Func�on Descrip�on

Precharge Current

The FC9054 is a linear charger circuit specially designed for

single cell lithium-ion ba�eries. When the FC9054 is

powered with a ba�ery connected, the IC first detects if the

cell voltage is ready for full charge current. If the cell voltage

is less than the prequal level (3V typ), the ba�ery is

precharged with a 55mA current un�l the cell reaches the

proper level. The full charging current, as set by PROG pin, is

then applied

Soft-Start

The FC9054 includes a soft-start function to control the rise rate

of the charging current rising from zero to the fast-charging

current level in constant current mode. During charger soft-start,

the FC9054 ramps up the voltage on PROG pin with constant

well-controlled slew rate. The charging current is proportional to

the PROG voltage. The soft-start time is 20us (typical), which is

independent of the fast-charging current level.

Charging Current Setting

The charge current is programmed by using a resistor from

the PROG pin to the ground. The ba�ery charge current is

1000 �mes the current out of the PROG pin. The ba�ery

charge current is calculated by the following equa�on:

charging current set factor and the PROG regula�on voltage

are shown in the Electrical Characteris�cs. The PROG

regula�on voltage is reduced by thermal regula�on func�on.

Battery Full Indication

the FC9054 stopped current mode charging, it keeps operating in

voltage mode without turning off the charger. When the PROG

pin's voltage down to 100mv over 2ms, the charger will stop

operating and the Vcc current down to 55uA.

Charge Status Outputs

The open-drain CHRG outputs can be used to drive LED indicate

four charger operations are shown in Table 1.

Charge state

Red LED（CHRG）

charging

bright

Charge Termination

extinguish

Vin too low; Temperature of

battery too low or too high; no

battery

extinguish

BAT PIN Connect 10u

Capacitance; No battery

Extinguish

(T=1-4s)

Table 1.

Increase the heat regulating current

Reduce the voltage drop across the internal MOSFET can

significantly reduce the power consump�on of the IC.

During thermal regula�on, this has an increased current

supplied to the ba�ery. One strategy is accomplished by an

external element (e.g., a resistor or a diode) will be part of

the power consump�on.

Example: FC9054 is powered by a 5V AC adapter, it charge to

one with a 3.75V voltage lithium-ion ba�ery, and set the

full-scale charge current 800mA by programming. Assuming

the charging current is approximately:

Increase the voltage across the resistor in series with a 5V

AC adapter(Figure 3), the on-chip power dissipa�on can be

reduced, thereby increasing the heat regula�ng current:

mA

FC9054

2019. 05. 13

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Revision No : 0