Datasheet

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±5ppm, I

C Real-Time Clock

DS3231M

For pricing, delivery, and ordering information, please contact Maxim Direct

at 1-888-629-4642, or visit Maxim’s website at www.maximintegrated.com.

19-5312; Rev 6; 8/14

+Denotes a lead(Pb)-free/RoHS-compliant package.

/V denotes an automotive qualified part.

Typical Operating Circuit

General Description

The DS3231M is a low-cost, extremely accurate, I

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 microelectromechanical systems (MEMS) resona-

tor enhances the long-term accuracy of the device and

reduces the piece-part count in a manufacturing line.

The DS3231M is available 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 I

C bidirectional

bus. A precision temperature-compensated voltage

reference and comparator circuit monitors the status of

to detect power failures, to provide a reset output,

and to automatically switch to the backup supply when

necessary. Additionally, the RST pin is monitored as a

pushbutton input for generating a microprocessor reset.

See the Block Diagram for more details.

Applications

Power Meters

Industrial Applications

Ordering Information

Features

S Timekeeping Accuracy ±5ppm (±0.432 Second/

Day) from -45°C to +85°C

S Battery Backup for Continuous Timekeeping

S Low Power Consumption

S Footprint and Functionally Compatible to DS3231

S Complete Clock Calendar Functionality Including

Seconds, Minutes, Hours, Day, Date, Month, and

Year with Leap Year Compensation Up to Year

2100

S Two Time-of-Day Alarms

S 1Hz and 32.768kHz Outputs

S Reset Output and Pushbutton Input with

Debounce

S Fast (400kHz) I

C-Compatible Serial Bus

S +2.3V to +5.5V Supply Voltage

S Digital Temp Sensor with ±3°C Accuracy

S -45°C to +85°C Temperature Range

S 8-Pin or 16-Pin SO Packages

S Underwriters Laboratories (UL) Recognized

EVALUATION KIT

AVAILABLE

DS3231M

SCL

SDA

32KHZ V

BAT

INT/SQW

RST

+3.3V+3.3V

CPU

I/O PORT

INTERRUPTS

Note: Some revisions of this device may incorporate deviations from published specifications known as errata. Multiple revisions of any device

may be simultaneously available through various sales channels. For information about device errata, go to: www.maximintegrated.com/errata.

PART TEMP RANGE PIN-PACKAGE

DS3231MZ+

-45NC to +85NC

8 SO

DS3231MZ/V+

-45NC to +85NC

8 SO

DS3231M+

-45NC to +85NC

16 SO

Summary of content (20 pages)

PAGE 1
DS3231M TION KIT EVALUA BLE IL AVA A ±5ppm, I2C Real-Time Clock General Description The 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 microelectromechanical systems (MEMS) resonator enhances the long-term accuracy of the device and reduces the piece-part count in a manufacturing line.
PAGE 2
DS3231M ±5ppm, I2C Real-Time Clock ABSOLUTE MAXIMUM RATINGS 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).......................................
PAGE 3
DS3231M ±5ppm, I2C Real-Time Clock 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.) PARAMETER SYMBOL MIN TYP MAX UNITS 2.45 2.575 2.70 V IOL = 3mA 0.4 V IOL = 1mA 0.4 V -0.1 +0.1 µA ILI -0.1 +0.
PAGE 4
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) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS 400 kHz SCL Clock Frequency fSCL 0 Bus Free Time Between STOP and START Conditions tBUF 1.3 Fs Hold Time (Repeated) START Condition tHD:STA 0.6 Fs Low Period of SCL tLOW 1.
PAGE 5
DS3231M ±5ppm, I2C Real-Time Clock Timing Diagrams SDA tBUF tF tLOW tHD:STA tSP SCL tHD:STA tHIGH tR tHD:DAT STOP START tSU:STA tSU:STO tSU:DAT REPEATED START NOTE: TIMING IS REFERENCED TO VILMAX AND VIHMIN. Figure 1. I2C Timing tVCCF tVCCR VPFMAX VPFMIN VCC tREC RST Figure 2. Power Switch Timing RST PBDB tRST Figure 3.
PAGE 6
DS3231M ±5ppm, I2C Real-Time Clock Typical Operating Characteristics (TA = +25°C, unless otherwise noted.) VBAT = 2.3V, EN32KHZ = 1, IOUT = 0mA 140 +85°C 120 110 100 +25°C 90 -40°C 80 INCREASE BELOW VPF DUE TO INTERNAL PULLUP RESISTOR ON RST 70 60 VCC = 0V, EN32KHZ = 1, BBSQW = 0 3.5 SUPPLY CURRENT (µA) +85°C 3.0 +25°C 2.5 2.0 1.5 50 -40°C 1.0 2 3 4 5 6 2 3 SUPPLY VOLTAGE (V) 0.2 0.1 0.3 0.
PAGE 7
DS3231M ±5ppm, I2C Real-Time Clock Pin Configuration TOP VIEW 32KHZ 1 + 16 SCL VCC 2 INT/SQW 3 TOP VIEW 15 SDA DS3231M 14 VBAT 32KHZ 1 RST 4 13 GND VCC 2 N.C. 5 12 N.C. INT/SQW N.C. 6 11 N.C. RST N.C. 7 10 N.C. N.C. 8 9 + 8 SCL 7 SDA 3 6 VBAT 4 5 GND DS3231M SO N.C. SO Pin Description PIN NAME FUNCTION 8 SO 16 SO 1 1 32KHZ 32.768kHz Output (50% Duty Cycle). This open-drain pin requires an external pullup resistor.
PAGE 8
DS3231M ±5ppm, I2C Real-Time Clock Pin Description (continued) PIN NAME FUNCTION 15 SDA 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. 16 SCL 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.
PAGE 9
DS3231M ±5ppm, I2C Real-Time Clock High-Accuracy Time Base +3.3V The temperature sensor, oscillator, and digital adjustment controller logic form the highly accurate time base. The controller reads the output of the on-board temperature 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.
PAGE 10
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, temperature conversions are executed once every 10s.
PAGE 11
DS3231M ±5ppm, I2C Real-Time Clock Table 2.
PAGE 12
DS3231M ±5ppm, I2C Real-Time Clock time information is read from these secondary registers, while the clock can continue to run. This eliminates the need to reread the registers in case the main registers update during a read. Clock and Calendar The time and calendar information is obtained by reading the appropriate register bytes. Table 2 shows the RTC registers. The time and calendar data are set or initialized by writing the appropriate register bytes.
PAGE 13
DS3231M ±5ppm, I2C Real-Time Clock Control Register (0Eh) BIT 7 BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1 BIT 0 EOSC 0 BBSQW CONV NA NA INTCN A2IE A1IE 0 0 1 1 1 0 0 BIT 7 EOSC: Enable oscillator. When set to logic 0, the oscillator is started. When set to logic 1, the oscillator is stopped when the device switches to VBAT. This bit is clear (logic 0) when power is first applied. When the device is powered by VCC, the oscillator is always on regardless of the status of the EOSC bit.
PAGE 14
DS3231M ±5ppm, I2C Real-Time Clock VCC POWERED INTERNAL 1Hz CLOCK BSY CONV THE USER SETS THE CONV BIT THE DEVICE CLEARS THE CONV BIT AFTER THE TEMPERATURE CONVERSION HAS COMPLETED BSY IS HIGH DURING THE TEMPERATURE CONVERSION VBAT POWERED 10 SECONDS INTERNAL 1Hz CLOCK BSY CONV THE USER SETS THE CONV BIT THE DEVICE CLEARS THE CONV BIT AFTER THE TEMPERATURE CONVERSION HAS COMPLETED Figure 7.
PAGE 15
DS3231M ±5ppm, I2C Real-Time Clock Status Register (0Fh) BIT 7 BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1 BIT 0 OSF 0 0 0 EN32KHZ BSY A2F A1F 1 0 0 0 1 X X X OSF: Oscillator stop flag. A logic 1 in this bit indicates that the oscillator either is stopped or was stopped for some period and could be used to judge the validity of the timekeeping data. This bit is set to logic 1 any time that the oscillator stops. This bit remains at logic 1 until written to logic 0.
PAGE 16
DS3231M ±5ppm, I2C Real-Time Clock Temperature Registers (11h-12h) Temperature Register (Upper Byte = 11h) BIT 7 BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1 BIT 0 SIGN DATA DATA DATA DATA DATA DATA DATA 0 0 0 0 0 0 0 0 Temperature Register (Lower Byte = 12h) BIT 7 BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1 BIT 0 DATA DATA 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Temperature is represented as a 10-bit code with a resolution of 0.25°C and is accessible at location 11h and 12h.
PAGE 17
DS3231M ±5ppm, I2C Real-Time Clock Repeated START Condition: The master can use a repeated START condition at the end of one data transfer to indicate that it immediately initiates a new data transfer following the current one. Repeated STARTs are commonly used during read operations to identify a specific memory address to begin a data transfer. A repeated START condition is issued identically to a normal START condition. See Figure 1 for applicable timing.
PAGE 18
DS3231M ±5ppm, I2C Real-Time Clock TYPICAL I2C WRITE TRANSACTION MSB START 1 LSB 1 0 1 0 0 0 R/W MSB SLAVE ACK b7 LSB b6 READ/ WRITE SLAVE ADDRESS b5 b4 b3 b2 b1 b0 MSB SLAVE ACK b7 LSB b6 b5 b4 REGISTER ADDRESS b3 b2 b1 b0 SLAVE ACK STOP DATA EXAMPLE I2C TRANSACTIONS D0h A) SINGLE BYTE WRITE -WRITE CONTROL REGISTER TO 44h START B) SINGLE BYTE READ -READ CONTROL REGISTER START 1 1 0 1 0 0 0 0 11010000 D0h 0Eh SLAVE 00001110 ACK 0Eh SLAVE SLAVE 00001110 ACK ACK D0h C)
PAGE 19
DS3231M ±5ppm, I2C Real-Time Clock Package Information For the latest package outline information and land patterns (footprints), go to www.maximintegrated.com/packages. Note that a “+”, “#”, or “-” in the package code indicates RoHS status only. Package drawings may show a different suffix character, but the drawing pertains to the package regardless of RoHS status. PACKAGE TYPE PACKAGE CODE OUTLINE NO. LAND PATTERN NO.
PAGE 20
DS3231M ±5ppm, I2C Real-Time Clock Revision History REVISION NUMBER REVISION DATE 0 6/10 Initial release 5/11 Updated the Features section; moved the temperature accuracy limit from ±3°C (max) to ±3°C (typ) in the DC Electrical Characteristics—General table; added the PowerSupply Current vs.