www.maximintegrated.com
1st Edition
Product Guide
ACCURATE
MEMS
REAL-TIME
CLOCKS
Table of Contents
2
www.maximintegrated.comAccurate MEMS Real-Time Clocks Product Guide
3 Introduction
4 Accurate MEMS RTCs at a Glance
6 Benefits of MEMS Technology in RTC Applications
7 Automotive
8 Video Security and Surveillance
9 Industrial and Medical
10 Power Meters
11 Evaluate MEMS RTC Technology with DS323x
Reference and Development Kits
WBGA Package
1999 2005 2010
Industry's First 32.768kHz TCXO
DS32kHz
16-Pin SO
Integrated Crystal
Industry's Most Accurate RTC
DS3231S
Industry's First Accurate MEMS RTC
DS3231M
16-Pin SO
8-Pin SO
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3
Introduction
Advancing Timekeeping Accuracy
In 1999, Maxim Integrated introduced the DS32kHz, a 32.768kHz temperature-compensated crystal
oscillator (TCXO), which was the industry's first accurate timekeeping product for real-time clock
(RTC) applications. The product boasted an accuracy of ±7.5ppm across the entire -40°C to +85°C
industrial temperature range.
By 2005, with the combination of innovative packaging technology and improved temperature sensor
capability, we introduced what would be considered the industry’s most accurate RTC, the DS3231S,
an extremely accurate I²C-integrated RTC/TCXO/crystal. The DS3231S featured a highly reliable and
innovative package that incorporated a 32kHz tuning fork crystal into a standard 16-pin, 300-mil SO.
This highly integrated device further enhanced timekeeping accuracy by providing a frequency accuracy
of less than ±3.5ppm over the -40°C to +85°C temperature range. This accuracy is equivalent to less
than ±0.3 seconds/day.
In 2009, Maxim Integrated embarked on a goal to create a quantum leap in technology advancement
by developing an RTC that would exceed the performance of the DS3231S, but provide it in a smaller
package with lower cost, higher accuracy standards, and substantially more ruggedness. The culmination
of this work is a product family based on microelectromechanical systems (MEMS) technology.
The DS3231M ±5ppm, I²C RTC was first introduced in 2010 with all the capability outlined in the
company’s development goals. The device has a timekeeping accuracy of ±5ppm over all conditions
including temperature, voltage, and aging. The design is extremely rugged, has achieved automotive
AEC-Q100 certification, and can sustain extreme levels of mechanical shock and variable frequency
vibration. Because of the extremely small size of the MEMS resonator, the device is packaged in a small
8-pin, 150-mil SO—something unattainable with tuning fork crystals.
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4
Accurate MEMS RTCs at a Glance
Industry's Single Most Integrated Solutions for Accurate Timekeeping
Maxim Integrated embarked on a goal to create a quantum leap in technology advancement by developing an RTC that would
exceed performance in a smaller package, with lower cost, higher accuracy standards, and be substantially more rugged for use in
power meters, video surveillance, and automotive, industrial, and medical applications. The culmination of this work is a product
family based on the MEMS technology: the DS3231M and DS3232M.
DS3231M
The DS3231M is the first temperature-compensated RTC with an internal MEMS resonator to reduce crystal mechanical failure.
Designed to be footprint and functionally compatible to the popular DS3231S, the DS3231M replicates the 16-pin, 300-mil SO for
users looking for a less-expensive solution but want the same functionally, firmware, and board layout found with the DS3231S.
The DS3231M integrates several important system features—resonator, RTC, TXCO, digital temperature sensor, and automatic
power switching—to support battery-backed applications in one device.
DS3232M
The DS3232M is an RTC that adds memory in the smallest package with 236 bytes of battery-backed user memory. The
DS3232M is a MEMS-equivalent to the popular DS3232S crystal-based RTC. Major space-saving gains are made with this
miniature MEMS resonator in the 8-pin, 150-mil package versus the 20-pin, 300-mil SO of the DS3232S.
MEMS technology, because of its size, enables significant space savings when compared to cylindrical crystals. A single MEMS
resonator occupies 47 times less area and 182 times less volume than a cylindrical crystal. This size differential allows for smaller
packaging options, provides significantly enhanced ruggedness in high vibration and shock environments, and demonstrates little
to no aging (< ±1ppm total) over the life of the device.
From Crystals to MEMS
CYLINDRICAL CRYSTAL
MEMS DIE
CRYSTAL BLANK
Simpler Assembly
• Standard IC plastic packaging
• Wire-bonding vs. welding
• Ultrasonic cleaning
• Facilitates large-scale assembly
operations
Smaller Packaging
• 8-pin (150 mil) vs. 16-pin (300 mil)
• Chip-scale packaging (CSP) possible
Lower Cost
• No special/custom crystals required
• Lower cost MEMS resonator
• Lower cost packaging
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5
MEMS
RESONATOR
DIVIDER
INT/SQW
32KHZ
GND
SDA
SCL
VBAT
VCC
RST
CLOCK/CALENDAR
WITH ALARM
CONTROL AND STATUS
REGISTERS
I2C
INTERFACE
User-accessible
temperature sensor
Each device
individually calibrated,
no blanket trims
Automatic power switching
±5ppm, 1Hz
accurate
pulse output
±3°C
TEMP
SENSOR
INTERRUPT
OR 1Hz
SELECT
DIGITAL
ADJUSTMENT
FACTORY TRIM
POWER
SUPPLY
CONTROL
Benefits
• Precise timekeeping accuracy (±5ppm) without user calibration
• Low power consumption (< 3.5μA) supports battery-powered applications
• Completely self-contained power-switching circuitry saves board space
• Fully contained digital temperature sensor saves additional system component cost
MEMS Real-Time Clocks
Part Number Package User Memory (Bytes) Temp Range (ºC) AEC-Q100
DS3231M+ 16-SO (300 mils) —-40 to +85 —
DS3231MZ+ 8-SO (150 mils) —-40 to +85 —
DS3231MZ/V+ 8-SO (150 mils) —-40 to +85 ✓
DS3232MZ+ 8-SO (150 mils) 236 -40 to +85 —
DS3232MZ/V+ 8-SO (150 mils) 236 -40 to +85 ✓
+Denotes a lead(Pb)-free/RoHS-compliant package.
/V denotes an AEC-Q100-qualified part.
DS3231M Block Diagram
-10
-8
-6
-4
-2
0
2
4
6
8
10
-40 -20 0 20 40 60 80
TEMPERATURE
(°C)
1Hz FREQUENCY ACCURACY (ppm)
-10
-8
-6
-4
-2
0
2
4
6
8
10
-40 -30 -20 -10 0 10 20 30 40 50 60 70 80
TEMPERATURE
(°C)
1Hz FREQUENCY ACCURACY (ppm)
DS3231M
specification
limits
DS3231M
specification
limits
Actual
performance
Actual
performance
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6
Benefits of MEMS Technology in RTC Applications
Environmental and Manufacturing Ruggedness
Maxim Integrated’s MEMS-based RTC products have proven, demonstrable performance advantages based on environmental
criteria and observation. In reflow operations that replicate customer attachment, MEMS devices demonstrate frequency shifts
of less than ±1ppm (Figures 1a and 1b). Crystal-based products that face the same regimen of reflow temperature exposure
demonstrate shifts as high as ±5ppm. One of the most important criteria for establishing how well a device operates is its
frequency performance prior to attachment to a motherboard compared to its performance after this attachment process. The
attachment process can have temperature excursions as high as +260°C for several seconds and be above +200°C for several
10s of seconds. Dependable frequency performance over the life of the device is the most important criteria for choosing accurate
timekeeping products. Maxim Integrated MEMS RTCs guarantee ±5ppm frequency accuracy and stability regardless of voltage,
time (aging), or temperature.
Additionally, MEMS-based RTCs have demonstrable shock and vibration performance and have passed AEC-Q100 qualification,
making them one of the most rugged, dependable, and accurate solutions in the industry.
Benefits
• Higher manufacturing temperature processes (+260°C reflows, < 1ppm frequency shifts, fully RoHS)
• Significantly higher shock and vibration capability (> 50g)
• Wide operational temperature environments (-40°C to +85°C)
1Hz FREQUENCY ERROR TESTED WITH MULTIPLE DS3231M DEVICES
Figure 1a. DS3231M Pre-reflow Figure 1b. DS3231M Post-reflow
SO-8/µMAX
8-Pin SO
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7
Automotive
Automotive Embraces Ruggedness of MEMS Accurate RTC Products
Automotive environments are demanding and require component technologies that can withstand harsh environments. Maxim
Integrated's MEMS RTC products are tough enough to withstand even the most rugged needs.
The MEMS resonator includes wider operating margins for temperature, greater shock and vibration capability than crystals,
more precise frequency accuracy and stability, and less aging over the lifetime of the product.
GPSBODY CONTROL MODULE
AEC-Q100
CERTIFIED
INFOTAINMENT
SATELLITE RADIO
Reliability
• Crystal-less design for tough or harsh environments
Size and Ruggedness
• Extremely durable, small 8-pin SO packages can withstand
mechanical shock and vibrations
· Up to 2900g: 5 shocks x 6 axes, JESD22-B104C
Condition-H
· Variable frequency of 20g: 20/2000Hz, JESD22-B103B
Condition-1
Automotive Certified
• DS3231MZ/V+ and DS3232MZ/V+ AEC-Q100 certified
High Operating Temperature Ranges
• -40°C to +85°C (DS3231MZ/V+ and DS3232MZ/V+)
High Accuracy
• < ±5ppm (under all conditions)
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8
Video Security and Surveillance
Security and Surveillance Systems Benefit from Accurate Timestamping and
Small Size of RTC Products
Accurate timestamping of event data is an important aspect of video security and surveillance systems. MEMS-based
RTCs further enhance this by providing timekeeping accuracy far exceeding the most robust crystal designs. Besides less
aging, Maxim Integrated’s MEMS-accurate RTC products support accuracy and stability standards of much less than
±5ppm lifetime over voltage, temperature, and time. This translates to less than ±0.432 seconds/day, much better than ±3
minutes/year. A smaller product package size (8-pin SO) provides users with small footprint solutions to accommodate
space-constrained designs. Power consumption of < 3.5μA make the devices suitable for battery-backed applications.
Instanteanous
accuracy bounded
by ±5ppm for all
conditions
1Hz FREQUENCY ERROR
(MEASURED EVERY SECOND)
INSTANTANEOUS
TIME (MINUTES)
FREQUENCY ERROR (ppm)
-8
-6
-4
-2
0
2
4
6
8
10
-10
0 30252015105
VCC = 3.3V
TA = +25°C
Long-term
accuracy
approaches
tight limits
(error < ±1ppm)
Timing
accuracy converges
for long periods
of observation
AVERAGED
1Hz FREQUENCY ERROR
TIME (MINUTES)
FREQUENCY ERROR (ppm)
0 30252015105
VCC = 3.3V
TA = +25°C
-4
-3
-2
-1
0
1
2
3
4
5
-5
INSTANTANEOUS vs. LONG-TERM ACCURACY
OVER LONG PERIODS OF OBSERVATION (REAL-LIFE RESULTS)
Benefits
• Extreme accuracy: < ±0.432 seconds/day
• 8-pin SO supports space-constrained designs
• Suitable for battery-backed applications
< 3.5μA
• Automatic power switching between supplies
WED SEP-12-2012 16:10:30
Simulated Image
High accuracy
across wide
temperature ranges
Battery-backed
mode critical
for portable
applications
BATTERY-SUPPLY CURRENT
vs. BATTERY-SUPPLY VOLTAGE
SUPPLY VOLTAGE (V)
SUPPLY CURRENT (µA)
543
1.5
2.0
2.5
3.0
3.5
4.0
1.0
2 6
TA = +85°C
TA = +25°C
TA = -40°C
VCC = 0V, EN32KHZ = 1, BBSQW = 0
FREQUENCY ERROR
vs. TEMPERATURE
TEMPERATURE (°C)
FREQUENCY ERROR (ppm)
500
-8
-6
-4
-2
0
2
4
6
8
10
-10
-50 100
LIMITS
V
CC
= 3.3V
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9
Industrial and Medical
MEMS RTCs Meet Critical Factors for Industrial and Medical Applications in
Ruggedness, Size, and Temperature
Applications
• Patient Monitoring
• Heavy Machinery
• Portable Medical Devices
• Environmental Systems
Blood Glucose
Monitor
Industrial and medical markets have expanded their acceptance of MEMS-
accurate RTCs based on the newly introduced 8-pin, 150-mil SO package,
the inherent ruggedness of the MEMS design, and the status and success
of the standard device’s AEC-Q100 automotive qualification. Long-term
accuracy (< ±5ppm) of the MEMS RTC contributes to its acceptance
in these applications, where demand for highly reliable and accurate
timekeeping/time-stamping of event data is extremely critical.
Temperature performance is extremely important for industrial
applications. The standard device provides a wide (-40°C to +85°C)
operating temperature range by keeping accurate time across this band
of temperatures. Low operating currents (< 3.5μA) and the 2.3V to 5.5V
wide-operating voltage range aid critical portable medical applications
that are battery powered. Heavy machinery, blood glucose meters, and
environmental system controls benefit from the high accuracy, low power
consumption, device ruggedness, and small package size.
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10
Power Meters
MEMS RTCs Deliver Pinpoint Precision for Metering
Maxim Integrated is a premier supplier of electronic component technology designed for smart grid and metering applications.
Accurate timekeeping is an essential part of smart power meter design. Applications such as multirate billing drive the need
to use accurate timekeeping products like the DS3231M+ and DS3231MZ+. Temperature variations cause frequency drift in
crystal-based RTCs. Frequency drift causes timekeeping errors sometimes approaching ±30 minutes/year in standard RTCs.
This attribute negatively affects billing accuracy and resolution. Additionally, high-humidity environments adversely affect
timekeeping accuracy when over-molded crystals are not used. Maxim Integrated’s MEMS-based RTCs eliminate these
environmental concerns and provide timekeeping accuracy over the entire industrial -40°C to +85°C temperature range and
operate in high-humidity environments without accuracy issues.
Newport Smart Meter Reference Platform
The Newport Smart Meter reference platform is a smart meter reference design featuring all its premier technologies. Explore
the capability of this technology and accelerate your time to market with proven solutions. This includes products in energy
measurement (metrology), robust G3-PLC™ communications, and integrated security. Pluggable NAN and HAN communication
modules, form-factor design, and complete system software make the Newport Smart Meter reference platform the ultimate
development tool.
Power and Timing
In addition to metrology, communication, and security, the Newport Smart Meter reference platform offers enhanced timing
accuracy with the DS3231M MEMS-based RTC. Power for both the metrology and communications boards is regulated by the
MAX17498 flyback controller.
Metrology and Security
The 71M6541 sits at the heart of the system and measures
electricity to 0.1% accuracy across a dynamic range of 2000:1
in all four quadrants. An ARM® core hosts system software to
ensure compatibility with existing development software, while
the MAXQ1050 provides multilayered secure authentication to
thwart the most determined security threats.
Communications
The MAX2991 and MAX2992 communicate to and from points
in the grid through the power line. They support speeds up to
300kbps, following the G3-PLC specification. Adaptive tone
mapping, a robust mode, and programmable tone matching
make communications quick and reliable in high-noise scenarios,
and compatible with older PLC solutions. An isolated RS-485
communications interface (MAX13256 and MAX13412E) is also
provided for any serial communications needs.
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VBOARD GND
VCC
DS3900H2 I/O MODULE 32kHz VBAT
PULLUP RESISTOR
JUMPERS J6-J8
RST PUSHBUTTON
AND LED TEST POINTS
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11
Part Number Description
DS3231MEVKIT# 16-Pin Package EV Kit for the DS3231M+
DS3231MZEVKIT# 8-Pin Package EV Kit for the DS3231MZ+
DS3232MEVKIT# 8-Pin Package EV Kit for the DS3232MZ+
MEMS Real-Time Clock Evaluation Kits
+Denotes a lead(Pb)-free/RoHS-compliant package.
#Denotes RoHS-compliant.
The DS323x evaluation kits (EV kits) are fully assembled and tested circuit boards with an accompanying application
program that demonstrate the operation of the DS3231M and DS3232M RTCs. Maxim Integrated’s accurate MEMS RTCs
constantly monitor operating temperature and periodically adjust the internal oscillator frequency to maintain highly
accurate timing information.
The EV kits allow devices to be operated in all possible power-supply configurations. The application program provides easy
access to device register settings, while observing various device functions for timekeeping. The EV kits also allow users to
connect their I2C master to the sample component for operational verification and/or code development. The EV kits are
Windows®-compatible (Windows XP® or later version, requires USB port and USB cable).
Evaluate MEMS RTC Technology with DS323x
Reference and Development Kits
EV kit includes:
• Demonstration board
• USB I/O module (DS3900H2)
• CD containing the application
program and instructions
Contact Maxim Direct at 1.888.629.4642 or for more information, visit www.maximintegrated.com.
© 2012 Maxim Integrated Products, Inc. All rights reserved. Maxim Integrated and the Maxim Integrated logo are trademarks of Maxim Integrated Products, Inc.,
in the United States and other jurisdictions throughout the world. All other company names may be trade names or trademarks of their respective owners.
Rev. 0; October 2012
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ARM is a registered trademark and registered service mark of ARM Limited
G3-PLC is a trademark of Maxim Integrated Products, Inc.
Windows and Windows XP are registered trademarks and registered service marks of Microsoft Corp.
