ISL12029 Intersil Corporation, ISL12029 Datasheet - Page 9

• Manufacturer Part Number: ISL12029
• Description: Real Time Clock/Calendar
• Manufacturer: Intersil Corporation

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Description
The ISL12029 device is a Real Time Clock with clock/calendar,
two polled alarms with integrated 512x8 EEPROM, oscillator
compensation, CPU Supervisor (Power-on Reset, Low Voltage
Sensing and Watchdog Timer) and battery backup switch.
The oscillator uses an external, low-cost 32.768kHz crystal.
All compensation and trim components are integrated on the
chip. This eliminates several external discrete components
and a trim capacitor, saving board area and component cost.
The Real-Time Clock keeps track of time with separate
registers for Hours, Minutes, Seconds. The Calendar has
separate registers for Date, Month, Year and Day-of-week.
The calendar is correct through 2099, with automatic leap
year correction.
The Dual Alarms can be set to any Clock/Calendar value for a
match. For instance, every minute, every Tuesday, or 5:23 AM
on March 21. The alarms can be polled in the Status Register
or can provide a hardware interrupt (IRQ/F
repeat mode for the alarms allowing a periodic interrupt.
The IRQ/F
frequency output of 1Hz, 4096Hz, or 32,768Hz or inactive.
The ISL12029 device integrates CPU Supervisory functions
(POR, WDT) and Battery Switch. There is Power-On-Reset
(RESET) output with 250ms delay from power-on when the
VDD supply crosses the V
also assert RESET when V
V
selectable via VTS2/VTS1/VTS0 registers to five (5)
preselected levels. Their is WatchDog Timer (WDT) with 3
selectable time-out periods (0.25s, 0.75s and 1.75s) and
disabled setting. The WatchDog Timer activates the RESET pin
when it expires. Normally, the I
RESET output is active, but this can be changed by using a
register bit to enable I
The device offers a backup power input pin. This V
allows the device to be backed up by battery or SuperCap. The
entire ISL12029 device is fully operational from 2.7 to 5.5V and
the clock/calendar portion of the ISL12029 device remains fully
operational down to 1.8V (Standby Mode).
The ISL12029 device provides 4K bits of EEPROM with 8
modes of BlockLock™ control. The BlockLock allows a safe,
secure memory for critical user and configuration data, while
allowing a large user storage area.
Pin Descriptions
Serial Clock (SCL)
The SCL input is used to clock all data into and out of the
device. The input buffer on this pin is always active (not
gated). The pull-up resistor on this pin must use the same
voltage source as V
RESET
threshold for the device. The V
OUT
pin may be software selected to provide a
DD
2
C operation in battery backup mode.
.
RESET
DD
2
goes below the specified
C Interface is disabled when the
9
threshold for the device. It will
RESET
OUT
threshold is
Pin). There is a
BAT
pin
ISL12029
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 wire
ORed with other open drain or open collector outputs. The
input buffer is always active (not gated).
This open drain output requires the use of a pull-up resistor.
The pull-up resistor on this pin must use the same voltage
source as V
output signal with the use of a slope controlled pull-down. The
circuit is designed for 400kHz I
V
This input provides a backup supply voltage to the device.
V
supply fails. This pin can be connected to a battery, a
SuperCap or tied to ground if not used.
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
The IRQ/F
resistor which was intended to be used for clocking
applications for microcontrollers. Choose the pullup resistor
with care, since low values will cause high currents to flow in
the V
contribute to faulty oscillator function. For a 32kHz output,
values up to 10kΩ can be used with some degradation of the
square waveform.
RESET
The RESET signal output can be used to notify a host
processor that the watchdog timer has expired or the VDD
voltage supply has dipped below the V
an open drain, active LOW output. Recommended value for
the pullup resistor is 10kΩ. If unused it can be tied to ground.
X1, X2
The X1 and X2 pins are the input and output, respectively, of
an inverting amplifier. An external 32.768kHz quartz crystal is
used with the ISL12029 to supply a timebase for the real time
clock. Internal compensation circuitry provides high accuracy
over the operating temperature range from -40°C to +85°C.
This oscillator compensation network can be used to calibrate
the crystal timing accuracy over temperature either during
manufacturing or with an external temperature sensor and
BAT
BAT
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.
DD
supplies power to the device in the event the V
OUT
and ground traces around the device which can
OUT
DD
(Interrupt Output/Frequency Output)
. The output circuitry controls the fall time of the
pin is an open drain output requiring a pullup
2
C interface speed.
OUT
mode is selected via
RESET
threshold. It is
2
C bus. It is
April 17, 2006
DD
FN6206.4