AIC1804 Datasheet, PDF (9/12 Pages) Analog Intergrations Corporation – Three- Or Four-Cell Lithium-Ion Battery Protection IC

to protection of external MOSFETs
Cell-Balancing Bleeding after
Overcharge
When either of the battery cells is overcharged,
the AIC1804 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 (V_OCR or V_OCP-V_HYS).
Connecting UD1, UD2, UD3 and UD4 pins to the
positive terminals of battery cells BAT1, BAT2,
BAT3 and BAT4 accomplish this function,
respectively. Inserting resistors along UD2 pin to
BAT2 positive terminal path and UD4 pin to
BAT4 positive terminal path can decrease the
bleeding current.
Power-Down after Overdischarge
When overdischarge occurs, the AIC1804 will go
into power-down mode, turning off all the timing
generation and detection circuitry to reduce the
quiescent current to about 2.2µA (V_CC=9.2V). In
the unusual case where one battery cell is
overdischarged while another one under
overcharge condition, the AIC1804 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
AIC1804 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
AIC1804
V_CH).
DESIGN GUIDE
Cell Number Selection
The user must configure the AIC1804 for three
or four series cells application. For three-cell
application, NSL pin should be connected
directly to VCC pin. For four-cell application,
NSL pin should be connected directly to GND
pin.
No. of Series Cells
3-cell
4-cell
NSL Pin
Connected to VCC
Connected to GND
The protection circuit for three-cell lithium-ion
battery pack is shown in application examples
Fig. 1.
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.
C_TC ‚C_TD(nF)
1
5
10
22
33
47
68
82
100
T_OC ‚T_OD(mS)
21
52
132
253
347
617
748
1004
1630
The delay time can also be approximately
calculated by the following equations (if C_TC, C_TD
≤ 82nF) :
T_OC (mS) = 11.8 x C_TC(nF)
T_OD (mS) = 11.8 x C_TD(nF)
Setting the Overcurrent Delay Time 1
The overcurrent delay time 1 (T_OI1) at 0.15V <
9