AIC1803CCS datasheet(9/12 Pages) AIC

9 / 12 page

AIC1803

beyond the overdischarge delay time (T

OD) period,

discharging is inhibited by the turning-off of the

discharge

control

MOSFET

M1.

The

overdischarge delay time is set by the external

capacitor

TD.

Inhibition

discharging

immediately released when the voltage of the

overdischarge

cell

becomes

higher

than

the

overdischarge

release

voltage

ODR)

through

charging.

Overcurrent Protection

In normal

mode,

the

AIC1803

continuously

monitors the discharge current by sensing the

voltage of CS pin. If the voltage V

CC-VCS exceeds

the overcurrent protection voltage (VOIP) beyond

the

overcurrent

delay

time

(TOI) period, the

overcurrent

protection

circuit

operates

and

discharging is inhibited by the 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

BATT+

and

BATT-

terminals.

The

overcurrent condition returns to normal mode

when the load is released and the

impedance

between the BATT+ and BATT- terminals is

20M

Ω or higher.

The

AIC1803

provided

with

the

three

overcurrent detection levels (0.15V, 0.3V and

1.0V) and the three overcurrent delay time (T

OI1,

OI2 and TOI3) corresponding to each overcurrent

detection level. T

OI1 is set by the external capacitor

TI.

OI2

and T

OI3

default to 4mS and 300

µs

respectively, and can not be adjusted due to

protection of external MOSFETs

Cell-Balancing

Bleeding

after

Overcharge

When either of the battery cells is overcharged,

the AIC1803 provides the cell-balancing bleeding

function to discharge the overcharged cell at

about 9mA until the voltage of the overcharged

cell decreases to overcharge release voltage

OCR or VOCP-vHYS ). This function is accomplished

by connecting UD1, UD2, UD3 pins to the positive

terminals of battery cells BAT1, BAT2, BAT3

respectively.

The

bleeding

current

can

decreased by inserting resistors along UD1 pin to

BAT1 positive terminal path and UD3 pin to BAT3

positive terminal path.

Power-Down after Overdischarge

When overdischarge occurs, the AIC1803 will go

into power-down mode, turning off all the timing

generation and detection circuitry to reduce the

quiescent current to about 1.3

µA (V

CC=6.9V). In

the unusual case where one battery cell is

overdischarged

while

another

one

under

overcharge condition, the AIC1803 will turn off all

the detection circuitry except the overcharge

detection circuit for the cell under overcharge

condition.

Charge Detection after Overdischarge

When overdischarge 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 AIC1803

immediately turns on all the timing generation and

detection circuitry and goes into normal mode.

Charging is determined to be in progress if the CS

pin voltage is higher than VCC + 0.4V (charge

detection threshold voltage V

CH).

• DESIGN GUIDE

Setting

the

Overcharge

and

Overdischarge Delay Time

The overcharge delay time is set by the external

capacitor C

TC and the overdischarge delay time is

set by the external capacitor C

TD. The relationship

between capacitance of the external capacitors

and delay time is tabulated as below.

AIC1803CCS Datasheet(PDF) 9 Page - Analog Intergrations Corporation

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