ISL12027IBZ Intersil, ISL12027IBZ Datasheet - Page 24

• Manufacturer Part Number: ISL12027IBZ
• Description: IC RTC/CAL W/EEPROM 8-SOIC
• Manufacturer: Intersil
• Type: Clock/Calendar/Supervisor/EEPROMr

Specifications of ISL12027IBZ

• Memory Size: 4K (512 x 8)
• Time Format: HH:MM:SS (12/24 hr)
• Date Format: YY-MM-DD-dd
• Interface: I²C, 2-Wire Serial
• Voltage - Supply: 2.7 V ~ 5.5 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 8-SOIC (3.9mm Width)
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

supercapacitor used, backup time can last from a few days
to two weeks (with >1F). A simple silicon or Schottky barrier
diode can be used in series with V
supercapacitor, which is connected to the V
use Schottky diodes with very low leakages, <1µA desirable.
Do not use the diode to charge a battery (especially lithium
batteries!).
Note that whether a battery or supercap is used, if the V
voltage drops below the data sheet minimum of 1.8V and the
V
RESET output may stay low and the I
not operate. The V
to 0V together to allow normal operation again.
There are two possible modes for battery backup operation,
Standard and Legacy mode. In Standard mode, there are no
operational concerns when switching over to battery backup
since all other devices functions are disabled. Battery drain
is minimal in Standard mode, and return to Normal V
powered operations predictable. In Legacy modes the V
pin can power the chip if the voltage is above V
V
communicate with the device under battery backup, but the
supply current drain is much higher than the Standard mode
and backup time is reduced. During initial power-up, the
default mode is the Legacy mode.
2.7V TO 5.5V
DD
TRIP
FIGURE 28. SUPERCAPACITOR CHARGING CIRCUIT
power cycles to 0V then back to V
. This makes it possible to generate alarms and
BAT
V
DD
and V
V
SS
DD
V
24
BAT
power will need to be cycled
DD
2
to charge the
C communications will
DD
voltage, then the
SUPERCAPACITOR
BAT
DD
pin. Try to
ISL12027, ISL12027A
and
DD
BAT
BAT
I
LVR Operation
Operation in Battery Backup mode and LVR is affected by
the BSW and SBIB bits as described earlier. These bits allow
flexible operation of the serial bus and EEPROM in battery
backup mode, but certain operational details need to be
clear before utilizing the different modes. The most
significant detail is that once V
I
is programmed for I
Table 10 describes 4 different modes possible with using the
BSW and SBIB bits, and how they are affect LVR and battery
backup operation.
• Mode A - In this mode, selection bits indicate a low V
• Mode B - In this mode, the selection bits indicate
• Mode C - In this mode, the selection bits indicate a low
• Mode D - In this mode, the selection bits indicate
2
2
C communications cease regardless of whether the device
C Communications During Battery Backup and
switchover combined with I
mode. In actuality the V
switching to battery backup, which will disable I
ANYTIME the device goes into battery backup mode.
Regardless of the battery voltage, the I
to the V
switchover to battery backup at V
communications in battery backup. In order to
communicate in battery backup mode, the V
must be less than the V
greater than V
must go to V
as the normal operating mode of the X1228 device.
V
battery backup. Operation is actually identical to Mode A
with I
communications (see Figure 28).
switchover to battery backup at V
communications in battery backup. This mode is unique in
that there is I
than V
the safest for guaranteeing I
there is a Valid V
DD
switchover combined with no communications in
2
C communications down to V
RESET
RESET
BAT
2
or V
C communication as long as V
RESET
voltage (see Figure 29).
to communicate. This mode is the same
DD
2
BAT
C operation in battery backup mode.
(see Figure 29).
. Also, pull-ups on the I
, whichever is greater. This mode is
DD
BAT
2
will go below V
2
C operation in battery backup
voltage AND V
DD
C communications only when
goes below V
DD
DD
DD
<V
< V
2
BAT
= V
C will work down
BAT
RESET
, and I
RESET
DD
RESET
2
, and no I
C bus pins
DD
RESET
must be
August 12, 2010
2
C
is higher
, then no
2
before
C
voltage
, then
FN8232.8
2
DD
C