Liteon Semiconductor Corporation
LSP3103
500mA Synchronous Step-Down Converter
Rev1.2
1/9
APPLICATIONS
Cellular and Smart Phones
PDAs
MP3 Player
Digital Still and Video Cameras
Portable instruments
Microprocessors and DSP Core Supplies
Wireless and DSL Modems
PIN CONFIGURATION
(Top View)
PIN DESCRIPTION
Pin Number Pin Name Pin Function
1 RUN
Regulator Enable control input. Drive RUN above 1.5V to turn on the part.
Drive RUN below 0.3V to turn it off. In shutdown, all functions are disable
drawing ＜1µA supply current. Do not leave RUN floating.
2 GND Ground
3 SW
Power Switch Output. It is the Switch node connection to inductor. This pin
connects to the drains of the internal P-CH and N-CH MOSFET switches.
4 VIN Supply Input Pin. Must be closely decoupled to GND, pin2, with a 2.2µF or
greater ceramic capacitor.
5 VFB/VOUT
VFB (LSP3103): Feedback Input Pin. Connected FB to the center point of
the external resistor divider. The feedback threshold voltage is 0.6V.
VOUT (LSP3103-1.2/1.8): Output Voltage Feedback Pin. An internal resistive
divider divides the output voltage down for comparison to the internal
reference voltage.
GENERAL DESCRIPTION
The LSP3103 is a 1.5MHz constant frequency; slope
compensated current mode PWM step-down
converter. The device integrates a main switch and a
synchronous rectifier for high efficiency without an
external Schottky diode. It is ideal for powering
portable equipment that runs from a single cell
lithium-Ion (Li+) battery. The LSP3103 can suppl
y
500mA of load current from a 2.5V to 6.5V inpu
t
voltage. The output voltage can be regulated as low as
0.6V. The LSP3103 can also run at 100% duty cycle fo
r
low dropout operation, extending battery life in portable
system. Idle mode operation at light loads provides
very low output ripple voltage for noise sensitive
applications.
The LSP3103 is offered in a low profile 5-pin, SO
T
package, and is available in an adjustable version and
fixed output voltage of 1.2V, 1.8V.
5
4
1
2
3VIN
VFB/VOUT
SW
GND
Run
FEATURES
High Efficiency : Up to 96%
1.5MHz Constant Switching Frequency
500mA Output Current at VIN=3.6V, VOUT=1.2V,
Integrated Main switch and synchronous rectifier.
No Schottky Diode Required
2.5V to 6.5V Input Voltage Range
Output Voltage as low as 0.6V
100% Duty Cycle in Dropout
Low Quiescent Current : 300µA
＜1µA Shutdown Current
Slope Compensated Current Mode Control fo
r
Excellent Line and Load Transient Response
Short Circuit and Thermal Fault Protection
Space Saving 5-pin SOT23 package
Liteon Semiconductor Corporation
LSP3103
500mA Synchronous Step-Down Converter
Rev1.2
2/9
BLOCK DIAGRAM
*
V
FB
/V
OUT
Note: For adjustable output, R1and R2 is external.
THERMAL RESISTANCE (NOTE 1)
Package θJA (℃/W) θJC (℃/W)
SOT23-5L 220 110
Note 1: Thermal Resistance is specified with approximately 1 square of 1 oz cooper.
ABSOLUTE MAXIMUM RATINGS (NOTE 2)
Parameter Rating Unit
Input Supply Voltage -0.3 to +7 V
RUN, VFB Voltages -0.3 to VIN +0.3 V
SW，Vout Voltages -0.3 to VIN+0.3 V
Peak SW Sink and Source Current 800 mA
Operating Temperature Range -40 to +85 ℃
Junction Temperature (Note 3) +125 ℃
Storage Temperature Range -65 to 150 ℃
Lead Temperature ( solding, 10 sec.) +300 ℃
Note 2: Absolute Maximum Ratings are those values beyond which the life of a device may be impaired.
Note 3: TJ is calculated from the ambient temperature TA and power dissipation PD according to the following formula:
TJ=TA+PD×θJA
ELECTRICAL CHARACTERISTICS (NOTE 4)
Liteon Semiconductor Corporation
LSP3103
500mA Synchronous Step-Down Converter
Rev1.2
3/9
(VIN=VRUN=3.6V, TA=25℃, Unless otherwise noted)
Parameter Condition Min. Typ. Max. Unit
Input Voltage Range 2.5 6.5 V
Input DC Supply Current
Active Mode
Shutdown Mode
VFB=0.5V
VFB=0V, VIN=4.2V
300
0.1
500
1.0 µA
TA=+25℃ 0.5880 0.6000 0.6120 V
TA=0℃≤TA≤85℃ 0.5865 0.6000 0.6135 V
Regulated Feedback Voltage
TA=-40℃≤TA≤85℃ 0.5820 0.6000 0.6180 V
VFB Input Bias Current VFB=0.65V ±30 nA
Reference Voltage Line Regulation VIN=2.5V to 5.5V, VOUT=VFB (R2=0) 0.04 0.40 %/V
LSP3103C12AD: -40℃≤TA≤85℃ 1.164 1.200 1.236 V
Regulated Output Voltage LSP3103C18AD: -40℃≤TA≤85℃ 1.746 1.800 1.854 V
Output Voltage Line Regulation VIN=2.5V to 5.5V, IOUT=10mA 0.04 0.40 %/V
Output Voltage Load Regulation IOUT from 0 to 500mA 0.5 %
Maximum Output Current VIN=3.0V 500 mA
Oscillator Frequency VFB=0.6V or VOUT=100% 1.2 1.5 1.8 MHz
RDS(ON) of P-CH MOSFET ISW=300mA 0.50 0.60 Ω
RDS(ON) of N-CH MOSFET ISW=-300mA 0.45 0.55 Ω
Peak Inductor Current VIN=3V, VFB=0.5V or VOUT=90%,
Duty Cycle＜35% 0.55 0.60 0.80 A
SW Leakage VRUN=0V, VSW=0V or 5V, VIN=5V ±0.01 ±1 µA
RUN Threshold -40℃≤TA≤85℃ 0.55 1.30 V
RUN Leakage Current ±0.01 ±1 µA
Note 4: 100% production test at +25℃. Specifications over the temperature range are guaranteed by design and
characterization.
TYPICAL PERFORMANCE CHARACTERISTICS
Liteon Semiconductor Corporation
LSP3103
500mA Synchronous Step-Down Converter
Rev1.2
4/9
(Test Figure 1 below unless otherwise specified)
TYPICAL PERFORMANCE CHARACTERISTICS (CONTINUED)
Liteon Semiconductor Corporation
LSP3103
500mA Synchronous Step-Down Converter
Rev1.2
5/9
FUNCTIONAL DESCRIPTION
Liteon Semiconductor Corporation
LSP3103
500mA Synchronous Step-Down Converter
Rev1.2
6/9
tep-Down DC-DC converter. It utilizes internal MOSFETs to achieve high
URRENT MODE PWM CONTROL
WM control provides stable switching and cycle-by-cycle current limit for
ROPOUT OPERATION
creases toward the value of the output voltage, the LSP3103 allows the main switch to
OPERATION
onolithic switching mode SLSP3103 is a m
efficiency and can generate very low output voltage by using internal reference at 0.6V. It operates at a fixed
switching frequency, and uses the slope compensated current mode architecture. This Step-Down DC-DC
Converter suppliers 500mA output current at VIN=3V with input voltage range from 2.5V to 6.5V.
C
Slope compensated current mode P
excellent load and line responses and protection of the internal main switch (P-Ch MOSFET) and synchronous
rectifier (N-Ch MOSFET). During normal operation, the internal P-Ch MOSFET is turned on for a certain time to
ramp the inductor current at each rising edge of the internal oscillator, and switched off when the peak inductor
current is above the error voltage. The current comparator, ICOMP, limits the peak inductor current. When the main
switch is off, the synchronous rectifier will be turned on immediately and stay on until either the inductor current
starts to reverse, as indicated by the current reversal comparator, IZERO, or the beginning of the next clock cycle. The
OVDET comparator controls output transient overshoots by turning the main switch off and keeping it off until the
faults is no longer present.
D
When the input voltage de
remain on for more than one switching cycle and increases the duty cycle until it reaches 100%.
The duty cycle D of a step-down converter is defined as:
OUT
V
D=T f 100% 100%×× ≈ ×
ON OSC IN
V
Where TON is the main switch on time and fOSC is the oscillator frequency (1.5MHz).
he outp voltage then is the input voltage minus the voltage drop across the main switch and the inductor. At low
AXIMUM LOAD CURRENT
input supply voltages as low as 2.5V, however, the maximum load current decreases
utT
input supply voltage, the RDS(ON) of the P-Channel MOSFET increase, and the efficiency of the converter decreases.
Caution must be exercised to ensure the heat dissipated not to exceed the maximum junction temperature of the IC.
M
The LSP3103 will operate with
at lower input due to large IR drop on the main switch and synchronous rectifier. The slope compensation signal
reduces the peak inductor current as a function of the duty cycle to prevent sub harmonic oscillations at duty cycles
greater than 50%. Conversely the current limit increases as the duty cycle decreases.
Liteon Semiconductor Corporation
LSP3103
500mA Synchronous Step-Down Converter
Rev1.2
7/9
APPLICATION INFORMATION
R2
316K
R1
2
C3
10µF
5
3
4
1
Vout 1.8V
GND
VFB
SW
Run
2.2µHVin 2.7V-4.2V L1
22pFC2
C1
4.7µF
632K
Vin
Fig.1 Basic Application Circuit with LSP3103 adjustable version
2
C3
10µF
5
3
4
1
Vout 1.8V
GND
VOUT
SW
Run
2.2µHVin 2.5V-5.5V L1
C1
4.7µF
Vin
Fig.2 Basic Application Circuit with fixed output versions
ETTING THE OUTPUT VOLTAGE
lication circuit with LSP3103 adjustable output version. The external resistor
S
Figure 1 above shows the basic app
sets the output voltage according to the following equation:
⎟
⎟
⎠
⎞
⎛R
⎜
⎜
⎝+×=
2
1
OUT R
1V6.0V
For example, fixed R1=300kΩ for all outputs; R2=300kΩ for VOUT=1.2V, R2=200kΩ for VOUT=1.5V, R2=150kΩ for
DUCTOR SELECTION
3103 operates with inductors of 1µH to 4.7µH. Low inductance values are physically
)
VOUT=1.8V and R2=95.3kΩ for VOUT=2.5V.
IN
For most designs, the LSP
smaller but require faster switching, which results in some efficiency loss. The inductor value can be derived from
the following equation:
(
OUT IN OUT
IN L OSC
VVV×−
LVIf
=×∆ ×
Where ∆IL is inductor Ripple Current. Large value inductors lower ripple current and small value inductors result in
ltages above 2.0V, when light-load efficiency is important, the minimum recommended inductor is
high ripple currents. Choose inductor ripple current approximately 35% of the maximum load current 500mA, or
∆IL=175mA.
For output vo
2.2µH. For optimum voltage-positioning load transients, choose an inductor with DC series resistance in the 50mΩ
to 150mΩ range. For higher efficiency at heavy loads (above 200mA), or minimal load regulation (but some transient
overshoot), the resistance should be kept below 100mΩ. The DC current rating of the inductor should be at least
equal to the maximum load current plus half the ripple current to prevent core saturation (500mA+87.5mA). Table 1
lists some typical surface mount inductors that meet target applications for the LSP3103.
Liteon Semiconductor Corporation
LSP3103
500mA Synchronous Step-Down Converter
Rev1.2
8/9
Part # L (µH) Max DCR (mΩ)Rated D.C. Current
(A)
Size W×L×H (mm)
14 56.2 2.52
2.2 71.2 1.75
3.3 86.2 1.44
Sumida
4.7 108.7 1.15
4.5×4.0×3.5
1.5 60 1.45
2.2 75 1.32
3.3 110 1.04
Sumida
CDRH4D18
4.7 162 0.84
4.7×4.7×2.0
1.5 120 1.29
2.2 140 1.14
3.3 180 0.98
Toko
D312C
4.7 240 0.79
3.6×3.6×1.2
INPUT CAPACITOR SELECTION
The input capacitor reduces the surge current drawn from the input and switching noise from the device. The input
capacitor impedance at the switching frequency shall be less than input source impedance to prevent high
frequency switching current passing to the input. A low ESR input capacitor sized for minimum RMS current must be
used. Ceramic capacitors with X5R or X7R dielectrics are highly recommended because of their low ESR and small
temperature coefficients. A 4.7µF ceramic capacitor for most applications is sufficient.
OUTPUT CAPACITOR SELECTION
The output capacitor is requires to keep the output voltage ripple small and to ensure regulation loop stability. The
output capacitor must have low impedance at the switching frequency. Ceramic capacitors with X5R or X7R
dielectrics are recommended due to their low ESR and high ripple current. The output ripple VOUT is determined by:
()
OUT IN OUT
OUT IN OSC OSC
VVV 1
VESR
Vf L 8f C3
×− ⎛⎞
∆≤ × +
⎜⎟
×× ××
⎝⎠
ORDERING INFORMATION
MARKING INFORMATION
PACKAGE INFORMATION
Liteon Semiconductor Corporation
LSP3103
500mA Synchronous Step-Down Converter
Rev1.2
9/9
L1
L
A
2
A
A
1
M1
E1
e
e1
D
b
c
SEATING PLANE
GAUGE PLANE
E
M2
L2
Dimensions In Millimeters
Symbol Min Typ Max
A 1.05 1.20 1.35
A1 0.05 0.10 0.15
A2 1.00 1.10 1.20
b 0.30 - 0.50
c 0.08 - 0.22
D 2.80 2.90 3.00
E 2.60 2.80 3.00
E1 1.50 1.60 1.70
e 0.95 BSC
e1 1.90 BSC
L 0.30 0.45 0.55
L1 0.60 REF
L2 0.25 BSC
∠M1 3° 5° 7°
∠M2 6° 8° 10°
