M41ST87WMX6TR STMicroelectronics, M41ST87WMX6TR Datasheet - Page 31
![IC SUPERVISOR RTC 160X8 28-SOIC](/photos/6/56/65690/stmicroelectronics-28-soic_sml.jpg)
M41ST87WMX6TR
Manufacturer Part Number
M41ST87WMX6TR
Description
IC SUPERVISOR RTC 160X8 28-SOIC
Manufacturer
STMicroelectronics
Type
Clock/Calendar/Supervisorr
Specifications of M41ST87WMX6TR
Memory Size
160B
Time Format
HH:MM:SS:hh (24 hr)
Date Format
YY-MM-DD-dd
Interface
I²C, 2-Wire Serial
Voltage - Supply
2.7 V ~ 3.6 V
Operating Temperature
-40°C ~ 85°C
Mounting Type
Surface Mount
Package / Case
28-SOIC, 28-SOH (8.48mm Width)
Bus Type
Serial (2-Wire, I2C)
Operating Supply Voltage (typ)
3.3V
Operating Supply Voltage (max)
3.6V
Operating Supply Voltage (min)
2.7V
Operating Temperature Classification
Industrial
Operating Temperature (max)
85C
Operating Temperature (min)
-40C
Pin Count
28
Mounting
Surface Mount
Lead Free Status / RoHS Status
Lead free / RoHS Compliant
Other names
497-6457-2
M41ST87WMX6TR
M41ST87WMX6TR
Available stocks
Company
Part Number
Manufacturer
Quantity
Price
Company:
Part Number:
M41ST87WMX6TR
Manufacturer:
MBI
Quantity:
12 000
M41ST87Y, M41ST87W
Figure 21. Crystal accuracy across temperature
Frequency (ppm)
–100
–120
–140
–160
–20
–40
–60
–80
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 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 M41ST87Y/W 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, “TIMEKEEPER
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 the SQW/FT pin. The pin will toggle at 512 Hz, when the stop bit (ST) is '0,' the frequency
test bit (FT) is '1,' and SQWE is '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 output frequency.
If the SQWOD Bit = '1,' the SQW/FT pin is an open drain output which requires a pull-up
resistor to V
control the rise time. The FT bit is cleared on power-down.
20
0
–40
–30
CC
for proper operation. A 500 to10 k resistor is recommended in order to
–20
–10
0
®
calibration.” This allows the designer to give the end user the
10
Temperature C
F
K
F = K x (T – T
= –0.036 ppm/ C
20
T
30
O
= 25 C ± 5 C
O
)
2
40
2
± 0.006 ppm/ C
50
60
2
70
80
Clock operation
AI07888
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