FS325C datasheet(21/28 Pages) FORTUNE

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11. Description of Operation

Normal Condition

If VODP<VCC<VOCP and VST<VCS<VOI1, M1 and

M2 are both turned on. The charging and

discharging processes can be operated normally.

Overcharge Protection

When the voltage of the battery cell exceeds the

overcharge protection voltage (VOCP) beyond the

overcharge delay time (TOC) period, charging is

inhibited by turning off of the charge control

MOSFET. The overcharge condition is released in

two cases:

The voltage of the battery cell becomes lower than

the overcharge release voltage (VOCR) through

self-discharge.

The voltage of the battery cell falls below the

overcharge protection voltage (VOCP) and a load is

connected.

When the battery voltage is above VOCP, the

overcharge condition will not release even a load is

connected to the pack.

Overdischarge Protection

When the voltage of the battery cell goes below the

overdischarge protection voltage (VODP) beyond

the overdischarge delay time (TOD) period,

discharging is inhibited by turning off the discharge

control MOSFET.

The default of overdischarge delay time is 100ms.

Inhibition of discharging is immediately released

when the voltage of the battery cell becomes higher

than overdischarge release voltage (VODR) through

charging.

Overcurrent Protection

In normal mode, the FS325 continuously monitors

the discharge current by sensing the voltage of CS

pin. If the voltage of CS pin exceeds the overcurrent

protection voltage (VOIP) beyond the overcurrent

delay time (TOI1) period, the overcurrent protection

circuit operates and discharging is inhibited by

turning off the discharge control MOSFET. The

overcurrent condition returns to the normal mode

when the load is released or the impedance between

BATT+ and BATT- is larger than 150kΩ. The FS325

provides two overcurrent detection levels (0.13V and

0.9V) with two overcurrent delay time (TOI1 and

TOI2) corresponding to each overcurrent detection

level.

Charge Detection after Overdischarge

When overdischarge occurs, the discharge control

MOSFET turns off and discharging is inhibited.

However, charging is still permitted through the

parasitic diode of MOSFET. Once the charger is

connected to the battery pack, the FS325

immediately turns on all the timing generation and

detection circuitry. Charging progress is sensed if

the voltage between CS and GND is below charge

detection threshold voltage (VST).

Power Down after Overdischarge

When overdischarge occurs, the FS325 will enter

into power-down mode, turning off all the timing

generation and detection circuitry to reduce the

quiescent current to 0.05μ A (VCC=2.0V). At the

same time, the CS pin is pull-up to VCC through an

internal resistor.

Auto Power Down recovery

The IC continues to operate even after the

overdischarge state has been entered. The battery

voltage rising to the overdischarge release

voltage(VODR) or higher is the only required

condition for the IC to return to the normal state.

Supervising charger voltage

By supervising the charge voltage, charging can be

prohibited instantly when a charger with overvoltage

is connevted. The charger voltage detection circuit

supervises the voltage between the VDD and CSI

pins. When this voltage exceeds Vdet(Vdet <

(VDD – VCSI)),regardless of the battery voltage,the

charge FET control pin output alow level(CSI

level)signal and the charge FET is turned off. When

the charger voltage drops to Vrec or lower, the

charger FET control output level is dependent on

battery voltage.

Note: When a battery is connected to FS325

for the first time, it may not enter the normal

condition

(dischargeable

may

not

enabled). In this case, short the CS and VSS

pins or connect to a charger to restore to

the normal condition.

FS325C 数据表(PDF) 21 Page - Fortune Semiconductor Corp.

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