DS1314S-2+T&R Maxim Integrated Products, DS1314S-2+T&R Datasheet - Page 2

• Manufacturer Part Number: DS1314S-2+T&R
• Description: IC CTRLR NV W/BATT MON 3V 8-SOIC
• Manufacturer: Maxim Integrated Products

Specifications of DS1314S-2+T&R

• Controller Type: Nonvolatile RAM
• Voltage - Supply: 3 V ~ 3.6 V
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 8-SOIC (3.9mm Width)
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

In addition to battery-backup support, the DS1314 performs the important function of monitoring the
remaining capacity of the lithium battery and providing a warning before the battery reaches end-of-life.
Because the open-circuit voltage of a lithium backup battery remains relatively constant over the majority
of its life, accurate battery monitoring requires loaded-battery voltage measurement. The DS1314
performs such measurement by periodically comparing the voltage of the battery as it supports an internal
resistive load with a carefully selected reference voltage. If the battery voltage falls below the reference
voltage under such conditions, the battery will soon reach end-of-life. As a result, the Battery Warning
pin is activated to signal the need for battery replacement.
MEMORY BACKUP
The DS1314 performs all the circuit functions required to provide battery-backup for an SRAM. First, the
device provides a switch to direct power from the battery or the system power supply (V
V
switched in to provide backup power to the SRAM. This switch has voltage drop of less than 0.2 volts.
Second, the DS1314 handles power failure detection and SRAM write protection. V
monitored, and when the supply goes out of tolerance, a precision comparator detects power failure and
inhibits chip enable output (
power failure is detected, the
brought high,
specific scheme for delaying write protection for up to 1.5 ms guarantees that any memory access in
progress when power failure occurs will complete properly. Power failure detection occurs at 3.0V
nominal (3.3V supply) when the TOL pin is wired to GND or at 2.7V nominal (3.0V supply) when TOL
is connected to V
BATTERY VOLTAGE MONITORING
The DS1314 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 re-tested 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
CEO
CEI
CCI
is not brought high by 1.5 ms after power failure is detected,
is less than the switch point V
to within 0.2 volts of V
INT
) for one second (t
CEO
BW
BW
BW
CCO
BW
is taken high and held high until after V
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.
BDBA
CEO
BTCN
CCO
) must be met or
CEO
BW
) in order to write-protect the SRAM. This is accomplished by holding
) has elapsed, the DS1314 connects V
when V
BTPW
activation is normally done with V
signal is kept low until
SW
). During this one second, if V
CC
BTP
and V
BTP
CCI
power-up, however, even if
), the battery warning output
during such testing,
is out of tolerance. If
CCI
BW
2 of 11
is less than the battery voltage V
will not deactivate following attachment of the new
REC
BTCW
after V
CCI
to detect battery removal and replacement.
has returned to its nominal voltage level. If
CEI
CCI
BW
is brought high again. Once
CEO
rises above V
CEI
BW
is deasserted and regular 24-hour
CCI
is forced high at that time. This
BAT
is (active) low at the time that
nominal so that SRAM data is
BAT
BW
was active on power-down. If
to an internal 1.2 MW test
falls below the factory-
is asserted. While
CCTP
BAT
, and is suspended
BDBA
CCI
, the battery is
CCI
is constantly
). Whenever
and then re-
CEI
BW
is
is