ISL12024IRTC Datasheet, PDF (14/24 Pages) Intersil Corporation – Real-Time Clock/Calendar

ISL12024IRTC
V_DD must drop below the battery trip point yet stay above
approximately 1.0V (limit of active circuit operation). After
that, the power-up ramp must be slower than 0.25V/ms to
trigger the delay. To be safe, serial interface software may
need to consider the 90ms delay in all power-up routines.
OPTION 1 - STANDARD (POWER CONTROL) MODE
In the Standard Mode, the supply will switch over to the
battery when V_DD drops below V_TRIP or V_BAT, 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 ISL12024IRTCZ 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: VBAT < VTRIP and VBAT > VTRIP.
These two power control situations are illustrated in
Figures 9 and 10.
V_DD
BATTERY BACKUP
MODE
V_DD
V_BAT
V_TRIP
V_TRIP
BATTERY BACKUP
MODE
3.0V
2.2V
V_TRIP + V_TRIPHYS
FIGURE 10. BATTERY SWITCHOVER WHEN V_BAT > V_TRIP
OPTION 2 - LEGACY (POWER CONTROL) MODE
(DEFAULT)
The Legacy Mode follows conditions set in X1226 products.
In this mode, switching from V_DD to V_BAT is simply done by
comparing the voltages and the device operates from
whichever is the higher voltage. Care should be taken when
changing from Normal to Legacy Mode. If the V_BAT voltage is
higher than V_DD, then the device will enter battery backup
and unless the battery is disconnected or the voltage
decreases, the device will no longer operate from V_DD.
To select Option 2, the BSW bit in the Power Register must
be set to “BSW = 1”.
• Normal Mode (V_DD) to Battery Backup Mode (V_BAT)
To transition from the V_DD to V_BAT mode, the following
conditions must be met:
V_DD < V_BAT - V_BATHYS
• Battery Backup Mode (V_BAT) to Normal Mode (V_DD)
The device will switch from the V_BAT to V_DD mode when
the following condition occurs:
V_DD > V_BAT +V_BATHYS
The Legacy Mode power control conditions are illustrated in
Figure 11..
V_BAT
V_DD
OFF
VOLTAGE
ON
In
V_TRIP
V_BAT
2.2V
1.8V
V_BAT - V_BATHYS
V_BAT + V_BATHYS
FIGURE 9. BATTERY SWITCHOVER WHEN V_BAT < V_TRIP
FIGURE 11. BATTERY SWITCHOVER IN LEGACY MODE
Serial Communication
The device supports the I²C protocol.
Clock and Data
Data states on the SDA line can change only during SCL
LOW. SDA state changes during SCL HIGH are reserved for
indicating start and stop conditions (see Figure 12).
14
FN6749.1
December 15, 2011