19-5170; Rev 8; 7/10
Extremely Accurate I
2
C-Integrated
RTC/TCXO/Crystal
General Description
The DS3231 is a low-cost, extremely accurate I
2
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
2
C bidirectional bus.
A precision temperature-compensated voltage refer-
ence 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 nec-
essary. Additionally, the
RST
pin is monitored as a
pushbutton input for generating a µP reset.
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) I
2
C Interface
♦
3.3V Operation
♦
Digital Temp Sensor Output: ±3°C Accuracy
♦
Register for Aging Trim
♦
RST
Output/Pushbutton Reset Debounce Input
♦
Underwriters Laboratories (UL) Recognized
DS3231
Ordering Information
PART
DS3231S#
DS3231SN#
TEMP RANGE
0°C to +70°C
-40°C to +85°C
PIN-PACKAGE
16 SO
16 SO
Applications
Servers
Telematics
Utility Power Meters
GPS
#Denotes a RoHS-compliant device that may include lead 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 a RoHS-compliant device.
Pin Configuration appears at end of data sheet.
Typical Operating Circuit
V
CC
V
CC
R
PU
= t
R
/C
B
R
PU
SCL
μP
SDA
RST
PUSHBUTTON
RESET
R
PU
V
CC
SCL
SDA
RST
N.C.
N.C.
N.C.
N.C.
GND
INT/SQW
32kHz
V
BAT
V
CC
DS3231
N.C.
N.C.
N.C.
N.C.
______________________________________________
Maxim Integrated Products
1
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,
or visit Maxim’s website at www.maxim-ic.com.
Extremely Accurate I
2
C-Integrated
RTC/TCXO/Crystal
DS3231
ABSOLUTE MAXIMUM RATINGS
Voltage Range on V
CC
, V
BAT
, 32kHz, SCL, SDA,
RST,
INT/SQW
Relative to Ground.............................-0.3V to +6.0V
Junction-to-Ambient Thermal Resistance (θ
JA
) (Note 1)....73°C/W
Junction-to-Case Thermal Resistance (θ
JC
) (Note 1) ......23°C/W
Operating Temperature Range
(noncondensing) .............................................-40°C to +85°C
Junction Temperature ......................................................+125°C
Note 1:
Storage Temperature Range ...............................-40°C to +85°C
Lead Temperature (soldering, 10s) .................................+260°C
Soldering Temperature (reflow, 2 times max)
Lead(Pb)-free...............................................................+260°C
Containing lead(Pb) .....................................................+240°C
(See the
Handling, PC Board Layout, and Assembly
section.)
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.maxim-ic.com/thermal-tutorial.
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.
RECOMMENDED OPERATING CONDITIONS
(T
A
= T
MIN
to T
MAX
, unless otherwise noted.) (Notes 2, 3)
PARAMETER
Supply Voltage
Logic 1 Input SDA, SCL
Logic 0 Input SDA, SCL
SYMBOL
V
CC
V
BAT
V
IH
V
IL
CONDITIONS
MIN
2.3
2.3
0.7 x
V
CC
-0.3
TYP
3.3
3.0
MAX
5.5
5.5
V
CC
+
0.3
0.3 x
V
CC
UNITS
V
V
V
V
ELECTRICAL CHARACTERISTICS
(V
CC
= 2.3V to 5.5V, V
CC
= Active Supply (see Table 1), T
A
= 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 2, 3)
PARAMETER
Active Supply Current
SYMBOL
I
CCA
(Notes 4, 5)
I
2
C bus inactive, 32kHz
output on, SQW output off
(Note 5)
I
2
C bus inactive, 32kHz
output on, SQW output off
CONDITIONS
V
CC
= 3.63V
V
CC
= 5.5V
V
CC
= 3.63V
V
CC
= 5.5V
V
CC
= 3.63V
V
CC
= 5.5V
2.45
I
OL
= 3mA
I
OL
= 1mA
Output high impedance
-1
-1
RST
high impedance (Note 6)
-200
25
0
2.575
MIN
TYP
MAX
200
300
110
μA
170
575
650
2.70
0.4
0.4
+1
+1
+10
100
μA
V
V
V
μA
μA
μA
nA
UNITS
μA
Standby Supply Current
I
CCS
Temperature Conversion Current
Power-Fail Voltage
Logic 0 Output, 32kHz,
INT/SQW,
SDA
Logic 0 Output,
RST
Output Leakage Current 32kHz,
INT/SQW,
SDA
Input Leakage SCL
RST
Pin I/O Leakage
V
BAT
Leakage Current
(V
CC
Active)
I
CCSCONV
V
PF
V
OL
V
OL
I
LO
I
LI
I
OL
I
BATLKG
2
_____________________________________________________________________
Extremely Accurate I
2
C-Integrated
RTC/TCXO/Crystal
ELECTRICAL CHARACTERISTICS (continued)
(V
CC
= 2.3V to 5.5V, V
CC
= Active Supply (see Table 1), T
A
= 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 2, 3)
PARAMETER
Output Frequency
Frequency Stability vs.
Temperature (Commercial)
SYMBOL
f
OUT
f/f
OUT
CONDITIONS
V
CC
= 3.3V or V
BAT
= 3.3V
V
CC
= 3.3V or
V
BAT
= 3.3V,
aging offset = 00h
V
CC
= 3.3V or
V
BAT
= 3.3V,
aging offset = 00h
0°C to +40°C
>40°C to +70°C
-40°C to <0°C
0°C to +40°C
>40°C to +85°C
1
-40°C
Trim Register Frequency
Sensitivity per LSB
Temperature Accuracy
Crystal Aging
f/LSB
Specified at:
+25°C
+70°C
+85°C
Temp
f/f
O
V
CC
= 3.3V or V
BAT
= 3.3V
After reflow,
not production tested
First year
0–10 years
-3
±1.0
±5.0
0.7
0.1
0.4
0.8
+3
°C
ppm
ppm
MIN
TYP
32.768
±2
ppm
±3.5
±3.5
±2
±3.5
ppm/V
ppm
MAX
UNITS
kHz
DS3231
Frequency Stability vs.
Temperature (Industrial)
Frequency Stability vs. Voltage
f/f
OUT
f/V
ELECTRICAL CHARACTERISTICS
(V
CC
= 0V, V
BAT
= 2.3V to 5.5V,
T
A
= T
MIN
to T
MAX
, unless otherwise noted.) (Note 2)
PARAMETER
Active Battery Current
SYMBOL
I
BATA
CONDITIONS
EOSC
= 0, BBSQW = 0,
SCL = 400kHz (Note 5)
V
BAT
= 3.63V
V
BAT
= 5.5V
0.84
1.0
MIN
TYP
MAX
70
150
3.0
μA
3.5
575
μA
V
BAT
= 5.5V
650
100
nA
UNITS
μA
Timekeeping Battery Current
I
BATT
EOSC
= 0, BBSQW = 0,
V
BAT
= 3.63V
EN32kHz = 1,
SCL = SDA = 0V or
SCL = SDA = V
BAT
(Note 5) V
BAT
= 5.5V
EOSC
= 0, BBSQW = 0,
SCL = SDA = 0V or
SCL = SDA = V
BAT
V
BAT
= 3.63V
Temperature Conversion Current
Data-Retention Current
I
BATTC
I
BATTDR
EOSC
= 1, SCL = SDA = 0V, +25°C
_____________________________________________________________________
3
Extremely Accurate I
2
C-Integrated
RTC/TCXO/Crystal
DS3231
AC ELECTRICAL CHARACTERISTICS
(V
CC
= V
CC(MIN)
to V
CC(MAX)
or V
BAT
= V
BAT(MIN)
to V
BAT(MAX)
, V
BAT
> V
CC
, T
A
= T
MIN
to T
MAX
, unless otherwise noted.) (Note 2)
PARAMETER
SCL Clock Frequency
Bus Free Time Between STOP
and START Conditions
Hold Time (Repeated) START
Condition (Note 7)
Low Period of SCL Clock
High Period of SCL Clock
Data Hold Time (Notes 8, 9)
Data Setup Time (Note 10)
START Setup Time
Rise Time of Both SDA and SCL
Signals (Note 11)
Fall Time of Both SDA and SCL
Signals (Note 11)
Setup Time for STOP Condition
Capacitive Load for Each Bus
Line
Capacitance for SDA, SCL
Pulse Width of Spikes That Must
Be Suppressed by the Input Filter
Pushbutton Debounce
Reset Active Time
Oscillator Stop Flag (OSF) Delay
Temperature Conversion Time
SYMBOL
f
SCL
t
BUF
t
HD:STA
t
LOW
t
HIGH
t
HD:DAT
t
SU:DAT
t
SU:STA
t
R
t
F
t
SU:STO
C
B
C
I/O
t
SP
PB
DB
t
RST
t
OSF
t
CONV
(Note 12)
Fast mode
Standard mode
Fast mode
Standard mode
Fast mode
Standard mode
Fast mode
Standard mode
Fast mode
Standard mode
Fast mode
Standard mode
Fast mode
Standard mode
Fast mode
Standard mode
Fast mode
Standard mode
Fast mode
Standard mode
Fast mode
Standard mode
(Note 11)
10
30
250
250
100
125
200
CONDITIONS
MIN
100
0
1.3
4.7
0.6
4.0
1.3
4.7
0.6
4.0
0
0
100
250
0.6
4.7
20 +
0.1C
B
20 +
0.1C
B
0.6
4.7
400
300
1000
300
300
0.9
0.9
TYP
MAX
400
100
UNITS
kHz
μs
μs
μs
μs
μs
ns
μs
ns
ns
μs
pF
pF
ns
ms
ms
ms
ms
POWER-SWITCH CHARACTERISTICS
(T
A
= T
MIN
to T
MAX
)
PARAMETER
V
CC
Fall Time; V
PF(MAX)
to
V
PF(MIN)
V
CC
Rise Time; V
PF(MIN)
to
V
PF(MAX)
Recovery at Power-Up
SYMBOL
t
VCCF
t
VCCR
t
REC
(Note 13)
CONDITIONS
MIN
300
0
250
300
TYP
MAX
UNITS
μs
μs
ms
4
_____________________________________________________________________
Extremely Accurate I
2
C-Integrated
RTC/TCXO/Crystal
Pushbutton Reset Timing
RST
DS3231
PB
DB
t
RST
Power-Switch Timing
V
CC
V
PF(MAX)
V
PF
V
PF(MIN)
V
PF
t
VCCF
t
VCCR
t
REC
RST
_____________________________________________________________________
5
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