ISL12025 Intersil Corporation, ISL12025 Datasheet - Page 15

• Manufacturer Part Number: ISL12025
• Description: Real-Time Clock/Calendar
• Manufacturer: Intersil Corporation

Standard Mode Power Switchover
• Normal Operating Mode (V
• Battery Backup Mode (V
There are two discrete situations that are possible when
using Standard Mode:
These two power control situations are illustrated in
Figures 13 and 14.
OPTION 2 - LEGACY (POWER CONTROL) MODE
(DEFAULT)
The Legacy Mode follows conditions set in X1226 products.
In this mode, switching from V
comparing the voltages and the device operates from
(V
To transition from the V
following conditions must be met:
- Condition 1:
- Condition 2:
The ISL12025 device will switch from the V
mode when one of the following conditions occurs:
- Condition 1:
- Condition 2:
FIGURE 13. BATTERY SWITCHOVER WHEN V
FIGURE 14. BATTERY SWITCHOVER WHEN V
V
V
V
BAT
V
where V
V
where V
V
where V
V
where V
V
V
V
TRIP
TRIP
DD
BAT
BAT
DD
DD
DD
DD
DD
V
BAT
)
< V
< V
> V
> V
- V
BATHYS
TRIP
BATHYS
TRIPHYS
V
BAT
TRIP
BAT
TRIP
BATHYS
TRIP
- V
+ V
≈ 2.2V
+ V
BATHYS
BATHYS
≈ 50mV
≈ 50mV
TRIPHYS
≈ 30mV
V
BATTERY BACKUP
BATTERY BACKUP
BAT <
DD
BAT
MODE
15
to V
DD
DD
MODE
) to Normal Mode (V
V
) to Battery Backup Mode
TRIP and
BAT
to V
BAT
mode, both of the
is simply done by
V
V
TRIP
V
BAT >
BAT
BAT
BAT
BAT
+ V
+ V
TRIPHYS
to V
V
< V
> V
DD
BATHYS
TRIP .
3.0V
2.2V
2.2V
1.8V
DD
TRIP
TRIP
)
ISL12025
whichever is the higher voltage. Care should be taken when
changing from Normal to Legacy Mode. If the V
higher than V
and unless the battery is disconnected or the voltage
decreases, the device will no longer operate from V
To select the Option 2, BSW bit in the Power Register must
be set to “BSW = 1”.
• Normal Mode (V
• Battery Backup Mode (V
The Legacy Mode power control conditions are illustrated in
Figure 15 below.
Power-On Reset
Application of power to the ISL12025 activates a
Power-On-Reset Circuit that pulls the RESET pin active.
This signal provides several benefits.
When V
typically 250ms the circuit releases RESET, allowing the
system to begin operation. Recommended slew rate is
between 0.2V/ms and 50V/ms.
Watchdog Timer Operation
The watchdog timer timeout period is selectable. By writing a
value to WD1 and WD0, the watchdog timer can be set to 3
different time out periods or off. When the Watchdog timer is
set to off, the watchdog circuit is configured for low power
operation. See Table 6.
V
To transition from the V
conditions must be met:
V
The device will switch from the V
the following condition occurs:
V
- It prevents the system microprocessor from starting to
- It prevents the processor from operating prior to
- It allows time for an FPGA to download its configuration
- It prevents communication to the EEPROM, greatly
BAT
FIGURE 15. BATTERY SWITCHOVER IN LEGACY MODE
DD
DD
operate with insufficient voltage.
stabilization of the oscillator.
prior to initialization of the circuit.
reducing the likelihood of data corruption on power-up.
< V
> V
DD
BAT
BAT
exceeds the device V
DD
- V
+V
OFF
, then the device will enter battery back up
BATHYS
BATHYS
DD
) to Battery Backup Mode (V
V
DD
DD
BAT
to V
) to Normal Mode (V
BAT
RESET
BAT
VOLTAGE
mode, the following
to V
threshold value for
DD
BAT
mode when
ON
October 18, 2006
BAT
DD
voltage is
DD
.
FN6371.1
)
)
IN