Aic1802.doc

Two-Cell Lithium-Ion Battery Protection IC
n FEATURES
n DESCRIPTION
l Ultra-Low Quiescent Current at 10µA (VCC=7V, The AIC1802 battery protection IC is designed to protect lithium-ion batteries from damage due l Ultra-Low Power-Down Current at 0.2µA (VCC overcurrent for two series cells in portable phones and laptop computers. It can be a part of l Precision Overcharge Protection Voltage the low-cost charge control system within a two- Safe and full utilization charging is ensured by the accurate ±30mV overcharge detection.
l Built-in Delay Circuits for Overcharge, Over- discharge and Overcurrent Protection.
overcharge protection voltage are provided for l Overcharge and Overdischarge Delay Time can be Extended by External Capacitors.
various protection requirements. The very low standby current drains little current from the l Built-in Cell-balancing Bleeding Network under n APPLICATIONS
l Protection IC for Two-Cell Lithium-Ion Battery n TYPICAL APPLICATION CIRCUIT
*CTC & CTD are optional for delay time adjustment.
**R1 & R2: Refer application informations.
Protection Circuit for Two-Cell Lithium-Ion Battery Pack
Analog Integrations Corporation
4F, 9 Industry E. 9th Rd, Science-Based Industrial Park, Hsinchu, Taiwan n ORDERING INFORMATION
OVERCHARGEPROTECTION VOLTAGEA: 4.35VB: 4.30VC: 4.25V à 4.35V version, in SO-8 Package & Tape & n ABSOLUTE MAXIMUM RATINGS
.… … … … … . 18V
DC Voltage Applied on VC, CS, OC, OD Pins .… … … … … . 18V
DC Voltage Applied on TC, TD Pins .… … … … … … … .… … . 5V
.… .… … … … . -40°C~85°C
.… … … … … … … . - 65°C~150°C
n TEST CIRCUIT
n ELECTRICAL CHARACTERISTICS (TA=25°C, unless otherwise specified.)
PARAMETER
TEST CONDITIONS
n ELECTRICAL CHARACTERISTICS (Continued)
PARAMETER
TEST CONDITIONS
n TYPICAL PERFORMANCE CHARACTERISTICS
Fig. 2 Power-down Current vs. Supply Voltage Fig. 3 Overcharge Protection Voltage vs. Temperature Fig. 4 Overcurrent Protection Voltage vs. Temperature n TYPICAL PERFORMANCE CHARACTERISTICS (Continued)
Fig. 6 Power-Down Current vs. Temperature Fig. 7 Overdischarge Protection Voltage vs. Temperature Fig. 8 Overcharge Release Voltage vs. Temperature Overdischarge Release Voltage (V) 3.005-20 Fig. 9 Overdischarge Release Voltage vs. Temperature n BLOCK DIAGRAM
n PIN DESCRIPTIONS
turning off the charge controlMOSFET M2.
n APPLICATION INFORMATIONS
THE OPERATION
detection circuits except the overcharge detection circuit for the cell under overcharge condition.
Overcharge Protection
When the voltage of either of the battery cells Charge Detection after Overdischarge
When overcharge occurs, the discharge control charging is inhibited by the turning-off of the 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 charging is immediately released when the immediately turns on all the timing generation and voltage of the overcharged cell becomes lower 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 Overdischarge Protection
When the voltage of either of the battery cells Overcurrent Protection
voltage) beyond the overdischarge delay time monitors the discharge current by sensing the period, discharging is inhibited by the turning-off voltage of CS pin. If the voltage of CS pin exceeds VOIP (overcurrent protection voltage) beyond overcurrent delay time TOI period, the and can be extended by adding a capacitor C overcurrent protection circuit operates and Inhibition of discharging is immediately released discharging is inhibited by turning-off of the when the voltage of the overdischarged cell 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 Power-Down after Overdischarge
overcurrent condition returns to the normal mode When overdischarge occurs, the AIC1802 will go when the load is released and the impedance into power-down mode, turning off all the timing between the VBAT+ and VBAT- terminals is 10MΩ or generation and detection circuitry to reduce the higher. For the sake of protection of the external quiescent current to 0.8µA (VCC=4.8V). In the MOSFETs, the larger the CS pin voltage (which means the larger discharge current) the shorter overdischarged while the other under overcharge the overcurrent delay time. The relationship condition, the AIC1802 will turn off all the between voltage of CS pin and overcurrent delay Unbalanced Discharge after Overcharge
When either of the battery cells is overcharged, the AIC1802 will automatically discharge the overcharged cell at about 7.7mA until the voltage of the overcharged cell is equal to the voltage of the other cell. If the voltage of the other cell is Selection of External Control MOSFETs
below VOCR, the internal cell-balance “bleeding” Because the overcurrent protection voltage is will proceed until the voltage of the overcharged preset, the threshold current for overcurrent detection is determined by the turn-on resistance of the discharge control MOSFET M1. The turn- on resistance of the external control MOSFETs DESIGN GUIDE
can be determined by the equation: RON=VOIP/IT (IT is the overcurrent threshold current). For Adjustment of Overcharge and
example, if the overcurrent threshold current I Overdischarge Delay Time
designed to be 5A, the turn-on resistance of the Both the overcharge and overdischarge delay external control MOSFETs must be 30mΩ. Users times default to 25mS and can be extended by should be aware that turn-on resistance of the adding the external capacitors CTC and CTD, MOSFET changes with temperature variation due respectively. Increasing the capacitance value will to heat dissipation. It changes with the voltage increase the delay time. The relationship between between gate and source as well. (Turn-on capacitance of the external capacitors and delay resistance of a MOSFET increases as the voltage between gate and source decreases). Once the turn-on resistance of the external MOSFET changes, the overcurrent threshold current will release voltage and bleeding function. The relationship among Vrelease1,Vrelease2, R1, and Suppressing the Ripple and Disturbance
from Charger
To suppress the ripple and disturbance from charger, connecting C1 to cell 1 and C2 to cell 2 is Vrelease1 is Battery 1, real overcharge release Vrelease2 is Battery 2, real overcharge release Controlling the Charge Control MOSFET
R3, R4, R5 and NPN transistor Q1 are used to Therefore, resistance of R1 and R2 should not higher than 30Ω. Otherwise, overcharge release overcharge does not occur, no current flows out from OC pin and Q1 are turned off, then M2 is protection voltage and the charging current may turned on. When overcharge occurs, current flows oscillate. In addition, if overcharge protection out from OC pin and Q1 is turned on, which turns function occurs, AIC1802 will discharge the off M2 in turn. High resistance for R3, R4, and R5 overcharged cell and will stop bleeding function is recommended for reducing loading of the even if the voltage is not equal to the other. The recommended resistance of R1 and R2 is from 20 Latch-Up Protection at CS Pin
Effect of C3
R6 is used for latch-up protection when charger is C3 has to be applied to the circuit. Because C3 connected under overdischarge condition, and also for overstress protection when charger is overdischarge occurred. In addition, when the connected in reverse. The charge detection differential voltage between charger and battery function after overdischarge is possibly disabled by larger value of R6. Resistance of 1KΩ is protection function work, C3 will avoid battery pack from being charged even if the battery Selection of R1 and R 2
voltage lower than 4V (To avoid battery pack from R1 and R2 are used to avoid large current flow through the battery pack under the situation of IC situation). The battery pack can be charged again resistance of R1 and R2 will affect overcharge n PHYSICAL DIMENSIONS
l 8 LEAD PLASTIC SO (unit: mm)

Source: http://www.metatech.com.hk/datasheet/aic/battery_man_ic_pdf/Aic1802.pdf