isl12022m Intersil Corporation, isl12022m Datasheet - Page 9

• Manufacturer Part Number: isl12022m
• Description: Real Time Clock With Embedded Crystal, ??5ppm Accuracy
• Manufacturer: Intersil Corporation

Pin Descriptions
V
This input provides a backup supply voltage to the device.
V
supply fails. This pin can be connected to a battery, a
supercapacitor or tied to ground if not used. See the Battery
Monitor parameter in the “DC Operating Characteristics-RTC”
table on page 3.
IRQ/F
This dual function pin can be used as an interrupt or
frequency output pin. The IRQ/F
the frequency out control bits of the control/status register.
• Interrupt Mode. The pin provides an interrupt signal
• 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 bi-directional pin used to transfer data into and out
of the device. It has an open drain output and may be OR’ed
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 ISL12022M
for up to 10 years. Another option is to use a supercapacitor for
applications where V
the “Application Section” on page 24 for more information.
BAT
BAT
BAT
DD
output. This signal notifies a host processor that an alarm
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 output.
, GND
supplies power to the device in the event that the V
pin is activated to minimize power consumption.
OUT
(Interrupt Output/Frequency Output)
DD
2
C interface speeds. It is disabled
is interrupted for up to a month. See
DD
9
= 2.7V to 5.5VDC. A 0.1µF
OUT
DD
DD
mode is selected via
and a V
pin to ground.
BAT
pin is activated.
BAT
2
C bus. It is
input.
DD
ISL12022M
Normal Mode (V
(V
To transition from the V
following conditions must be met:
Condition 1:
V
where V
Condition 2:
V
where V
Battery Backup Mode (V
(V
The ISL12022M device will switch from the V
mode when one of the following conditions occurs:
Condition 1:
V
where V
Condition 2:
V
where V
These power control situations are illustrated in Figures 12
and 13.
The I
power consumption. Aside from this, all RTC functions are
operational during battery backup mode. Except for SCL and
SDA, all the inputs and outputs of the ISL12022M are active
during battery backup mode unless disabled via the control
register.
DD
DD
DD
DD
BAT
DD
FIGURE 12. BATTERY SWITCHOVER WHEN V
FIGURE 13. BATTERY SWITCHOVER WHEN V
V
V
V
V
V
V
< V
< V
> V
> V
2
TRIP
TRIP
BAT
DD
BAT
)
V
C bus is deactivated in battery backup mode to reduce
DD
BAT
)
BATHYS
TRIP
BATHYS
TRIPHYS
BAT
TRIP
BAT
TRIP
- V
BATHYS
- V
+ V
V
≈ 2.2V
+ V
TRIP
BATHYS
BATHYS
≈ 50mV
≈ 50mV
TRIPHYS
≈ 30mV
DD
) to Battery Backup Mode
BATTERY BACKUP
DD
BATTERY BACKUP
to V
MODE
BAT
MODE
BAT
) to Normal Mode
mode, both of the
V
V
TRIP
BAT
BAT
+ V
BAT
BAT
December 18, 2008
+ V
BATHYS
to V
TRIPHYS
< V
> V
3.0V
2.2V
2.2V
1.8V
DD
FN6668.4
TRIP
TRIP