AIC1802 데이터 시트보기 (PDF) - Analog Intergrations

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AIC1802

Two-Cell Lithium-Ion Battery Protection IC

Analog Intergrations 

AIC1802

n APPLICATION INFORMATIONS

THE OPERATION

Overcharge Protection

When the voltage of either of the battery cells

exceeds VOCP (overcharge protection voltage)

beyond the overcharge delay time period,

charging is inhibited by the turning-off of the

charge control MOSFET M2. The overcharge

delay time (TOC ) defaults to 25mS and can be

extended by adding a capacitor CTC. Inhibition of

charging is immediately released when the

voltage of the overcharged cell becomes lower

than VOCR (overcharge release voltage) through

discharge.

Overdischarge Protection

When the voltage of either of the battery cells

goes below VODP (overdischarge protection

voltage) beyond the overdischarge delay time

period, discharging is inhibited by the turning-off

of the discharge control MOSFET M1. The

overdischarge delay time (TOD) defaults to 25mS

and can be extended by adding a capacitor CTD.

Inhibition of discharging is immediately released

when the voltage of the overdischarged cell

becomes higher than VODR (overdischarge

release voltage) through charging.

Power-Down after Overdischarge

When overdischarge occurs, the AIC1802 will go

into power-down mode, turning off all the timing

generation and detection circuitry to reduce the

quiescent current to 0.8µA (VCC=4.8V). In the

unusual case where one battery cell is

overdischarged while the other under overcharge

condition, the AIC1802 will turn off all the

detection circuits except the overcharge detection

circuit for the cell under overcharge condition.

Charge Detection after Overdischarge

When overcharge occurs, the discharge control

MOSFET M1 turns off and discharging is inhibited.

However, charging is still permitted through the

parasitic diode of M1. Once the charger is

connected to the battery pack, the AIC1802

immediately turns on all the timing generation and

detection circuitry and goes into normal mode.

Charging is determined to be in progress if the

voltage between CS and GND is below –0.4V

(charge detection threshold voltage VCH)

Overcurrent Protection

In normal mode, the AIC1802 continuously

monitors the discharge current by sensing the

voltage of CS pin. If the voltage of CS pin

exceeds VOIP (overcurrent protection voltage)

beyond overcurrent delay time TOI period, the

overcurrent protection circuit operates and

discharging is inhibited by turning-off of the

discharge control MOSFET M1. Discharging must

be inhibited for at least 256mS after overcurrent

takes place to avoid damage to external control

MOSFETs due to rapidly switching transient

between VBAT+ and VBAT- terminals. The

overcurrent condition returns to the normal mode

when the load is released and the impedance

between the VBAT+ and VBAT- terminals is 10MΩ or

higher. For the sake of protection of the external

MOSFETs, the larger the CS pin voltage (which

means the larger discharge current) the shorter

the overcurrent delay time. The relationship

between voltage of CS pin and overcurrent delay

7

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