ISL1209 Intersil Corporation, ISL1209 Datasheet - Page 8

• Manufacturer Part Number: ISL1209
• Manufacturer: Intersil Corporation

• Frequency Output Mode. The pin outputs a clock signal
Serial Clock (SCL)
The SCL input is used to clock all serial data into and out of
the device. The input buffer on this pin is always active (not
gated). It is disabled when the backup power supply on the
V
Serial Data (SDA)
SDA is a bidirectional pin used to transfer data into and out
of the device. It has an open drain output and may be ORed
with other open drain or open collector outputs. The input
buffer is always active (not gated) in normal mode.
An open drain output requires the use of a pull-up resistor.
The output circuitry controls the fall time of the output signal
with the use of a slope controlled pull-down. The circuit is
designed for 400kHz I
when the backup power supply on the V
V
Chip power supply and ground pins. The device will operate
with a power supply from V
capacitor is recommended on the V
Functional Description
Power Control Operation
The power control circuit accepts a V
Many types of batteries can be used with Intersil RTC
products. For example, 3.0V or 3.6V Lithium batteries are
appropriate, and battery sizes are available that can power
the ISL1209 for up to 10 years. Another option is to use a
Super Cap for applications where V
to a month. See the Applications Section for more
information.
Normal Mode (V
(V
To transition from the V
following conditions must be met:
Condition 1:
Condition 2:
Battery Backup Mode (V
(V
The ISL1209 device will switch from the V
when one of the following conditions occurs:
BAT
DD
has occurred and requests action. It is an open drain
active low output.
which is related to the crystal frequency. The frequency
output is user selectable and enabled via the I
an open drain active low output.
BAT
DD
V
where V
V
where V
DD
DD
, GND
)
pin is activated to minimize power consumption.
)
< V
< V
BATHYS
TRIP
BAT
TRIP
- V
≈ 2.2V
BATHYS
DD
≈ 50mV
2
) to Battery Backup Mode
C interface speeds. It is disabled
DD
to V
DD
BAT
8
=2.7V to 5.5VDC. A 0.1µF
BAT
) to Normal Mode
mode, both of the
DD
DD
DD
pin to ground.
is interrupted for up
BAT
and a V
BAT
pin is activated.
to V
2
BAT
C bus. It is
DD
input.
mode
ISL1209
∆
Condition 1:
Condition 2:
These power control situations are illustrated in Figures 9
and 10.
The I
lower power. Aside from this, all RTC functions are
operational during battery backup mode. Except for SCL and
SDA, all the inputs and outputs of the ISL1209 are active
during battery backup mode unless disabled via the control
register. The User SRAM is operational in battery backup
mode down to 1.8V.
Power Failure Detection
The ISL1209 provides a Real Time Clock Failure Bit (RTCF)
to detect total power failure. It allows users to determine if
the device has powered up after having lost all power to the
device (both V
Low Power Mode
The normal power switching of the ISL1209 is designed to
switch into battery backup mode only if the V
lost. This will ensure that the device can accept a wide range
of backup voltages from many types of sources while reliably
switching into backup mode. Another mode, called Low
FIGURE 10. BATTERY SWITCHOVER WHEN V
V
where V
V
where V
FIGURE 9. BATTERY SWITCHOVER WHEN V
V
V
V
V
V
DD
DD
V
TRIP
2
TRIP
BAT
DD
BAT
V
DD
C bus is deactivated in battery backup mode to provide
BAT
> V
> V
- V
BATHYS
TRIPHYS
BAT
TRIP
BATHYS
V
TRIP
DD
+ V
+ V
and V
BATHYS
≈ 50mV
TRIPHYS
≈ 30mV
BATTERY BACKUP
BAT
BATTERY BACKUP
).
MODE
MODE
V
V
TRIP
BAT
DD
BAT
+ V
BAT
+ V
power is
February 1, 2005
BATHYS
TRIPHYS
< V
> V
3.0V
2.2V
2.2V
1.8V
TRIP
FN6109.0
TRIP