ISL12026 Intersil Corporation, ISL12026 Datasheet - Page 21

• Manufacturer Part Number: ISL12026
• Manufacturer: Intersil Corporation

The best way to analyze the RTC circuit is to power it up and
read the real time clock as time advances, or if the chip has
the IRQ/F
oscilloscope (after enabling it with the control register, and
using a pull-up resistor for an open-drain output).
Alternatively, the ISL12026 device has an IRQ/F
which can be checked by setting an alarm for each minute.
Using the pulse interrupt mode setting, the once-per-minute
interrupt functions as an indication of proper oscillation.
Backup Battery Operation
Many types of batteries can be used with the Intersil RTC
products. 3.0V or 3.6V Lithium batteries are appropriate, and
sizes are available that can power a Intersil RTC device for
up to 10 years. Another option is to use a supercapacitor for
applications where V
short periods of time. Depending on the value of
supercapacitor used, backup time can last from a few days
to two weeks (with >1F). A simple silicon or Schottky barrier
diode can be used in series with V
supercapacitor, which is connected to the V
use Schottky diodes with very low leakages, <1
Do not use the diode to charge a battery (especially lithium
batteries!).
There are two possible modes for battery backup operation,
Standard and Legacy mode. In Standard mode, there are no
operational concerns when switching over to battery backup
since all other devices functions are disabled. Battery drain
is minimal in Standard mode, and return to Normal V
powered operations is predictable. In Legacy mode the V
pin can power the chip if the voltage is above V
than V
communicate with the device, unless SBI = 1, but the supply
current drain is much higher than the Standard mode and
backup time is reduced. In this case if alarms are used in
backup mode, the IRQ/F
connected to V
the default mode is the Standard mode.
Alarm Operation Examples
Below are examples of both Single Event and periodic
Interrupt Mode alarms.
Example 1 – Alarm 0 set with single interrupt (IM = ”0”)
2.7-5.5V
FIGURE 24. SUPERCAPACITOR CHARGING CIRCUIT
TRIP
OUT
.
,
In this mode, it is possible to generate alarm and
output, look at the output of that pin on an
BAT
V
voltage source. During initial power up
CC
DD
V
may disappear intermittently for
OUT
SS
V
21
back
pull up resistor must be
DD
to charge the
BAT
Supercapacitor
µA
DD
pin. Try to
OUT
desirable.
and less
DD
output
BAT
ISL12026
A single alarm will occur on January 1 at 11:30am.
A. Set Alarm 0 registers as follows:
B. Also the AL0E bit must be set as follows:
After these registers are set, an alarm will be generated when
the RTC advances to exactly 11:30am on January 1 (after
seconds changes from 59 to 00) by setting the AL0 bit in the
status register to “1” and also bringing the IRQ/F
low.
Example 2 – Pulsed interrupt once per minute (IM = ”1”)
Interrupts at one minute intervals when the seconds register
is at 30 seconds.
A. Set Alarm 0 registers as follows:
B. Set the Interrupt register as follows:
REGISTER
REGISTER
REGISTER
REGISTER
CONTROL
CONTROL
ALARM0
ALARM0
MNA0
MOA0
DWA0
HRA0
DWA0
SCA0
DTA0
MNA0
MOA0
SCA0
HRA0
DTA0
INT
INT
7 6 5 4 3 2 1 0 HEX
0 0 0 0 0 0 0 0
1 0 1 1 0 0 0 0
1 0 0 1 0 0 0 1
1 0 0 0 0 0 0 1
1 0 0 0 0 0 0 1
0 0 0 0 0 0 0 0
7 6 5 4 3 2 1 0 HEX
1 0 1 0 0 0 0 0 x0h Enable Alarm and Int
7 6 5 4 3 2 1 0 HEX
1 0 1 1 0 0 0 0 B0h Seconds set to 30,
0 0 0 0 0 0 0 0 00h Minutes disabled
0 0 0 0 0 0 0 0 00h Hours disabled
0 0 0 0 0 0 0 0 00h Date disabled
0 0 0 0 0 0 0 0 00h Month disabled
0 0 0 0 0 0 0 0 00h Day of week disabled
7 6 5 4 3 2 1 0 HEX
0 0 1 0 0 0 0 0
BIT
BIT
BIT
BIT
00h Seconds disabled
B0h Minutes set to 30,
91h Hours set to 11,
81h Date set to 1,
81h Month set to 1,
00h Day of week
x0h Enable Alarm
Mode
enabled
DESCRIPTION
DESCRIPTION
enabled
enabled
enabled
enabled
disabled
DESCRIPTION
DESCRIPTION
OUT
April 13, 2006
output
FN8231.3