm SMT
65 kΩ
–40/+85
±20 ppm
7 pF
Package
(1)
ESR
Ecliptek
E4WCDA06-32.768K
Ecliptek
E5WSDC 07 - 32.768K
ECS
ECS-.327-6-17X-TR
3.8 x 8.5 x 2.5 mm SMT
50 kΩ
–40/+85
±20 ppm
6 pF
ECS
ECS-.327-7-34B-TR
3.2 x 1.5 x 0.9 mm SMT
70 kΩ
–40/+85
±20 ppm
7 pF
ECS
ECS-.327-7-38-TR
7 x 1.5 x 1.4 mm SMT
65 kΩ
–40/+85
±20 ppm
7 pF
Epson
MC-146 32.7680KA-AG: ROHS
7 x 1.5 x 1.4 mm SMT
65 kΩ
–40/+85
±20 ppm
7 pF
Fox
298LF-0.032768-19
1.5 x 5.0 mm thru-hole
50 kΩ
–20/+60
±20 ppm
6 pF
Fox
299LF-0.032768-37
2.0 x 6.0 mm thru-hole
50 kΩ
–20/+60
±20 ppm
6 pF
Fox
414LF-0.032768-12
3.8 x 8.5 x 2.5 mm SMT
50 kΩ
–40/+85
±20 ppm
6 pF
Fox
501LF-0.032768-5
7 x 1.5 x 1.4 mm SMT
65 kΩ
–40/+85
±20 ppm
7 pF
Micro
Crystal
MS3V-T1R 32.768KHZ 7PF
20PPM
6.7 x 1.4 mm
leaded SMT
65 kΩ
–40/+85
±20 ppm
7 pF
Pletronics
SM20S - 32.768K - 6pF
3.8 x 8.5 x 2.5 mm SMT
50 kΩ
–40/+85
±20 ppm
6 pF
Seiko
SSPT7F-7PF20PPM
7 x 1.5 x 1.4 mm SMT
65 kΩ
–40/+85
±20 ppm
7 pF
Seiko
VT200F-6PF20PPM
2.0 x 6.0 mm thru-hole
50 kΩ
–10/+60
±20 ppm
6 pF
(2)
Notes:
(1)
ST has been informed that this crystal has been terminated by the vendor.
(2)
Epson MC-146 32.7680KA-E: ROHS is 6 pF version.
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DC and AC parameters
M41T62, M41T64, M41T65
Table 16: Oscillator characteristics
Sym
Parameter
VSTA
Oscillator start voltage
tSTA
Oscillator start time
Cg
XIN capacitance
Conditions
Min
≤ 10 seconds
1.5
Typ
Unit
V
VCC = 3.0 V
1
s
12
pF
12
XOUT capacitance
Cd
Max
IC-to-IC frequency variation
(1)(2)
–10
pF
+10
ppm
Notes:
(1)
Devices in LCC8 package ((M41T62LC6F) are tested not to exceed ±20 ppm oscillator frequency error at 25 °C, which equates
to about 52 seconds per month.
(2)
Reference value. TA = 25 °C, VCC = 3.0 V, CMJ-145 (CL = 6 pF, 32,768 Hz) manufactured by Citizen, CL = Cg · Cd / (Cg + Cd).
Figure 24: Bus timing requirements sequence
SDA
tBUF
tHD:STA
tHD:STA
tR
tF
SCL
tHIGH
P
tSU:DAT
tHD:DAT
tLOW
S
SR
tSU:STA
P
tSU:STO
Table 17: AC characteristics
Sym
Parameter
(1)
Min
Max
Units
0
400
kHz
fSCL
SCL clock frequency
tLOW
Clock low period
1.3
Clock high period
600
tHIGH
µs
ns
tR
SDA and SCL rise time
300
ns
tF
SDA and SCL fall time
300
ns
tHD:STA
START condition hold time
(after this period the first clock pulse is generated)
600
ns
tSU:STA
START condition setup time
(only relevant for a repeated start condition)
600
ns
Data setup time
100
ns
tHD:DAT
Data hold time
0
µs
tSU:STO
STOP condition setup time
600
ns
tBUF
Time the bus must be free before a new
transmission can start
1.3
µs
trec
Watchdog output pulse width
96
tSU:DAT
(2)
98
ms
Notes:
(1)
(2)
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Valid for ambient operating temperature: TA = –40 to 85 °C; VCC = 1.3 to 4.4 V (except where noted).
Transmitter must internally provide a hold time to bridge the undefined region (300 ns max) of the falling edge of SCL.
DocID10397 Rev 22
M41T62, M41T64, M41T65
6
Package information
Package information
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.
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Package information
6.1
M41T62, M41T64, M41T65
QFN16 package information
Figure 25: QFN16 — 16-pin, quad, flat package, no-lead, 3x3 mm, package outline
7509604_4
Note: Drawing is not to scale.
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Package information
Table 18: QFN16 — 16-pin, quad, flat package, no-lead, 3x3 mm, package mechanical data
mm
inches
Symbol
Min
Typ
Max
Min
Typ
Max
A
0.80
0.90
1.00
0.032
0.035
0.039
A1
0.00
0.02
0.05
0.000
0.001
0.002
A3
b
0.20
0.18
D
D2
1.55
0.007
1.70
1.55
1.70
1.80
0.061
0.30
0.012
0.067
0.071
0.118
1.80
0.061
0.50
0.20
0.010
0.118
3.00
e
L
0.30
3.00
E
E2
0.25
0.008
0.067
0.071
0.020
0.40
0.008
0.012
K
0.20
0.008
aaa
0.50
0.020
bbb
0.10
0.004
ccc
0.10
0.004
ddd
0.05
0.002
eee
0.08
0.003
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0.016
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Package information
M41T62, M41T64, M41T65
Figure 26: QFN16 — 16-pin, quad, flat package, no-lead, 3 x 3 mm recommended footprint
Note: Dimensions shown are in millimeters (mm).
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M41T62, M41T64, M41T65
6.2
Package information
LCC8 package information
Figure 27: LCC8 — 8-pin, 1.5 x 3.2 mm leadless chip carrier package outline
8241725_2
Table 19: LCC8 — 8-pin, 1.5 x 3.2 mm leadless chip carrier package mechanical data
mm
inches
Symbol
Min
Typ
A
Max
Min
Typ
0.80
Max
0.031
b
0.30
0.40
0.50
0.012
0.016
0.020
D
1.40
1.50
1.60
0.055
0.059
0.063
D1
0.40
0.50
0.60
0.016
0.020
0.024
E
3.10
3.20
3.30
0.122
0.126
0.130
E1
2.20
2.30
2.40
0.087
0.091
0.094
e
0.80
0.90
1.00
0.032
0.035
0.039
L
0.32
0.42
0.52
0.013
0.017
0.020
N
8
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Package information
M41T62, M41T64, M41T65
Figure 28: LCC8 — 8-pin, 1.5 x 3.2 mm leadless chip carrier recommended footprint
0.9
0.9
0.9
0.8
3.2
Note: Dimensions shown are typical values, in millimeters (mm).
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DocID10397 Rev 22
2.0
0.4
0.8
0.5
M41T62, M41T64, M41T65
Packing information
7
Packing information
7.1
QFN16 carrier tape
Figure 29: Carrier tape for QFN16 3 x 3 mm package
P0
E
P2
D
T
A0
F
TOP COVER
TAPE
W
B0
P1
CENTERLINES
OFCAVITY
K0
USER DIRECTION OF FEED
Table 20: Carrier tape dimensions for QFN16 3 x 3 mm package
Package
W
D
E
P0
P2
F
A0
B0
K0
P1
T
Unit
Bulk
qty
QFN16
12.00
±0.30
1.50
+0.10
/-0.00
1.75
±0.10
4.00
±0.10
2.00
±0.10
5.50
±0.05
3.30
±0.10
3.30
±0.10
1.10
±0.10
8.00
±0.10
0.30
±0.05
mm
3000
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Packing information
7.2
M41T62, M41T64, M41T65
LCC8 carrier tape
1.75 ±0.1
User Direction of Feed
Note: Dimensions shown are in millimeters (mm).
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0.3 ±0.02
12 ±0.2
76 04
76 04
4 ±0.1
1.75 ±0.1
5.5 ±0.05
Ø1
.5 ±0
.1
3.45 ±0.1
2 ±0.1
Ø1
.5 ±0
4 ±0.1
.1
Figure 30: Carrier tape for LCC8 1.5 x 3.2 mm package
DocID10397 Rev 22
M41T62, M41T64, M41T65
7.3
Packing information
Reel information for QFN16 and LCC8
Figure 31: 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
Table 21: Reel dimensions for 12 mm carrier tape - QFN16 and LCC8 packages
A
B
(max)
(min)
QFN16
330 mm
(13-inch)
1.5 mm
LCC8
180 mm
(7-inch)
1.5 mm
Package
D
N
(min)
(min)
13 mm
± 0.2 mm
20.2 mm
60 mm
12.4 mm
+ 2/–0 mm
18.4 mm
13 mm
± 0.2 mm
20.2 mm
60 mm
12.4 mm
+ 2/–0 mm
18.4 mm
C
G
T
(max)
Note: The dimensions given in Table 21: "Reel dimensions for 12 mm carrier tape - QFN16
and LCC8 packages" incorporate tolerances that cover all variations on critical parameters.
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Part numbering
8
M41T62, M41T64, M41T65
Part numbering
Table 22: Ordering information scheme
Example:
M41T
62
Q
6
F
Device family
M41T
Device type and supply voltage
62 = VCC = 1.3 V to 4.4 V
64 = VCC = 1.3 V to 4.4 V
65 = VCC = 1.3 V to 4.4 V
Package
Q = QFN16 (3 x 3 mm)
LC = LCC8 (1.5 x 3.2 mm) (M41T62 only)
Temperature range
6 = –40 °C to 85 °C
Shipping method
®
F = ECOPACK package, tape & reel
For other options, or for more information on any aspect of this device, please contact the
ST sales office nearest you.
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9
Revision history
Revision history
Table 23: Document revision history
Date
Revision
Changes
20
Updated title of datasheet; updated Section 3.8: "Century bits";
added Figure 21: "Century bits CB1 and CB0; moved and modified
Table 8: "Examples using century bits"; added Section 3.9: "Leap
year"; added footnote 1 to Table 15: "Crystals suitable for use with
M41T6x series RTCs.
21-Aug-2015
21
Removed M41T63 part number and all references to it from
document.
Moved Table 1: "Device summary" to Section 1: "Description"
TM
Replaced Figure 10: "Hardware hookup for SuperCap backup
operation"
Updated Section 6.1: "QFN16 package information"
Updated dimension e in Table 19: "LCC8 – 8-pin, 1.5 x 3.2 mm
leadless chip carrier package mechanical data"
01-Oct-2015
22
Clarified open drain pull-up supply voltage for devices in Table 13:
"DC characteristics"
21-Feb-2013
DocID10397 Rev 22
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M41T62, M41T64, M41T65
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© 2015 STMicroelectronics – All rights reserved
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