Datasheet

ManualsBrandsMAXIM INTEGRATED ManualsIntegrated Circuits (ICs)Timer IC t- real time clock Clock/calendar SOIC 16 W

DS3231

Extremely Accurate I

C-Integrated

RTC/TCXO/Crystal

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

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

General Description

The DS3231 is a low-cost, extremely accurate I

C 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 I

C bidirectional bus.

A precision temperature-compensated voltage refer-

ence and comparator circuit monitors the status of V

to detect power failures, to provide a reset output, and

to automatically switch to the backup supply when nec-

essary. Additionally, the RST pin is monitored as a

pushbutton input for generating a µP reset.

Applications

Servers Utility Power Meters

Telematics GPS

Features

o Accuracy ±2ppm from 0°C to +40°C

o Accuracy ±3.5ppm from -40°C to +85°C

o Battery Backup Input for Continuous

Timekeeping

o Operating Temperature Ranges

Commercial: 0°C to +70°C

Industrial: -40°C to +85°C

o Low-Power Consumption

o Real-Time Clock Counts Seconds, Minutes,

Hours, Day, Date, Month, and Year with Leap Year

Compensation Valid Up to 2100

o Two Time-of-Day Alarms

o Programmable Square-Wave Output

o Fast (400kHz) I

C Interface

o 3.3V Operation

o Digital Temp Sensor Output: ±3°C Accuracy

o Register for Aging Trim

o RST Output/Pushbutton Reset Debounce Input

o Underwriters Laboratories (UL) Recognized

19-5170; Rev 9; 1/13

Ordering Information

PART TEMP RANGE PIN-PACKAGE

DS3231S# 0°C to +70°C 16 SO

DS3231SN# -40°C to +85°C 16 SO

Pin Configuration appears at end of data sheet.

Typical Operating Circuit

#Denotes an RoHS-compliant device that may include lead

(Pb) that is exempt under RoHS requirements. The lead finish

is JESD97 category e3, and is compatible with both lead-

based and lead-free soldering processes. A "#" anywhere on

the top mark denotes an RoHS-compliant device.

DS3231

SCL

= t

INT/SQW

32kHz

BAT

PUSHBUTTON

RESET

SDA

RST

N.C.

GND

µP

N.C.

SCL

SDA

RST

Summary of content (20 pages)

PAGE 1
DS3231 Extremely Accurate I2C-Integrated RTC/TCXO/Crystal General Description Features The DS3231 is a low-cost, extremely accurate I2C real- o Accuracy ±2ppm from 0°C to +40°C o Accuracy ±3.
PAGE 2
DS3231 Extremely Accurate I2C-Integrated RTC/TCXO/Crystal ABSOLUTE MAXIMUM RATINGS Voltage Range on Any Pin Relative to Ground......-0.3V to +6.0V Junction-to-Ambient Thermal Resistance (θJA) (Note 1)....73°C/W Junction-to-Case Thermal Resistance (θJC) (Note 1) ......23°C/W Operating Temperature Range DS3231S ..............................................................0°C to +70°C DS3231SN ........................................................-40°C to +85°C Note 1: Junction Temperature ................
PAGE 3
DS3231 Extremely Accurate I2C-Integrated RTC/TCXO/Crystal ELECTRICAL CHARACTERISTICS (continued) (VCC = 2.3V to 5.5V, VCC = Active Supply (see Table 1), TA = TMIN to TMAX, unless otherwise noted.) (Typical values are at VCC = 3.3V, VBAT = 3.0V, and TA = +25°C, unless otherwise noted.) (Notes 2, 3) PARAMETER Output Frequency Frequency Stability vs. Temperature (Commercial) Frequency Stability vs. Temperature (Industrial) Frequency Stability vs.
PAGE 4
DS3231 Extremely Accurate I2C-Integrated RTC/TCXO/Crystal AC ELECTRICAL CHARACTERISTICS (VCC = VCC(MIN) to VCC(MAX) or VBAT = VBAT(MIN) to VBAT(MAX), VBAT > VCC, TA = TMIN to TMAX, unless otherwise noted.
PAGE 5
DS3231 Extremely Accurate I2C-Integrated RTC/TCXO/Crystal Pushbutton Reset Timing RST PBDB tRST Power-Switch Timing VCC VPF(MAX) VPF VPF VPF(MIN) tVCCF tVCCR tREC RST Maxim Integrated 5
PAGE 6
DS3231 Extremely Accurate I2C-Integrated RTC/TCXO/Crystal Data Transfer on I2C Serial Bus SDA tBUF tHD:STA tLOW tR tSP tF SCL tHD:STA STOP tSU:STA tHIGH tSU:DAT START REPEATED START tSU:STO tHD:DAT WARNING: Negative undershoots below -0.3V while the part is in battery-backed mode may cause loss of data. Note 2: Note 3: Note 4: Note 5: Note 6: Note 7: Note 8: Note 9: Note 10: Note 11: Note 12: Note 13: 6 Limits at -40°C are guaranteed by design and not production tested.
PAGE 7
DS3231 Extremely Accurate I2C-Integrated RTC/TCXO/Crystal Typical Operating Characteristics (VCC = +3.3V, TA = +25°C, unless otherwise noted.) BSY = 0, SCL = SDA = VCC 125 1.2 DS3231 toc01 1.1 RST ACTIVE 1.0 IBAT (μA) ICCS (μA) 100 75 EN32kHz = 0 0.8 25 0.7 0 0.6 3.0 3.5 4.0 4.5 5.5 5.0 2.3 3.3 4.3 5.3 VCC (V) VBAT (V) SUPPLY CURRENT vs. TEMPERATURE FREQUENCY DEVIATION vs. TEMPERATURE vs.
PAGE 8
DS3231 Extremely Accurate I2C-Integrated RTC/TCXO/Crystal Block Diagram 32kHz X1 OSCILLATOR AND CAPACITOR ARRAY N CONTROL LOGIC/ DIVIDER X2 SQUARE-WAVE BUFFER; INT/SQW CONTROL 1Hz VCC VBAT N TEMPERATURE SENSOR POWER CONTROL GND INT/SQW ALARM, STATUS, AND CONTROL REGISTERS 1Hz CLOCK AND CALENDAR REGISTERS SCL SDA I2C INTERFACE AND ADDRESS REGISTER DECODE USER BUFFER (7 BYTES) DS3231 8 VOLTAGE REFERENCE; DEBOUNCE CIRCUIT; PUSHBUTTON RESET VCC RST N Maxim Integrated
PAGE 9
DS3231 Extremely Accurate I2C-Integrated RTC/TCXO/Crystal Pin Description PIN NAME 1 32kHz 2 VCC 3 4 FUNCTION 32kHz Output. This open-drain pin requires an external pullup resistor. When enabled, the output operates on either power supply. It may be left open if not used. DC Power Pin for Primary Power Supply. This pin should be decoupled using a 0.1μF to 1.0μF capacitor. If not used, connect to ground. Active-Low Interrupt or Square-Wave Output.
PAGE 10
DS3231 Extremely Accurate I2C-Integrated RTC/TCXO/Crystal 32kHz TCXO The 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 capacitance selection registers.
PAGE 11
DS3231 Extremely Accurate I2C-Integrated RTC/TCXO/Crystal Figure 1.
PAGE 12
DS3231 Extremely Accurate I2C-Integrated RTC/TCXO/Crystal Alarms the binary-coded decimal (BCD) format. The DS3231 can be run in either 12-hour or 24-hour mode. Bit 6 of the hours register is defined as the 12- or 24-hour mode select bit. When high, the 12-hour mode is selected. In the 12-hour mode, bit 5 is the AM/PM bit with logic-high being PM. In the 24-hour mode, bit 5 is the 20-hour bit (20–23 hours).
PAGE 13
DS3231 Extremely Accurate I2C-Integrated RTC/TCXO/Crystal Control Register (0Eh) BIT 7 BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1 BIT 0 NAME: EOSC BBSQW CONV RS2 RS1 INTCN A2IE A1IE POR: 0 0 0 1 1 1 0 0 Special-Purpose Registers The DS3231 has two additional registers (control and status) that control the real-time clock, alarms, and square-wave output. shows the square-wave frequencies that can be selected with the RS bits. These bits are both set to logic 1 (8.
PAGE 14
DS3231 Extremely Accurate I2C-Integrated RTC/TCXO/Crystal Status Register (0Fh) BIT 7 BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1 BIT 0 NAME: OSF 0 0 0 EN32kHz BSY A2F A1F POR: 1 0 0 0 1 X X X Status Register (0Fh) ters. If the A1IE bit is logic 1 and the INTCN bit is set to logic 1, the INT/SQW pin is also asserted. A1F is cleared when written to logic 0. This bit can only be written to logic 0. Attempting to write to logic 1 leaves the value unchanged.
PAGE 15
DS3231 Extremely Accurate I2C-Integrated RTC/TCXO/Crystal Temperature Register (Upper Byte) (11h) BIT 7 BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1 BIT 0 NAME: Sign Data Data Data Data Data Data Data POR: 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 NAME: Data Data 0 0 0 0 0 0 POR: 0 0 0 0 0 0 0 0 Temperature Registers (11h–12h) Temperature is represented as a 10-bit code with a resolution of 0.
PAGE 16
DS3231 Extremely Accurate I2C-Integrated RTC/TCXO/Crystal SDA MSB SLAVE ADDRESS R/W DIRECTION BIT ACKNOWLEDGEMENT SIGNAL FROM RECEIVER ACKNOWLEDGEMENT SIGNAL FROM RECEIVER SCL 1 2 6 7 8 9 1 2 3–7 8 ACK 9 ACK Figure 2. I2C Data Transfer Overview slave by not generating an acknowledge bit on the last byte that has been clocked out of the slave. In this case, the slave must leave the data line high to enable the master to generate the STOP condition. the slave address.
PAGE 17
DS3231 Extremely Accurate I2C-Integrated RTC/TCXO/Crystal S 1101000 0 XXXXXXXX A XXXXXXXX A A XXXXXXXX Sr 1101000 1 A S - START MASTER TO SLAVE Sr - REPEATED START A - ACKNOWLEDGE (ACK) P - STOP A - NOT ACKNOWLEDGE (NACK) R/W - READ/WRITE OR DIRECTION BIT ADDRESS XXXXXXXX A A ...
PAGE 18
DS3231 Extremely Accurate I2C-Integrated RTC/TCXO/Crystal Handling, PC Board Layout, and Assembly The DS3231 package contains a quartz tuning-fork crystal. Pick-and-place equipment can be used, but precautions should be taken to ensure that excessive shocks are avoided. Ultrasonic cleaning should be avoided to prevent damage to the crystal. Avoid running signal traces under the package, unless a ground plane is placed between the package and the signal line. All N.C.
PAGE 19
DS3231 Extremely Accurate I2C-Integrated RTC/TCXO/Crystal Revision History REVISION NUMBER REVISION DATE 0 1/05 DESCRIPTION Initial release. Changed Digital Temp Sensor Output from ±2°C to ±3°C. 1 2 2/05 6/05 Updated Typical Operating Circuit. Changed TA = -40°C to +85°C to TA = TMIN to TMAX.
PAGE 20
DS1086L 3.3V Spread-Spectrum EconOscillator Revision History (continued) REVISION NUMBER REVISION DATE DESCRIPTION Updated the Typical Operating Circuit. 6 10/08 PAGES CHANGED 1 Removed the V PU parameter from the Recommended DC Operating Conditions table and added verbiage about the pullup to the Pin Description table for INT/SQW, SDA, and SCL. 2, 9 Added the Delta Time and Frequency vs. Temperature graph in the Typical Operating Characteristics section. 7 Updated the Block Diagram.