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PDF PT4103B23F Data sheet ( Hoja de datos )
| Número de pieza | PT4103B23F | |
| Descripción | White LED Step-Up Converter | |
| Fabricantes | Powtech | |
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PT4103
White LED Step-Up Converter
GENERAL DESCRIPTION
The PT4103 is a step-up DC/DC converter designed for
driving up to 8 white LEDs in series from a single cell
Lithium Ion battery with constant current. Because it
directly regulates output current, the PT4103 is ideal for
driving light emitting diodes (LEDs) whose light
intensity is proportional to the current passing through
them, not the voltage across their terminals. A single
external resistor sets LED current between 5mA and
20mA, which can then be easily adjusted using either a
DC voltage or a pulse width modulated (PWM) signal.
Its low 104mV feedback voltage reduces power loss
and improves efficiency. The OV pin monitors the
output voltage and turns off the converter if an
over-voltage condition is present due to an open circuit
condition. The PT4103 is available in SOT23-6
packages.
FEATURES
z Drives Up to 5 Series White LEDs from 2.5V
z Drives Up to 8 Series White LEDs from 3.6V
z Up to 87% Efficiency
z 1.2MHz Fixed Switching Frequency
z Low 104mV Feedback Voltage
z Open Load Shutdown
z Soft Start/PWM Dimming
z SOT23-6 Packages
APPLICATIONS
z Cell Phones
z Handheld Computers and PDAs
z Digital Cameras
z Small LCD Displays
ORDERING INFORMATION
PACKAGE
SOT23-6
TEMPERATURE
RANGE
-40 oC to 85 oC
ORDERING PART
NUMBER
PT4103B23F
TRANSPORT
MEDIA
Tape and Reel
3000 units
MARKING
4103
TYPICAL APPLICATIONS
Figure1. Li-Ion Driver for Six White LEDs
KEY PERFORMANCE CHART
90.00%
85.00%
80.00%
75.00%
5
Efficiency vs n(LED)
3LED
4LED
5LED
6LED
7LED
8LED
10 15
Iout (mA)
20 25
Vin=3.6V
Figure2. Efficiency vs Number of LEDs
China Resources Powtech (Shanghai) Limited
PT4103_DS Rev EN_2.2
WWW.CRPOWTECH.COM
Page 1
1 page  
PT4103
White LED Step-Up Converter
TYPICAL PERFORMANCE CHARACTERISTICS
Quiescent Current vs VIN and Temperature
Switching Frequency vs Temperature
Iq VS Temperature
Fosc VS Temp.
250
200
150
100 Temp=-40℃
50 Temp=25℃
0 Temp=100℃
2.5 3 3.5 4 4.5 5 5.5 6
Vin(V)
1.6
1.4
1.2
1
0.8
0.6
0.4
0.2
0
-40
25
Temp(℃)
100
APPLICATION INFORMATION
Inductor Selections
For most of the applications of the PT4103, it is
recommended to use an inductor of 22uH. Although
small size is one of the major factors in selecting an
inductor, the smaller and thinner inductors give higher
core losses at 1.25MHz and DRC, resulting in lower
efficiencies. The following tab le provides a list of
recommended inductors:
Part
Number
LQH3C220
CDRH3D16-220
LB2012B220M
LEM2520-220
EJPC220KF
DCR
（Ω）
0.71
0.53
1.7
5.5
4.0
Current
Rating
（mA）
250
350
75
125
160
Manufacture
MURATA
SUMIDA
TAIYO YUDEN
TAIYO YUDEN
PANASONIC
Capacitor Selection
The small size of ceramic capacitors makes them ideal
for PT4103 applications. X5R and X7R types are
recommended because they retain their capacitance
over wider voltage and temperature ranges than other
types such as Y5V or Z5U. A 1μF input capacitor and a
0.22 μF output capacitor are sufficient for most PT4103
applications.
Diodes Selection
Schottky diodes, with their low forward voltage drop
and fast reverse recovery, are the ideal choices for
PT4103 applications. The forward voltage drop of a
Schottky diode represents the conduction losses in the
diode, while the diode capacitance (CT or CD)
represents the switching losses. For diode selection,
both forward voltage drop and diode capacitance need
to be considered. Schottky diodes with higher current
ratings usually have lower forward voltage drop and
larger diode capacitance, which can cause significant
switching losses at the 1.25MHz switching frequency
of the PT4103. A Schottky diode rated at 100mA to
200mA is sufficient for most PT4103 applications.
Some recommended Schottky diodes are listed in the
following table:
Part
Number
CMDSH-3
CMDSH2-3
BAT54
Forward
Current
(mA)
100
200
200
Voltage
Drop
(V)
0.58@100mA
0.49@200mA
0.53@100mA
Diode
CAP
(Pf)
7.0@10V
15@10v
10@25v
Manu
facture
Central
Central
Zetex
LED Current Control
The LED current is controlled by the feedback resistor.
The feedback reference is 104mV. The LED current is
104mV/Rfb. In order to have accurate LED current,
precision resistors are preferred (1% is recommended).
The formula and table for RFB selection are shown
below:
RFB = 104mV/ILED
ILED（mA）
5
RFB Value（Ω）
20.8
10 10.4
15 6.93
20 5.2
China Resources Powtech (Shanghai) Limited
PT4103_DS Rev EN_2.2
WWW.CRPOWTECH.COM
Page 5
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