ISL12029_1012 Datasheet, PDF (16/29 Pages) Intersil Corporation – Real Time Clock/Calendar with I2C Bus™ and EEPROM

ISL12029, ISL12029A
overlapping to the following Alarm's Seconds register is
advised.
2. Other non-volatile writes: It is possible to do writes of
less than an entire page, but the final byte must always
be addresses 0000h through 0004h or 0008h though
000Ch to trigger a non-volatile write. Writing to those
blocks of 5 bytes sequentially, or individually, will trigger a
non-volatile write. If the DWA0 or DWA1 registers need to
be set, then enough bytes will need to be written to
overlap with the other Alarm register and trigger the
non-volatile write. For Example, if the DWA0 register is
being set, then the code can start with a multiple byte
write beginning at address 0006h, and then write 3 bytes
ending with the SCA1 register as follows:
Addr Name
0006h DWA0
0007h Y2K0
0008h SCA1
If the Alarm1 is used, SCA1 would need to have the correct
data written.
Power Control Operation
The power control circuit accepts a V_DD and a V_BAT 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
an Intersil RTC device for up to 10 years. Another option is
to use a SuperCap for applications where V_DD is interrupted
for up to a month. See “Application Section” on page 23 for
more information.
There are two options for setting the change-over conditions
from V_DD to Battery back-up mode. The BSW bit in the PWR
register controls this operation.
Option 1 - Standard Mode (Default for ISL12029A)
Option 2 - Legacy Mode (Default for ISL12029)
TABLE 7. V_BAT TRIP POINT WITH DIFFERENT BSW SETTING
V_BAT TRIP POINT
BSW BIT
(V)
POWER CONTROL SETTING
0
2.2
Standard Mode (ISL12029A)
1
V_DD < V_BAT
Legacy Mode (ISL12029)
Note that applications that have V_BAT > V_DD will require the
ISL12029A (standard mode) for proper startup. Note that the
I²C bus may or may not be operational during battery
backup, that function is controlled by the SBIB bit. That
operation is covered after the power control section.
OPTION 1 - STANDARD POWER CONTROL MODE
(DEFAULT FOR ISL12029A)
In the Standard mode, the supply will switch over to the
battery when V_DD drops below VTRIP or VBAT, whichever is
lower. In this mode, accidental operation from the battery is
prevented since the battery backup input will only be used
when the V_DD supply is shut off.
To select Option 1, BSW bit in the Power Register must be
set to “BSW = 0”. A description of power switchover follows.
Standard Mode Power Switchover
• Normal Operating Mode (V_DD) to Battery Backup Mode
(V_BAT)
To transition from the V_DD to V_BAT mode, both of the
following conditions must be met:
- Condition 1:
V_DD < V_BAT - V_BATHYS
where V_BATHYS ≈ 50mV
- Condition 2:
V_DD < V_TRIP
where V_TRIP ≈ 2.2V
• Battery Backup Mode (V_BAT) to Normal Mode (V_DD)
The ISL12029 device will switch from the V_BAT to V_DD mode
when one of the following conditions occurs:
- Condition 1:
V_DD > V_BAT + V_BATHYS
where V_BATHYS ≈ 50mV
- Condition 2:
V_DD > V_TRIP + V_TRIPHYS
where V_TRIPHYS ≈ 30mV
There are two discrete situations that are possible when using
Standard Mode: V_BAT < V_TRIP and V_BAT > V_TRIP. These two
power control situations are illustrated in Figures 13 and 14.
BATTERY
BACKUP
V_DD
MODE
V_TRIP
V_BAT
2.2V
1.8V
V_BAT - V_BATHYS
V_BAT + V_BATHYS
FIGURE 13. BATTERY SWITCHOVER WHEN V_BAT < V_TRIP
V_DD
V_BAT
V_TRIP
V_TRIP
BATTERY BACKUP
MODE
3.0V
2.2V
V_TRIP + V_TRIPHYS
FIGURE 14. BATTERY SWITCHOVER WHEN V_BAT > V_TRIP
16
FN6206.10
December 16, 2010