DS3231 ,Extremely Accurate I2C-Integrated RTC/TXO/CrystalELECTRICAL CHARACTERISTICS (continued)(V = 2.3V to 5.5V, V > V , T = T to T , unless otherwise note ..
DS3231M+ ,±5ppm, I2C Real-Time ClockElectrical Characteristics—V Current ConsumptionBAT(V = 0V, V = +2.3V to +5.5V, T = -45NC to +85NC, ..
DS3231M+ ,±5ppm, I2C Real-Time ClockApplicationsTypical Operating CircuitOrdering Information+3.3V +3.3VPART TEMP RANGE PIN-PACKAGEDS32 ..
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
EA2-12 ,COMPACT AND LIGHTWEIGHTAPPLICATIONSElectronic switching systems, PBX, key telephone systems, automatic test equipment and ..
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 ..
DS3231-DS3231S-DS3231SN
Extremely Accurate I2C-Integrated RTC/TXO/Crystal
General DescriptionThe DS3231 is a low-cost, extremely accurate I2C real-
time clock (RTC) with an integrated temperature-
compensated crystal oscillator (TCXO) and crystal. The
device incorporates a battery input, and maintains accu-
rate timekeeping when main power to the device is inter-
rupted. The integration of the crystal resonator enhances
the long-term accuracy of the device as well as reduces
the piece-part count in a manufacturing line. The DS3231
is available in commercial and industrial temperature
ranges, and is offered in a 16-pin, 300-mil SO package.
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 programmable square-wave 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 nec-
essary. Additionally, the RSTpin is monitored as a
pushbutton input for generating a reset externally.
ApplicationsServersUtility Power Meters
TelematicsGPS
FeaturesAccuracy ±2ppm from 0°C to +40°CAccuracy ±3.5ppm from -40°C to +85°CBattery Backup Input for Continuous
TimekeepingOperating Temperature Ranges
Commercial: 0°C to +70°C
Industrial: -40°C to +85°CLow-Power ConsumptionReal-Time Clock Counts Seconds, Minutes,
Hours, Day, Date, Month, and Year with Leap Year
Compensation Valid Up to 2100Two Time-of-Day AlarmsProgrammable Square-Wave OutputFast (400kHz) I2C Interface3.3V OperationDigital Temp Sensor Output: ±3°C AccuracyRegister for Aging TrimRST
Input/OutputUL Recognized
DS3231
Extremely Accurate I2C-Integrated
RTC/TCXO/CrystalRev 2; 6/05
Ordering InformationPurchase of I2C componentsfrom Maxim Integrated Products, Inc., or one of its sublicensed Associated Companies, conveys a
license under the Philips I2C Patent Rights to use these components in an I2C system, provided that the system conforms to the I2C
Standard Specification as defined by Philips.
+Denotes lead-free
DS3231
Extremely Accurate I2C-Integrated
RTC/TCXO/Crystal
ABSOLUTE MAXIMUM RATINGS
RECOMMENDED DC OPERATING CONDITIONS(TA
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 VCC, VBAT, 32kHz, SCL, SDA, RST,
INT/SQW Relative to Ground.............................-0.3V to +6.0V
Operating Temperature Range
(noncondensing).............................................-40°C to +85°C
Junction Temperature......................................................+125°C
Storage Temperature Range...............................-40°C to +85°C
Lead Temperature
(Soldering, 10s).....................................................+260°C/10s
Soldering Temperature....................................See the Handling,
PC Board Layout, and Assemblysection.
ELECTRICAL CHARACTERISTICS(VCC= 2.3V to 5.5V, VCC> VBAT, TA= TMINto TMAX, unless otherwise noted.) (Typical values are at VCC = 3.3V, VBAT= 3.0V, and
DS3231
Extremely Accurate I2C-Integrated
RTC/TCXO/Crystal
ELECTRICAL CHARACTERISTICS (continued)(VCC= 2.3V to 5.5V, VCC> VBAT, TA= TMINto TMAX, unless otherwise noted.) (Typical values are at VCC = 3.3V, VBAT= 3.0V, and
ELECTRICAL CHARACTERISTICS(VCC
DS3231
Extremely Accurate I2C-Integrated
RTC/TCXO/Crystal
AC ELECTRICAL CHARACTERISTICS
POWER-SWITCH CHARACTERISTICS
DS3231
Extremely Accurate I2C-Integrated
RTC/TCXO/Crystal
Pushbutton Reset Timing
Power-Switch Timing
DS3231
Extremely Accurate I2C-Integrated
RTC/TCXO/Crystal
Data Transfer on I2C Serial Bus
Note 1:Limits at -40°C are guaranteed by design and not production tested.
Note 2:All voltages are referenced to ground.
Note 3:ICCA—SCL clocking at max frequency = 400kHz.
Note 4:Current is the averaged input current, which includes the temperature conversion current.
Note 5:The RSTpin has an internal 50kΩ(nominal) pullup resistor to VCC.
Note 6:After this period, the first clock pulse is generated.
Note 7:A device must internally provide a hold time of at least 300ns for the SDA signal (referred to the VIH(MIN)of the SCL signal)
to bridge the undefined region of the falling edge of SCL.
Note 8:The maximum tHD:DATneeds only to be met if the device does not stretch the low period (tLOW) of the SCL signal.
Note 9:A fast-mode device can be used in a standard-mode system, but the requirement tSU:DAT≥250ns must then be met. This
is automatically the case if the device does not stretch the low period of the SCL signal. If such a device does stretch the
low period of the SCL signal, it must output the next data bit to the SDA line tR(MAX)+ tSU:DAT= 1000 + 250 = 1250ns
before the SCL line is released.
Note 10:CB—total capacitance of one bus line in pF.
Note 11:The parameter tOSFis the period of time the oscillator must be stopped for the OSF flag to be set over the voltage range of
0.0V ≤VCC≤VCC(MAX) and 2.3V ≤VBAT≤3.4V.
Note 12:This delay applies only if the oscillator is enabled and running. If the EOSCbit is a 1, the startup time of the oscillator is
added to this delay.
DS3231
Extremely Accurate I2C-Integrated
RTC/TCXO/Crystal
Typical Operating Characteristics(VCC= +3.3V, TA = +25°C, unless otherwise noted.)
DS3231
Extremely Accurate I2C-Integrated
RTC/TCXO/Crystal
Block Diagram
DS3231
Extremely Accurate I2C-Integrated
RTC/TCXO/Crystal
Detailed DescriptionThe DS3231 is a serial RTC driven by a temperature-
compensated 32kHz crystal oscillator. The TCXO pro-
vides a stable and accurate reference clock, and
maintains the RTC to within ±2 minutes per year accu-
racy from -40°C to +85°C. The TCXO frequency output
is available at the 32kHz pin. The RTC is a low-power
clock/calendar with two programmable time-of-day
alarms and a programmable square-wave output. The
INT/SQW provides either an interrupt signal due to
alarm conditions or a square-wave output. The clock/cal-
endar 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 12-hour format
with an AM/PM indicator. The internal registers are
accessible though an I2C bus interface.
A temperature-compensated voltage reference and
comparator circuit monitors the level of VCCto detect
power failures and to automatically switch to the back-
up supply when necessary. The RSTpin provides an
external pushbutton function and acts as an indicator
of a power-fail event.
DS3231
OperationThe block diagram shows the main elements of the
DS3231. The eight blocks can be grouped into four
functional groups: TCXO, power control, pushbutton
function, and RTC. Their operations are described sep-
arately in the following sections.
32kHz TCXOThe temperature sensor, oscillator, and control logic
form the TCXO. The controller reads the output of the
on-chip temperature sensor and uses a lookup table to
determine the capacitance required, adds the aging
correction in AGE register, and then sets the capaci-
tance selection registers. New values, including
changes to the AGE register, are loaded only when a
change in the temperature value occurs, or when a
user-initiated temperature conversion is completed.
The temperature is read on initial application of VCC
and once every 64 seconds afterwards.
Power ControlThis function is provided by a temperature-compensat-
ed voltage reference and a comparator circuit that
monitors the VCClevel. When VCCis greater than VPF,
the part is powered by VCC. When VCCis less than VPF
but greater than VBAT, the DS3231 is powered by VCC.
If VCCis less than VPFand is less than VBAT, the
device is powered by VBAT. See Table1.
To preserve the battery, the first time VBATis applied to
the device, the oscillator will not start up until VCCis
applied, or until a valid I2C address is written to the
part. Typical oscillator startup time is less than one sec-
ond. Approximately 2 seconds after VCCis applied, or
a valid I2C address is written, the device makes a tem-
perature measurement and applies the calculated cor-
rection to the oscillator. Once the oscillator is running, it
continues to run as long as a valid power source is
available (VCCor VBAT), and the device continues to
measure the temperature and correct the oscillator fre-
quency every 64 seconds.
Pushbutton Reset FunctionThe DS3231 provides for a pushbutton switch to be con-
nected to the RSToutput pin. When the DS3231 is not in
a reset cycle, it continuously monitors the RSTsignal for a
low going edge. If an edge transition is detected, the
DS3231 debounces the switch by pulling the RSTlow.
After the internal timer has expired (PBDB), the DS3231
continues to monitor the RSTline. If the line is still low, the
DS3231 continuously monitors the line looking for a rising
edge. Upon detecting release, the DS3231 forces theRSTpin low and holds it low for tRST.
The same pin, RST, is used to indicate a power-fail con-
dition. When VCCis lower than VPF, an internal power-fail
signal is generated, which forces the RSTpin low. When
VCCreturns to a level above VPF, the RSTpin is held low
for approximately 250ms (tREC) to allow the power sup-
ply to stabilize. If the oscillator is not running (see the
Power Control section) when VCCis applied, tRECis
bypassed and RSTimmediately goes high.
Real-Time ClockWith the clock source from the TCXO, the RTC provides
seconds, minutes, hours, day, date, month, and year
information. The date at the end of the month is automati-
cally adjusted for months with fewer than 31 days, includ-
ing corrections for leap year. The clock operates in either
the 24-hour or 12-hour format with an AM/PM indicator.
The clock provides two programmable time-of-day
alarms and a programmable square-wave output. The
INT/SQW pin either generates an interrupt due to alarm
condition or outputs a square-wave signal and the
selection is controlled by the bit INTCN.
Address MapFigure1 shows the address map for the DS3231 time-
keeping registers. During a multibyte access, when the
address pointer reaches the end of the register space
(12h), it wraps around to location 00h. On an I2C
START or address pointer incrementing to location 00h,
the current time is transferred to a second set of regis-
ters. The time information is read from these secondary
registers, while the clock may continue to run. This
eliminates the need to reread the registers in case the
main registers update during a read.
2C InterfaceThe I2C interface is accessible whenever either VCCor
VBATis at a valid level. If a microcontroller connected to
the DS3231 resets because of a loss of VCCor other
event, it is possible that the microcontroller and DS3231
I2C communications could become unsynchronized,
e.g., the microcontroller resets while reading data from
the DS3231. When the microcontroller resets, the
Extremely Accurate I2C-Integrated
RTC/TCXO/Crystal
