MP2618EV-LF [MPS]
Power Supply Support Circuit, Adjustable, 1 Channel, 4 X 5 MM, ROHS COMPLIANT, MO-220VHGD-3, QFN-28;
| 型号： | MP2618EV-LF |
| 厂家： | 
MONOLITHIC POWER SYSTEMS |
| 描述： | Power Supply Support Circuit, Adjustable, 1 Channel, 4 X 5 MM, ROHS COMPLIANT, MO-220VHGD-3, QFN-28 |
| 文件： | 总19页 (文件大小：611K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
MP2618
2A, 24V Input, 600kHz
2-3 Cell Switching Li-Ion Battery Charger
With System Power Path Management
The Future of Analog IC Technology
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.
•
•
•
•
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
•
•
•
•
•
•
•
•
•
•
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.
APPLICATIONS
•
•
•
Netbook PC
Distributed Power Systems
Chargers for 2-Cell or 3-Cell Li-Ion
Batteries
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.
•
Pre-Regulator for Linear Regulators
“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
www.MonolithicPower.com
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© 2010 MPS. All Rights Reserved.
1
MP2618 – 2A, 24V INPUT, 600kHz 2-3CELL SWITCHING LI-ION BATTERY CHARGER
TYPICAL APPLICATION
M3
M1
RS2
20m
VIN
VSYS
C8
C10
10µF
RG2
51
RG1
51
22uF
LED1
LED2
R1 510
M2
510
R2
L
CHGOK ACOK VCC RG1 RG2
PIN
4.7µF
RS1
VBAT
C2
4.7µF
SW
2/3 cells
battery
C7
110m
C9
0.1µF
D1
22uF
BST
AIN
C1
10µF
CELLS
OUT1
CSP
RGS1 280
RGS2 280
VREF33
MP2618
R3
10k
C3
10µF
VREF25
NTC
BATT
RNTC
10k
OUT2
NC
EN
ON OFF
SHDN COMPV COMPI GND TMR
CTMR
0.1uF
R4
2.7k
R5
750
C4
2.2nF
C5
2.2nF
Figure 1—Typical Application Circuit
MP2618 Rev. 0.92
7/14/2010
www.MonolithicPower.com
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2
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
N/C
1
2
3
4
5
6
7
8
22
21
20
19
18
GND
NTC
ACOK
CSP
CHGOK
BATT
COMPI
VREF33
VREF25
17 CELLS
EN
COMPV
16
VCC
SHDN
15
9
10 11 12 13 14
RG1
N/C GND N/C
OUT1 RG2
ABSOLUTE MAXIMUM RATINGS (1)
Supply Voltage VIN ....................................... 26V
VSW........................................-0.3V to VIN + 0.3V
Thermal Resistance (4)
4mmx5mm QFN28..................40 ....... 9....°C/W
θJA
θJC
Notes:
VBS .......................................................VSW + 6V
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.
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
3) The device is not guaranteed to function outside of its operating
conditions.
4) Measured on JESD51-7, 4-layer PCB
Recommended Operating Conditions (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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© 2010 MPS. All Rights Reserved.
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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
Min
Typ
Max
8.463
12.695
Units
CELLS=0V
8.337
8.4
Terminal Battery Voltage
VBATT
V
CELLS= Float
ICSP,IBATT Charging disabled
RDS(ON)
12.505 12.6
CSP, BATT Current
1
µA
Switch On Resistance
0.28
Ω
Switch Leakage
0
10
µA
EN
= 4V, VSW = 0V
CC Mode
4.1
2
A
A
Peak Current Limit
Trickle Mode
RS1=100mꢀ
CC current
ICC
1.8
5%
2.0
10%
3
2.2
A
Trickle charge current
Trickle charge voltage threshold
ITRICKLE
Icc
V/Cell
Trickle charge hysteresis
Termination current threshold
Oscillator Frequency
350
10%
600
190
mV/Cell
Icc
IBF
fSW
15%
230
VFB = 1.2V
VFB = 0V
kHz
kHz
%
Fold-back Frequency
Maximum Duty Cycle
VFB = 1.2V
90
Maximum current Sense Voltage
(CSP to BATT)
VSENSE
tON
170
200
100
3.2
mV
ns
V
Minimum On Time
VFB = 1.5V
Under Voltage Lockout Threshold
Rising
3
5
3.4
Under Voltage Lockout Threshold
Hysteresis
200
1000
mV
mA
min
Open-drain sink current
Vdrain=0.3V
Stay at trickle charge,
Dead-battery indication
30
1
C
TMR=0.1µF
Time after IBF reached,
CTMR=0.1µF
Termination delay
Min
Recharge threshold at Vbatt
Recharge Hysteresis
Vrechg
4.0
V/cell
100
mV/Cell
RNTC=NCP18XH103 (0°C)
73
%of
VREF33
NTC Low Temp Rising Threshold
Recovery Hysteresis
3
30
2
RNTC=NCP18XH103, (50°C)
Recovery Hysteresis
NTC
High
Temp
Falling
%of
VREF33
Threshold
Vin min head-room (reverse
blocking)
Vin-Vbatt
180
mV
0.4
V
V
EN Input Low Voltage
EN Input High Voltage
1.8
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 (continued)
VIN = 19V, TA = +25°C, CELLS=0V, unless otherwise noted.
Parameters
Symbol Condition
Min
Typ
Max
Units
4
EN = 4V
µA
EN Input Current
0.2
0.5
EN = 0V
mA
mA
EN= 4V
EN= 4V,
Consider VREF33 pin
output current.
Supply Current (Shutdown)
0.665
R3=10k,RNTC=10k
EN= 0V,
CELLS=0V
Supply Current (Quiescent)
IAIN
2.0
mA
Thermal Shutdown
150
2.5
3.3
30
°C
V
VREF25 output voltage
VREF33 output voltage
VREF33 load regulation
Input Current Sense Section
Supply Voltage
V
ILOAD=0 to 10mA
mV
VCC
IIN
2.5
40
30
V
µA
V
Supply Current
ILOAD= 0A, VCC = 40V
VCC > VIN Low
12
1.4
40
0.4
4
Common Mode Input Voltage(5)
VIN_CM
VCC > VIN High
V
OUT1 Input Offset Voltage
Input Bias Current
VOS1
2
20
±5
1
mV
nA
%
IRG1, IRG2
OUT1 Current Accuracy
No-Load OUT1 Error
Low-Level OUT1 Error
Shutdown Supply Current
IRG1/IGS VSENSE = 100mV
VSENSE = 0V
±2
0.1
0.3
3
µA
µA
µA
VSENSE = 5mV
2
IIN(SHDN) VSHDN = 3V
6
VTH_SHUTD
SHDN Threshold Voltage
SHDN Hysteresis
(Low Æ High)
0.7
0.9
30
1.2
V
OWN
mV
VSENSE = 40mV,
R
GS = 20kꢀ,
tR
17
29
µs
µs
ROUT = 100kꢀ,
RG1 = RG2 = 2kꢀ,
C
COUT = 100pF, 10% to
90%
OUT1 Rise, Fall Time (5)
GS = 100pF,
tF
VCC
0.15
–
OUT1 Output Voltage Range
VGS
IGS
24
V
Maximum OUT1 Current (5)
500
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 Description
1,10,12,22
NC
No Connection
Thermistor Input. Connect a resistor from this pin to the pin VREF33 and the Thermistor
from this pin to ground.
2
3
4
5
6
NTC
Valid Input Supply Indicator. A logic LOW on this pin indicates the presence of a valid
input supply.
ACOK
Charging status Indicator. A logic LOW indicates charging operation. The pin will become
an open drain once the charging is stopped.
CHGOK
VREF33
Internal linear regulator 3.3V reference output. Bypass to GND with a 1µF ceramic
capacitor.
VREF25 Internal linear regulator 2.5V reference output.
7
8
9
On/Off Control Input.
EN
SHDN
RG1
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
care must be taken in its layout. This node should be placed outside of the D1 to C1
ground path to prevent switching current spikes from inducing voltage noise into the part.
Connect exposed pad to ground plane for optional thermal performance.
GND,
Exposed
Pad
11, 21
13
14
15
16
OUT1 Output for Driving Resistor Load.
RG2
VCC
Gain Resistor of current sense amplifier.
Power Input of current sense amplifier.
COMPV VLOOP 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.
17
CELLS
18
19
20
COMPI ILOOP Compensation. Decouple this pin with a capacitor and a resistor.
BATT Positive Battery Terminal.
CSP
TMR
Battery Current Sense Positive Input. Connect a resistor RS1 between CSP and BATT.
Set time constant. 0.1uA charge and discharge the external cap. Connect TMR pin to
GND to disable the internal timer.
23
24
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.
BST
25, 26
27
SW
PIN
AIN
Switch Output.
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
Controller 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
TYPICAL PERFORMANCE CHARACTERISTICS
VIN=19V, C1=10µF, C2=4.7µF, C9=22µF, L=4.7µH, RS1=110mΩ, RS2=20mꢀ, Real Battery Load,
TA=25ºC, unless otherwise noted.
2 Cells I
vs. V
Curve
2 Cells Battery Charge Curve
3 Cells Battery Charge Curve
CHG
BATT
2.5
2
8.5
2.5
2
12.8
2.5
2
8.4
8.3
8.2
8.1
8
12.6
12.4
12.2
12
V
BATT
V
BATT
V
=19V
IN
1.5
1
1.5
1
1.5
1
V
=12V
IN
11.8
11.6
11.4
11.2
11
I
BATT
7.9
7.8
7.7
7.6
7.5
I
BATT
V
=24V
0.5
0
IN
0.5
0
0.5
0
0
20 40 60
80 100 120
0
2
4
6
8
10
0
50
100
150
BATTERY VOLTAGE(V)
TIMES(MIN)
TIMES(MIN)
3 Cells I
vs. V
Curve
CHG
BATT
Effciency vs. I
Effciency vs. I
CHG
CHG
2.5
100.0
90.0
80.0
100.0
V
=15V
IN
V
=15V
IN
V
=15V
V
=12V
IN
IN
2
1.5
1
V
=19V
IN
90.0
80.0
V
=19V
IN
V
=24V
IN
V
=19V
IN
V
=24V
IN
V
=24V
IN
70.0
60.0
70.0
60.0
0.5
0
3 Cells Battery
1.2 1.6
(A)
2 Cells Battery
0
2
4
6
8
10 12 14
0
0.4
0.8
1.2
(A)
1.6
2
0
0.4
0.8
2
BATTERY VOLTAGE(V)
I
I
CHG
CHG
BATT Float Voltage
vs. Temperature
Charge Current
vs. Temperature
BATT Float Voltage vs. V
IN
8.5
8.4
8.3
8.5
2.2
2
8.4
8.3
8.2
8.1
1.8
1.6
1.4
1.2
8.2
8.1
8
2 Cells Battery
2 Cells Battery
23 28
2 Cells Battery
8
8
13
18
-20
0
20
40
60
80
-20
0
20
40
60
80
TEMPERATURE (OC)
TEMPERATURE (OC)
V
(V)
IN
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=110mꢀ, RS2=20mꢀ, Real Battery Load,
TA=25ºC, unless otherwise noted.
Efficiency vs. V
IN
BATT
NTC Control Window
Current Sharing
V
=7.4V, I =2A
CHG
3
2.5
2
2.5
2
95
92
89
86
83
80
Low Temp Off
Low Temp On
1.5
1
1.5
1
High Temp On
High Temp Off
0.5
0
0.5
0
2 Cells Battery
15 20
5
10
25
8
12
16
20
24
28
0
0.5
1
1.5
(A)
2
2.5
V
(V)
V
(V)
I
IN
IN
SYS
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=110mꢀ, RS2=20mꢀ, Real Battery Load,
TA=25ºC, unless otherwise noted.
MP2618 Rev. 0.92
7/14/2010
www.MonolithicPower.com
MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited.
© 2010 MPS. All Rights Reserved.
9
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=110mꢀ, RS2=20mꢀ, Real Battery Load,
TA=25ºC, unless otherwise noted.
Power Path
Power Path
Management_Current Sharing Management_Steady State
2 Cells, I
= 2A, V
BATT
= 7.4V
2 Cells, I
= 2A, V
CHG BATT
= 8V, I =0.8A
SYS
CHG
V
V
IN
10V/div.
V
IN
IN
10V/div.
10V/div.
V
V
SW
BATT
10V/div.
5V/div.
V
BATT
5V/div.
I
I
BATT
SYS
1A/div.
1A/div.
I
SYS
V
SYS
500mA/div.
I
BATT
1A/div.
5V/div.
I
BATT
1A/div.
4s/div.
1us/div.
MP2618 Rev. 0.92
7/14/2010
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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.
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.”
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.
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.
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.
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
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.
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
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.
CHGOK and ACOK outputs.
Table 1―Charging Status Indication
Charger status
ACOK
low
CHGOK
low
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.
In charging
End of charge, NTC fault,
timer out, thermal
low
high
high
shutdown EN disable
VIN –VBAT<0.3V.
VIN<UVLO
high
Timer Operation
Charge Cycle (Mode change: TrickleÆ CCÆ
CV)
MP2618 uses internal timer to terminate the
charge if the timer times out. The timer duration
is programmed by an external capacitor at the
TMR pin.
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.
The trickle mode charge time is:
CTMR
TTICKLE_TMR = 30mins×
0.1uF
The total charge time is:
CTMR
TTOTAL_TMR = 3hours×
0.1uF
MP2618 Rev. 0.92
7/14/2010
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© 2010 MPS. All Rights Reserved.
11
MP2618 – 2A, 24V INPUT, 600kHz 2-3CELL SWITCHING LI-ION BATTERY CHARGER
Negative
Thermal
Coefficient
(NTC)
Power Path Management
Thermistor
MP2618 can implement a switching charger
circuit with power path management function,
which realizes the current sharing of the charger
and system load. In other words, MP2618 senses
the system current and feeds it back, then
reduces charge current according to the increase
of the system current.
The MP2618 has a built-in NTC resistance
window comparator, which allows MP2618 to
sense the battery temperature via the thermistor
packed internally in the battery pack to ensure a
safe operating environment of the battery. A
resistor with appropriate value should be
connected from VREF33 to NTC pin and the
thermistor is connected from NTC pin to GND.
The voltage on NTC pin is determined by the
resistor divider whose divide ratio depends on
the battery temperature. When the voltage of pin
NTC falls out of NTC window range, MP2618 will
stop the charging. The charger will restart if the
temperature goes back into NTC window range.
However, after the charge current decrease to 0,
the system current can only be limited by the
adapter.
The system current is satisfied first and always. It
chooses the adapter as its power source when
the adapter plugs in, and the battery is the
backup power source when the adapter is
removed.
Figure 3 to Figure 6 shows the charge profile,
operation waveform and flow chart, respectively.
MP2618 Rev. 0.92
7/14/2010
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MP2618 – 2A, 24V INPUT, 600kHz 2-3CELL SWITCHING LI-ION BATTERY CHARGER
BLOCK DIAGRAM
Figure 2—Function Block Diagram
MP2618 Rev. 0.92
7/14/2010
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MP2618 – 2A, 24V INPUT, 600kHz 2-3CELL SWITCHING LI-ION BATTERY CHARGER
CHARGE PROFILE AND POWER PATH MANAGEMENT FUNCTION
Figure 3—Li-Ion Battery Charge Profile
Power Path Management
Current Sharing
ISYS
When ICHG decreases to 0,
the system current can only
CC Charge
be limited by the adapter
current capacity
ICHG
Figure 4 — Power Path Management Function- Current Sharing
MP2618 Rev. 0.92
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MP2618 – 2A, 24V INPUT, 600kHz 2-3CELL SWITCHING LI-ION BATTERY CHARGER
OPERATION FLOW CHART
POR
VUVLO<VIN
VIN>VBATT+0.3V?
&
SYS powered by
BATT
No
Yes
ACOK is low
& SYS powered
by IN
No
Charging
Set up?
Yes
CELLS Float
CELLS= 0V
CELLS Status?
VBATT_TC =6V
VBATT_TC = 9V
BATT_FULL=12.6V
BATT_RECHG=12V
VBATT_FULL=8.4V
V
V
V
BATT_RECHG=8V
Normal Operation
Charger “On”,
CHGOK is low
Charge Mode?
VBATT>VBATT_FULL
VBATT_TC<VBATT<VBATT_FULL
VBATT<VBATT_TC
C.V.C
C.C.C
No
T.C.C
No
No
ICHG<IBF
Battery Full?
VBATT>VBATT_FULL
VBATT>VBATT_TC
Yes
Yes
Yes
Charger “Off”,
CHGOK is high
Yes
No
VBATT
<
VBATT_RECHG
?
Figure 5— Normal Charging Operation Flow Chart
MP2618 Rev. 0.92
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MP2618 – 2A, 24V INPUT, 600kHz 2-3CELL SWITCHING LI-ION BATTERY CHARGER
OPERATION FLOW CHART (continued)
Power Path Management
Normal Operation
Charger “On”,
CHGOK is low
SYS Output
Current Increase
Charge Mode?
ISYS+ICHG>Ilimit
?
No
VBATT>VBATT_FULL
VBATT_TC<VBATT<VBATT_FULL
VBATT<VBATT_TC
Yes
C.V.C
C.C.C
No
T.C.C
Charge Current
Decrease
No
No
ICHG<IBF
Battery Full?
VBATT>VBATT_FULL
VBATT>VBATT_TC
Charge Current
<0 ?
No
Yes
Yes
Yes
Charger “Off”,
CHGOK is high
Yes
Yes
No
ISYS out of control
No charge current
VBATT
<
VBATT_RECHG
?
No
No
No
Tj>=150oC?
Yes
Timer Out ?
NTC Fault?
Yes
Yes
Charge
Termination,
CHGOK is high
Charge Current
Thermal Shutdown,
CHGOK is high
Charge Suspend,
CHGOK is high
No
No
NTC OK?
Yes
Tj<=130oC?
Yes
Charger Recovery,
Return to Normal
Operation
Fault Protection
Figure 6— Power Path Management Operation and Fault Protection Flow Chart
MP2618 Rev. 0.92
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MP2618 – 2A, 24V INPUT, 600kHz 2-3CELL SWITCHING LI-ION BATTERY CHARGER
APPLICATION INFORMATION
RGS1/2 causes the charge current sense error
as it changes the sense gain of A2, which can be
calculated from:
Setting the Charge Current
1. Standalone Switching Charger
The charge current of MP2618 is set by the
sense resistor RS1. The charge current
programmable formula is as following:
12.3
(
kꢀ
)
GA2
=
(6)
2
(
kꢀ + RGS
)
(
kꢀ
)
The charge current is set as:
200mV
ICHG
(
A =
)
(1)
1230
ICHG
(
A =
)
RS1
(
mꢀ
)
(7)
GA2 ×RS1
(
mꢀ
)
2. Switching Charger with Power Path
Management
Then the influence of RGS1 to the charge current
is:
Figure 7 shows the charge current sharing with
the system current.
2000 + RGS
10×RS1
( )
ꢀ
ICHG
(
A =
)
(8)
(
mꢀ
)
To decrease the power loss of the sensing circuit,
choose RS2 as small as possible, 20m is
recommended. Too small RG1 results in too big
current sense error of the system current, 50ꢀ is
at least.
Substitute these two values into equation (5),
then the calibrated charge current set formula in
power path application is got from equation (8):
2000 + 2.5×RS1
(
mꢀ
)
ICHG
(
A =
)
(9)
(
10×RS1mꢀ
)
Figure 7— Charge current sharing with
System current
Following table is the calculated RS1 and RGS1
value for setting different charge current.
The gain of the system current is set as:
RGS1
Table2—ICHG Set in Power Path Application
ICHG(A)
Gain =
(2)
RGS(ꢀ)
RS1(mꢀ)
RG1
2
280
402
665
909
2k
110
160
260
360
800
The voltage of OUT1 pin, VOUT1 can be calculated
from:
1.5
1
ISYS ×RS2×RGS1
VOUT1 =ISYS ×RS2×Gain =
(3)
0.8
0.5
RG1
When the system current increased ∆ISYS, to
satisfy the charge current decreased ∆ISYS
accordingly, the relationship should be:
If choose different RS2 and RG1, re-calculated
from equation (5) and equation (8), then get the
different equation (9) and the table.
∆VOUT1 ∆ISYS ×RS2×RGS1
∆IBAT
=
=
(4)
Also, any relationship between ∆ISYS and ∆IBATT
can be realized by re-calculate equation (4), (5)
and (8).
RS1
RS1×RG1
Because ∆ISYS=∆IBAT, we can get:
RS1 RGS1
(5)
=
MP2618 Rev. 0.92
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MP2618 – 2A, 24V INPUT, 600kHz 2-3CELL SWITCHING LI-ION BATTERY CHARGER
To be simple in project, making R3=10k and R6
no connect will approximately meet the
specification.
Selecting the Inductor
A 1µH to 10µH inductor is recommended for
most applications. The inductance value can be
derived from the following equation.
VOUT ×(V − VOUT
)
IN
L =
(10)
VREF33
V × ∆IL × fOSC
IN
Where ∆IL is the inductor ripple current. VOUT is
Low Temp Threshold
the 2/3 cell battery voltage.
R3
VTH_Low
NTC
Choose inductor current to be approximately
30% if the maximum charge current, 2A. The
maximum inductor peak current is:
RNTC
R6
∆IL
2
High Temp Threshold
IL(MAX) = ICHG
+
(11)
VTH_High
Under light load conditions below 100mA, larger
inductance is recommended for improved
efficiency.
Figure 8— NTC function block
Selecting the Input Capacitor
For optimized efficiency, the inductor DC
resistance is recommended to be less than
200mꢀ.
The input capacitor reduces the surge current
drawn from the input and also the switching noise
from the device. The input capacitor impedance
at the switching frequency should be less than
the input source impedance to prevent high
frequency switching current passing to the input.
Ceramic capacitors with X5R or X7R dielectrics
are highly recommended because of their low
ESR and small temperature coefficients. For
most applications, a 4.7µF capacitor is sufficient.
NTC Function
As Figure 8 shows, the low temperature
threshold and high temperature threshold are
preset internally via a resistive divider, which are
73%·VREF33 and 30%·VREF33. For a given
NTC thermistor, we can select appropriate R3
and R6 to set the NTC window.
In detail, for the thermistor (NCP18XH103) noted
in above electrical characteristic,
Selecting the Output Capacitor
The output capacitor keeps output voltage ripple
small and ensures regulation loop stability. The
output capacitor impedance should be low at the
switching frequency. Ceramic capacitors with
X5R or X7R dielectrics are recommended.
At 0ºC, RNTC_Cold = 27.445k;
At 50ºC, RNTC_Hot = 4.1601k.
Assume that the NTC window is between 0ºC
and 50ºC, the following equations could be
derived:
PC Board Layout
The high frequency and high current paths (GND,
IN and SW) should be placed to the device with
short, direct and wide traces. The input capacitor
needs to be as close as possible to the IN and
GND pins. The external feedback resistors
should be placed next to the FB pin. Keep the
switching node SW short and away from the
feedback network.
R6//RNTC_Cold
VTH_Low
=
= 73%
= 30%
R3 + R6//RNTC_Cold VREF33
(12)
(13)
R6//RNTC_Hot
VTH_High
=
R3 + R6//RNTC_Hot VREF33
According to equation (12) and equation (13), we
can find that R3 = 9.63k and R6 = 505k.
MP2618 Rev. 0.92
7/14/2010
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MP2618 – 2A, 24V INPUT, 600kHz 2-3CELL SWITCHING LI-ION BATTERY CHARGER
PACKAGE INFORMATION
QFN28 (4mm x 5mm)
2.50
2.80
3.90
4.10
23
28
PIN 1 ID
PIN 1 ID
MARKING
SEE DETAIL A
22
1
0.50
BSC
PIN 1 ID
INDEX AREA
4.90
5.10
3.50
3.80
0.18
0.30
8
15
14
9
0.35
0.45
TOP VIEW
BOTTOM VIEW
PIN 1 ID OPTION A
0.30x45º TYP.
PIN 1 ID OPTION B
R0.25 TYP.
0.80
1.00
0.20 REF
0.00
0.05
DETAIL A
SIDE VIEW
3.90
2.70
NOTE:
1) ALL DIMENSIONS ARE IN MILLIMETERS.
2) EXPOSED PADDLE SIZE DOES NOT INCLUDE MOLD FLASH.
3) LEAD COPLANARITY SHALL BE 0.10 MILLIMETER MAX.
4) DRAWING CONFORMS TO JEDEC MO-220, VARIATION VHGD-3.
5) DRAWING IS NOT TO SCALE.
0.70
0.25
3.70 4.90
0.50
RECOMMENDED LAND PATTERN
NOTICE: The information in this document is subject to change without notice. Please contact MPS for current specifications.
Users should warrant and guarantee that third party Intellectual Property rights are not infringed upon when integrating MPS
products into any application. MPS will not assume any legal responsibility for any said applications.
MP2618 Rev. 0.92
7/14/2010
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19
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