DS32B35_10 Datasheet, PDF (1/22 Pages) Maxim Integrated Products – Accurate I2C RTC with Integrated TCXO/Crystal/FRAM

19-5340; Rev 3; 7/10
Accurate I²C RTC with Integrated
TCXO/Crystal/FRAM
General Description
The DS32B35/DS32C35 accurate real-time clocks
(RTC) are clock/calendars that include an integrated
temperature-compensated crystal oscillator (TCXO),
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 I²C 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.
Servers
Telematics
Applications
Utility Power Meters
GPS
Typical Operating Circuit, Pin Configuration, and Selector
Guide appear at end of data sheet.
Features
♦ Integrated 32.768kHz Crystal
♦ Fast (400kHz) I²C 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
Ordering Information
PART
TEMP RANGE PIN-PACKAGE
DS32B35-33#
0°C to +70°C 20 SO
DS32B35-33IND#
-40°C to +85°C 20 SO
DS32C35-33#
0°C to +70°C 20 SO
DS32C35-33IND#
-40°C to +85°C 20 SO
#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.
______________________________________________ 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.