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ISL12082IUZ View Datasheet(PDF) - Intersil

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ISL12082IUZ Datasheet PDF : 26 Pages
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ISL12082
The ISL12082 has the ReSeal™ function, which allows the
device to enter into the InterSeal™ Battery Saver mode after
manufacture testing for board functionality. To use the
ReSeal™ function, simply set RESEAL bit to “1” (address
07h) after the testing is completed. It will enable the
InterSeal™ Battery Saver mode and prevents battery current
drain before it is first used.
Real Time Clock Operation
The Real Time Clock (RTC) uses an external 32.768kHz
quartz crystal to maintain an accurate internal representation
of sub-second, second, minute, hour, day of week, date,
month, and year. The RTC also has leap-year correction.
The RTC also corrects for months having fewer than 31 days
and has a bit that controls 24 hour or AM/PM format. When
the ISL12082 powers up after the loss of both VDD and
VBAT, the clock will not begin incrementing until at least one
byte is written to the clock register.
Accuracy of the Real Time Clock
The accuracy of the Real Time Clock depends on the
frequency of the quartz crystal that is used as the time base
for the RTC. Since the resonant frequency of a crystal is
temperature dependent, the RTC performance will also be
dependent upon temperature. The frequency deviation of
the crystal is a function of the turnover-temperature of the
crystal from the crystal’s nominal frequency. For example, a
~20ppm frequency deviation translates into an accuracy of
~1 minute per month. These parameters are available from
the crystal manufacturer. The ISL12082 provides on-chip
crystal compensation networks to adjust load capacitance to
tune oscillator frequency from -94ppm to +140ppm. For
more detailed information, see “Application Section” on
page 22.
Single Event and Interrupt
The alarm mode is enabled via the ALME bit (address 08h).
Choosing single event or interrupt alarm mode is selected
via the IM bit (address 08h). Note that when the frequency
output function is enabled, the alarm function is disabled.
The standard alarm allows for alarms of time, date, day of
the week, month, and year. When a time alarm occurs in
single event mode, an IRQ1/fOUT and/or IRQ2 pin will be
pulled low and the alarm status bit (ALM) will be set to “1”.
The pulsed interrupt mode allows for repetitive or recurring
alarm functionality. Hence, once the alarm is set, the device
will continue to alarm for each occurring match of the alarm
and present time. Thus, it will alarm as often as every minute
(if only the nth second is set) or as infrequently as once a
year (if at least the nth month is set). During pulsed interrupt
mode, the IRQ1/fOUT and/or IRQ2 pin will be pulled low for
210ms and the alarm status bit (ALM) will be set to “1”.
Note: The ALM bit can be reset by the user or cleared
automatically using the auto reset mode (see ARST bit,
address 07h).
The alarm function can be enabled/disabled during battery
backup mode using the FOBATB bit (address 08h). For more
information on the alarm, see “Alarm Registers” on page 14.
Frequency Output Mode
The ISL12082 has the option to provide a frequency output
signal using the IRQ/fOUT pin. The frequency output mode is
set by using the FO bits to select 4 possible output frequency
values from 1kHz to 32.768kHz. The frequency output can
be enabled/disabled during battery backup mode using the
FOBATB bit (address 08h).
I2C Serial Interface
The ISL12082 has an I2C serial bus interface that provides
access to the control and status registers and the user
SRAM. The I2C serial interface is compatible with other
industry I2C serial bus protocols using a bi-directional data
signal (SDA) and a clock signal (SCL).
Oscillator Compensation
The ISL12082 provides the option of timing correction due to
temperature variation of the crystal oscillator for either
manufacturing calibration or active calibration. The total
possible compensation is typically -94ppm to +140ppm. Two
compensation mechanisms that are available are as follows:
1. An analog trimming (ATR) register that can be used to
adjust individual on-chip digital capacitors for oscillator
capacitance trimming. The individual digital capacitor is
selectable from a range of 9pF to 40.5pF (based upon
32.758kHz). This translates to a calculated
compensation of approximately -34ppm to +80ppm. See
“ATR description” on page 22.
2. A digital trimming register (DTR) that can be used to
adjust the timing counter by -63ppm to +126ppm. See
“DTR description” on page 22.
Also provided is the ability to adjust the crystal capacitance
when the ISL12082 switches from VDD to battery backup
mode.
Register Descriptions
The battery-backed registers are accessible following a
slave byte of “1101111x” and reads or writes to addresses
[00h:1Fh]. The defined addresses and default values are
described in Table 1. Address 16h to 1Eh are not used.
Reads or writes to addresses 16h to 1Eh will not affect
operation of the device but should be avoided.
Register Access
The contents of the registers can be modified by performing
a byte or a page write operation directly to any register
address.
The registers are divided into 4 sections. These are:
1. Real Time Clock (8 bytes): Address 00h to 06h, and 1Fh,
with address 1Fh as read-only byte.
2. Control and Status (5 bytes): Address 07h to 0Bh.
10
FN6731.3
November 24, 2008
 

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