MP2618
The Future of Analog IC Technology
2A, 24V Input, 600kHz
2-3 Cell Switching Li-Ion Battery Charger
With System Power Path Management
DESCRIPTION
FEATURES
The MP2618 is a monolithic switching charger
for 2-3 cell Li-Ion battery packs with a built-in
internal power MOSFET. It achieves up to 2A
charge current with current mode control for
fast loop response and easy compensation.
The charge current can be programmed by
sensing the current through an accurate sense
resistor.
•
•
•
•
MP2618 regulates the charge voltage and
charge current using two control loops to realize
high accuracy CC charge and CV charge.
The system power path management function
ensures continuous supply to the system by
automatically selecting the input or the battery.
Power path management separates charging
current from system load. When the MP2618
realizes current sharing of the input current,
charge current will drop down according to the
increase of the system current.
Fault condition protection includes cycle-by-cycle
current limiting, and thermal shutdown. Other
safety features include battery temperature
monitoring, charge status indication and
programmable timer to cease the charging cycle.
•
•
•
•
•
•
•
•
•
•
Charges 2-3 cell Li-Ion battery packs
Wide Operating Input Range
Up to 2A Programmable Charging Current
Power Path Management with Current
Sharing
±0.75% VBATT Accuracy
0.28Ω Internal Power MOSFET Switch
Up to 90% Efficiency
Fixed 600kHz Frequency
Preconditioning for fully depleted batteries
Charging Operation Indicator
Input Supply and battery fault indicator
Thermal Shutdown
Cycle-by-Cycle Over Current Protection
Battery Temperature Monitor and Protection
APPLICATIONS
•
•
•
•
Netbook PC
Distributed Power Systems
Chargers for 2-Cell or 3-Cell
Batteries
Pre-Regulator for Linear Regulators
Li-Ion
“MPS” and “The Future of Analog IC Technology” are Registered Trademarks
of Monolithic Power Systems, Inc.
The MP2618 is available in a 28-pin, 4mmx5mm
QFN package.
MP2618 Rev. 0.92
7/14/2010
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1
MP2618 – 2A, 24V INPUT, 600kHz 2-3CELL SWITCHING LI-ION BATTERY CHARGER
TYPICAL APPLICATION
M3
M1
RS2
VIN
VSYS
20m
C10
10µF
R1 510
R2 510
RG2
51
RG1
51
LED1
RG1
PIN
OUT1
VREF33
C3
10µF
C7
0.1µF
MP2618
VREF25
D1
VBAT
C9
22uF
2/3 cells
battery
RGS1 280
CSP
BATT
RGS2 280
NTC
RNTC
10k
RS1
110m
BST
CELLS
R3
10k
L
4.7µF
RG2
SW
AIN
C1
10µF
22uF
M2
LED2
CHGOK ACOK VCC
C2
4.7µF
C8
OUT2
NC
EN
ON OFF
SHDN
COMPV COMPI
R4
2.7k
C4
2.2nF
R5
750
GND TMR
CTMR
0.1uF
C5
2.2nF
Figure 1—Typical Application Circuit
MP2618 Rev. 0.92
7/14/2010
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MP2618 – 2A, 24V INPUT, 600kHz 2-3CELL SWITCHING LI-ION BATTERY CHARGER
ORDERING INFORMATION
Part Number*
Package
Top Marking
Free Air Temperature (TA)
MP2618EV
4mmx5mm QFN28
2618EV
-20°C to +85°C
* For Tape & Reel, add suffix –Z (eg. MP2618EV–Z).
For RoHS compliant packaging, add suffix –LF (eg. MP2618EV–LF–Z)
PACKAGE REFERENCE
TOP VIEW
AIN
PIN
SW
SW
BST
TMR
28
27
26
25
24
23
N/C
1
22
N/C
NTC
2
21
GND
ACOK
3
20
CSP
CHGOK
4
19
BATT
VREF33
5
18
COMPI
VREF25
6
17
CELLS
EN
7
16
COMPV
SHDN
8
15
VCC
9
10
11
12
13
14
RG1
N/C
GND
N/C
OUT1 RG2
ABSOLUTE MAXIMUM RATINGS (1)
Thermal Resistance
Supply Voltage VIN ....................................... 26V
VSW ........................................-0.3V to VIN + 0.3V
VBS ....................................................... VSW + 6V
VCSP, VBATT,....................................-0.3V to +18V
All Other Pins ..................................-0.3V to +6V
(2)
Continuous Power Dissipation (TA = +25°C)
............................................................. 3.1W
Junction Temperature ...............................150°C
Lead Temperature ....................................260°C
Storage Temperature............... -65°C to +150°C
VCC, RG1, RG2 to GND...............-0.3V to +42V
Max Differential Input Voltage (RG1 to RG2). 5V
4mmx5mm QFN28..................40 ....... 9 .... °C/W
Recommended Operating Conditions
(4)
θJA
θJC
Notes:
1) Exceeding these ratings may damage the device.
2) The maximum allowable power dissipation is a function of the
maximum junction temperature TJ (MAX), the junction-to-ambient
thermal resistance θJA, and the ambient temperature TA. The
maximum allowable continuous power dissipation at any
ambient temperature is calculated by PD (MAX) = (TJ (MAX)TA)/θJA. Exceeding the maximum allowable power dissipation will
cause excessive die temperature, and the regulator will go into
thermal shutdown. Internal thermal shutdown circuitry protects
the device from permanent damage.
3) The device is not guaranteed to function outside of its operating
conditions.
4) Measured on JESD51-7, 4-layer PCB
(3)
Supply Voltage VIN ...........................5.5V to 24V
VCC, RG1, RG2 to GND..................2.5V to 40V
Operating Junct. Temp. (TJ)..... -20°C to +125°C
MP2618 Rev. 0.92
7/14/2010
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MP2618 – 2A, 24V INPUT, 600kHz 2-3CELL SWITCHING LI-ION BATTERY CHARGER
ELECTRICAL CHARACTERISTICS
VIN = 19V, TA = +25°C, CELLS=0V, unless otherwise noted.
Parameters
Symbol Condition
Terminal Battery Voltage
VBATT
CSP, BATT Current
Switch On Resistance
ICSP,IBATT
RDS(ON)
Switch Leakage
CELLS=0V
CELLS= Float
Charging disabled
Min
Typ
Max
Units
8.337
12.505
8.4
12.6
1
0.28
8.463
12.695
V
0
10
EN = 4V, VSW = 0V
CC Mode
Peak Current Limit
Trickle Mode
CC current
ICC
Trickle charge current
RS1=100mΩ
1.8
ITRICKLE
Trickle charge voltage threshold
Trickle charge hysteresis
Termination current threshold
Oscillator Frequency
Fold-back Frequency
Maximum Duty Cycle
Maximum current Sense Voltage
(CSP to BATT)
Minimum On Time
IBF
fSW
Under Voltage Lockout Threshold
Rising
Under Voltage Lockout Threshold
Hysteresis
Open-drain sink current
Vin min
blocking)
Temp
Falling
head-room
(reverse
VFB = 1.5V
Vdrain=0.3V
Stay at trickle charge,
CTMR=0.1µF
Time after IBF reached,
CTMR=0.1µF
Termination delay
NTC
High
Threshold
170
A
2
A
2.0
MP2618 Rev. 0.92
7/14/2010
2.2
A
10%
Icc
3
V/Cell
350
mV/Cell
10%
600
190
15%
Icc
kHz
kHz
%
200
230
mV
100
ns
3.2
3.4
V
200
1000
mV
5
mA
30
min
1
Min
4.0
100
V/cell
mV/Cell
RNTC=NCP18XH103 (0°C)
73
Recovery Hysteresis
RNTC=NCP18XH103, (50°C)
Recovery Hysteresis
3
30
2
%of
VREF33
Vin-Vbatt
180
Vrechg
%of
VREF33
mV
0.4
EN Input Low Voltage
EN Input High Voltage
µA
4.1
90
3
Dead-battery indication
NTC Low Temp Rising Threshold
VFB = 1.2V
VFB = 0V
VFB = 1.2V
VSENSE
tON
Recharge threshold at Vbatt
Recharge Hysteresis
5%
µA
Ω
1.8
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V
V
4
MP2618 – 2A, 24V INPUT, 600kHz 2-3CELL SWITCHING LI-ION BATTERY CHARGER
ELECTRICAL CHARACTERISTICS (continued)
VIN = 19V, TA = +25°C, CELLS=0V, unless otherwise noted.
Parameters
Symbol
EN Input Current
Thermal Shutdown
VREF25 output voltage
VREF33 output voltage
VREF33 load regulation
Input Current Sense Section
Supply Voltage
Supply Current
Common Mode Input Voltage(5)
OUT1 Input Offset Voltage
Input Bias Current
OUT1 Current Accuracy
No-Load OUT1 Error
Low-Level OUT1 Error
Shutdown Supply Current
SHDN Threshold Voltage
Min
IAIN
VIN_CM
0.2
EN = 4V
0.5
mA
0.665
mA
EN = 0V,
CELLS=0V
150
2.5
3.3
30
ILOAD= 0A, VCC = 40V
VCC > VIN Low
VCC > VIN High
SHDN Hysteresis
tF
VSENSE = 40mV,
RGS = 20kΩ,
ROUT = 100kΩ,
RG1 = RG2 = 2kΩ,
CGS = 100pF,
COUT = 100pF, 10% to
90%
µA
2.0
2.5
OWN
OUT1 Rise, Fall Time (5)
Units
EN = 0V
VOS1
IRG1, IRG2
IRG1/IGS VSENSE = 100mV
VSENSE = 0V
VSENSE = 5mV
IIN(SHDN) VSHDN = 3V
VTH_SHUTD
(Low Æ High)
tR
Max
4
ILOAD=0 to 10mA
VCC
IIN
Typ
EN = 4V
EN = 4V,
Consider VREF33 pin
output current.
R3=10k,RNTC=10k
Supply Current (Shutdown)
Supply Current (Quiescent)
Condition
12
1.4
40
0.4
4
±2
0.1
0.3
3
0.7
0.9
mA
°C
V
V
mV
40
30
2
20
±5
1
2
6
V
µA
V
V
mV
nA
%
µA
µA
µA
1.2
V
30
mV
17
µs
29
µs
OUT1 Output Voltage Range
VGS
VCC –
0.15
Maximum OUT1 Current (5)
IGS
500
24
V
µA
Notes:
5) Input common mode range cannot exceed the supply voltage.
MP2618 Rev. 0.92
7/14/2010
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MP2618 – 2A, 24V INPUT, 600kHz 2-3CELL SWITCHING LI-ION BATTERY CHARGER
PIN FUNCTIONS
Pin #
Name
1,10,12,22
NC
2
3
4
5
6
No Connection
Thermistor Input. Connect a resistor from this pin to the pin VREF33 and the Thermistor
NTC
from this pin to ground.
Valid Input Supply Indicator. A logic LOW on this pin indicates the presence of a valid
ACOK input supply.
Charging status Indicator. A logic LOW indicates charging operation. The pin will become
CHGOK an open drain once the charging is stopped.
Internal linear regulator 3.3V reference output. Bypass to GND with a 1µF ceramic
VREF33
capacitor.
VREF25 Internal linear regulator 2.5V reference output.
7
EN
8
SHDN
9
RG1
11, 21
Description
On/Off Control Input.
Shutdown control of current sense amplifier. Connect this pin to EN .
Gain Resistor of current sense amplifier.
Ground. This pin is the voltage reference for the regulated output voltage. For this reason
GND,
care must be taken in its layout. This node should be placed outside of the D1 to C1
Exposed
ground path to prevent switching current spikes from inducing voltage noise into the part.
Pad
Connect exposed pad to ground plane for optional thermal performance.
13
OUT1
Output for Driving Resistor Load.
14
RG2
Gain Resistor of current sense amplifier.
15
VCC
Power Input of current sense amplifier.
16
COMPV VLOOP Compensation. Decouple this pin with a capacitor and a resistor.
17
CELLS
18
COMPI ILOOP Compensation. Decouple this pin with a capacitor and a resistor.
Command Input for the Number of Li-Ion Cells. Make this pin float for 3-cell operation or
connect this pin to ground for 2-cell operation.
19
BATT
Positive Battery Terminal.
20
CSP
Battery Current Sense Positive Input. Connect a resistor RS1 between CSP and BATT.
23
TMR
24
BST
25, 26
SW
Switch Output.
27
PIN
Power Supply Voltage. The MP2618 operates from a +5.5V to +24V unregulated input.
C1 is needed to prevent large voltage spikes from appearing at the input.
28
AIN
Controller Supply Voltage.
MP2618 Rev. 0.92
7/14/2010
Set time constant. 0.1uA charge and discharge the external cap. Connect TMR pin to
GND to disable the internal timer.
Bootstrap. This capacitor is needed to drive the power switch’s gate above the supply
voltage. It is connected between SW and BST pins to form a floating supply across the
power switch driver.
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MP2618 – 2A, 24V INPUT, 600kHz 2-3CELL SWITCHING LI-ION BATTERY CHARGER
TYPICAL PERFORMANCE CHARACTERISTICS
VIN=19V, C1=10µF, C2=4.7µF, C9=22µF, L=4.7µH, RS1=110mΩ, RS2=20mΩ, Real Battery Load,
TA=25ºC, unless otherwise noted.
2 Cells ICHG vs. VBATT Curve
8.5
3 Cells Battery Charge Curve
2.5
2.5
12.8
1.5
8
7.9
1
7.8
IBATT
7.7
0.5
7.6
0
20
3 Cells ICHG vs. VBATT Curve
VIN=12V
1
VIN=24V
0.5
100.0
VIN=15V
VIN=19V
EFFICIENCY(%)
1.5
VIN=24V
1
2
4
6
8
BATTERY VOLTAGE(V)
VIN=19V
0.5
70.0
0
60.0
VIN=24V
1.5
12
11.8
IBATT
1
11.6
11.4
0.5
11.2
0
0
2
4
6
8
10
12
14
0
0.4
0.8
VIN=15V
90.0
VIN=19V
VIN=24V
80.0
70.0
3 Cells Battery
8.4
8.4
BATT VOLTAGE(V)
8.5
8.3
8.2
VIN (V)
MP2618 Rev. 0.92
7/14/2010
0.4
28
1.2
1.6
2
Charge Current
vs. Temperature
8.2
8
-20
0.8
ICHG (A)
8.3
2 Cells Battery
2 Cells Battery
23
0
2.2
8.1
8.1
18
2
BATT Float Voltage
vs. Temperature
8.5
13
1.6
60.0
ICHG (A)
BATT Float Voltage vs. VIN
88
1.2
0
150
50
100
TIMES(MIN)
2 Cells Battery
B ATTER Y V OL TAGE(V )
VBATT(V)
12.2
100.0
90.0
80.0
2
Effciency vs. ICHG
VIN=15V
VIN=12V
VBATT
12.4
11
10
0
20
40
60
TEMPERATURE ( C)
O
80
C HA R G E C U R R E NT(A )
C HA R G E C U R R E NT(A )
1.5
Effciency vs. ICHG
2.5
2
VIN=19V
0
0
0
100 120
40 60
80
TIMES(MIN)
BATTERY VOLTAGE(V)
8.1
2
EFFICIENCY(%)
2
VBATT
8.2
CHARGE CURRENT(A)
8.3
7.5
2.5
12.6
BATTERY CURRENT(A)
BATTERY VOLTAGE(V)
8.4
BATTERY CURRENT(A)
2 Cells Battery Charge Curve
2
1.8
1.6
1.4
2 Cells Battery
1.2
-20
0
20
40
60
80
TEMPERATURE ( C)
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7
MP2618 – 2A, 24V INPUT, 600kHz 2-3CELL SWITCHING LI-ION BATTERY CHARGER
TYPICAL PERFORMANCE CHARACTERISTICS (continued)
VIN=19V, C1=10µF, C2=4.7µF, C9=22µF, L=4.7µH, RS1=110mΩ, RS2=20mΩ, Real Battery Load,
TA=25ºC, unless otherwise noted.
Efficiency vs. VIN
Current Sharing
NTC Control Window
VBATT=7.4V, ICHG=2A
3
2.5
Low Temp Off
2.5
2
89
86
83
5
10
MP2618 Rev. 0.92
7/14/2010
15
VIN (V)
20
1.5
High Temp On
1
High Temp Off
25
0
1.5
1
0.5
0.5
2 Cells Battery
80
2
Low Temp On
ICHG(A)
92
VNTC(V)
EFFICIENCY (%)
95
0
8
12
16
20
VIN (V)
24
28
0
0.5
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1
1.5
ISYS(A)
2
2.5
8
MP2618 – 2A, 24V INPUT, 600kHz 2-3CELL SWITCHING LI-ION BATTERY CHARGER
TYPICAL PERFORMANCE CHARACTERISTICS (continued)
VIN=19V, C1=10µF, C2=4.7µF, C9=22µF, L=4.7µH, RS1=110mΩ, RS2=20mΩ, Real Battery Load,
TA=25ºC, unless otherwise noted.
MP2618 Rev. 0.92
7/14/2010
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MP2618 – 2A, 24V INPUT, 600kHz 2-3CELL SWITCHING LI-ION BATTERY CHARGER
TYPICAL PERFORMANCE CHARACTERISTICS (continued)
VIN=19V, C1=10µF, C2=4.7µF, C9=22µF, L=4.7µH, RS1=110mΩ, RS2=20mΩ, Real Battery Load,
TA=25ºC, unless otherwise noted.
Power Path
Power Path
Management_Current Sharing Management_Steady State
2 Cells, ICHG = 2A, VBATT = 7.4V
VIN
10V/div.
VIN
10V/div.
VIN
10V/div.
VSW
10V/div.
VBATT
5V/div.
ISYS
1A/div.
IBATT
1A/div.
VBATT
5V/div.
IBATT
1A/div.
VSYS
5V/div.
ISYS
500mA/div.
IBATT
1A/div.
4s/div.
MP2618 Rev. 0.92
7/14/2010
2 Cells, ICHG = 2A, VBATT = 8V, ISYS=0.8A
1us/div.
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MP2618 – 2A, 24V INPUT, 600kHz 2-3CELL SWITCHING LI-ION BATTERY CHARGER
OPERATION
The MP2618 is a peak current mode controlled
switching charger for use with Li-Ion batteries.
Figure 2 shows the block diagram. At the
beginning of a cycle, M1 is off. The COMP
voltage is higher than the current sense result
from amplifier A1’s output and the PWM
comparator’s output is low. The rising edge of the
600 kHz CLK signal sets the RS Flip-Flop. Its
output turns on M1 thus connecting the SW pin
and inductor to the input supply.
The increasing inductor current is sensed and
amplified by the Current Sense Amplifier A1.
Ramp compensation is summed to the output of
A1 and compared to COMP by the PWM
comparator.
When the sum of A1’s output and the Slope
Compensation signal exceeds the COMP
voltage, the RS Flip-Flop is reset and M1 turns
off. The external switching diode D1 then
conducts the inductor current.
If the sum of A1’s output and the Slope
Compensation signal does not exceed the COMP
voltage, then the falling edge of the CLK resets
the Flip-Flop.
The MP2618 have two internal linear regulators
power internal circuit, VREF33 and VREF25. The
output of 3.3V reference voltage can also power
external circuitry as long as the maximum current
(50mA) is not exceeded. A 1µF bypass capacitor
is required from VREF33 to GND to ensure
stability.
Charge Cycle (Mode change: TrickleÆ CCÆ
CV)
The battery current is sensed via RS1 (Figure 2)
and amplified by A2. The charge will start in
“trickle charging mode” (10% of the RSEN
programmed current ICC) until the battery voltage
reaches 3V/cell. If the charge stays in the “trickle
charging mode” till “timer out” condition triggered,
and the charge is terminated. Otherwise, the
output of A2 is then regulated to the level set by
RS1. The charger is operating at “constant
current charging mode.” The duty cycle of the
switcher is determined by the COMPI voltage
that is regulated by the amplifier GMI.
MP2618 Rev. 0.92
7/14/2010
When the battery voltage reaches the “constant
voltage mode” threshold, the amplifier GMV will
regulate the COMP pin, and then the duty cycle.
The charger will then operate in “constant voltage
mode.”
Automatic Recharge
Once the battery charging current drops below
the termination threshold, the charger will cease
charging and the CHGOK pin becomes an open
drain. If for some reason, the battery voltage is
lowered to 4.0V/Cell, recharge will automatically
kick in.
Charger Status Indication
MP2618 has two open-drain status outputs:
CHGOK and ACOK . The ACOK pin pulls low
when an input voltage is greater than battery
voltage 300mV and over the under voltage
lockout threshold. CHGOK is used to indicate the
status of the charge cycle. Table 1 describes the
status of the charge cycle based on the
CHGOK and ACOK outputs.
Table 1―Charging Status Indication
ACOK
low
CHGOK
low
low
high
high
high
Charger status
In charging
End of charge, NTC fault,
timer out, thermal
shutdown EN disable
VIN –VBAT
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