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AIC1802
Two-Cell Lithium-Ion Battery Protection IC
n FEATURES
l
n DESCRIPTION
The AIC1802 battery protection IC is designed to protect lithium-ion batteries from damage due to overcharging, overdischarging, and overcurrent for two series cells in portable phones and laptop computers. It can be a part of the low-cost charge control system within a twocell lithium-ion battery pack. Safe and full utilization charging is ensured by the accurate 30mV overcharge detection. Three different specification values for overcharge protection voltage are provided for various protection requirements. The very low standby current drains little current from the cells while in storage.
Ultra-Low Quiescent Current at 10A (V CC =7V, VC =3.5V). Ultra-Low Power-Down Current at 0.2A (V CC =3.8V, VC =1.9V). Wide Supply Range: 2 to 18V. Precision Overcharge Protection Voltage 4.35V 30mV for the AIC1802A 4.30V 30mV for the AIC1802B 4.25V 30mV for the AIC1802C
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Built-in Delay Circuits for Overcharge, Overdischarge and Overcurrent Protection. Overcharge and Overdischarge Delay Time can be Extended by External Capacitors. Built-in Cell-balancing Bleeding Network under Overcharge Condition.
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n APPLICATIONS
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Protection IC for Two-Cell Lithium-Ion Battery Pack.
n TYPICAL APPLICATION CIRCUIT
V BAT+ **R1 C1 1 F C2 1 F **R2 M1 CEM9926 2 OD AIC1802 CS 7 8 VCC TC 5 *CTC 6 VC TD 3 *CTD 4 GND OC 1 R3 1M Q1 R6 1K M2 CEM9926
BATTERY 1
BATTERY 2
R4 1M R5 C3 0.01F 1M VBAT-
*CTC & CTD are optional for delay time adjustment. **R1 & R2: Refer application informations.
Protection Circuit for Two-Cell Lithium-Ion Battery Pack
DS-1802-03 July 13, 00 www.analog.com.tw
1
AIC1802
n
ORDERING INFORMATION
AIC1802 XCX PACKAGE TYPE S: SOP-8 OVERCHARGE PROTECTION VOLTAGE A: 4.35V B: 4.30V C: 4.25V
ORDER NUMBER
AIC1802ACS AIC1802BCS AIC1802CCS (PLASTIC SO8)
PIN CONFIGURATION
TOP VIEW
OC 1 OD 2 TD 3 GND 4
8 VC 7 CS 6 VC 5 TC
n ABSOLUTE MAXIMUM RATINGS
Supply Voltage ....................................... ... ... ... ... ..................................................... 18V 18V 5V DC Voltage Applied on VC, CS, OC, OD Pins .................. ... ... ... ... .............................. DC Voltage Applied on TC, TD Pins .................. ... ... ... ... ... ... ..... ... .............................. Operating Temperature Range Storage Temperature Range ............................ ... ... ... ... ... ... .....................
.......................................... .... ... ... ... .............. -40C~85C - 65C~150C
n TEST CIRCUIT
ICO 1 2 3
OC VCC
8
ICC VCC VCS
VOD
OD
CS 7 VC 6 TC 5
TD
IC VC
4 GND + CTD
AIC1802
+
CTC
2
AIC1802
n ELECTRICAL CHARACTERISTICS (Ta=25C, unless otherwise specified.)
PARAMETER
Supply Current in Normal Mode Supply Current in Power-Down Mode VC Pin Input Current
TEST CONDITIONS SYMBOL
VCC =7V, VC =3.5V VCC =4.8V, VC =2.4V VCC =7V, VC =3.5V AIC1802A ICC IPD IC
MIN.
TYP.
10 0.8 400
MAX.
15 1.2 600 4.38 4.33 4.28 4.15 2.55 3.15 165 38
UNIT
A A nA
4.32 VOCP 4.27 4.22 VOCR VODP VODR 3.85 2.25 2.85 135 12
4.35 4.30 4.25 4.0 2.4 3.0 150 25
Overcharge Protection Voltage
AIC1802B AIC1802C
V
Overcharge Release Voltage Overdischarge Protection Voltage Overdischarge Release Voltage Overcurrent Protection Voltage Overcharge Delay Time (1) VCC =7V VCC =8.6V, VC =4.3V, CTC =0F VCC =8.6V, VC =4.3V, CTC =0.47F VCC =4.8V, VC =2.4V, CTD =0F VCC =4.8V, VC =2.4V, CTD =0.47F VCC =7V, VC =3.5V, VCS=0.15V VCC =7V, VC =3.5V, VCS=0.36V VCC =8.6V, VC =4.3V, OC Pin Short to GND
V V V mV mS
VOIP TOC1
Overcharge Delay Time (2)
TOC2
0.7
1.1
1.5
S
Overdischarge Delay Time (1)
TOD1
12
25
38
mS
Overdischarge Delay Time (2)
TOD2
0.7
1.1
1.5
S
Overcurrent Delay Time (1)
TOI1
4
9
14
mS
Overcurrent Delay Time (2)
TOI2
1.0
2.0
3.0
mS
OC Pin Source Current OD Pin Output "H" Voltage
ICO VDL
270
400
530
A V
VCC -0.1 VCC -0.02
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AIC1802
n ELECTRICAL CHARACTERISTICS (Continued)
PARAMETER
OD Pin Output "L" Voltage Charge Detection Threshold Voltage Unbalance Discharge Current VCC =4.8V
TEST CONDITIONS SYMBOL
VDH VCH
MIN.
TYP.
0.01
MAX.
0.1
UNIT
V V
-0.55
-0.4
VCC =8.3V, VC =4V
IUD
5.4
7.7
10
mA
n TYPICAL PERFORMANCE CHARACTERISTICS
Supply Current vs. Supply Voltage
10.7
Power-down Current vs. Supply Voltage
0.8
10.5
10.3
Power-Down Current (A)
VC=1/2VC C TA=25C
Supply Current (A)
0.65
VC=1/2VCC TA=25C
0.5
10.1
9.9
0.35
9.7 5.5 6.5 7.5 8.5
0.2 3.8 4.3 4.8 5.3 5.8
Supply Voltage (V)
Supply Voltage (V)
Overcharge Protection Voltage vs. Temperature Overcurrent Protection Voltage (mV)
4.32
150
Overcurrent Protection Voltage vs. Temperature
VCC=7V VC=3.5V
Overcharge Protection Voltage (V)
4.315
147.5
AIC1802B
4.31
145
4.305
142.5
4.3 -20
140 -20 -10 0 10 20 30 40 50 60 70
-10
0
10
Temperature (C)
20
30
40
50
60
70
Temperature (C)
4
AIC1802
n TYPICAL PERFORMANCE CHARACTERISTICS (Continued)
Supply Current vs. Temperature
12.5
Power-Down Current vs. Temperature
1.1
Power-Down Current (A)
Supply Current (A)
VCC=7V VC=3.5V
11.5
VCC=4.8V VC=2.4V
0.9
10.5
0.7
9.5
8.5 -20 -10 0 10
0.5
Temperature (C)
20
30
40
50
60
70
-20
-10
0
10
20
30
40
50
60
70
Temperature (C)
Overdischarge Protection Voltage vs. Temperature Overdischarge Protection Voltage (V)
2.420
Overcharge Release Voltage vs. Temperature
4.025
2.415
2.410
2.405
2.400
2.395 -20
Overcharge Release Voltage (V)
4.020
4.015
4.010
-10
0
10
Temperature (C)
20
30
40
50
60
70
4.005 -20
-10
0
10
20
30
40
50
60
70
Temperature (C)
Overdischarge Release Voltage (V)
3.025
Overdischarge Release Voltage vs. Temperature
3.020
3.015
3.010
3.005 -20
-10
0
10
20
30
40
50
60
70
Temperature (C)
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AIC1802
n BLOCK DIAGRAM
VCC 8 450
OVERCHARGE DETECTOR 1
OVERCHARGE DELAY CIRCUIT
5 TC
OVERDISCHARGE DETECTOR 1
OVERDISCHARGE DELAY CIRCUIT
VC
6
UNBALANCE DISCHARGE LOGIC CONTROL POWERDOWN
3 TD VCC
OVERCHARGE DETECTOR 2
450 GND 4
OVERDISCHARGE DETECTOR 2
WAKEUP TIMING GENERATION
1
OC
OVERCURRENT DELAY CIRCUIT
OVERCURRENT DETECTOR
CHARGE DETECTION
OD
2
7
CS
n PIN DESCRIPTIONS
PIN 1: OC - PMOS open drain output for control of the charge control MOSFET M2. When overcharge occurs, this pin sources current to switch the external NPN Q1 on, and charging is inhibited by turning off the charge control MOSFET M2. - Output pin for control of discharge control MOSFET When overdischarge occurs, pin goes low to turn off discharge control MOSFET and discharging is inhibited. the M1. this the M1 PIN 5: TC PIN 6: VC - Overcharge delay time setting pin. - To be connected to the positive terminal of the lower cell and the negative terminal of the upper cell. - Input pin for current sensing. Using the drain-source voltage of the discharge control MOSFET M1 (voltage between CS and GND), it senses discharge current during normal mode and detects whether charging current is present during power down mode.
PIN 7: CS
PIN 2: OD
PIN 3: TD
- Overdischarge delay time setting pin.
PIN 4: GND - Ground pin. This pin is to be connected to the negative terminal of the lower battery cell.
PIN 8: VCC - Power supply pin. It is to be connected to the positive terminal of the upper cell.
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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 C . Inhibition of TC charging is immediately released when the voltage of the overcharged cell becomes lower than VOCR (overcharge release voltage) through discharge. 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 )
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.
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 T period, the OI 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 VBATterminals. The
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 0.8A (V CC =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
overcurrent condition returns to the normal mode when the load is released and the impedance between the VBAT+ and VBAT- terminals is 10M 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
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AIC1802
time TOI is tabulated as below. CTC (F) VCS (V) 150m 200m 300m 360m 1V 3V 5V TOI (S) 9.0m 5.6m 2.8m 0.47 2.0m 0.57 540 290 270 CTD (F) 0 0.1 TOD (S) 25m 320m 820m 1.08 1.39 1.43 0 0.1 0.3 TOC (S) 25m 320m 890m 1.12
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 below VOCR, the internal cell-balance "bleeding" will proceed until the voltage of the overcharged cell decreases to VOCR.
0.3 0.47 0.57
Selection of External Control MOSFETs
Because the overcurrent protection voltage is preset, the threshold current for overcurrent detection is determined by the turn-on resistance of the discharge control MOSFET M1. The turnon resistance of the external control MOSFETs
DESIGN GUIDE
Adjustment of Overcharge Overdischarge Delay Time and
can be determined by the equation: R =VOIP/IT ON (I T is the overcurrent threshold current). For example, if the overcurrent threshold current IT is designed to be 5A, the turn-on resistance of the external control MOSFETs must be 30m. Users should be aware that turn-on resistance of the MOSFET changes with temperature variation due to heat dissipation. It changes with the voltage between gate and source as well. (Turn-on resistance of a MOSFET increases as the voltage between gate and source decreases). Once the turn-on resistance of the external MOSFET
Both the overcharge and overdischarge delay times default to 25mS and can be extended by adding the external capacitors C TC and C TD , respectively. Increasing the capacitance value will increase the delay time. The relationship between capacitance of the external capacitors and delay time is tabulated as below:
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AIC1802
changes, the overcurrent threshold current will change accordingly.
release
voltage
and
bleeding
function.
The
relationship among Vrelease1,Vrelease2, R1, and R2 is shown as following equations: Vrelease1=VOCR+IUD*R1 Vrelease2=VOCR+IUD*R2 where Vrelease1 is Battery 1, real overcharge release voltage Vrelease2 is Battery 2, real overcharge release voltage Therefore, resistance of R1 and R2 should not higher than 30. Otherwise, overcharge release voltage would be higher than overcharge protection voltage and the charging current may oscillate. In addition, if overcharge protection function occurs, AIC1802 will discharge the overcharged cell and will stop bleeding function even if the voltage is not equal to the other. The recommended resistance of R1 and R2 is from 20 to 30.
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 necessary.
Controlling the Charge Control MOSFET
R3, R4, R5 and NPN transistor Q1 are used to switch the charge control MOSFET M2. If overcharge does not occur, no current flows out from OC pin and Q1 are turned off, then M2 is turned on. When overcharge occurs, current flows out from OC pin and Q1 is turned on, which turns off M2 in turn. High resistance for R3, R4, and R5 is recommended for reducing loading of the batteries.
Latch-Up Protraction at CS Pin
R6 is used for latch-up protection when charger is connected under overdischarge condition, and also for overstress protection when charger is connected in reverse. The charge detection function after overdischarge is possibly disabled by larger value of R6. Resistance of 1K is recommended.
Effect of C3
C3 has to be applied to the circuit. Because C3 will keep AIC1802 to be charged after overdischarge occurred. In addition, when the differential voltage between charger and battery pack is higher than 2.1V and overcharge protection function work, C3 will avoid battery pack from being charged even if the battery voltage lower than 4V (To avoid battery pack from being charged under charger malfunction situation). The battery pack can be charged again till remove it from charger.
Selection of R1 and R 2
R1 and R2 are used to avoid large current flow through the battery pack under the situation of IC damage or pin short. On the other hand, resistance of R1 and R2 will affect overcharge
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AIC1802
n
PHYSICAL DIMENSIONS
l 8 LEAD PLASTIC SO (unit: mm)
D
SYMBOL A A1
H E
MIN 1.35 0.10 0.33 0.19 4.80 3.80
MAX 1.75 0.25 0.51 0.25 5.00 4.00
B C D
e A C A1
E e H L
L
1.27(TYP) 5.80 0.40 6.20 1.27
B
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