3. TECHNICAL BRIEF
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Only for training and service purposes
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3.10.3. Charging control
The RT8965 integrates a single-cell Li-ion battery charger IC with pre-charge mode, a fast charge mode
(constant current mode) or constant voltage mode. The charge current is programmable via the I
2
C interface
as shown in the control register address tables, CHG_Ctrl1 and CHG_Ctrl2. The CV mode voltage is fixed at
4.2V. The pre-charge threshold is fixed at 2.6V. If the battery voltage is below the pre-charge threshold, the
RT8965 charges the battery with a trickle current until the battery voltage rises above the pre-charge
threshold. The RT8965 is capable of being powered up from AC adapter and USB (Universal Serial Bus) port
inputs. Moreover, the RT8965 includes a linear regulator (LDO 4.9V, 50mA) for supplying low power external
circuitry.
3.10.3.1. Pre-Charge Mode
Figure 1 shows the RT8965 charging state of the charging function. During a charge cycle, if the battery
voltage is below the V
PRECH
threshold (typical value is 2.6V), the charger enters pre-charge mode. This feature
revives deeply discharged cells and protects battery life. The precharge current has a typical value of 50mA
.
Figure. RT8965 Charging State of the Charger Function
Pre-charge
Mode
Constant
Current
Mode
Constant
Voltage
Mode
Recharge
Phase
Battery
Charge
Current
Programmed
Charge
Current
Precharge
Threshold
4.V
Battery
Regulation
Voltage
threshold
Battery
Full
CHG pull
High