FLY E185
Service Manual
2. Pre-Charging mode
When the battery voltage is below the CC threshold, the charging status is in the pre-charging
mode. There are two steps in this mode. While the battery voltage is deeply discharged below 2.7V,
a 50mA trickle current is used for charging the battery. This is the pre-CC1 state. When the battery
voltage exceeds 2.7V, the self-calibrated pre-charge mode is enabled, which allows 20mV
(typically) voltage drop across the external current sense resistor. This is the pre-CC2 state. The
pre-charge current in this state can be calculated as:
Typically, I
CONST
=100mA with V
SENSE
=20mV and R
SEN
=0.2
Ω
.
3. Constant Current Charging Mode
Once the battery voltage has exceeded the CC threshold, a constant current is used for periodical
charging With periodical charging, charger circuit could detect CHRIN state and battery state in
non-charging period. This is called the constant current charging mode. An up-to-800mA constant
charging current could be programmed via the register setting. The relation between the voltage
drop across the external current sense resistor and the charging current is as follows:
Typically, I
CONST
=800mA with V
SENSE
=160mV and R
SEN
=0.2
Ω
.
Before the battery voltage reaches 4.1V, the charger will be in the constant current charging mode.
4. Full/Constant Voltage Charging Mode
While the batteryvoltagereaches4.1V, a constant current with much shorter period is used for
charging. It could allow more often full battery detection in non-charging period. This is called
full voltage charging mode or constant voltage charging mode in correspondence to a linear
charger. While the battery voltage reaches 4.2V more than the pre-setting times within the limited
charging cycles, the end-of-charging process starts. It may prolong the charging and detecting
period for getting the optimized the full charging volume. This end of charging process is fully
controlled by the baseband and could be easily optimized for different battery pack.
5. Over-Voltage Protection
Once the battery voltage exceeds 4.35V, a hardware over voltage protection (OV) should be
activated and turn off the charger immediately.
6. Watchdog Timer
An internal watchdog timer is used as a protection for charging period control. In the constant
current charging mode or the full voltage charging mode, the baseband must refresh the timer
periodically to keep the charging alive. Once, the watchdog timer out, charger will stop charging.
This provides the time domain protection for charging control.
7. CSDAC
CSDAC is an 8-bit current DAC for current sink. Typically, the step for 1 LSB current sink is
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