Rainbow Electronics DS3231 User Manual

General Description

The DS3231 is a low-cost, extremely accurate I2C real­time clock (RTC) with an integrated temperature­compensated crystal oscillator (TCXO) and crystal. The
device incorporates a battery input, and maintains accu­rate timekeeping when main power to the device is inter­rupted. 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-of­day 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 refer­ence and comparator circuit monitors the status of V

CC

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 reset externally.

Applications

Servers Utility Power Meters

Telematics GPS

Features

♦ Accuracy ±2ppm from 0°C to +40°C
♦ Accuracy ±3.5ppm from -40°C to +85°C
♦ Battery Backup Input for Continuous

Timekeeping

♦ Operating Temperature Ranges

Commercial: 0°C to +70°C
Industrial: -40°C to +85°C

♦ Low-Power Consumption
♦ Real-Time Clock Counts Seconds, Minutes,

Hours, Day, Date, Month, and Year with Leap Year
Compensation Valid Up to 2100

♦ Two Time-of-Day Alarms
♦ Programmable Square-Wave Output
♦ Fast (400kHz) I2C Interface
♦ 3.3V Operation
♦ Digital Temp Sensor Output: ±3°C Accuracy
♦ Register for Aging Trim
♦ RST Input/Output
♦ UL Recognized

DS3231

Extremely Accurate I2C-Integrated

RTC/TCXO/Crystal

______________________________________________ Maxim Integrated Products 1

Rev 2; 6/05

For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.

Ordering Information

PART

TEMP RANGE

PIN-PACKAGE

TOP

MARK

DS3231S

16 SO

DS3231

DS3231SN

16 SO

DS3231N

DS3231S+

16 SO

DS3231+

DS3231SN+

16 SO

DS3231N+

Pin Configuration appears at end of data sheet.

Purchase of I

2

C components from Maxim Integrated Products, Inc., or one of its sublicensed Associated Companies, conveys a

license under the Philips I

2

C Patent Rights to use these components in an I2C system, provided that the system conforms to the I2C

Standard Specification as defined by Philips.

DS3231

V

CC

SCL

R

PU

R

PU

= tR/C

B

R

PU

INT/SQW

32kHz

V

BAT

PUSHBUTTON

RESET

SDA

RST

N.C.
N.C.
N.C.
N.C.

V

CC

V

CC

GND

V

CC

CPU

N.C.
N.C.
N.C.
N.C.

Typical Operating Circuit

+Denotes lead-free

0°C to +70°C

-40°C to +85°C

0°C to +70°C

-40°C to +85°C

DS3231

Extremely Accurate I2C-Integrated
RTC/TCXO/Crystal

2 _____________________________________________________________________

ABSOLUTE MAXIMUM RATINGS

RECOMMENDED DC OPERATING CONDITIONS

(TA= T

MIN

to T

MAX

, unless otherwise noted.) (Notes 1, 2)

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, V

BAT

, 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 Assembly section.

PARAMETER

CONDITIONS

UNITS

V

CC

2.3 3.3 5.5 V

Supply Voltage

V

BAT

2.3 3.0 5.5 V

Logic 1 Input SDA, SCL V

IH

0.7 x

VCC +

0.3

V

Logic 0 Input SDA, SCL V

IL

+0.3 x

V

Pullup Voltage
(SDA, SCL, 32kHz, INT/SQW)

V

PU

VCC = 0V

V

ELECTRICAL CHARACTERISTICS

(VCC= 2.3V to 5.5V, VCC> V

BAT

, TA= T

MIN

to T

MAX

, unless otherwise noted.) (Typical values are at V

CC

= 3.3V, V

BAT

= 3.0V, and

T

A

= +25°C, unless otherwise noted.) (Notes 1, 2)

PARAMETER

CONDITIONS

UNITS

VCC = 3.63V

Active Supply Current I

CCA

(Notes 3, 4)

V

CC

= 5.5V

µA

VCC = 3.63V

Standby Supply Current I

CCS

I2C bus inactive, 32kHz

(Note 4)

V

CC

= 5.5V

µA

VCC = 3.63V

Temperature Conversion Current

I2C bus inactive, 32kHz

VCC = 5.5V

µA

Power-Fail Voltage V

PF

V

Logic 0 Output, 32kHz, INT/SQW,
SDA

V

OL

IOL = 3mA

0.4

V

Logic 0 Output, RST

V

OL

IOL = 1mA

0.4

V

Output Leakage Current 32kHz,
INT/SQW, SDA

I

LO

Output high impedance

-1

0

+1 µA

Input Leakage SCL

I

LI

-1

+1 µA

RST Pin I/O Leakage

I

OL

RST high impedance (Note 5)

µA

V

BAT

Leakage Current

(V

CC

Active)

25

nA

SYMBOL

MIN TYP MAX

V

CC

-0.3

SYMBOL

I

CCSCONV

I

BATLKG

output on, SQW output off

output on, SQW output off

MIN TYP MAX

2.45 2.575 2.70

-200

V

5.5V

200

300

110

170

575

650

+10

100

CC

DS3231

Extremely Accurate I2C-Integrated

RTC/TCXO/Crystal

_____________________________________________________________________ 3

ELECTRICAL CHARACTERISTICS (continued)

(VCC= 2.3V to 5.5V, VCC> V

BAT

, TA= T

MIN

to T

MAX

, unless otherwise noted.) (Typical values are at V

CC

= 3.3V, V

BAT

= 3.0V, and

T

A

= +25°C, unless otherwise noted.) (Notes 1, 2)

PARAMETER

CONDITIONS

UNITS

Output Frequency

f

OUT

VCC = 3.3V or V

BAT

= 3.3V

kHz

0°C to +40°C

±2

Frequency Stability vs.
Temperature (Commercial)

∆f/f

OUT

VCC = 3.3V or
V

BAT

= 3.3V,

aging offset = 00h

ppm

-40°C to <0°C

0°C to +40°C

±2

Frequency Stability vs.
Temperature (Industrial)

∆f/f

OUT

VCC = 3.3V or
V

BAT

= 3.3V,

aging offset = 00h

ppm

Frequency Stability vs. Voltage

∆f/V

1

ppm/V

-40°C

0.7

+25°C

0.1

+70°C

0.4

Trim Register Frequency
Sensitivity per LSB

∆f/LSB Specified at:

+85°C

0.8

ppm

Temperature Accuracy Temp VCC = 3.3V or V

BAT

= 3.3V -3 +3 °C

First year

Crystal Aging ∆f/f

0

After reflow,
not production tested

0–10 years

ppm

ELECTRICAL CHARACTERISTICS

(VCC= 0V, V

BAT

= 2.3V to 5.5V, TA= T

MIN

to T

MAX

, unless otherw.ise noted.) (Note 1)

PARAMETER

CONDITIONS

UNITS

V

BAT

= 3.63V 70

Active Battery Current I

BATA

EOSC = 0, BBSQW = 0,
SCL = 400kHz (Note 4)

V

BAT

= 5.5V 150

µA

V

BAT

= 3.63V

3.0

Timekeeping Battery Current I

BATT

EOSC = 0, BBSQW = 0,
EN32kHz = 1,
SCL = SDA = 0V or

V

BAT

= 5.5V 1.0 3.5

µA

V

BAT

= 3.63V 575

I

BATTC

EOSC = 0, BBSQW = 0,
SCL = SDA = 0V or
SCL = SDA = V

BAT

V

BAT

= 5.5V 650

µA

Data-Retention Current

EOSC = 1, SCL = SDA = 0V, +25°C 100 nA

SYMBOL

>40°C to +70°C

>40°C to +85°C

MIN TYP MAX

32.768

±1.0

±5.0

±3.5

±3.5

±3.5

Temperature Conversion Current

SYMBOL

I

BATTDR

MIN TYP MAX

S C L = S D A = V

( Note 4)

BAT

0.84

DS3231

Extremely Accurate I2C-Integrated
RTC/TCXO/Crystal

4 _____________________________________________________________________

AC ELECTRICAL CHARACTERISTICS

(VCC= V

CC(MIN)

to V

CC(MAX)

or V

BAT

= V

BAT(MIN)

to V

BAT(MAX)

, V

BAT

> VCC, TA= T

MIN

to T

MAX

, unless otherwise noted.) (Note 1)

PARAMETER

CONDITIONS

UNITS

Fast mode

400

SCL Clock Frequency f

SCL

Standard mode 0 100

kHz

Fast mode 1.3

Bus Free Time Between STOP
and START Conditions

t

BUF

Standard mode 4.7

µs

Fast mode 0.6

Hold Time (Repeated) START
Condition (Note 6)

Standard mode 4.0

µs

Fast mode 1.3

Low Period of SCL Clock t

LOW

Standard mode 4.7

µs

Fast mode 0.6

High Period of SCL Clock t

HIGH

Standard mode 4.0

µs

Fast mode 0 0.9

Data Hold Time (Notes 7, 8)

Standard mode 0 0.9

µs

Fast mode

Data Setup Time (Note 9)

Standard mode

ns

Fast mode 0.6

Start Setup Time t

SU:STA

Standard mode 4.7

µs

Fast mode 300

Rise Time of Both SDA and SCL
Signals (Note 10)

t

R

Standard mode

20 +

ns

Fast mode 300

Fall Time of Both SDA and SCL
Signals (Note 10)

t

F

Standard mode

20 +

300

ns

Fast mode 0.6

Setup Time for STOP Condition

Standard mode 4.7

µs

Capacitive Load for Each Bus
Line (Note 10)

C

B

400 pF

Capacitance for SDA, SCL C

I/O

10 pF

Pulse Width of Spikes That Must

Be Suppressed by the Input Filter

t

SP

30 ns

Pushbutton Debounce PB

DB

ms

Reset Active Time t

RST

ms

Oscillator Stop Flag (OSF) Delay

t

OSF

(Note 11)

ms

Temperature Conversion Time t

CONV

200 ms

POWER-SWITCH CHARACTERISTICS

(TA= T

MIN

to T

MAX

)

PARAMETER

CONDITIONS

UNITS

VCC Fall Time; V

PF(MAX)

to

V

PF(MIN)

t

VCCF

µs

VCC Rise Time; V

PF(MIN)

to

V

PF(MAX)

t

VCCR

0µs

Recovery at Power-Up t

REC

(Note 12)

300 ms

SYMBOL

t

HD:STA

t

HD:DAT

MIN TYP MAX

100

t

SU:DAT

100

250

0.1C

B 1000

0.1C

t

SU:STO

B

SYMBOL

MIN TYP MAX

300

250

250

100

125

250

DS3231

Extremely Accurate I2C-Integrated

RTC/TCXO/Crystal

_____________________________________________________________________ 5

Pushbutton Reset Timing

t

RST

PB

DB

RST

Power-Switch Timing

V

CC

t

VCCF

t

VCCR

t

REC

V

PF(MAX)

V

PF

V

PF

V

PF(MIN)

RST

DS3231

Extremely Accurate I2C-Integrated
RTC/TCXO/Crystal

6 _____________________________________________________________________

Data Transfer on I2C Serial Bus

SDA

SCL

t

HD:STA

t

LOW

t

HIGH

t

R

t

F

t

BUF

t

HD:DAT

t

SU:DAT

REPEATED

START

t

SU:STA

t

HD:STA

t

SU:STO

t

SP

STOP START

Note 1: Limits at -40°C are guaranteed by design and not production tested.
Note 2: All voltages are referenced to ground.
Note 3: I

CCA

—SCL clocking at max frequency = 400kHz.

Note 4: Current is the averaged input current, which includes the temperature conversion current.
Note 5: The RST pin has an internal 50kΩ (nominal) pullup resistor to V

CC

.

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 V

IH(MIN)

of the SCL signal)

to bridge the undefined region of the falling edge of SCL.

Note 8: The maximum t

HD:DAT

needs only to be met if the device does not stretch the low period (t

LOW

) of the SCL signal.

Note 9: A fast-mode device can be used in a standard-mode system, but the requirement t

SU: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 t

R(MAX)

+

t

SU:DAT

= 1000 + 250 = 1250ns

before the SCL line is released.

Note 10: C

B

—total capacitance of one bus line in pF.

Note 11: The parameter t

OSF

is the period of time the oscillator must be stopped for the OSF flag to be set over the voltage range of

0.0V ≤ V

CC

≤ V

CC(MAX)

and 2.3V ≤ V

BAT

≤ 3.4V.

Note 12: This delay applies only if the oscillator is enabled and running. If the EOSC bit is a 1, the startup time of the oscillator is

added to this delay.