Preliminary Datasheet
LP6218S
High Efficiency 2.6A Boost DC/DC Convertor
General Description
The LP6218S is a current mode boost DC-DC
converter. Its PWM circuitry with built-in 2.6A
Current power MOSFET makes this converter
highly power efficiently. Selectable high switching
frequency allows faster loop response and easy
filtering with a low noise output. The non-inverting
input its error amplifier is connected to an internal
0.6V precision reference voltage. Soft-Start time
can be programmed with an external capacitor,
which sets the input current ramp rate. Current
mode control and external compensation network
make it easy and flexible to stabilize the system.
Features
Up to 94% efficiency
Output to Input Disconnect at Shutdown Mode
Shut-down current:<1uA
Output voltage Up to 12V
Internal Compensation, Soft-start
1.2MHz fixed frequency switching
High switch on current:2.6A
Available in SOT23-6 Package
Applications
Battery products
Host Products
Panel
Ordering Information
LP6218S -
□ □
□
Pin Configurations
F: Pb-Free
Package Type
B6: SOT23-6
6
5
4
LP6218SB6F
Typical Application Circuit
Vin
4.7uH
C1
22uF
5
4
1
C2
22uF
C3
22pF
FB
GND
ISET
3
6
R3
30K
R2
30K
R1
180K
Vout
1
2
3
LX
Marking Information
Please see website:www.lowpowersemi.com.
Vin
EN
LP6218S –01 Version 1.1Datasheet
2
LP6218SB6F
Jul.-2013
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Preliminary Datasheet
Functional Pin Description
PIN
5
2
6
1
LP6218S
PIN Name
VIN
GND
NC
SW/LX
Description
Power Supply pin.
Ground.
No connecter.
Output switching node. SW is the drain of the internal low-side
N-Channel MOSFET and high-side P-Channel MOSFET. Connect the
inductor to SW to Complete the step-up converter.
Regulator On/off Control Input. A logic high input(VEN>1.4V) turns on
the regulator. A logic low input(VEN<0.4V) puts the LP6218S into low
current shutdown mode.
Regulation Feedback Input. Connect to an external resistive voltage
divider from the output to FB to set the output voltage.
4
EN
3
FB
Function Block Diagram
LP6218S –01 Version 1.1Datasheet
Jul.-2013
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Preliminary Datasheet
Absolute Maximum Ratings
LP6218S
Supply Input Voltage---------------------------------------------------------------------------------------------------------------6V
Power Dissipation, PD @ TA = 25°C
SOT23-6----------------------------------------------------------------------------------------------------------450mW
Package Thermal Resistance
SOT23-6, θJA ---------------------------------------------------------------------------------------------------------------165°C/W
Lead Temperature (Soldering, 10 sec.) ----------------------------------------------------------------------------------260°C
Recommended Operating Conditions
Supply Input Voltage-------------------------------------------------------------------------------------------------2.2V to 6V
EN Input Voltage -------------------------------------------------------------------------------------------------------0V to 5.5V
Operation Junction Temperature Range ------------------------------------------------------------------−40°C to 125°C
Operation Ambient TemperatureRange----------------------------------------------------------------------−40°C to 85°C
Electrical Characteristics
(Vin=2.4V,Vout=3.5V,Cin=10uF,Cout=22uF,L1=4.7uH,R1=178K,R2=100K)
Parameter
Supply Voltage
Output Voltage Range
Supply Current(Shutdown)
Supply Current
Feedback Voltage
Feedback Input Current
Switching Frequency
Maximum Duty Cycle
EN Input Low Voltage
EN Input High Voltage
Switch mosfet Current Limit
High-side On Resistance
Mosfet Voltage
Vout=3.3V
VFB=1.2V
Conditions
Min
1.6
2.5
VEN=VOUT=0V,VSW=5V
VFB=1.3V
LP6218S
Typ
Max
6
6
0.05
0.19
0.6
50
1.20
80
1.4
2.6
220
14
300
90
95
0.4
1
Units
V
V
uA
mA
V
nA
MHz
%
V
V
A
V
LP6218S –01 Version 1.1Datasheet
Jul.-2013
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Page 3 of 6
Preliminary Datasheet
Operation Information
The LP6218S uses a 1.2MHz fixed-frequency,
current-mode regulation architecture to regulate the
output voltage. The LP6218S measures the output
voltage through an external resistive voltage divider
and compares that to the internal 0.6V reference to
generate the error voltage to the inductor current to
regulate the output voltage. the use of current-mode
regulation improves transient response and control
loop stability.
When the LP6218S is disable(EN=Low),both power
switches are off. There is no current path from SW
to OUT. There fore, the output voltage discharges to
ground. When the LP6218S is enabled(EN=High),a
limited start-current charges the output voltage
rising to SW, then the part operates in force PWM
mode for regulating the output voltage to the target
value. At the beginning of each cycle, the N-channel
MOSFET switch is turned on, forcing the inductor
current to rise, The current at the source of the
switch is internally measured and converted to a
voltage by the current sense amplifier. That voltage
is compared to the error voltage. When the inductor
current rises sufficiently, the PWM comparator
turns off the switch, forcing the inductor current to
the output capacitor through the internal P-Channel
MOSFET rectifier, which forces the inductor
current to decrease. The peak inductor current is
controlled by the error voltage. Thus the output
voltage controls the inductor current to satisfy the
lode.
LP6218S
1.6A (Typ.). When the switch current reaches the
limited value, the internal power-MOS is turned off
immediately until the next cycle. Keep traces at this
pin as short as possible. Do not put capacitance at this
pin.
Inductor Selection
For a better efficiency in high switching frequency
converter, the inductor selection has to use a proper
core material such as ferrite core to reduce the core
loss and choose low ESR wire to reduce copper loss.
The most important point is to prevent the core
saturated when handling the maximum peak current.
Using a shielded inductor can minimize radiated
noise in sensitive applications. The maximum peak
inductor current is the maximum input current plus
the half of inductor ripple current. The calculated
peak current has to be smaller than the current
limitation in the electrical characteristics. A typical
setting of the inductor ripple current is 20% to 40%
of the maximum input current. If the selection is
40%, the maximum peak inductor current is
The minimum inductance value is derived from the
following equation :
Setting the Output Voltage
Set the output voltage by selecting the resistive
voltage divider ratio. The voltage divider drops the
output voltage to the 0.6V feedback voltage. Use a
100K resistor for R2 of the voltage divider.
Determine the high-side resistor R1 by the equation:
Vout=(R1/R2+1) x V
FB
Current Limitation
The internal power-MOS switch current is monitored
cycle-by-cycle and is limited to the value not exceed
LP6218S –01 Version 1.1Datasheet
Jul.-2013
Depending on the application, the recommended
inductor value is between 2.2μH to 10μH.
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Preliminary Datasheet
Diode Selection
To achieve high efficiency, Schottky diode is good
choice for low forward drop voltage and fast
switching time. The output diode rating should be
able to handle the maximum output voltage, average
power dissipation and the pulsating diode peak
current.
LP6218S
bigger than ceramic capacitor. The output voltage
ripple consists of two components: one is the
pulsating output ripple current flows through the
ESR, and the other is the capacitive ripple caused by
charging and discharging.
Input Capacitor Selection
For better input bypassing, low-ESR ceramic
capacitors are recommended for performance. A
10μF input capacitor is sufficient for most
applications. For a lower output power requirement
application, this value can be decreased.
Output Capacitor Selection
For lower output voltage ripple, low-ESR ceramic
capacitors are recommended. The tantalum
capacitors can be used as well, but the ESR is
Layout Guideline
For high frequency switching power supplies, the
PCB layout is important step in system application
design. In order to let IC achieve good regulation,
high efficiency and stability, it is strongly
recommended the power components should be
placed as close as possible. The set races should be
wide and short. The feedback pin and then works of
feedback and compensation should keep away from
the power loops, and be shielded with a ground
trace or plane to prevent noise coupling.
LP6218S –01 Version 1.1Datasheet
Jul.-2013
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Page 5 of 6
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