GENERAL DESCRIPTION
The PT4103 is a step-up DC/DC converter designed for driving up to 8 white LEDs in ries from a single cell Lithium Ion battery with constant current. Becau it directly regulates output current, the PT4103 is ideal for driving light emitting diodes (LEDs) who light intensity is proportional to the current passing through them, not the voltage across their terminals. A single external resistor ts LED current between 5mA and 20mA, which can then be easily adjusted using either a DC voltage or a pul 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 prent 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 V oltage
z Open Load Shutdown
z Soft Start/PWM Dimming
z SOT23-6 Packages
z RoHS compliant
APPLICATIONS陆阿采与黄飞鸿
z Cell Phones
z Handheld Computers and PDAs
z Digital Cameras
z Small LCD Displays
ORDERING INFORMATION
PACKAGE TEMPERATURE
RANGE
ORDERING PART
NUMBER
TRANSPORT
MEDIA
被难日MARKING
SOT23-6 -40 o C to 85 o C PT4103B23F Tape and Reel
3000 units
4103
TYPICAL APPLICATIONS KEY PERFORMANCE CHART
Figure1. Li-Ion Driver for Six White LEDs Figure2. Efficiency vs Number of LEDs
PIN ASSIGNMENT
PIN DESCRIPTIONS
SOT PIN No. PIN Names DESCRIPTION
1
SW
Power Switch Output. Connect the inductor and the blocking Schottky diode to SW.
2 GND Ground 3
FB
Feedback input pin. The reference voltage at this pin is 104mV . Connect the cathode of the lowest LED to FB and a current n resistor between FB and GND.
4 EN Enable pin. A high input at EN enables the device and a low input disables the devices. When not ud, connect EN to the input source for automatic startup.
5 OV Over V oltage Input. OV measures the output voltage for open circuit protection. Connect OV to the output at the top of the LED string. 6
IN
Input Supply Pin. Must be locally bypasd.
ABSOLUTE MAXIMUM RATINGS (Note 1)
SYMBOL
ITEMS
V ALUE UNIT V IN Input V oltage
-0.3～6 V V SW V oltage at SW Pin -0.5～35 V V IO All Other I/O Pins
党课的意义
GND-0.3 to VDD+0.3
V
P TR1
Thermal Resistance ，SOT-23-6
θJA θJC
220 110
℃/W Tstg Storage Temperature -55 to 150 ℃ Tsolder
Package Lead Soldering Temperature
260, 10s ℃
RECOMMENDED OPERATING RANGE (Note 2)
SYMBOL ITEMS
V ALUE UNIT V IN VIN Supply V oltage 2.5 to +6 V V SW Output V oltage
V IN to 28 V T OPT
Operating Temperature
-40 to +85
℃
Note 1: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur.
Note 2: Recommended operating Range indicates conditions for which the device is functional, but does not guarantee specific
广州有多少大学performance limits.
ELECTRICAL CHARACTERISTICS (Note 3,4,5)
V IN =V EN =3V , Topt=25℃ unless specified otherwi.
SYMBOL ITEMS
地产销售
CONDITIONS Min. Typ. Max. UNIT V IN Input Voltage 2.5
6
V
Feedback
V FB FB Pin Voltage 89 104 119 mV Ibias FB Pin Input Bias Current
0.05 1 µA Operating Current
Ioff Operating Current （Shutdown ）V SW-ON =0V
0.1
1
µA
Isby Operating Current （Quiescent ）V FB =
0.3V 100 350 µA
Fsw Switching Frequency
1.0 1.25 1.5 MHz
Dmax Maximum Duty Cycle
V FB =
0V 85 90 % Chip Enable V EN_H EN Minimum High Level 1.5 V V EN_L EN Maximum Low Level 0.4 V V HYS EN Hysteresis 90 mV
EN Input Bias Current V SW-ON =0V, 5V 1 µA Output Switch
R ON SW On Resistance (Note 3) 0.5 Ω I LIMIT
五月天丁香婷深爱综合网SW Current Limit
400
mA
I LEAK SW Leakage Current Vsw ＝5V
0.01 1 µA Open Circuit Protection
V OV Open Circuit Shutdown Threshold
V OV Rising
30 V
北极星在哪个星座中
Soft Start
tss
Soft Start Time (Note 3)
V IN Power On
160 µS
Note 3: Electrical Characteristics state DC and AC electrical specifications under particular test conditions which guarantee specific performance limits. This assumes that the device is within the recommended operating Range. Specifications are not guaranteed for parameters where no limit is given, however, the typical value is a good indication of device performance.
Note 4: Typicals are measured at 25˚C and reprent the parametric norm.
Note 5: Datasheet min/max specification limits are guaranteed by design, test, or statistical analysis.
SIMPLIFIED BLOCK DIAGRAM
Figure 3. Simplified Block Diagram of the PT4103
OPERATION DESCRIPTION
The PT4103 us a constant frequency, peak current mode boost regulator architecture to regulate the ries string of white LEDs. The operation of the PT4103 can be understood by referring to the simplified block diagram shown above. At the start of each oscillator cycle, the control logic turns on the power switch M1. The signal at the non-inverting input of the PWM comparator is proportional to the switch current, summed together with a portion of the oscillator ramp.
When this signal reaches the level t by the output of error amplifier, the PWM comparator rets the latch in the control logic and turns off the power switch. In this manner, error amplifier ts the correct peak current level to keep the LED current in regulation. If the feedback voltage starts to drop, the output of the error amplifier increas. This results in more current to flow through M1, hence increasing the power delivered to the output.
TYPICAL PERFORMANCE CHARACTERISTICS
Driving Capability
Vin I LED =15mA I LED =20mA 2.5V 5 x LED 4 x LED 3.0V 6 x LED 5 x LED 3.6V
8 x LED
8 x LED
Efficiency vs Vin and I LED
Efficiency vs Temperature
Eff ici ency vs. Tem per atur e
10m A
15mA
20m A
80.00%
81.00%82.00%83.00%84.00%85.00%86.00%87.00%88.00%89.00%90.00%-50
050100150
Tem p (C )
Efficiency
TYPICAL PERFORMANCE CHARACTERISTICS
Quiescent Current vs V IN and Temperature
Switching Frequency vs Temperature
APPLICATION INFORMATION
Inductor Selections
For most of the applications of the PT4103, it is recommended to u an inductor of 22uH. Although small size is one of the major factors in lecting an inductor, the smaller and thinner inductors give higher core loss at 1.25MHz and DRC, resulting in lower efficiencies. The following tab le provides a list of recommended inductors:
Part Number
DCR （Ω）
Current Rating （mA ）
Manufacture
LQH3C220 0.71 250 MURATA CDRH3D16-220 0.53 350 SUMIDA LB2012B220M 1.7 75 TAIYO YUDEN LEM2520-220 5.5 125 TAIYO YUDEN
EJPC220KF 4.0 160 PANASONIC
Capacitor Selection
The small size of ceramic capacitors makes them ideal for PT4103 applications. X5R and X7R types are recommended becau 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.
现场施工管理制度Diodes Selection
Schottky diodes, with their low forward voltage drop and fast rever recovery, are the ideal choices for PT4103 applications. The forward voltage drop of a Schottky diode reprents the conduction loss in the
diode, while the diode capacitance (C T or C D ) reprents the switching loss. For diode lection, 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 cau significant switching loss at the 1.25MHz switching frequency of the PT4103. A S
chottky diode rated at 100mA to 200mA is sufficient for most PT4103 applications. Some recommended Schottky diodes are listed in the following table:
Part Number
Forward Current (mA)
Voltage Drop (V)
Diode CAP (Pf)
Manu
facture
CMDSH-3 100
0.58@100mA 7.0@10V
Central CMDSH2-3 200 0.49@200mA 15@10v Central BAT54 200 0.53@100mA 10@25v 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 R FB lection are shown below:
R FB = 104mV/I LED
I LED （mA ） R FB Value （Ω）
5 20.8 10 10.4 15 6.93 20 5.2
