crystal, and a bank of nonvolatile memory (FRAM) in a
single package. The nonvolatile memory is available in
two densities: 2048 x 8 and 8192 x 8 bits. The integra-
tion of the crystal resonator enhances the long-term
accuracy of the devices as well as reduces the piece
part count in a manufacturing line. The devices operate
as a slave device on an I
2
C serial interface, and are
available in both commercial and industrial temperature
ranges in a 300-mil, 20-pin SO package.
The clock/date provides 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 DS32B35/DS32C35 include a bank of nonvolatile
memory that does not require a backup energy source
to maintain memory contents. In addition, there are no
read or write cycle limitations. The memory array can
be accessed at maximum cycle rates for the life of the
product with no wear-out mechanisms.
Other device features include two time-of-day alarms, a
selectable output that provides either an interrupt or
programmable square wave, and a calibrated
32.768kHz square-wave output. A reset input/output pin
provides a power-on reset for other devices.
Additionally, the reset pin is monitored as a pushbutton
input for generating a reset externally.
A precision temperature-compensated voltage refer-
ence and comparator circuit monitor the status of V
CC
to detect power failures, to provide a reset output, and
to automatically switch to the backup supply for the
RTC/TCXO when necessary. Additionally, the
RST
pin is
monitored as a pushbutton input for generating a reset
externally.
Features
♦
Integrated 32.768kHz Crystal
♦
Fast (400kHz) I
2
C Interface
♦
RTC Counts Seconds, Minutes, Hours, Day, Date,
Month, and Year with Leap Year Compensation
Valid Up to 2100
♦
RTC Accuracy ±2ppm from 0°C to +40°C
♦
RTC Accuracy ±3.5ppm from -40°C to 0°C and
+40°C to +85°C
♦
Nonvolatile Memory with 10 Years of Guaranteed
Backup Time and Write Protection
♦
Two Available Densities of Nonvolatile Memory
2048 Bytes (DS32B35)
8192 Bytes (DS32C35)
♦
No Cycle Limitations on Memory
♦
Power-Switching Circuit Selects Between Main
Power and Battery Backup for the RTC
♦
Programmable Square Wave with Frequency of
32.768kHz, 8.192kHz, 4.096kHz, or 1Hz
♦
Two Time-of-Day Alarms
♦
Reset Output/Pushbutton Reset (Debounced)
Input
♦
Programmable Output Provides Interrupt or
Square Wave
♦
Calibrated 32.768kHz Open-Drain Output
♦
Temp Sensor with ±3°C Accuracy
♦
3.3V Operating Voltage
♦
Commercial and Industrial Temperature Ranges
♦
300-mil, 20-Pin SO Package
♦
Underwriters Laboratories (UL) Recognized
DS32B35/DS32C35
Ordering Information
PART
DS32B35-33#
DS32B35-33IND#
DS32C35-33#
DS32C35-33IND#
TEMP RANGE
0°C to +70°C
-40°C to +85°C
0°C to +70°C
-40°C to +85°C
PIN-PACKAGE
20 SO
20 SO
20 SO
20 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.
Typical Operating Circuit, Pin Configuration, and Selector
Guide appear at end of data sheet.
______________________________________________
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.
Accurate I
2
C RTC with Integrated
TCXO/Crystal/FRAM
DS32B35/DS32C35
ABSOLUTE MAXIMUM RATINGS
Voltage Range on Any Pin Relative to Ground......-0.3V to +5.0V
Operating Temperature Range ..........................-40°C to +85°C
Junction Temperature ......................................................+125°C
Storage Temperature Range ...............................-40°C to +85°C
Junction-to-Ambient Thermal Resistance (θ
JA
) (Note 1)....55°C/W
Note 1:
Junction-to-Case Thermal Resistance (θ
JC
) (Note 1) ......24°C/W
Lead Temperature (soldering, 10s) .................................+260°C
Soldering Temperature (reflow, 2x max)..........................+260°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
= -40°C to +85°C, unless otherwise noted.) (Notes 2, 3)
PARAMETER
Supply Voltage
Battery Voltage
Input High Voltage
Input Low Voltage
SYMBOL
V
CC
V
BAT
V
IH
V
IL
(Note 4)
(Note 5)
CONDITIONS
MIN
2.70
2.3
0.7 x
V
CC
-0.3
TYP
3.3
3.0
MAX
3.63
3.6
V
CC
+
0.3
+0.3 x
V
CC
UNITS
V
V
V
V
ELECTRICAL CHARACTERISTICS
(V
CC
= 2.7V to 3.63V,
T
A
= -40°C to +85°C, unless otherwise noted.) (Note 2)
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