DS3234
Extremely Accurate SPI Bus RTC
with Integrated Crystal and SRAM
Maxim Integrated | 9
www.maximintegrated.com
Block Diagram
CLOCK AND CALENDAR
REGISTERS
SRAM
USER BUFFER
(7 BYTES)
SPI INTERFACE AND
ADDRESS REGISTER
DECODE
POWER CONTROL
V
CC
V
BAT
GND
SCLK
SCLK
DIN
CS
DOUT
TEMPERATURE
SENSOR
CONTROL LOGIC/
DIVIDER
CONTROL AND STATUS
REGISTERS
OSCILLATOR AND
CAPACITOR ARRAY
X1
X2
DS3234
N
N
RST
V
CC
INT/SQW
SQUARE-WAVE BUFFER;
INT/SQW CONTROL
VOLTAGE REFERENCE;
DEBOUNCE CIRCUIT;
PUSHBUTTON RESET
32kHz
Detailed Description
The DS3234 is a TCXO and RTC with integrated crystal
and 256 bytes of SRAM. An integrated sensor periodi-
cally samples the temperature and adjusts the oscilla-
tor load to compensate for crystal drift caused by
temperature variations. The DS3234 provides user-
selectable sample rates. This allows the user to select
a temperature sensor sample rate that allows for vari-
ous temperature rates of change, while minimizing cur-
rent consumption by temperature sensor sampling. The
user should select a sample rate based upon the
expected temperature rate of change, with faster sam-
ple rates for applications where the ambient tempera-
ture changes significantly over a short time. The TCXO
provides a stable and accurate reference clock, and
maintains the RTC to within ±2 minutes per year accu-
racy from -40°C to +85°C. The TCXO frequency output
is available at the 32kHz pin. The RTC is a low-power
clock/calendar with two programmable time-of-day
alarms and a programmable square-wave output. The
INT
/SQW provides either an interrupt signal due to
alarm conditions or a square-wave output. The
clock/calendar provides seconds, minutes, hours, day,
