
ISL12022MR5421
11
FN7576.3
June 7, 2012
General Description
The ISL12022MR5421 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
ISL12022MR5421 can be programmed for automatic Daylight
Saving Time (DST) adjustment by entering local DST information.
The ISL12022MR5421’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 supercapacitor
with automatic switchover from VDD to VBAT. The
ISL12022MR5421 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 ISL12022MR5421 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.
FIGURE 10. IDD vs TEMPERATURE, 3 DIFFERENT FOUT
FIGURE 11. IBAT WITH TSE = 1, BTSE = 1 vs TEMPERATURE
FIGURE 12. IDD WITH TSE = 1 vs TEMPERATURE
FIGURE 13. OSCILLATOR CHANGE vs TEMPERATURE AT
DIFFERENT AGING SETTINGS (IATR) (BETA SET FOR
1ppm STEPS)
Typical Performance Curves Temperature is +25°C unless otherwise specified. (Continued)
2.5
3.0
3.5
4.0
4.5
5.0
5.5
-40
-20
0
204060
80
TEMPERATURE (°C)
SUP
P
LY
CURRENT
(A)
FOUT = 32kHz
FOUT = 64Hz
FOUT = 1Hz
20
30
40
50
60
70
80
90
100
110
-40
-20
0
20
406080
TEMPERATURE (°C)
I BA
T
(A)
VDD = 1.8V
VBAT = 5.5V
VDD = 3.0V
40
50
60
70
80
90
100
110
-40
-20
0
20
406080
TEMPERATURE (°C)
I DD
(A)
VDD = 2.7V
VBAT = 5.5V
VDD = 3.3V
-80
-60
-40
-20
0
20
40
60
80
-40
-20
0
20406080
TEMPERATURE (°C)
FREQU
E
NCY
CHANGE
(
p
pm)
62.5ppm
32ppm
-31ppm
-61.5ppm
0ppm