DS3231M+TRL ,±5ppm, I2C Real-Time ClockElectrical Characteristics—General (continued)(V = +2.3V to +5.5V, T = -45NC to +85NC, unless other ..
DS3231M+TRL ,±5ppm, I2C Real-Time ClockFeatures2The DS3231M is a low-cost, extremely accurate, I C real-● Highly Accurate RTC With Integra ..
DS3231S ,Extremely Accurate I2C-Integrated RTC/TXO/CrystalDS3231Rev 2; 6/052Extremely Accurate I C-IntegratedRTC/TCXO/Crystal
DS3231SN ,Extremely Accurate I2C-Integrated RTC/TXO/CrystalFeatures2♦ Accuracy ±2ppm from 0°C to +40°CThe DS3231 is a low-cost, extremely accurate I C real-ti ..
DS3231SN# ,Extremely Accurate I²C-Integrated RTC/TCXO/CrystalApplicationsautomatically switch to the backup supply when necessary. ● Servers ● Utility Power Met ..
DS3231SN#T&R ,Extremely Accurate I²C-Integrated RTC/TCXO/CrystalElectrical Characteristics(V = 2.3V to 5.5V, V = Active Supply (see Table 1), T = T to T , unless o ..
EA2-12NU ,COMPACT AND LIGHTWEIGHTFEATURESª Low power consumptionª Compact and light weightª 2 form c contact arrangementª Low magnet ..
EA2-12S ,COMPACT AND LIGHTWEIGHTFEATURESª Low power consumptionª Compact and light weightª 2 form c contact arrangementª Low magnet ..
EA2-12TNU ,COMPACT AND LIGHTWEIGHTAPPLICATIONSElectronic switching systems, PBX, key telephone systems, automatic test equipment and ..
EA2-4.5NU ,COMPACT AND LIGHTWEIGHTAPPLICATIONSElectronic switching systems, PBX, key telephone systems, automatic test equipment and ..
EA2-4.5T ,COMPACT AND LIGHTWEIGHTDATA SHEETMINIATURE SIGNAL RELAYEA2 SERIESCOMPACT AND LIGHTWEIGHTDESCRIPTIONThe EA2 series has red ..
EA25 ,COMPACT AND LIGHTWEIGHTFEATURESª Low power consumptionª Compact and light weightª 2 form c contact arrangementª Low magnet ..
DS3231M+-DS3231M+TRL
±5ppm, I2C Real-Time Clock
+Denotes a lead(Pb)-free/RoHS-compliant package.
/V denotes an automotive qualified part.
Typical Operating Circuit
General DescriptionThe DS3231M is a low-cost, extremely accurate, I2C real-
time clock (RTC). The device incorporates a battery input
and maintains accurate timekeeping when main power to
the device is interrupted. The integration of the microelec-
tromechanical systems (MEMS) resonator enhances the
long-term accuracy of the device and reduces the piece-
part count in a manufacturing line. The DS3231M is avail-
able in the same footprint as the popular DS3231 RTC.
The RTC maintains seconds, minutes, hours, day, date,
month, and year information. The date at the end of the
month is automatically adjusted for months with fewer
than 31 days, including corrections for leap year. The
clock operates in either the 24-hour or 12-hour format
with an AM/PM indicator. Two programmable time-of-
day alarms and a 1Hz output are provided. Address and
data are transferred serially through an I2C bidirectional
bus. A precision temperature-compensated voltage refer-
ence and comparator circuit monitors the status of VCC
to detect power failures, to provide a reset output, and to
automatically switch to the backup supply when neces-
sary. Additionally, the RST pin is monitored as a pushbutton
input for generating a microprocessor reset. See the
Block Diagram for more details.
ApplicationsPower Meters
Industrial Applications
Ordering Information
Beneits and Features●Highly Accurate RTC With Integrated MEMS
Resonator Completely Manages All Timekeeping
Functions Complete Clock Calendar Functionality Including
Seconds, Minutes, Hours, Day, Date, Month, and
Year, with Leap-Year Compensation Up to Year
2100Timekeeping Accuracy ±5ppm (±0.432 Second/Day)
from -45°C to +85°CFootprint and Functionally Compatible to DS3231Two Time-of-Day Alarms1Hz and 32.768kHz OutputsReset Output and Pushbutton Input with DebounceDigital Temp Sensor with ±3°C Accuracy+2.3V to +5.5V Supply Voltage●Simple Serial Interface Connects to Most
MicrocontrollersFast (400kHz) I2C Interface●Battery-Backup Input for Continuous TimekeepingLow Power Operation Extends Battery-Backup
Run Time●Operating Temperature Range: -40°C to +85°C●8-Pin or 16-Pin SO Packages●Underwriters Laboratories® (UL) Recognized
Underwriters Laboratories is a registered certification mark of
Underwriters Laboratories Inc.
DS3231M
SCL
SDA
32KHZVBAT
INT/SQW
RST
+3.3V+3.3V
CPU
I/O PORT
INTERRUPTS
PARTTEMP RANGEPIN-PACKAGE
DS3231MZ+-45NC to +85NC8 SO
DS3231MZ/V+-45NC to +85NC8 SO
DS3231M+-45NC to +85NC16 SO
DS3231M±5ppm, I2C Real-Time Clock
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute
maximum rating conditions for extended periods may affect device reliability.
Voltage Range on Any Pin Relative to GND ........-0.3V to +6.0V
Operating Temperature Range ..........................-45NC to +85NC
Storage Temperature Range ............................-55NC to +125NC
Junction Temperature .....................................................+150NC
Lead Temperature (soldering, 10s) ................................+300NC
Soldering Temperature (reflow) ......................................+260NC
Recommended Operating Conditions(TA = -45NC to +85NC, unless otherwise noted.) (Note 2)
Electrical Characteristics—Frequency And Timekeeping(VCC or VBAT = +3.3V, TA = -45NC to +85NC, unless otherwise noted. Typical values are at VCC = +3.3V, VBAT = +3.0V, and
TA = +25NC, unless otherwise noted.)
DC Electrical Characteristics—General(VCC = +2.3V to +5.5V, TA = -45NC to +85NC, unless otherwise noted. Typical values are at VCC = +3.3V, VBAT = +3.0V, and TA =
+25NC, unless otherwise noted.)
Absolute Maximum Ratings8 SO
Junction-to-Ambient Thermal Resistance (qJA) ........120°C/W
16 SO
Junction-to-Ambient Thermal Resistance (qJA) ..........90°C/W
Note 1: Package thermal resistances were obtained using the method described in JEDEC specification JESD51-7, using a four-layer
board. For detailed information on package thermal considerations, refer to www.maximintegrated.com/thermal-tutorial.
Package Thermal Characteristics (Note 1)PARAMETERSYMBOLCONDITIONSMINTYPMAXUNITS
Supply VoltageVCC2.33.35.5VVBAT2.33.05.5
Logic 1VIH0.7 x
VCC
VCC +
0.3V
Logic 0VIL-0.30.3 x
VCCV
PARAMETERSYMBOLCONDITIONSMINTYPMAXUNITS
1Hz Frequency ToleranceDf/fOUTMeasured over R 10s intervalQ5ppm
1Hz Frequency Stability vs. VCC
VoltageDf/VQ1ppm/V
Timekeeping AccuracytKAQ0.432Seconds/
Day
32kHz Frequency ToleranceDf/fOUTQ2.5%
PARAMETERSYMBOLCONDITIONSMINTYPMAXUNITS
Active Supply Current
(I2C Active: Includes
Temperature Conversion Current)
ICCA
VCC = +3.63V200
VCC = VCCMAX300
Standby Supply Current
(I2C Inactive: Includes
Temperature Conversion Current)
ICCS
VCC = +3.63V130
VCC = VCCMAX200
Temperature Conversion CurrentVCC = +3.63V575
DS3231M±5ppm, I2C Real-Time Clock
AC Electrical Characteristics—Power Switch(TA = -45NC to +85NC, unless otherwise noted.) (Figure 2)
DC Electrical Characteristics—General (continued)(VCC = +2.3V to +5.5V, TA = -45NC to +85NC, unless otherwise noted. Typical values are at VCC = +3.3V, VBAT = +3.0V, and TA =
+25NC, unless otherwise noted.)
DC Electrical Characteristics—VBAT Current Consumption(VCC = 0V, VBAT = +2.3V to +5.5V, TA = -45NC to +85NC, unless otherwise noted. Typical values are at VCC = 0V, VBAT = +3.0V, and
TA = +25NC, unless otherwise noted.)
PARAMETERSYMBOLCONDITIONSMINTYPMAXUNITS
Power-Fail VoltageVPF2.452.5752.70V
Logic 0 Output
(32KHZ, INT/SQW, SDA)VOLIOL = 3mA0.4V
Logic 0 Output
(RST)VOLIOL = 1mA0.4V
Output Leakage
(32KHZ, INT/SQW, SDA)ILO-0.1+0.1µA
Input Leakage
(SCL)ILI-0.1+0.1µA
RST I/O LeakageIOL-200+10µA
VBAT LeakageIBATLKG25100nA
Temperature AccuracyTEMPACCVCC or VBAT = +3.3VQ3NC
Temperature Conversion TimetCONV10ms
Pushbutton DebouncePBDB250ms
Reset Active TimetRST250ms
Oscillator Stop Flag (OSF) Delay tOSF(Note 3)125200ms
PARAMETERSYMBOLCONDITIONSMINTYPMAXUNITS
Active Battery Current
(I2C Active) (Note 4)IBATAVBAT = +3.63V70µAVBAT = VBATMAX150
Timekeeping Battery Current
(I2C Inactive) (Note 4)IBATTVBAT = +3.63V, EN32KHZ = 023.0µAVBAT = VBATMAX, EN32KHZ = 023.5
Temperature Conversion Current
(I2C Inactive)IBATTCVBAT = +3.63V575µAVBAT = VBATMAX650
Data Retention Current
(Oscillator Stopped and I2C
Inactive)
IBATDRTA = +25NC100nA
PARAMETERSYMBOLCONDITIONSMINTYPMAXUNITS
VCC Fall Time, VPFMAX to
VPFMINtVCCF300Fs
VCC Rise Time, VPFMIN to
VPFMAXtVCCR0Fs
Recovery at Power-UptREC(Note 5)250300ms
DS3231M±5ppm, I2C Real-Time Clock
AC Electrical Characteristics—I2C Interface(VCC or VBAT = +2.3V to +5.5V, TA = -45NC to +85NC, unless otherwise noted. Typical values are at VCC = +3.3V, VBAT = +3.0V, and
TA = +25NC, unless otherwise noted.) (Note 6, Figure 1)
Note 2: All voltages are referenced to ground.
Note 3: The parameter tOSF is the period of time the oscillator must be stopped for the OSF flag to be set.
Note 4: Includes the temperature conversion current (averaged).
Note 5: This delay applies only if the oscillator is enabled. If the EOSC bit is 1, tREC is bypassed and RST immediately goes high.
The state of RST does not affect the I2C interface or RTC functions.
Note 6: Interface timing shown is for fast-mode (400kHz) operation. This device is also backward-compatible with standard mode
I2C timing.
Note 7: CB: Total capacitance of one bus line in picofarads.
Note 8: Guaranteed by design; not 100% production tested.
PARAMETERSYMBOLCONDITIONSMINTYPMAXUNITS
SCL Clock FrequencyfSCL0400kHz
Bus Free Time Between STOP
and START ConditionstBUF1.3Fs
Hold Time (Repeated) START
ConditiontHD:STA0.6Fs
Low Period of SCLtLOW1.3Fs
High Period of SCLtHIGH0.6Fs
Data Hold TimetHD:DAT00.9Fs
Data Set-Up TimetSU:DAT100ns
START Set-Up TimetSU:STA0.6Fs
SDA and SCL Rise TimetR(Note 7)20 +
0.1CB300ns
SDA and SCL Fall TimetF(Note 7)20 +
0.1CB300ns
STOP Set-Up TimetSU:STO0.6Fs
SDA, SCL Input CapacitanceCBIN(Note 8)10pF
DS3231M±5ppm, I2C Real-Time Clock
Timing DiagramsFigure 3. Pushbutton Reset Timing
Figure 1. I2C Timing
Figure 2. Power Switch Timing
SCL
NOTE: TIMING IS REFERENCED TO VILMAX AND VIHMIN.SDA
STOPSTARTREPEATED
START
tBUF
tHD:STA
tHD:DATtSU:DAT
tSU:STO
tHD:STAtSP
tSU:STAtHIGH
tLOW
tRSTPBDB
RST
tVCCFtVCCR
tREC
VPFMAX
VCC
RST
VPFMIN
DS3231M±5ppm, I2C Real-Time Clock
FREQUENCY ERROR
vs. TEMPERATURE
DS3231M toc06
FREQUENCY ERROR (ppm)0
LIMITS
VCC = 3.3V
RST OUTPUT VOLTAGE
vs. POWER SUPPLY VOLTAGE
DS3231M toc05
SUPPLY VOLTAGE (V)
OUTPUT VOLTAGE (V)2
VBAT = 3.0V,
TA = +25°C
TRACKS WITH VCC
RST OUTPUT VOLTAGE
vs. OUTPUT CURRENT
DS3231M toc04
OUTPUT CURRENT (mA)
OUTPUT VOLTAGE (V)321
VCC = 2.45V,
VBAT = 3.0V,
TA = +25°C
INT/SQW OUTPUT VOLTAGE
vs. OUTPUT CURRENT
DS3231M toc03
OUTPUT CURRENT (mA)
OUTPUT VOLTAGE (V)642
VCC = 2.3V,
VBAT = 0V,
TA = +25°C
BATTERY-SUPPLY CURRENT
vs. BATTERY-SUPPLY VOLTAGE
DS3231M toc02
SUPPLY VOLTAGE (V)
SUPPLY CURRENT (µA)43
VCC = 0V, EN32KHZ = 1, BBSQW = 0
+85°C
+25°C
-40°C
POWER-SUPPLY CURRENT
vs. POWER-SUPPLY VOLTAGE
DS3231M toc01
SUPPLY VOLTAGE (V)
SUPPLY CURRENT (µA)43
VBAT = 2.3V, EN32KHZ = 1, IOUT = 0mA
INCREASE BELOW VPF
DUE TO INTERNAL PULLUP
RESISTOR ON RST
+85°C
+25°C
-40°C
POWER-SUPPLY CURRENT
vs. SCL FREQUENCY
DS3231M toc07
SUPPLY CURRENT (µA)
TA = +25°C
+5.5V
+2.7V
+3.5V
DS3231M±5ppm, I2C Real-Time Clock
Typical Operating Characteristics(TA = +25°C, unless otherwise noted.)
Pin Coniguration
Pin Description32KHZSCL
SDA
VBAT
GND
N.C.
N.C.
N.C.
N.C.
TOP VIEW
VCC
INT/SQW
N.C.
RST
N.C.
N.C.
N.C.
DS3231M
DS3231M
VBAT
GNDRST
SCL
SDAVCC
INT/SQW
32KHZ
TOP VIEW
PINNAMEFUNCTION8 SO16 SO132KHZ
32.768kHz Output (50% Duty Cycle). This open-drain pin requires an external pullup resistor.
When enabled with the EN32KHZ bit in the Status register (0Fh), this output operates on either
power supply. This pin can be left open circuit if not used.2VCCDC Power Pin for Primary Power Supply. This pin should be decoupled using a 0.1FF to 1.0FF
capacitor. Connect to ground if not used.3INT/
SQW
Active-Low Interrupt or 1Hz Square-Wave Output. This open-drain pin requires an external pullup
resistor connected to a supply at 5.5V or less. It can be left open if not used. This multifunction
pin is determined by the state of the INTCN bit in the Control register (0Eh). When INTCN is set to
logic 0, this pin outputs a 1Hz square wave. When INTCN is set to logic 1, a match between the
timekeeping registers and either of the alarm registers activates the INT/SQW pin (if the alarm is
enabled). Because the INTCN bit is set to logic 1 when power is first applied, the pin defaults to
an interrupt output with alarms disabled.4RST
Active-Low Reset. This pin is an open-drain input/output. It indicates the status of VCC relative
to the VPF specification. As VCC falls below VPF, the RST pin is driven low. When VCC exceeds
VPF, for tRST, the RST pin is pulled high by the internal pullup resistor. The active-low, open-drain
output is combined with a debounced pushbutton input function. This pin can be activated by a
pushbutton reset request. It has an internal 50kI (RPU) nominal value pullup resistor to VCC. No
external pullup resistors should be connected. If the oscillator is disabled, tREC is bypassed and
RST immediately goes high.5–12N.C.No Connection. These pins must be connected to ground.13GNDGround14VBAT
Backup Power-Supply Input. When using the device with the VBAT input as the primary power source,
this pin should be decoupled using a 0.1FF to 1.0FF low-leakage capacitor. When using the device
with the VBAT input as the backup power source, the capacitor is not required. If VBAT is not used,
connect to ground. The device is UL recognized to ensure against reverse charging when used with a
primary lithium battery. Go to www.maximintegrated.com/qa/info/ul for more information.
DS3231M±5ppm, I2C Real-Time Clock
Detailed DescriptionThe DS3231M is a serial real-time clock (RTC) driven by
an internal, temperature-compensated, microelectrome-
chanical systems (MEMS) resonator. The oscillator pro-
vides a stable and accurate reference clock and main-
tains the RTC to within Q0.432 seconds-per-day accu-
racy from -45NC to +85NC. The RTC is a low-power clock/
calendar with two programmable time-of-day alarms. INT/
SQW provides either an interrupt signal due to alarm
conditions or a 1Hz square wave. The clock/calendar
provides seconds, minutes, hours, day, date, month, and
year information. The date at the end of the month is auto-
matically adjusted for months with fewer than 31 days,
including corrections for leap year. The clock operates in
either the 24-hour or 12-hour format with an AM/PM indi-
cator. The internal registers are accessible though an I2C
bus interface. A temperature-compensated voltage refer-
ence and comparator circuit monitors the level of VCC to
detect power failures and to automatically switch to the
backup supply when necessary. The RST pin provides
an external pushbutton function and acts as an indicator
of a power-fail event.
OperationThe Block Diagram shows the device’s main elements.
Each of the major blocks is described separately in the
following sections.
Block Diagram
Pin Description (continued)DS3231M
TIME-BASE
RESONATOR
TEMP
SENSOR
INTERRUPT
OR 1Hz
SELECT
DIVIDER
INT/SQW
1Hz
DIGITAL
ADJUSTMENT
FACTORY TRIM
32KHZ
SDA
GND
SCL
VBAT
VCC
RST
RPU
CLOCK/CALENDAR
WITH ALARM
CONTROL AND STATUS
REGISTERS
I2C
INTERFACE
POWER
CONTROL
PINNAMEFUNCTION8 SO16 SO15SDA
Serial-Data Input/Output. This pin is the data input/output for the I2C serial interface. This open-drain
pin requires an external pullup resistor. The pullup voltage can be up to 5.5V, regardless of the
voltage on VCC.16SCL
Serial-Clock Input. This pin is the clock input for the I2C serial interface and is used to synchronize
data movement on the serial interface. The pullup voltage can be up to 5.5V, regardless of the
voltage on VCC.
DS3231M±5ppm, I2C Real-Time Clock
High-Accuracy Time BaseThe temperature sensor, oscillator, and digital adjust-
ment controller logic form the highly accurate time base.
The controller reads the output of the on-board tempera-
ture sensor and adjusts the final 1Hz output to maintain
the required accuracy. The device is trimmed at the
factory to maintain a tight accuracy over the operating
temperature range. When the device is powered by VCC,
the adjustment occurs once a second. When the device
is powered by VBAT, the adjustment occurs once every
10s to conserve power. Adjusting the 1Hz time base less
often does not affect the device’s long-term timekeeping
accuracy. The device also contains an Aging Offset reg-
ister that allows a constant offset (positive or negative) to
be added to the factory-trimmed adjustment value.
Power-Supply ConigurationsThe DS3231M can be configured to operate on a single
power supply (using either VCC or VBAT) or in a dual-
supply configuration, which provides a backup supply
source to keep the timekeeping circuits alive during
absence of primary system power.
Figure 4 illustrates a single-supply configuration using
VCC only, with the VBAT input grounded. When VCC < VPF,
the RST output is asserted (active low). Temperature
conversions are executed once per second.
Figure 5 illustrates a single-supply configuration using
VBAT only, with the VCC input grounded. The RST output
is disabled and is held at ground through the connection
of the internal pullup resistor. Temperature conversions
are executed once every 10s.
Figure 6 illustrates a dual-supply configuration, using
the VCC supply for normal system operation and the
VBAT supply for backup power. In this configuration, the
power-selection function is provided by a temperature-
compensated voltage reference and a comparator circuit
that monitors the VCC level. When VCC is greater than
VPF, the device is powered by VCC. When VCC is less
than VPF but greater than VBAT, the device is powered
Figure 4. Single Supply (VCC Only)
Figure 5. Single Supply (VBAT Only)
Figure 6. Dual Power Supply
Table 1. Power ControlVBAT
VCC
+3.3V
VBAT
VCC
VBAT
VCC
+3.3V
CONFIGURATIONCONDITIONI/O ACTIVEI/O INACTIVERST
VCC Only
(Figure 4)
VCC > VPFICCAICCSInactive (High)
VCC < VPFActive (Low)
VBAT Only
(Figure 5)
EOSC = 0IBATAIBATTDisabled (Low)EOSC = 1IBATDR
Dual Supply
VCC > VPFICCAICCSInactive (High)VCC > VBATICCAVCC > VBATICCS
DS3231M±5ppm, I2C Real-Time Clock
by VCC. If VCC is less than VPF and is less than VBAT, the
device is powered by VBAT (see Table 1).
When VCC < VPF, the RST output is asserted (active
low). When VCC is the presently selected power source,
temperature conversions are executed once per second.
When VBAT is the presently selected power source, tem-
perature conversions are executed once every 10s.
To preserve the battery, the first time VBAT is applied
to the device the oscillator does not start up until VCC
exceeds VPF or until a valid I2C address is written to
the device. Typical oscillator startup time is less than
1s. Approximately 2s after VCC is applied, or a valid
I2C address is written, the device makes a temperature
measurement and applies the calculated correction to
the oscillator. Once the oscillator is running, it continues
to run as long as a valid power source is available (VCC
or VBAT), and the device continues to measure the tem-
perature and correct the oscillator frequency. On the first
application of VCC power, or (if VBAT powered) when a
valid I2C address is written to the device, the time and
date registers are reset to 01/01/00 01 00:00:00 (DD/MM/
YY DOW HH:MM:SS).
Initial VBAT AttachmentDuring the initial battery attachment to the DS3231M, it
is important to eliminate the effects of contact bounce.
Contact bounce occurs when battery contact rapidly
and repeatedly alternates between connected and dis-
connected during the battery attachment before finally
settling to the connected state. This bounce can cause a
momentary power interruption to the DS3231M that can
result in memory recall corruption in the device.
There are two recommended ways to eliminate the
effects of contact bounce on the device. The preferred
way uses power sequencing by applying VCC to the part
before performing the battery attachment. An alternate
method to eliminate contact bounce is to filter the signal
using a small capacitor between VBAT and ground. For
this method, capacitor values between 0.1nf and 1nf are
recommended for the supply filtering.
VBAT OperationThere are several modes of operation that affect the
amount of VBAT current that is drawn. While the device
is powered by VBAT and the serial interface is active,
the active battery current IBATA is drawn. When the
serial interface is inactive, the timekeeping current IBATT
(which includes the averaged temperature-conversion
current IBATTC) is used. The temperature-conversion
able to support the periodic higher current pulse and
still maintain a valid voltage level. The data-retention
current IBATDR is the current drawn by the device when
the oscillator is stopped (EOSC = 1). This mode can be
used to minimize battery requirements for periods when
maintaining time and date information is not necessary,
e.g., while the end system is waiting to be shipped to a
customer.
Pushbutton Reset FunctionThe device provides for a pushbutton switch to be con-
nected to the RST input/output pin. When the device is
not in a reset cycle, it continuously monitors RST for a
low-going edge. If an edge transition is detected, the
device debounces the switch by pulling RST low. After
the internal timer has expired (PBDB), the device con-
tinues to monitor the RST line. If the line is still low, the
device continuously monitors the line looking for a rising
edge. Upon detecting release, the device forces RST
low and holds it low for tRST. RST is also used to indi-
cate a power-fail condition. When VCC is lower than VPF,
an internal power-fail signal is generated, which forces
RST low. When VCC returns to a level above VPF, RST
is held low for approximately 250ms (tREC) to allow the
power supply to stabilize. If the oscillator is not running
when VCC is applied, tREC is bypassed and RST imme-
diately goes high. Assertion of the RST output, whether
by pushbutton or power-fail detection, does not affect
the device’s internal operation. RST output operation and
pushbutton monitoring are only available if VCC power is
available.
Real-Time Clock (RTC)With the 1Hz source from the temperature-compensated
oscillator, the RTC provides seconds, minutes, hours,
day, date, month, and year information. The date at the
end of the month is automatically adjusted for months
with fewer than 31 days, including corrections for leap
year. The clock operates in either the 24-hour or the
12-hour format with an AM/PM indicator. The clock pro-
vides two programmable time-of-day alarms. INT/SQW
can be enabled to generate either an interrupt due to an
alarm condition or a 1Hz square wave. This selection is
controlled by the INTCN bit in the Control register.
I2C InterfaceThe I2C interface is accessible whenever either VCC or
VBAT is at a valid level. If a microcontroller connected
to the device resets because of a loss of VCC or other
event, it is possible that the microcontroller and device’s
DS3231M±5ppm, I2C Real-Time Clock
