Preliminary Datasheet LP3315 1.2MHz,30V/1A High Performance

Preliminary Datasheet
LP3315
1.2MHz,30V/1A High Performance, Boost Converter
General Description
Features
The LP3315 is a 1.2MHz PWM boost switching
regulator designed for constant-voltage boost
applications. The LP3315 can drive a string of up to
30V. The LP3315 implements a constant frequency
1.2MHz PWM control scheme. The high frequency
PWM operation also saves board space by reducing
external component sizes. To improve efficiency, the
feedback voltage is set to 1250mV, which reduces
the power dissipation in the voltage setting resistor.
Highly integration and internal compensation
network minimizes as 5 external component counts.
Optimized operation frequency can meet the
requirement of small LC filters value and low
operation current with high efficiency.
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Ordering Information
High Efficiency: 90% 1.2MHzFixed-Frequency PWM Operation
Maximum Output Voltage up to 30V
Guaranteed 13V/200mA Output with 5V input
Operating Range : 2.7V to 5.5V
Shutdown Supply Current:<1uA Programmable Soft-star
Available in SOT23-6/SOT23-5 Package Minimize the External Component
RoHS Compliant and 100% Lead (Pb)-Free
Applications
Panel Bais Voltage supply
OLED Backlight driver
Notebook Computers
Portable Applications
MID/PTV
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LP3315
Typical Application Circuit
Vin
VOUT
F: Pb-Free
4.7uH
C2
2.2uF
5
Package:
B5: SOT23-5
LX
1
C1
4.7uF
Vin
FB
SHDN
ON
2
OFF
R1
210K
R2
30K
GND
4
Pin Configurations
3
C3
1nF
LP3315
Marking information
Please view website.
Device No.
Marking
Package
Shipping
LP3315B5F
LPS
SOT23-5
3K/Reel
Fbxxx
x represents the date( year month day)of the producing day
of the products.
LP3315– 00
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Preliminary Datasheet
LP3315
Functional pin description
SOT-23-5
Pin Name
Pin Function
1
LX
Switch Pin. Connect this Pin to inductor and catch diode. Minimize the track
area to reduce EMI.
2
GND
Ground Pin
3
FB
Feedback Reference Voltage Pin. Series connect a resistor between Vout and
ground as a voltage sense. The feedback voltage is 1250mV.
4
SHDN
5
Vin
Chip Enable (Active High). Voltage sensing input to trigger the function of
over voltage protection. Note that this pin is high impedance. There should
be a pull low 100kΩ resistor connected to GND when the control signal is
floating.
Supply Input Voltage Pin. Bypass 1uF capacitor to GND to reduce the input
noise.
Function Block Diagram
LX
VIN
+
+
FB
-
+
-
EN
GND
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Preliminary Datasheet
LP3315
Absolute Maximum Ratings
Supply Input Voltage---------------------------------------------------------------------------------------------------−0.3V to 6.0V
LX Input Voltage --------------------------------------------------------------------------------------------------------−0.3V to 30V
The Other Pins ----------------------------------------------------------------------------------------------------------−0.3V to 5.5V
Power Dissipation, PD @ TA = 25°C TSOT-23-5/6-----------------------------------------------------------------------0.455W
Lead Temperature (Soldering, 10 sec.) -------------------------------------------------------------------------------- 260°C
Operation Temperature Range ---------------------------------------------------------------------------------−40°C to 80°C
Storage Temperature Range ----------------------------------------------------------------------------------------−65°C to 150°C
Electrical Characteristics
Parameter
Symbol
Test Condition
Min
Typ.
Max
Units
6
V
System Supply Input
Operation voltage Range
VDD
2.7
Under Voltage Lock Out
VDD
2.2
Supply Current
IDD
FB=1.2V, Switch
430
550
uA
Shut Down Current
IDD
VEN < 0.4V
0.1
1
uA
Line Regulation
VIN : 3.0~4.3V
2.4
2.6
V
2
%
1.2
MHz
Oscillator
Operation Frequency
FOSC
Maximum Duty Cycle
Feedback Voltage
93
LP3315
1.22
%
1.25
1.28
V
MOSFET
On Resistance of MOSFET
RDS(ON)
SW Current Limit
ILM
0.4
Ω
1
A
Protection
Shut Down Voltage
VEN
Enable on Voltage
VEN
LP3315– 00
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Preliminary Datasheet
LP3315
Typical Operating Characteristics
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Preliminary Datasheet
LP3315– 00
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LP3315
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Preliminary Datasheet
LP3315
Applications Information
Inductor Selection
The recommended value of inductor for 30V applications are 4.7 to 22µH. Small size and better efficiency are the
major concerns for portable device, such as LP3315 used for mobile phone. The inductor should have low core
loss at 1.2MHz and low DCR for better efficiency. To avoid inductor saturation current rating should be considered.
Constant Output Voltage Control
The output voltage of the LP3315 can be adjusted by the divider circuit on the FB pin. Typical FB voltage is
1250mV. The output voltage can be calculated by the following Equations.
Power Sequence
In order to assure the normal soft start function for suppressing the inrush current the input voltage should be
ready before EN pulls high.
Soft-Start
The function of soft-start is made for suppressing the inrush current to an acceptable value at the beginning of
power on. The LP3315 provides a built-in soft-start function by clamping the output voltage of error amplifier so
that the duty cycle of the PWM will be increased gradually in the soft-start period.
Current Limiting
The current flow through inductor as charging period is detected by a current sensing circuit. As the value comes
across the current limiting threshold, the N-MOSFET will be turned off so that the inductor will be forced to leave
charging stage and enter discharging stage. Therefore, the inductor current will not increase over the current
limiting threshold.
OVP/UVLO/OTP
The Over Voltage Protection is detected by a junction breakdown detecting circuit. Once VOUT goes over the
detecting voltage, LX pin stops switching and the power N-MOSFET will be turned off. Then, the VOUT will be
clamped to be near VOVP. As the output voltage is higher than a specified value or input voltage is lower than a
specified value, the chip will enter protection mode to
prevent abnormal function. As the die temperature is higher then 160°C, the chip also will enter protection mode.
The power MOSFET will be turned off during protection mode to prevent abnormal operation.
Thermal Considerations
For continuous operation, do not exceed absolute maximum operation junction temperature. The maximum power
dissipation depends on the thermal resistance of IC package, PCB layout, the rate of surroundings airflow and
temperature difference between junction to ambient. The maximum power dissipation can be calculated by
following formula :
Where TJ(MAX) is the maximum operation junction temperature, TA is the ambient temperature and the qJA is the
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Preliminary Datasheet
LP3315
junction to ambient thermal resistance.
For the recommended operating conditions specification of LP3315, the maximum junction temperature of the die
is 125°C. The junction to ambient thermal resistance Qja is layout dependent. The junction to ambient thermal
resistance for SOT23-5 package is 255°C/W and for WDFN-8L 2x2 package is 165°C/W on the standard JEDEC
51-3 single layer thermal test board. The maximum power dissipation at TA = 25°C can be calculated by
following formula :
Layout Consideration
For best performance of the LP3315, the following
guidelines must be strictly followed.
- Input and Output capacitors should be placed close to the IC and connected to ground plane to reduce noise
coupling.
- The GND and Exposed Pad should be connected to a strong ground plane for heat sinking and noise protection.
- Keep the main current traces as possible as short and wide.
- LX node of DC-DC converter is with high frequency voltage swing. It should be kept at a small area.
- Place the feedback components as close as possible to the IC and keep away from the noisy devices.
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Preliminary Datasheet
LP3315
Packing information
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