DS1321E+ Maxim Integrated Products, DS1321E+ Datasheet - Page 4

• Manufacturer Part Number: DS1321E+
• Description: IC CTRL NV W/BATT MON 5V 20TSSOP
• Manufacturer: Maxim Integrated Products

Specifications of DS1321E+

• Controller Type: Nonvolatile RAM
• Voltage - Supply: 4.75 V ~ 5.5 V
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 20-TSSOP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

BATTERY VOLTAGE MONITORING
The DS1321 automatically performs periodic battery voltage monitoring at a factory-programmed time
interval of 24 hours. Such monitoring begins within t
when power failure occurs.
After each 24-hour period (t
resistor (R
programmed battery voltage trip point (V
active, battery testing will be performed with period t
Once asserted,
The battery is still retested after each V
the battery is found to be higher than V
testing resumes.
Battery replacement following
not lost. During battery replacement, the minimum time duration between old battery detachment and
new battery attachment (t
battery. Should
attached to clear
NOTE: The DS1321 cannot constantly monitor an attached battery because such monitoring would
drastically reduce the life of the battery. As a result, the DS1321 only tests the battery for one second out
of every 24 hours and does not monitor the battery in any way between tests. If a good battery (one that
has not been previously flagged with
immediately sense the removal and may not activate
is then reattached to the DS1321, the battery may not be tested until the next scheduled test.
NOTE: Battery monitoring is only a useful technique when testing can be done regularly over the entire
life of a lithium battery. Because the DS1321 only performs battery monitoring when V
systems which are powered-down for excessively long periods can completely drain their lithium cells
without receiving any advanced warning. To prevent such an occurrence, systems using the DS1321
battery monitoring feature should be powered-up periodically (at least once every few months) in order to
perform battery testing. Furthermore, anytime
data integrity should be checked via checksum or other technique.
POWER MONITORING
The DS1321 automatically detects out-of-tolerance power supply conditions and warns a processor-based
system of impending power failure. When V
(V
(5% tolerance) when the TOL pin is connected to GND or in the range of 4.5 to 4.25 volts (10%
tolerance) when TOL is connected to V
for 200 ms nominal (t
power-on transients and to allow t
RST
CCTP
also serves as a power-on reset during power-up. After V
), the V
INT
) for one second (t
CCI
BW
BW
BW
BW
comparator activates the reset signal
remains active until the battery is physically removed and replaced by a fresh cell.
not deactivate for this reason, the new battery can be detached for t
.
has an open-drain output driver.
RPU
BDBA
). This reset period is sufficiently long to prevent system operation during
BTCN
) must be met or
BW
REC
) has elapsed, the DS1321 connects V
BTPW
activation is normally done with V
to expire.
CCO
CC
). During this one second, if V
BW
BTP
BTP
power-up, however, even if
.
) is removed between battery tests, the DS1321 may not
), the battery warning output
during such testing,
CCI
BW
RST
BW
4 of 12
falls below the trip point level defined by the TOL pin
is activated on the first battery test after a power-up,
will not deactivate following attachment of the new
has an open-drain output driver.
BW
REC
RST
BTCW
until the next scheduled battery test. If a battery
after V
. Reset occurs in the range of 4.75 to 4.5 volts
to detect battery removal and replacement.
CCI
CCI
exceeds V
BW
rises above V
BW
is deasserted and regular 24-hour
CCI
nominal so that SRAM data is
BAT
BAT
BW
was active on power-down. If
CCTP
to an internal 1 MW test
falls below the factory-
is asserted. While
,
RST
CCTP
will be held active
and is suspended
BDBA
CC
and then re-
is nominal,
BW
is