DS3232 Maxim, DS3232 Datasheet - Page 10

• Manufacturer Part Number: DS3232
• Description: The DS3232 is a low-cost temperature-compensated crystal oscillator (TCXO) with a very accurate, temperature-compensated, integrated real-time clock (RTC) and 236 bytes of battery-backed SRAM
• Manufacturer: Maxim

This function is provided by a temperature-compensat-
ed voltage reference and a comparator circuit that
monitors the V
the part is powered by V
but greater than V
If V
device is powered by V
To preserve the battery, the first time V
the device, the oscillator does not start up and no tem-
perature conversions take place until V
or until a valid I
the first time V
and the V
power-down and keeps the oscillator running. When
the DS3232 switches to V
abled by setting the EOSC bit.
There are several modes of operation that affect the
amount of V
is powered by V
active battery current, I
interface is inactive, timekeeping current (I
includes the averaged temperature conversion current,
I
Considerations for Accurate Real-Time Clocks for
details). Temperature conversion current, I
specified since the system must be able to support the
periodic higher current pulse and still maintain a valid
voltage level. Data retention current, I
current drawn by the part when the oscillator is
stopped (EOSC = 1). This mode can be used to mini-
mize battery requirements for times when maintaining
time and date information is not necessary, e.g., while
the end system is waiting to be shipped to a customer.
The DS3232 provides for a pushbutton switch to be con-
nected to the RST output pin. When the DS3232 is not in
a reset cycle, it continuously monitors the RST signal for a
low going edge. If an edge transition is detected, the
DS3232 debounces the switch by pulling the RST low.
Extremely Accurate I
Integrated Crystal and SRAM
Table 1. Power Control
10
BATTC
CC
V
V
V
V
SUPPLY CONDITION
____________________________________________________________________
CC
CC
CC
CC
, is used (refer to Application Note 3644: Power
is less than V
< V
< V
> V
> V
BAT
PF
PF
PF
PF
BAT
, V
, V
, V
, V
CC
CC
source powers the oscillator during
2
CC
CC
CC
CC
current that is drawn. While the device
BAT
C address is written to the part. After
is ramped up, the oscillator starts up
level. When V
BAT
< V
> V
< V
> V
Pushbutton Reset Function
and the serial interface is active,
, the DS3232 is powered by V
BAT
BAT
BAT
BAT
PF
BAT
BATA
CC
BAT
and is less than V
. See Table 1.
. When V
, is drawn. When the serial
, the oscillator may be dis-
V
CC
BAT
is greater than V
CC
POWERED BY
Power Control
BAT
CC
Operation
is less than V
BATTDR
V
V
V
V
BAT
CC
CC
CC
exceeds V
BATT
is applied to
BATTC
BAT
), which
, is the
, the
2
CC
, is
PF
PF
PF
C RTC with
,
.
After the internal timer has expired (PB
continues to monitor the RST line. If the line is still low, the
DS3232 continuously monitors the line looking for a rising
edge. Upon detecting release, the DS3232 forces the
RST pin low and holds it low for t
The same pin, RST, is used to indicate a power-fail con-
dition. When V
fail signal is generated, which forces the RST pin low.
When V
held low for t
If the oscillator is not running (see the Power Control
section) when V
RST immediately goes high.
Assertion of the RST output, whether by pushbutton or
power-fail detection, does not affect the internal opera-
tion of the DS3232.
With the clock source from the TCXO, the RTC provides
seconds, minutes, hours, day, date, month, and year
information. The date at the end of the month is automati-
cally adjusted for months with fewer than 31 days, includ-
ing corrections for leap year. The clock operates in either
the 24-hour or 12-hour format with an AM/PM indicator.
The clock provides two programmable time-of-day
alarms and a programmable square-wave output. The
INT/SQW pin either generates an interrupt due to alarm
condition or outputs a square-wave signal and the
selection is controlled by the bit INTCN.
The DS3232 provides 236 bytes of general-purpose
battery-backed read/write memory. The I
ranges from 14h to 0FFh. The SRAM can be written or
read whenever V
mum operating voltage.
Figure 1 shows the address map for the DS3232 time-
keeping registers. During a multibyte access, when the
address pointer reaches the end of the register space
(0FFh), it wraps around to location 00h. On an I
START or address pointer incrementing to location 00h,
the current time is transferred to a second set of regis-
ters. The time information is read from these secondary
registers, while the clock may continue to run. This
eliminates the need to reread the registers in case the
main registers update during a read.
The I
V
the DS3232 resets because of a loss of V
BAT
2
is at a valid level. If a microcontroller connected to
C interface is accessible whenever either V
CC
returns to a level above V
REC
CC
CC
to allow the power supply to stabilize.
CC
is lower than V
is applied, t
or V
BAT
is greater than the mini-
RST
REC
PF
Address Map
I
Real-Time Clock
.
2
, an internal power-
C Interface
PF
is bypassed and
DB
, the RST pin is
), the DS3232
2
CC
C address
or other
SRAM
CC
2
or
C