26V/2.1A Current Boost IN SOT23

Preliminary
LP6218
26V/2.1A Current Boost IN SOT23-6 Package
General Description
Features
— Up to 94% efficiency
— Shut-down current:<1uA 
— Output voltage Up to 24V
— 1MHz fixed frequency switching
—
High switch on current:2.1A,[email protected]
—
—
Adjustable OCP: 0.5A-2A
Available in SOT23-6 Package Applications
—
—
—
Battery products
Host Products
Motor Power Devices
Typical Application Circuit
Vin
Vout
4.7uH
Ordering Information
5
LP6218 -
4
C3
22pF
□
Vin
FB
EN
NC
6
F: Pb-Free
Package Type
B6: SOT23-6h
Pin Configurations
6
5
4
Marking Information
LP6218B6F
Please see website.
1
2
3
(SOT23-6)
LP6218 –00 Version 1.0 Datasheet
Sep.-2010
www.lowpowersemi.com
R1
45K
3
2
□ □
1
LP6218
C2
22uF
LX
C1
22uF
GND
The LP6218 is high efficiency Boost DC/DC
Converter, fixed frequency, current-mode step-up
converter with output to input disconnect. A PWM
step-up DC/DC converters optimized to provide a
high efficiency solution to medium power system.
Its PWM circuitry with built-in [email protected]
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. the devices
regulates the output voltage up to 12V from either a
2cell NiMH/NiCd or a single-cell Li-ion Battery
with a 1MHz fixed frequency switching. These
features minimize overall solution footprint by
allowing the use of tiny, low profile inductors and
ceramic capacitors.
Page 1 of 5
R2
10K
Preliminary
LP6218
Functional Pin Description
PIN
PIN Name
Description
1
LX
2
3
GND
FB
4
EN
5
6
Vin
NC
Output switching node. SW is the drain of the internal N-Channel
MOSFET and RDS-ON is 100mΩ. Connect the inductor to SW to
Complete the step-up converter.
Ground.
Regulation Feedback Input. Connect to an external resistive voltage
divider from the output to FB to set the output voltage.Vfb=0.6V.
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 LP6218 into low
current shutdown mode.
IC Power Supply.
No Connector.
Function Block Diagram
LP6218 –00 Version 1.0 Datasheet
Sep.-2010
www.lowpowersemi.com
Page 2 of 5
Preliminary
LP6218
Absolute Maximum Ratings
Supply Input Voltage---------------------------------------------------------------------------------------------------------------6V
Package Thermal Resistance
SOT23-6, θJA ---------------------------------------------------------------------------------------------------------------68°C/W
Lead Temperature (Soldering, 10 sec.) ----------------------------------------------------------------------------------260°C
Storage Temperature Range --------------------------------------------------------------------------------- −65°C to 150°C
Recommended Operating Conditions
Supply Input Voltage------------------------------------------------------------------------------------------------- 2.2V to 6V
SW Pin Voltage----------------------------------------------------------------------------------------------------------------- 26V
EN Input Voltage -------------------------------------------------------------------------------------------------------0V to 5.5V
Electrical Characteristics
Parameter
Conditions
LP6218
Supply Voltage
Min
2.2
Output Voltage Range
2.5
Supply Current(Shutdown)
Supply Current
Disable Supply Current
Feedback Voltage
Feedback Input Current
Switching Frequency
VEN=VOUT=0V,VSW=5V
VFB=1.3V
EN=GND
0.588
VFB=1.2V
Maximum Duty Cycle
EN Input Low Voltage
EN Input High Voltage
Mosfet On Resistance
Mosfet Voltage(VDS)
NMOS Current Limit
OCP Adjustable Range
Soft-start Reset Switch Resistance
Soft-start Input Source Current
LP6218 –00 Version 1.0 Datasheet
80
Typ.
0.05
0.2
0.1
0.6
50
1
Units
Max
5
V
24
V
1
uA
mA
uA
V
nA
MHz
0.612
85
90
%
0.6
V
V
mΩ
V
A
A
Ω
uA
1.4
200
26
2.1
0.5
R3=10k-100kΩ
VSS=1.2V
Sep.-2010
2.5
100
4.0
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Page 3 of 5
Preliminary
LP6218
Operation Information
Output Voltage
The error amplifier compares a sample of the dc-dc
converter output voltage with the 0.6V (VREF)
reference and generates an error signal for the PWM
comparator. Output voltage of dc-dc converter is
setting with the resistor divider by the following
equation:
Vout=(R1/R2+1) X 0.6V
Oscillator
The switching frequency of LP6218 up to operate at
either 1MHz.
Soft Start
The soft start is functional after power on. The
interval of soft start time is determined by a
capacitor connected to SS pin. When EN pin is
taken high, the soft start capacitor (CSS) is charged
by a constant current of 4μA (typ). During this
interval, the SS voltage directly controls the peak
inductor current. The maximum load current is
available after the soft-start interval is completed.
Once the EN pin is taken low, the soft-start
capacitor is discharged to ground to prepare for next
start-up.
The load must wait for the soft-start interval to
finish before drawing a significant amount of load
current. The duration after which the load can begin
to draw maximum load current is:
EN
The LP6218 can be turn off to reduce the supply
current to 0.1μA when EN is low. In this mode, the
internal reference, error amplifier, comparators, and
biasing circuitry turn off while the N-channel
MOSFET is turned off. The boost converter’s
output is connected to VCC by the external inductor
and catch diode.
Output Current Capability
The output current capability of the LP6218 is a
function of current limit, input voltage, operation
frequency, and inductor value. Because of the slope
compensation used to stabilize the feedback loop,
LP6218 –00 Version 1.0 Datasheet
Sep.-2010
the duty cycle affects the current limit. The output
current capability is governed by the following
equation:
Current Limitation
The internal power-MOS switch current is
monitored cycle-by-cycle and is limited to the value
not exceed 2A (Typ.). When the switch current
reaches the limited value, the internal power-MOS
is turned off immediately until the next cycle.
A resistor between OCP and GND pin programs
peak switch current. The resistor value should be
between 10k and 100k. The current limit will be set
from 2.5A to 0.5A. Keep traces at this pin as short
as possible. Do not put capacitance at this pin.
Layout considerations
Typical for all switching power supplies, the
layout is an important step in the design;
especially at high peak currents and
switching frequencies. If the layout is not
carefully done, the regulator might show
noise problem sand duty cycle jitter. The
input capacitor should be placed as close as
possible to the input pin for good input
voltage viltering. The inductor and diode
should be placed as close as possible to the
switch pin to minimize the noise coupling
into other circuits. Since the feedback pin
and network is a high impedance circuit the
feedback network should be routed away
from the inductor. The feedback pin and
feedback network should be shielded with a
ground plane or trace to minimize noise
coupling into this circuit.
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Page 4 of 5
Preliminary
LP6218
Packaging Information
LP6218 –00 Version 1.0 Datasheet
Sep.-2010
www.lowpowersemi.com
Page 5 of 5