MC45 Hardware Interface Description
P R E L I M I N A R Y
MC45_HD_01_V00.02a
Page 30 of 90
12.08.2002
3.2.3.3 Implemented charging technique
If the external charging circuit follows the recommendation of Figure 3, 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 POWER pin of the external
charging circuit. The charging current depends on the voltage difference between the
pins POWER and BATT+ of the external charging circuit.
·
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 m10% 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 POWER pins of the external charging circuit
and of the module. If MC45 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 5: Charging process
Note: Do
not connect the charger to the BATT+ lines. Only the POWER input of the
charging circuit is intended as input for charging current! The POWER pin of MC45
is the input only for indicating a connected charger!
The battery manufacturer must guarantee that the battery complies with the
described charging technique.
