ISL12028IB27Z Intersil, ISL12028IB27Z Datasheet - Page 25

• Manufacturer Part Number: ISL12028IB27Z
• Description: IC RTC W/EEPROM 2.7V 14SOIC
• Manufacturer: Intersil
• Type: Clock/Calendar/Supervisor/EEPROMr

Specifications of ISL12028IB27Z

• 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: 14-SOIC (3.9mm Width), 14-SOL
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Backup Battery Operation
Many types of batteries can be used with the Intersil RTC
products. 3.0V or 3.6V Lithium batteries are appropriate, and
sizes are available that can power a Intersil RTC device for up
to 10 years. Another option is to use a supercapacitor for
applications where V
periods of time. Depending on the value of 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
connected to the V
very low leakages, <1
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. In this case if alarms are used
in backup mode, the IRQ/F
connected to V
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
DD
BAT
to charge the supercapacitor, which is
BAT
BAT
voltage source..
DD
V
µA
DD
pin. Try to use Schottky diodes with
and V
may disappear intermittently for short
desirable. Do not use the diode to
V
SS
OUT
DD
V
25
BAT
pull up resistor must be
power will need to be cycled
2
C communications will
DD
voltage, then the
SUPERCAPACITOR
DD
ISL12028, ISL12028A
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 11 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
Note that the IRQ/F
backup for all modes. This should be considered if the load
on this pin is powered down, and could draw current from
the PMOS transistor and drain the battery. If that is the case,
the designer should consider the ISL12029 device which has
an open-drain output and avoids excessive current draw in
battery backup.
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 29).
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
OUT
2
BAT
C operation in battery backup mode.
(see Figure 30).
. Also, pull-ups on the I
, whichever is greater. This mode is
CMOS output pin is active in battery
DD
BAT
2
will go below V
2
DD
C operation in battery backup
voltage AND V
C communications only when
goes below VRESET, then
DD
DD
DD
<V
<V
2
BAT
= V
BAT
C will work down
RESET
, and I
RESET
, and no I
DD
RESET
2
C-bus pins
November 30, 2010
DD
must be
2
C
is higher
, then no
2
before
C
voltage
FN8233.9
2
C
DD