Datasheet

DS3232M
±5ppm, I
2
C Real-Time Clock with SRAM
9Maxim Integrated
Detailed Description
The DS3232M is a serial real-time clock (RTC) driven by
an internal, temperature-compensated, microelectrome-
chanical systems (MEMS) resonator. The oscillator pro-
vides a stable and accurate reference clock and main-
tains the RTC to within Q0.432 seconds-per-day accu-
racy from -40NC to +85NC. The RTC is a low-power clock/
calendar with two programmable time-of-day alarms. INT/
SQW provides either an interrupt signal due to alarm
conditions or a 1Hz square wave. The clock/calendar
provides seconds, minutes, hours, day, date, month, and
year information. The date at the end of the month is auto-
matically adjusted for months with fewer than 31 days,
including corrections for leap year. The clock operates in
either the 24-hour or 12-hour format with an AM/PM indi-
cator. The internal registers are accessible though an I
2
C
bus interface. A temperature-compensated voltage refer-
ence and comparator circuit monitors the level of V
CC
to
detect power failures and to automatically switch to the
backup supply when necessary. The RST pin provides
an external pushbutton function and acts as an indica-
tor of a power-fail event. Also available are 236 bytes of
general-purpose battery-backed SRAM.
Operation
The Block Diagram shows the device’s main elements.
Each of the major blocks is described separately in the
following sections.
Block Diagram
DS3232M
N
N
TIME-BASE
RESONATOR
TEMP
SENSOR
INTERRUPT
OR 1Hz
SELECT
DIVIDER
INT/SQW
1Hz
DIGITAL
ADJUSTMENT
FACTORY TRIM
N
32KHZ
GND
SDA
SCL
V
BAT
V
CC
RST
CLOCK/CALENDAR
WITH ALARM
CONTROL AND STATUS
REGISTERS
SRAM
I
2
C
INTERFACE
POWER
CONTROL*
P
*SELECTED
POWER