ISL12022M_10 Datasheet, PDF (10/31 Pages) Intersil Corporation – Low Power RTC with Battery Backed SRAM,Integrated ±5ppm Temperature Compensation and Auto Daylight Saving

ISL12022M
Typical Performance Curves Temperature is +25°C unless otherwise specified. (Continued)
5.5
5.0
F_OUT = 32kHz
4.5
4.0
3.5
F_OUT = 64Hz
3.0
F_OUT = 1Hz
2.5
-40 -20
0
20
40
60
80
TEMPERATURE (°C)
FIGURE 8. I_DD vs TEMPERATURE, 3 DIFFERENT F_OUT
110
100
90
V_BAT = 5.5V
80
70
60
50
V_DD = 3.0V
40
30
V_DD = 1.8V
20
-40 -20
0
20
40
60
80
TEMPERATURE (°C)
FIGURE 9. I_BAT WITH TSE = 1, BTSE = 1 vs
TEMPERATURE
110
100
90
V_BAT = 5.5V
80
V_DD = 3.3V
70
60
V_DD = 2.7V
50
40
-40 -20
0
20
40
60
80
TEMPERATURE (°C)
FIGURE 10. I_DD WITH TSE = 1 vs TEMPERATURE
80
60
32ppm
40
62.5ppm
20
0ppm
0
-20
-40
-61.5ppm
-31ppm
-60
-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 ISL12022M 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, the ISL12022M can be
programmed for automatic Daylight Saving Time (DST)
adjustment by entering local DST information.
The ISL12022M’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/F_OUT 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
V_BAT pin allows the device to be backed up by battery or
supercapacitor with automatic switchover from V_DD to
V_BAT. The ISL12022M device is specified for V_DD = 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 V_BAT level is monitored and
reported against preselected levels. The first report is
registered when the V_BAT level falls below 85% of
nominal level; the second level is set for 75%. Battery
levels are stored in PWR_V_BAT registers.
The ISL12022M offers a “Brownout” alarm once the V_DD
falls below a pre-selected trip level. This allows system
Micro to save vital information to memory before
complete power loss. There are six V_DD levels that
could be selected for initiation of the Brownout alarm.
10
FN6668.7
June 4, 2010