User's Manual

MC46 Hardware Interface Description
Confidential / Released
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MC46_HD_V03.05 Page 39 of 99 13.11.2003
3.5.2 Implemented charging technique
If the external charging circuit follows the recommendation of Figure 7, the charging process
consists of trickle charging and processor controlled fast charging. For this solution, the fast
charging current provided by the charger or any other external source must be limited to
500mA.
Trickle charging
· Trickle charging starts when the charger is connected to the charger input of the external
charging circuit and the module’s POWER pin. The charging current depends on the
voltage difference between the charger input of the external charging circuit and BATT+
of the module.
· Trickle charging stops when the battery voltage reaches 3.6V.
Fast charging
· After trickle charging has raised the battery voltage to 3.2V within 60 minutes +
10% from
connecting the charger, the power ASIC turns on and wakes up the baseband processor.
Now, processor controlled fast charging begins.
If the battery voltage was already above 3.2V, processor controlled fast charging starts
just after the charger was connected to the charger input of the external charging circuit
and the module’s POWER pin. If MC46 was in POWER DOWN mode, it turns on and
enters the Charge-only mode along with fast charging (see also Chapter 3.3.1.3).
· Fast charging delivers a constant current until the battery voltage reaches 4.2V and then
proceeds with varying charge pulses. As shown in Figure 5, the pulse duty cycle is
reduced to adjust the charging procedure and prevent the voltage from overshooting
beyond 4.2V. Once the pulse width reaches the minimum of 100ms and the duty cycle
does not change for 2 minutes, fast charging is completed.
· Fast charging can only be accomplished in a temperature range from 0°C to +45°C.
4.3
4.2
3.8
Voltage
3.4
3.0
Constant current
t
OFF
= 100 ms
t
ON
= 100 ms
Time
100ms 2 ... 0.1s
100ms 0.1 ... 2s
Figure 9: Charging process
Note: Do not connect the charger to the BATT+ lines. Only the charger input of the
external charging circuit is intended as input for charging current! The POWER pin
of MC46 is the input only for indicating a connected charger!
The battery manufacturer must guarantee that the battery complies with the
described charging technique.