M41ST87W
5.0 and 3.3/3.0 V secure serial RTC and NVRAM supervisor with
tamper detection and 128 bytes of clearable NVRAM
Datasheet - production data
•
•
28-pin, (300 mil)
SOX28, embedded crystal
•
•
SSOP20
•
•
•
•
•
•
Features
•
•
•
•
•
•
5.0, 3.3, or 3.0 V operation
2
400 kHz I C bus
NVRAM supervisor to non-volatize external
LPSRAM
2.5 to 5.5 V oscillator operating voltage
Automatic switchover and deselect circuitry
Choice of power-fail deselect voltages
−
M41ST87Y: (not recommended for new
design, contact ST sales office for
availability)
THS = 1: V
PFD
≈ 4.63 V;
V
CC
= 4.75 to 5.5 V
THS = 0: V
PFD
≈ 4.37 V;
V
CC
= 4.5 to 5.5 V
−
M41ST87W:
THS = 1: V
PFD
≈ 2.9 V;
V
CC
= 3.0 to 3.6 V
THS = 0: V
PFD
≈ 2.63 V;
V
CC
= 2.7 to 3.6 V
Two independent power-fail comparators
(1.25 V reference)
Counters for tenths/hundredths of seconds,
seconds, minutes, hours, day, date, month,
year, and century
128 bytes of clearable, general purpose
NVRAM
Programmable alarm and interrupt function
(valid even during battery backup mode)
Programmable watchdog timer
Unique electronic serial number (8-byte)
32 kHz frequency output available upon
power-on
Microprocessor power-on reset output
Battery low flag
Ultra-low battery supply current of 500 nA
(typ)
Security features
•
•
•
•
Tamper indication circuits with timestamp
and RAM clear
LPSRAM clear function (TP
CLR
)
Packaging includes a 28-lead, embedded
crystal SOIC and a 20-lead SSOP
Oscillator stop detection
May 2016
DocID9497 Rev 11
1/54
www.st.com
This is information on a product in full production.
Contents
M41ST87W
Contents
1
2
Description....................................................................................... 6
Operating modes ........................................................................... 12
2.1
2-wire bus characteristics ................................................................ 13
2.1.1
2.1.2
2.1.3
2.1.4
2.1.5
Bus not busy ..................................................................................... 13
Start data transfer ............................................................................. 13
Stop data transfer ............................................................................. 13
Data valid .......................................................................................... 13
Acknowledge .................................................................................... 13
2.2
2.3
2.4
2.5
2.6
READ mode .................................................................................... 15
WRITE mode................................................................................... 17
Data retention mode........................................................................ 17
Tamper detection circuit .................................................................. 18
Tamper register bits (tamper 1 and tamper 2) ................................. 18
2.6.1
2.6.2
2.6.3
2.6.4
2.6.5
2.6.6
Tamper enable bits (TEB1 and TEB2) ............................................. 18
Tamper bits (TB1 and TB2) .............................................................. 18
Tamper interrupt enable bits (TIE1 and TIE2) .................................. 19
Tamper connect mode bit (TCM1 and TCM2) ................................. 19
Tamper polarity mode bits (TPM1 and TPM2) ................................. 19
Tamper detect sampling (TDS1 and TDS2) ..................................... 21
2.6.7
Tamper current high/tamper current low (TCHI/1 and
TCHI/2).................................................................................................... 21
2.6.8
RAM clear (CLR1 and CLR2) ........................................................... 21
2.6.9
RAM clear external (CLR1
EXT
and CLR2
EXT
) - available in SOX28
package only .................................................................................................... 21
2.7
2.8
2.9
2.10
2.11
Tamper detection operation ............................................................ 25
Sampling ......................................................................................... 25
Internal tamper pull-up/down current............................................... 26
Avoiding inadvertent tampers (normally closed configuration) ........ 26
Tamper event time-stamp ............................................................... 27
Power-down time-stamp ................................................................. 28
TIMEKEEPER
®
registers................................................................. 29
Calibrating the clock ........................................................................ 31
Setting alarm clock registers ........................................................... 32
Watchdog timer ............................................................................... 34
DocID9497 Rev 11
3
Clock operation ............................................................................. 28
3.1
3.2
3.3
3.4
3.5
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M41ST87W
Contents
3.6
3.7
3.8
3.9
3.10
3.11
3.12
3.13
3.14
3.15
3.16
3.17
3.18
Square wave output ........................................................................ 35
Full-time 32 kHz square wave output .............................................. 36
Reset inputs (
and
)
................................................ 36
Power-on reset ................................................................................ 36
Power-fail comparators (1 and 2) .................................................... 37
Power-fail outputs ........................................................................... 37
Century bits ..................................................................................... 38
Output driver pin.............................................................................. 38
Battery low warning ......................................................................... 38
t
rec
bit ............................................................................................... 39
Electronic serial number .................................................................. 39
Oscillator stop detection .................................................................. 39
Initial power-on defaults .................................................................. 40
4
5
6
Maximum ratings ........................................................................... 41
DC and AC parameters ................................................................. 42
Package information ..................................................................... 46
6.1
6.2
SOX28 package information ........................................................... 46
SSOP20 package information ......................................................... 48
SOX28 carrier tape ......................................................................... 49
SSOP20 carrier tape ....................................................................... 50
Reel information for SOX28 and SSOP20 ...................................... 51
7
Packing information ...................................................................... 49
7.1
7.2
7.3
8
9
Part numbering .............................................................................. 52
Revision history ............................................................................ 53
DocID9497 Rev 11
3/54
List of tables
M41ST87W
List of tables
Table 1: Signal names ................................................................................................................................ 9
2
Table 2: I C slave address ........................................................................................................................ 12
Table 3: AC characteristics ....................................................................................................................... 15
Table 4: Tamper detection truth table ....................................................................................................... 20
Table 5: Tamper detection current (normally closed - TCMX = '0') .......................................................... 22
Table 6: Tamper detect timing .................................................................................................................. 24
Table 7: Calculated cutoff frequency for typical capacitance and resistance values ............................... 26
®
Table 8: TIMEKEEPER register map ...................................................................................................... 29
Table 9: Alarm repeat modes ................................................................................................................... 33
Table 10: Square wave output frequency ................................................................................................. 35
Table 11: Reset AC characteristics .......................................................................................................... 37
Table 12: Century bits examples .............................................................................................................. 38
Table 13: trec definitions ........................................................................................................................... 39
Table 14: Default values ........................................................................................................................... 40
Table 15: Default values ........................................................................................................................... 40
Table 16: Absolute maximum ratings ....................................................................................................... 41
Table 17: DC and AC measurement conditions ....................................................................................... 42
Table 18: Capacitance .............................................................................................................................. 42
Table 19: DC characteristics ..................................................................................................................... 43
Table 20: Crystal electrical characteristics ............................................................................................... 44
Table 21: Power down/up AC characteristics ........................................................................................... 45
Table 22: SOX28 – 28-lead plastic small outline, 300 mils, embedded crystal package mechanical data
.................................................................................................................................................................. 47
Table 23: SSOP20 – 20-lead, shrink, small outline package mechanical data ........................................ 48
Table 24: Carrier tape dimensions for SOX28 package ........................................................................... 49
Table 25: Reel dimensions for 24 mm carrier tape (SOX28 package) and 16 mm carrier tape (SSOP20
package) ................................................................................................................................................... 51
Table 26: Ordering information scheme ................................................................................................... 52
Table 27: Document revision history ........................................................................................................ 53
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DocID9497 Rev 11
M41ST87W
List of figures
List of figures
Figure 1: Logic diagram .............................................................................................................................. 7
Figure 2: 28-pin, 300 mil SOIC connections ............................................................................................... 8
Figure 3: 20-pin, SSOP connections .......................................................................................................... 8
Figure 4: Block diagram ............................................................................................................................ 10
Figure 5: Hardware hookup ...................................................................................................................... 11
Figure 6: Serial bus data transfer sequence ............................................................................................. 14
Figure 7: Acknowledgement sequence..................................................................................................... 14
Figure 8: Bus timing requirements sequence ........................................................................................... 14
Figure 9: Slave address location .............................................................................................................. 16
Figure 10: READ mode sequence ............................................................................................................ 16
Figure 11: Alternate READ mode sequence ............................................................................................ 16
Figure 12: WRITE mode sequence .......................................................................................................... 17
Figure 13: WRITE cycle timing: RTC and external SRAM control signals ............................................... 17
Figure 14: Tamper detect connection options .......................................................................................... 19
Figure 15: Basic tamper detect options .................................................................................................... 20
Figure 16: Tamper detect output options .................................................................................................. 20
Figure 17: Tamper detect sampling options ............................................................................................. 22
Figure 18: Tamper current options ........................................................................................................... 23
Figure 19: Tamper output timing (with CLR1EXT or CLR2EXT = '1') - available in SOX28 package only
.................................................................................................................................................................. 23
Figure 20: RAM clear hardware hookup (SOX28 package only) ............................................................. 24
Figure 21: Low-pass filter implementation for noise immunity.................................................................. 26
Figure 22: Crystal accuracy across temperature ...................................................................................... 32
Figure 23: Calibration waveform ............................................................................................................... 32
Figure 24: Alarm interrupt reset waveform ............................................................................................... 33
Figure 25: Backup mode alarm waveform ................................................................................................ 34
Figure 26:
and
timing waveforms .................................................................................. 36
Figure 27: AC testing input/output waveforms .......................................................................................... 42
Figure 28: Power down/up mode AC waveforms ..................................................................................... 45
Figure 29: SOX28 – 28-lead plastic small outline, 300 mils, embedded crystal package outline ............ 46
Figure 30: SSOP20 – 20-lead, shrink, small outline package outline ...................................................... 48
Figure 31: Carrier tape for SOX28 package ............................................................................................. 49
Figure 32: Carrier tape for SSOP20 package ........................................................................................... 50
Figure 33: Reel schematic ........................................................................................................................ 51
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