DS32X35 Datasheet, PDF (1/21 Pages) Maxim Integrated Products – Accurate I2C RTC with Integrated TCXO/Crystal/FRAM

Rev 0; 12/06
Accurate I²C RTC with Integrated
TCXO/Crystal/FRAM
General Description
The DS32x35 accurate real-time clock (RTC) is a tem-
perature-compensated clock/calendar that includes an
integrated 32.768kHz crystal and a bank of nonvolatile
memory in a single package. The nonvolatile memory is
available in two densities: 2048 x 8 and 8192 x 8 bits.
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 device
operates as a slave device on an I²C serial interface,
and is available in both commercial and industrial tem-
perature ranges in a 300-mil, 20-pin SO package.
The DS32x35 includes a bank of nonvolatile memory
that does not require a backup energy source to main-
tain 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 pro-
grammable square wave, and a calibrated 32.768kHz
square-wave output. A reset input/output pin provides a
power-on reset. Additionally, the reset pin is monitored
as a pushbutton input for generating a reset externally.
A precision temperature-compensated reference and
comparator circuit monitors the status of V_CC and auto-
matically switches to the backup supply when neces-
sary. The backup supply maintains operation of the
TCXO, clock, alarms, and RTC I²C operation.
Applications
Servers
Telematics
Utility Power Meters
GPS
V_CC
V_CC
R_PU = t_R/C_B
R_PU
R_PU
SCL
SCL
CPU
SDA
WP
RST
PUSHBUTTON
N.C.
RESET
N.C.
N.C.
N.C.
N.C.
Features
o Integrated 32.768kHz Crystal
o Fast (400kHz) I²C Interface
o RTC Counts Seconds, Minutes, Hours, Day, Date,
Month, and Year with Leap Year Compensation
Valid Up to 2100
o RTC Accuracy ±2ppm from 0°C to +40°C
o RTC Accuracy ±3.5ppm from -40°C to 0°C and
+40°C to +85°C
o Nonvolatile Memory with 10 Years of Guaranteed
Backup Time and Write Protection
o Two Available Densities of Nonvolatile Memory
2048 Bytes (DS32B35)
8192 Bytes (DS32C35)
o No Cycle Limitations on Memory
o Power-Switching Circuit Selects Between Main
Power and Battery Backup for the RTC
o Programmable Square Wave with Frequency of
32.768kHz, 8.192kHz, 4.096kHz, or 1Hz
o Two Time-of-Day Alarms
o Reset Output/Pushbutton Reset (Debounced)
Input
o Programmable Output Provides Interrupt or
Square Wave
o Calibrated 32.768kHz Open-Drain Output
o Temp Sensor with ±3°C Accuracy
o 3.3V Operating Voltage
o Commercial and Industrial Temperature Ranges
o 300-mil, 20-Pin SO Package
o Underwriters Laboratories (UL) Recognized
Pin Configuration and Ordering Information appear at end
of data sheet.
Typical Operating Circuit
V_CC
V_CC
DS32x35
GND
INT/SQW
32kHz
V_BAT
GND
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.