
General Description
The DS3234 is a low-cost, extremely accurate SPI bus
real-time clock (RTC) with an integrated temperature-
compensated crystal oscillator (TCXO) and crystal. The
DS3234 incorporates a precision, temperature-compen-
sated voltage reference and comparator circuit to moni-
tor V
CC
. When V
CC
drops below the power-fail voltage
(V
PF
), the device asserts the
RST
output and also dis-
ables 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 reset externally. The
device switches to the backup supply input and main-
tains accurate timekeeping when main power to the
device is interrupted. The integration of the crystal res-
onator enhances the long-term accuracy of the device
as well as reduces the piece-part count in a manufactur-
ing line. The DS3234 is available in commercial 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
Utility Power Meters
GPS
Servers
Telematics
Features
Accuracy ±2ppm from 0°C to +40°C
Accuracy ±3.5ppm from -40°C to +85°C
Battery Backup Input for Continuous
Timekeeping
Operating Temperature Ranges
Commercial: 0°C to +70°C
Industrial: -40°C to +85°C
Low-Power Consumption
Real-Time Clock Counts Seconds, Minutes,
Hours, Day, Date, Month, and Year with Leap Year
Compensation Valid Up to 2099
Two Time-of-Day Alarms
Programmable Square-Wave Output
4MHz SPI Bus Supports Modes 1 and 3
Digital Temp Sensor Output: ±3°C Accuracy
Register for Aging Trim
RST
Input/Output
300-Mil, 20-Pin SO Package
Underwriters Laboratory (UL) Recognized
Ordering Information
D
Extremely Accurate SPI Bus RTC with
Integrated Crystal and SRAM
______________________________________________
Maxim Integrated Products
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.
1
Rev 0; 2/06
PART
TEMP RANGE
PIN-
PACKAGE
TOP
MARK
DS3234S#
DS3234SN#
#
Denotes a RoHS-compliant device that may include lead 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 a RoHS-compliant device.
Pin Configuration
0°C to +70°C
-40°C to +85°C
20 SO
20 SO
DS3234S
DS3234SN
SPI is a trademark of Motorola, Inc.
DS3234
CS
SCLK
DIN
DOUT
INT/SQW
32kHz
V
BAT
PUSH-
BUTTON
RESET
RST
N.C.
N.C.
N.C.
V
CC
V
PU
V
CC
GND
V
CC
CPU
SS
SCLK
MOSI
MISO
RST
N.C.
N.C.
N.C.
N.C.
N.C.
N.C.
Typical Operating Circuit
TOP VIEW
20
19
18
17
16
15
14
13
1
2
3
4
5
6
7
8
SCLK
DOUT
SCLK
DIN
V
CC
32kHz
N.C.
CS
V
BAT
GND
N.C.
N.C.
N.C.
N.C.
RST
INT/SQW
12
11
9
10
N.C.
N.C.
N.C.
N.C.
SO
DS3234