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EUP8202-4.2/8.4 Switch Mode Li-Ion/Polymer Battery Charger
DESCRIPTION
The EUP8202 is a constant current, constant voltage Li-Ion battery charger controller that uses a current mode PWM step-down (buck) switching architecture. With a 500kHz switching frequency, the EUP8202 provides a small, simple and efficient solution to fast charge one (4.2V) or two (8.4V) cell lithium-ion batteries. The EUP8202 charges the battery in three phases: conditioning, constant current, and constant voltage. An external sense resistor sets the charge current with O 10% accuracy. An internal resistor divider and precision www..com reference set the final float voltage to 4.2V per cell with O 1% accuracy. An internal comparator detects the near end-of-charge condition while an internal timer sets the total charge time and terminates the charge cycle. The EUP8202 automatically re-starts the charge if the battery voltage falls below an internal threshold, 4.05V per cell. The EUP8202 also automatically enters sleep mode when DC supplies are removed. The EUP8202 is available in the 8-lead SOP and 10-lead TDFN packages.
FEATURES
Wide Input Supply Voltage Range: 4.7V to 20V - 4.2 Version 8.9V to 20V - 8.4 Version 500kHz Switching Frequency End-of-Charge Current Detection Output 3 Hour Charge Termination Timer O 1% Charge Voltage Accuracy O 10% Charge Current Accuracy Low 10A Reverse Battery Drain Current Automatic Battery Recharge Automatic Trickle Charging of Low Voltage Batteries Automatic Sleep Mode for Low Power Consumption Battery Temperature Sensing Stable with Ceramic Output Capacitor 8-Lead SOP and 10-Lead TDFN Packages RoHS Compliant and 100% Lead (Pb)-Free
APPLICATIONS
Small Notebook Computer Portable DVD Handheld Instruments
Typical Operating Performance
Efficiency vs Input voltage
100
Efficiency vs Input voltage
100
(Curves include input diode)
95 90
(Curves include input diode)
95 90
EFFICIENCY(%)
85 80 75 70 65 60 8 10 12 14 16 18 20
EFFICIENCY(%)
EUP8202-8.4 VBAT=7.0V VBAT=8.0V
85 80 75 70 65 60 5 10 15 20
EUP8202-4.2 VBAT=3.8V VBAT=4.0V
Input Voltage (V)
Input Voltage (V)
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Typical Application Circuit
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Figure 1. 2A Single/Dual Cells Li-Ion Battery Charger
Figure 2. 1.5A Single/Dual Cells Li-Ion Battery Charger
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Block Diagram
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Figure 3.
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Pin Configurations
Package Type Pin Configurations Package Type Pin Configurations
TDFN-10
SOP-8
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Pin Description
PIN TDFN-10 SOP-8 DESCRIPTION Compensation, Soft-Start and Shutdown Control Pin. Charging begins when the COMP pin reaches 850mV. The recommended compensation components are a 2.2F (or larger) capacitor and a 0.5k series resistor. A 100A current into the compensation capacitor also sets the soft-start slew rate. Pulling the COMP pin below 280mV will shut down the charger. Positive Supply Voltage Input. Gate Drive Output. Driver Output for the external P-Channel MOSFET. The voltage at this pin is internally clamped to 8V below VCC, allowing a low voltage MOSFET with gate-to-source breakdown voltage of 8V or less to be used. IC Ground. Charge Status Output. Battery Sense Input. A bypass capacitor of 22F is required to minimize ripple voltage. When VBAT is within 250mV of VCC, the EUP8202 is forced into sleep mode, dropping ICC to 10A. Current Amplifier Sense Input. A sense resistor, RSENSE, must be connected between the SENSE and BAT pins. The maximum charge current is equal to 100mV/RSENSE. NTC (Negative Temperature Coefficient) Thermistor Input. With an external 10k NTC thermistor to ground, this pin senses the temperature of the battery pack and stops the charger when the temperature is out of range. To disable the temperature qualification function, ground the NTC pin. No Connect.
COMP
1
1
VCC
GATE
2 3 4 5 6 7 8
2
3
PGND SGND
GND
4 5 6 7
CHRG
BAT SENSE
NTC NC
9 10
8 -
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Ordering Information
Order Number Package Type Marking Operating Temperature range
EUP8202-42JIR1 EUP8202-84JIR1 EUP8202-42DIR1 EUP8202-84DIR1
TDFN-10 TDFN-10 SOP-8 SOP-8
xxxxx P8202 1N xxxxx P8202 1P xxxxx P8202 1N xxxxx P8202 1P
-40 C to 85C -40 C to 85C -40 C to 85C -40 C to 85C
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EUP8202- 1/4
1/4
1/4
1/4
1/4
Lead Free Code 1: Lead Free 0: Lead Packing R: Tape & Reel Operating temperature range I: Industry Standard Package Type J: TDFN D:SOP Output Voltage Option
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Absolute Maximum Ratings
Supply Voltage (Vcc) ----------------------------------------------------------------------------------22V GATE ----------------------------------------------------------------------------------------- (Vcc-8V) to Vcc BAT, SENSE ------------------------------------------------------------------------------------- -0.3V to 14V
CHRG ,NTC -----------------------------------------------------------------------------------------
-0.3V to 8V J
Operating Temperature Range ---------------------------------------------------------------- -40J to 85J Storage Temperature Range ------------------------------------------------------------------ -65 to 125 J Lead Temperature (Soldering, 10sec) -------------------------------------------------------------------- 260J
Electrical Characteristics (TA = 25J , VCC = 10V, unless otherwise noted.) Symbol
DC Characteristics
VCC VCC www..comSupply Voltage Current Mode ICC VCC Supply Current Shutdown Mode Sleep Mode VBAT(FLT) Battery Regulated Float Voltage 5VO VSNS(CHG) Constant Current Sense Voltage VSNS(TRKL) Trickle Current Sense Voltage Trickle Charge Threshold VTRKL Voltage VCC Undervoltage Lockout VUV Threshold Voltage VCC Undervoltage Lockout VUV Hysteresis Voltage Manual shutdown Threshold VMSD Voltage Automatic shutdown Threshold VASD Voltage ICOMP COMP Pin Output Current ICHRG VCHRG REOC tTIMER INTC VNTC-HOT VNTC-COLD 3VO VCC O VBAT O 20V 0JO 4V 0JO TA O TA O 85J 85J 4.158 90 8 2.75 3.9 4.7 1.5 1.5 10 4.2 100 15 2.9 4.2 200 COMP Pin Falling VCC - VBAT VCOMP = 1.2V VCHRG = 1V ICHRG = 1mA VSNS(EOC) /VSNS(CHG) 0JO -40JO TA O TA O 50J 85J 10 75 70 340 2.35 15 150 280 250 100 25 20 25 85 85 360 5 2.4 100 2.45 35 50 32 10 VNTC = 0.85V VNTC = Falling Hysteresis VNTC = Rising Hysteresis 95 100 380 450 20 5 5 20 4.242 110 22 3.05 4.5 V mA mA A V mV mV V V mV mV mV A A mV % % A A mV mV V mV
Parameter
Conditions
EUP8202-4.2 Min. Typ. Max.
Unit
VBAT = 1V VBAT = Rising VCC = Rising
CHRG Pin Weak Pull-Down
Current
CHRG Pin Output Low Voltage End-of-Charge Ratio
Charge time Accuracy NTC Pin Output Current NTC Pin Thershold Voltage (Hot) NTC Pin Thershold Voltage (Cold)
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Electrical Characteristics (TA = 25J , VCC = 10V, unless otherwise noted.) Symbol Parameter Conditions EUP8202-4.2 Unit Min. Typ. Max.
100 150 200 1 mV A
Recharge Battery Voltage Offset VBAT(FULLCHARGD) -VRECHRG, VBAT VRECHRG from Full Charged Battery Falling Voltage ILEAK
CHRG Pin Leakage Current
Switching Frequency Maximum Duty Cycle
VCHRG= 8V, Charging Stops 450 500
Oscillator
fOSC DC 550 100 kHz %
Gate Drive
tr tf Rise Time Fall Time Output Clamp Voltage CGATE =2000pF, 10% to 90% CGATE =2000pF, 10% to 90% VCC -VGATE , VCCU 9V -40JO TA O 85J 20 50 8 0.3 4.5 ns ns V V V
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VGATE
VGATEHI Output High Voltage VGATELO Output Low Voltage
VGATEHI= VCC -VGATE , VCCU 7V VGATELO= VCC -VGATE , VCCU
CC
7V
Electrical Characteristics (TA = 25J, V Symbol
DC Characteristics
VCC ICC VCC Supply Voltage
= 12V, unless otherwise noted.)
Parameter
Conditions
EUP8202-8.4 Min. Typ. Max.
8.9 20 1.5 1.5 10 5 5 20 8.484 110 22 5.3 8.5
Unit
V mA mA A V mV mV V V mV
Current Mode VCC Supply Current Shutdown Mode Sleep Mode VBAT(FLT) Battery Regulated Float Voltage 9VO VSNS(CHG) Constant Current Sense Voltage 6VO VCC O VBAT O 20V 0JO 8V 0JO TA O TA O 85J 85J 8.316 90 8 4.7
8.4 100 15 5 7.5 500
VSNS(TRKL) Trickle Current Sense Voltage VBAT = 1V Trickle Charge Threshold VTRKL VBAT = Rising Voltage VCC Undervoltage Lockout VCC = Rising VUV Threshold Voltage VCC Undervoltage Lockout VUV Hysteresis Voltage Manual shutdown Threshold VMSD COMP Pin Falling Voltage Automatic shutdown Threshold VASD VCC - VBAT Voltage ICOMP COMP Pin Output Current VCOMP = 1.2V ICHRG
150
280 250 100
450
mV mV A
CHRG Pin Weak Pull-Down
Current
VCHRG = 1V
15
25
35
A
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Electrical Characteristics (TA = 25J , VCC = 12V, unless otherwise noted.) Symbol
VCHRG REOC tTIMER INTC VNTC-HOT VNTC-COLD
Parameter
CHRG Pin Output Low Voltage End-of-Charge Ratio
Charge time Accuracy NTC Pin Output Current NTC Pin Thershold Voltage (Hot) NTC Pin Thershold Voltage (Cold) ICHRG = 1mA
Conditions
EUP8202-8.4 Unit Min. Typ. Max.
20 5 15 85 85 360 5 2.35 2.4 100 200 300 400 1 2.45 50 25 10 95 100 380 mV % % A A mV mV V mV mV A
VSNS(EOC) /VSNS(CHG) 0JO -40JO TA O TA O 50J 85J
VNTC = 0.85V VNTC = Falling Hysteresis VNTC = Rising Hysteresis
75 70 340
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Recharge Battery Voltage Offset VBAT(FULLCHARGD) -VRECHRG, VBAT VRECHRG from Full Charged Battery Falling Voltage ILEAK
CHRG Pin Leakage Current
Switching Frequency Maximum Duty Cycle
VCHRG= 8V, Charging Stops 450 500
Oscillator
fOSC DC 550 100 kHz %
Gate Drive
tr tf VGATE Rise Time Fall Time Output Clamp Voltage CGATE =2000pF, 10% to 90% CGATE =2000pF, 10% to 90% VCC-VGATE , VCCU 9V 40JO TA O 85J 20 50 8 0.3 4.5 ns ns V V V
VGATEHI Output High Voltage VGATELO Output Low Voltage
VGATEHI= VCC -VGATE , VCCU 7V VGATELO= VCC -VGATE , VCCU 7V
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Typical Operating Characteristics
Supply Current vs Vcc
2.0
Oscillator Frequency vs Temperature
540
(Current mode)
1.8
520
1.6
fosc(kHz)
Icc(mA)
500
1.4
480
1.2
460
1.0 5 10 15 20
-40
-20
0
20
40
60
80
100
120
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Vcc (V)
TEMPERATURE(C)
Supply Current vs Temperature
4.0
9
Undervoltage Lockout Threshold vs Temperature
3.5
8
3.0
7
2.5
Vuv(V)
Icc(mA)
6
2.0
EUP8202-4.2 EUP8202-8.4
5
1.5
4
1.0
3
0.5 -40 -20 0 20 40 60 80 100 120
-40
-20
0
20
40
60
80
100
120
TEMPERATURE(C)
TEMPERATURE(C)
Oscillator Frequency vs Vcc
540
520
fosc(kHz)
500
480
460
5
10
15
20
Vcc (V)
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Typical Operating Characteristics (continued)
CHRG Pin Output Low Voltage vs Vcc
30
CHRG Pin Weak Pull-Down Current vs Vcc
28
Iload=1mA
VCHRG=8V
25
26
VCHRG(mV)
20
ICHRG(V)
24
15
10 5 10 15 20
22 5 10 15 20
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Vcc (V)
Vcc (V)
CHRG Pin Output Low Voltage vs Temperature
25
Recharge Voltage Offset from Full Charged Voltage vs Vcc
160
Iload=1mA
EUP8202-4.2
20
155
15
VRECHARGE(mV)
-40 -20 0 20 40 60 80 100 120
V CH R G (m V )
150
10
145
5
140 5 10 15 20
TEMPERATURE(C)
Vcc (V)
CHRG Pin Weak Pull-Down Current vs Temperature
32
Recharge Voltage Offset from Full Charged Voltage vs Vcc
320 315
VCHRG=8V
30
310
EUP8202-8.4
VRECHARGE(mV)
-40 -20 0 20 40 60 80 100 120
28
305 300 295 290 285
ICHRG(V)
26
24
22
280 5 10 15 20
TEMPERATURE(C)
Vcc (V)
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Typical Operating Characteristics (continued)
COMP Pin Output Current vs Vcc
104
Current Mode Sense Voltage vs Vcc
102
VBAT=4.0V EUP8202-4.2
100
VCOMP=1.2V
102
VSNS(mV)
98
ICOMP(V)
100
98
96
96
94 5 10 15 20
94 5 10 15 20
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Vcc (V)
Vcc (V)
Current Mode Sense Voltage vs Vcc
106
COMP Pin Output Current vs Temperature
120
VBAT=8V EUP8202-8.4
104
VCOMP=1.2V
118 116 114
ICOMP(A)
VSNS(mV)
112 110 108 106 104 102
102
100
98 5 10 15 20
-40
-20
0
20
40
60
80
100
120
Vcc (V)
TEMPERATURE(C)
Current Mode Sense Voltage vs Temperature
104 103 102 101
VSNS(mV)
100 99 98 97 96 -40 -20 0 20 40 60 80 100 120
TEMPERATURE(C)
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Typical Operating Characteristics (continued)
Trickle Charge Voltage vs Temperature
3.00
Trickle Charge Voltage vs Vcc
5.2
EUP8202-4.2
EUP8202-8.4
2.95
5.1
VTRKL(V)
VTRKL(V)
2.90
5.0
2.85
4.9
2.80 -40 -20 0 20 40 60 80 100 120
4.8 5 10 15 20
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TEMPERATURE(C)
Vcc (V)
Trickle Charge Voltage vs Vcc
3.0
Trickle Charge Sense Voltage vs Temperature
20
EUP8202-4.2
18
VBAT=2.5V EUP8202-4.2
16
VTRKL(V)
VSNS(mV)
2.9
14
12
10
2.8 5 10 15 20
8 -40 -20 0 20 40 60 80 100 120
Vcc (V)
TEMPERATURE(C)
Trickle Charge Voltage vs Temperature
5.2
Trickle Charge Sense Voltage vs Vcc
25
EUP8202-8.4
20
VBAT=2.5V EUP8202-4.2V
5.1
VTRKL(V)
VSNS(mV)
5.0
15
4.9
10
4.8 -40 -20 0 20 40 60 80 100 120
5 5 10 15 20
TEMPERATURE(C)
Vcc (V)
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Typical Operating Characteristics (continued)
Trickle Charge Sense Voltage vs Temperature
20
22
End-of-Charge Ratio vs Temperature
EUP8202-8.4
20
18
VBAT=4V EUP8202-8.4
16
18
VSNS(mV)
14
REOC(%)
16
12
14
10
8 -40 -20 0 20 40 60 80 100 120
12 -40 -20 0 20 40 60 80 100 120
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TEMPERATURE(C)
TEMPERATURE(C)
Trickle Charge Sense Voltage vs Vcc
25
End-of-Charge Ratio vs Vcc
EUP8202-4.2
28
VBAT=4V EUP8202-8.4V
20
26
VSNS(mV)
15
REOC(%)
24
10
22
5 5 10 15 20
5
10
15
20
Vcc (V)
Vcc (V)
End-of-Charge Ratio vs Temperature
30
22
End-of-Charge Ratio vs Vcc
EUP8202-8.4
EUP8202-4.2
28
20
REOC(%)
REOC(%)
26
18
24
16
22
20 -40 -20 0 20 40 60 80 100 120
14 5 10 15 20
TEMPERATURE(C)
Vcc (V)
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Typical Operating Characteristics (continued)
NTC Pin Output Current vs Temperature
94
NTC Pin Output Current vs Vcc
88
VNTC=0V
92
VNTC=0V
90
INTC(V)
INTC(V)
-40 -20 0 20 40 60 80 100 120
88
86
86
84
82
80
84 5 10 15 20
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TEMPERATURE(C)
Vcc (V)
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Application Information
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.
D
a
t
a
S
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t
4
U
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m
Figure 4. Operational Flow Chart
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OPERATION
The EUP8202 is a constant current, constant voltage Li-Ion battery charger controller that uses a current mode PWM step-down (buck) switching architecture. The charge current is set by an external sense resistor (RSENSE) across the SENSE and BAT pins. The final battery float voltage is internally set to 4.2V per cell. For batteries like lithium-ion that require accurate final float voltage, the internal 2.4V reference, voltage amplifier and the resistor divider provide regulation with O 1% accuracy. and the CHRG pin is forced high impedance. To restart the charge cycle, remove and reapply the input voltage or momentarily shut the charger down. Also, a new charge cycle will begin if the battery voltage drops below the recharge threshold voltage of 4.05V per cell. When the input voltage is present, the charger can be shut down (ICC =1.5mA) by pulling the COMP pin low. When the input voltage is not present, the charger goes into sleep mode, dropping ICC to 10A. This will greatly reduce the current drain on the battery and increase the standby time. A 10k NTC (negative temperature coefficient) thermistor can be connected from the NTC pin to ground for battery temperature qualification. The charge cycle is suspended when the temperature is outside of the 0X to C 50X window. C
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APPLICATIONS INFORMATION
Undervoltage Lockout (UVLO) An undervoltage lockout circuit monitors the input voltage and keeps the charger off until VCC rises above the UVLO threshold (4.2V for the 4.2 version, 7.5V for the 8.4 version) and at least 250mV above the battery voltage. To prevent oscillation around the threshold voltage, the UVLO circuit has 200mV per cell of built-in hysteresis. When specifying minimum input voltage requirements, the voltage drop across the input blocking diode must be added to the minimum VCC supply voltage specification. Trickle Charge and Defective Battery Detection At the beginning of a charge cycle, if the battery voltage is below the trickle charge threshold, the charger goes into trickle charge mode with the charge current reduced to 15% of the full-scale current. If the low-battery voltage persists for 30 minutes, the battery is considered defective, the charge cycle is terminated and the CHRG pin is forced high impedance.
Figure 5.Typical Charge Profile A charge cycle begins when the voltage at the VCC pin rises above the UVLO level and is 250mV or more greater than the battery voltage. At the beginning of the charge cycle, if the battery voltage is less than the trickle charge threshold, 2.9V for the 4.2 version and 5V for the 8.4 version, the charger goes into trickle charge mode. The trickle charge current is internally set to 15% of the full-scale current. If the battery voltage stays low for 30 minutes, the battery is considered faulty and the charge cycle is terminated. When the battery voltage exceeds the trickle charge threshold, the charger goes into the full-scale constant current charge mode. In constant current mode, the charge current is set by the external sense resistor RSENSE and an internal 100mV reference;
I TRKL =
VSNS(CHG) 100mV = R SENSE R SENSE When the battery voltage approaches the programmed float voltage, the charge current will start to decrease. When the current drops to 25% (4.2 version) or 15% (8.4 version) of the full-scale charge current, an internal comparator turns off the internal pull-down N-channel MOSFET at the CHRG pin, and connects a weak current source to ground to indicate a near end-of-charge condition. An internal 3 hour timer determines the total charge time. After a time out occurs, the charge cycle is terminated I CHG =
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VSNS(TRKL) 15mV = R SENSE R SENSE
Shutdown The EUP8202 can be shut down by pulling the COMP pin to ground which pulls the GATE pin high turning off the external P-channel MOSFET. When the COMP pin is released, the internal timer is reset and a new charge cycle starts. In shutdown, the output of the CHRG pin is high impedance and the quiescent current remains at 1.5mA. Removing the input power supply will put the charger into sleep mode. If the voltage at the VCC pin drops below (VBAT + 250mV) or below the UVLO level, the EUP8202 goes into a low current (ICC = 10A) sleep mode, reducing the battery drain current.
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CHRG Status Output Pin
When a charge cycle starts, the CHRG pin is pulled to ground by an internal N-channel MOSFET which is capable of driving an LED. When the charge current drops below the End-of-Charge threshold for more than 120s, the N-channel MOSFET turns off and a weak 25A current source to ground is connected to the CHRG pin. This weak 25A pull-down remains until the timer ends the charge cycle, or the charger is in manual shutdown or sleep mode. Table1: CHRG Status Pin Summary CHARGE STATE Trickle Charge in Process Constant Current Charge in Process Constant Voltage www..com Charge in Process
CHRG Pin
Strong On Strong On Strong On Strong On (remains the same) Hi-Z Hi-Z Weak On Weak On
Charge Suspend (Temperature) Timer Fault Sleep / Shutdown End of Charge Battery Disconnected
After a time out occurs (charge cycle ends), the pin will become high impedance. By using two different value resistors, a microprocessor can detect three states from this pin (charging, end-of-charge and charging stopped) see Figure 6.
pin changes to a high impedance state and the 390k resistor will then pull the pin high to indicate charging has stopped. Gate Drive The EUP8202gate driver can provide high transient currents to drive the external pass transistor. The rise and fall times are typically 20ns and 50ns respectively when driving a 2000pF load, which is typical for a P-channel MOSFET with RDS(ON) in the range of 50m. A voltage clamp is added to limit the gate drive to 8V below VCC. For example, if VCC is 10V then the GATE output will pull down to 2V max. This allows low voltage P-channel MOSFETs with superior RDS(ON) to be used as the pass transistor thus increasing efficiency. Stability Both the current loop and the voltage loop share a common, high impedance, compensation node (COMP pin). A series capacitor and resistor on this pin compensates both loops. The resistor is included to provide a zero in the loop response and boost the phase margin. The compensation capacitor also provides a soft-start function for the charger. Upon start-up, then ramp at a rate set by the internal 100A pullup current source and the external capacitor. Battery charge current starts ramping up when the COMP pin voltage reaches 0.85V and full current is achieved with the COMP pin at 1.3V. With a 2.2F capacitor, time to reach full charge current is about 10ms. Capacitance can be increased if a longer start-up time is needed. Automatic Battery Recharge After the 3 hour charge cycle is completed and both the battery and the input power supply (wall adapter) are still connected, a new charge cycle will begin if the battery voltage drops below 4.05V per cell due to self-discharge or external loading. This will keep the battery capacity at more than 80% at all times without manually restarting the charge cycle. Battery Temperature Detection A negative temperature coefficient (NTC) thermistor located close to the battery pack can be used to monitor battery temperature and will not allow charging unless the battery temperature is within an acceptable range. Connect a 10k thermistor from the NTC pin to ground. If the temperature rises to 50X the resistance of the C, NTC will be approximately 4.2k. With the 85A pull-up current source, the Hot temperature voltage threshold is 360mV. For Cold temperature, the voltage threshold is set at 2.4V which is equal to 0X (RNTC C 28k) with 85A of pull-up current. If the temperature is outside the window, the GATE pin will be pulled up to VCC and the timer frozen while the output status at the CHRG pin remains the same. The charge cycle begins or resumes once the temperature is within the acceptable
Figure 6. Microprocessor Interface To detect the charge mode, force the digital output pin, OUT, high and measure the voltage at the CHRG pin. The N-channel MOSFET will pull the pin low even with a 2k pull-up resistor. Once the charge current drops below the End-of-Charge threshold, the N-channel MOSFET is turned off and a 25A current source is connected to the CHRG pin. The IN pin will then be pulled high by the 2k resistor connected to OUT. Now force the OUT pin into a high impedance state, the current source will pull the pin low through the 390k resistor. When the internal timer has expired, the CHRG
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range. Short the NTC pin to ground to disable the temperature qualification feature. However the user may modify these thresholds by adding two external resistor. See figure 8. for filtering and has the necessary RMS current rating. Switching ripple current splits between the battery and the output capacitor depending on the ESR of the output capacitor and the battery impedance. EMI considerations usually make it desirable to minimize ripple current in the battery leads. Ferrite beads or an inductor may be added to increase battery impedance at the 500kHz switching frequency. If the ESR of the output capacitor is 0.2 and the battery impedance is raised to 4 with a bead or inductor, only 5% of the current ripple will flow in the battery. Design Example As a design example, take a charger with the following specifications: For single cell charge, VIN = 5V to 20V, VBAT = 4V nominal, IBAT =1.5A, fOSC = 500kHz, IEOC=0.375A, see Figure 2. First, calculate the SENSE resistor :
R SENSE = 100mV = 68m 1.5A
Figure 7. Temperature Sensing Configuration
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Figure 8. Temperature Sensing Thresholds Input and Output Capacitors Since the input capacitor is assumed to absorb all input switching ripple current in the converter, it must have an adequate ripple current rating. Worst-case RMS ripple current is approximately one-half of output charge current. Actual capacitance value is not critical. Solid tantalum capacitors have a high ripple current rating in a relatively small surface mount package, but caution must be used when tantalum capacitors are used for input bypass. High input surge currents can be created when the adapter is hot-plugged to the charger and solid tantalum capacitors have a known failure mechanism when subjected to very high turn-on surge currents. Selecting the highest possible voltage rating on the capacitor will minimize problems. Consult with the manufacturer before use. The selection of output capacitor COUT is primarily determined by the ESR required to minimize ripple voltage and load step transients. The output ripple VOUT is approximately bounded by:
VOUT I L ESR +
Choose the inductor for about 65% ripple current at the maximum VIN: 4V 4V L= = 6.56 H 1 - (500 kHz )(0.65)(1.5A ) 20V Selecting a standard value of 6.8H results in a maximum ripple current of :
I = 4V = 941.2mA 1 - (500kHz )(6.8H ) 20V 4V
L
I LPK = I
CHG
+
I
L = 1.5A + 941.2mA 1.975A 2 2
Next, choose the P-channel MOSFET. For example, a TSSOP-8 package with RDS(ON) = 42m (nom), 55m (max) offers a small solution. The maximum power dissipation with VIN = 5V and VBAT = 4V at 50J ambient temperature is: (1.5A )2 (55m )(4V ) = 0.099 W P= D 5V TJ = 50J + (0.099W)(65J /W) = 56.5J CIN is chosen for an RMS current rating of about 0.8A at 85J . The output capacitor is chosen for an ESR similar to the battery impedance of about 100m The ripple voltage on the BAT pin is:

1 8f OSC C OUT

Since IL increases with input voltage, the output ripple is highest at maximum input voltage. Typically, once the ESR requirement is satisfied, the capacitance is adequate
DS8202 Ver 1.1 Nov.2007
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EUP8202-4.2/8.4
VOUT ( RIPPLE ) =
=
I L(max ) (ESR ) 2
(0.94A )(0.1 ) = 47mV
2
For dual cells charge, VIN = 5V to 20V, VBAT = 8V nominal, IBAT =3A, fOSC = 500kHz, IEOC=0.45A,
R SENSE = 100mV = 33m 3A
Choose the inductor for about 50% ripple current at the maximum VIN:
8V = 6 .4 H 1 - www..com 0.5 )(3A ) 20 V (500 kHz )( L= 8V
Selecting a standard value of 6.8H results in a maximum ripple current of :
I = 8V = 1.441A 1 - (500kHz )(6.8H ) 20V 8V I
L
Board Layout Suggestions When laying out the printed circuit board, the following considerations should be taken to ensure proper operation of the EUP8202. GATE pin rise and fall times are 20ns and 50ns respectively (with CGATE = 2000pF). To minimize radiation, the catch diode, pass transistor and the input bypass capacitor traces should be kept as short as possible. The positive side of the input capacitor should be close to the source of the P-channel MOSFET; it provides the AC current to the pass transistor. The connection between the catch diode and the pass transistor should also be kept as short as possible. The SENSE and BAT pins should be connected directly to the sense resistor (Kelvin sensing) for best charge current accuracy. Avoid routing the NTC PC board trace near the MOSFET switch to minimize coupling switching noise into the NTC pin. The compensation capacitor connected at the COMP pin should return to the ground pin of the IC or as close to it as possible. This will prevent ground noise from disrupting the loop stability. The ground pin also works as a heat sink, therefore use a generous amount of copper around the ground pin. This is especially important for high VCC and/or high gate capacitance applications.
L = 3A + 1.441A 3.720 A CHG 2 2 The maximum power dissipation with VIN = 9V and VBAT = 8V at 50J ambient temperature is: I LPK = I + P= D
(3A )2 (55m )(8V ) = 0.44 W
9V
TJ = 50J
+ (0.44W)(65J /W) = 78.6J
I L(max ) (ESR ) 2
VOUT ( RIPPLE ) = =
(1.441A )(0.1 ) = 72mV
2
The Schottky diode D2 shown in Figure 2 conducts current when the pass transistor is off. In a low duty cycle case, the current rating should be the same or higher than the charge current. Also it should withstand reverse voltage as high as VIN.
DS8202 Ver 1.1 Nov.2007
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EUP8202-4.2/8.4
Packaging Information
TDFN-10
www..com
SYMBOLS A A1 D E1 E L b e D1
MILLIMETERS MIN. MAX. 0.70 0.80 0.00 0.05 2.90 3.10 1.70 2.90 3.10 0.30 0.50 0.18 0.30 0.50 2.40
INCHES MIN. 0.028 0.000 0.114 0.067 0.114 0.012 0.007 0.020 0.094 0.122 0.020 0.012 MAX. 0.031 0.002 0.122
DS8202 Ver 1.1 Nov.2007
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EUP8202-4.2/8.4
SOP-8
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SYMBOLS A A1 D E E1 L b e
MILLIMETERS MIN. 1.35 0.10 4.90 5.80 3.90 0.40 0.31 1.27 1.27 0.51 6.20 0.228 MAX. 1.75 0.25
INCHES MIN. 0.053 0.004 0.193 0.244 0.153 0.016 0.012 0.050 0.050 0.020 MAX. 0.069 0.010
DS8202 Ver 1.1 Nov.2007
21

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