DS3234
Extremely Accurate SPI Bus RTC
with Integrated Crystal and SRAM
General Description
The DS3234 is a low-cost, extremely accurate SPI bus
real-time clock (RTC) with an integrated temperature-com-
pensated crystal oscillator (TCXO) and crystal. The
DS3234 incorporates a precision, temperature-compen-
sated voltage reference and comparator circuit to monitor
V
CC
. When V
CC
drops below the power-fail voltage (V
PF
),
the device asserts the
RST
output and also disables read
and write access to the part when V
CC
drops below both
V
PF
and V
BAT
. The
RST
pin is monitored as a pushbutton
input for generating a µP reset. The device switches to the
backup supply input and maintains accurate timekeeping
when main power to the device is interrupted. The integra-
tion of the crystal resonator enhances the long-term accu-
racy of the device as well as reduces the piece-part count
in a manufacturing line. The DS3234 is available in com-
mercial and industrial temperature ranges, and is offered
in an industry-standard 300-mil, 20-pin SO package.
The DS3234 also integrates 256 bytes of battery-backed
SRAM. In the event of main power loss, the contents of
the memory are maintained by the power source con-
nected to the V
BAT
pin. The RTC maintains seconds,
minutes, hours, day, date, month, and year information.
The date at the end of the month is automatically adjust-
ed for months with fewer than 31 days, including correc-
tions for leap year. The clock operates in either the
24-hour or 12-hour format with
AM
/PM indicator. Two
programmable time-of-day alarms and a programmable
square-wave output are provided. Address and data
are transferred serially by an SPI bidirectional bus.
Applications
Servers
Utility Power Meters
Telematics
GPS
Benefits and Features
•
Highly Accurate RTC with Integrated Crystal and
SRAM Completely Manages All Timekeeping
Functions
•
Accuracy ±2ppm from 0°C to +40°C
•
Accuracy ±3.5ppm from -40°C to +85°C
•
Real-Time Clock Counts Seconds, Minutes, Hours,
Day, Date, Month, and Year, with Leap Year
Compensation Valid Up to 2099
•
Digital Temp Sensor Output: ±3°C Accuracy
•
Register for Aging Trim
•
RST
Input/Output
•
Two Time-of-Day Alarms
•
Programmable Square-Wave Output
•
Simple Serial Interface Connects to Most
Microcontrollers
•
4MHz SPI Bus Supports Modes 1 and 3
•
Battery-Backup Input for Continuous Timekeeping
•
Low Power Operation Extends Battery Backup Run
Time
•
Operating Temperature Ranges: Commercial: 0°C to
+70°C, Industrial: -40°C to +85°C
•
300-Mil, 20-Pin SO Package
•
Underwriters Laboratories
®
(UL) Recognized
19-5339; Rev 4; 3/15
Ordering Information
PART TEMP
RANGE
PIN-
PACKAGE
TOP
MARK
DS3234S#
0°C to +70°C
20 SO
DS3234S
DS3234SN#
-40°C to +85°C
20 SO
DS3234SN
DS3234
CS
INT/SQW
32kHz
V
BAT
PUSH-
BUTTON
RESET
SCLK
RST
N.C.
N.C.
N.C.
V
CC
V
PU
V
CC
GND
V
CC
µ
P
SS
SCLK
DIN
MOSI
DOUT
MISO
RST
N.C.
N.C.
N.C.
N.C.
N.C.
N.C.
Typical Operating Circuit
#
Denotes an RoHS-compliant device that may include lead(Pb)
that is exempt under the RoHS requirements. 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 an RoHS-compliant device.
Underwriters Laboratories Inc. is a registered certification mark
of Underwriters Laboratories Inc.
