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ISL12020MIRZ-T View Datasheet(PDF) - Intersil

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ISL12020MIRZ-T Datasheet PDF : 32 Pages
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ISL12020M
Typical Performance Curves Temperature is +25°C unless otherwise specified. (Continued)
110
100
90
VDD = 5.5V
80
VDD = 3.3V
70
60
VBAT = 2.7V
50
40-40
-20
0
20
40
60
80
TEMPERATURE (°C)
FIGURE 10. IDD with TSE = 1 vs TEMPERATURE
80
62.5ppm
60
40
32ppm
20
0ppm
0
-20
-31ppm
-40
-60
-61.5ppm
-80
-40
-20
0
20
40
60
80
TEMPERATURE (°C)
FIGURE 11. OSCILLATOR CHANGE vs TEMPERATURE
AT DIFFERENT AGING SETTINGS (IATR)
(BETA SET FOR 1ppm STEPS)
General Description
The ISL12020M device is a low power real time clock
(RTC) with embedded temperature sensor and crystal.
It contains crystal frequency compensation circuitry
over the operating temperature range good to ±5ppm
accuracy. It also contains a clock/calendar with Daylight
Savings Time (DST) adjustment, power fail and low
battery monitors, brownout indicator, 1 periodic or
polled alarm, intelligent battery-backup switching and
128 Bytes of battery-backed user SRAM.
The oscillator uses an internal 32.768kHz crystal. The
real time clock tracks time with separate registers for
hours, minutes and seconds. The device has calendar
registers for date, month, year and day of the week. The
calendar is accurate through 2099, with automatic leap
year correction. In addition, both the ISL12020M could
be programmed for automatic Daylight Savings Time
(DST) adjustment by entering local DST information.
The ISL12020M’s alarm can be set to any clock/calendar
value for a match. For example, every minute, every
Tuesday or at 5:23 AM on March 21. The alarm status is
available by checking the Status Register, or the device
can be configured to provide a hardware interrupt via the
IRQ/FOUT pin. There is a repeat mode for the alarm
allowing a periodic interrupt every minute, every hour,
every day, etc.
The device also offers a backup power input pin. This
VBAT pin allows the device to be backed up by battery or
Super Capacitor with automatic switchover from VDD to
VBAT. The ISL12020M device is specified for VDD = 2.7V
to 5.5V and the clock/calendar portion of the device
remains fully operational in battery-backup mode down
to 1.8V (Standby Mode). The VBAT level is monitored
and reported against preselected levels. The first report
is registered when the VBAT level falls below 85% of
nominal level, the second level is set for 75%. Battery
levels are stored in PWR_VBAT registers.
The ISL12020M offers a “Brownout” alarm once the VDD
falls below a pre-selected trip level. This allows system
Micro to save vital information to memory before
complete power loss. There are six VDD levels that could
be selected for initiation of the Brownout alarm.
Functional Description
Power Control Operation
The power control circuit accepts a VDD and a VBAT
input. 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 ISL12020M for up to 10 years.
Another option is to use a Super Capacitor for
applications where VDD is interrupted for up to a month.
See the “Application Section” on page 27 for more
information.
Normal Mode (VDD) to Battery-Backup Mode
(VBAT)
To transition from the VDD to VBAT mode, both of the
following conditions must be met:
Condition 1:
VDD < VBAT - VBATHYS
where VBATHYS 50mV
Condition 2:
VDD < VTRIP
where VTRIP 2.2V
Battery-Backup Mode (VBAT) to Normal
Mode (VDD)
The ISL12020M device will switch from the VBAT to VDD
mode when one of the following conditions occurs:
Condition 1:
VDD > VBAT + VBATHYS
where VBATHYS 50mV
Condition 2:
VDD > VTRIP + VTRIPHYS
where VTRIPHYS 30mV
These power control situations are illustrated in
Figures 12 and 13.
10
FN6667.4
February 11, 2010
 

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