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PDF MP3205 Data sheet ( Hoja de datos )
| Número de pieza | MP3205 | |
| Descripción | 1.3MHz Fixed Frequency 5 White LED Driver | |
| Fabricantes | MPS | |
| Logotipo |  |
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Hay una vista previa y un enlace de descarga de MP3205 (archivo pdf) en la parte inferior de esta página. Total 6 Páginas | ||
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www.DataSheet4U.com
TM
The Future of Analog IC Technology TM
DESCRIPTION
The MP3205 is a step-up converter designed
for driving up to 5 series white LEDs from a
single cell Lithium Ion battery. The MP3205
uses current mode, fixed frequency architecture
to regulate the LED current, which is measured
through an external current sense resistor. Its
low 104mV feedback voltage reduces power
loss and improves efficiency.
The MP3205 includes under-voltage lockout,
current limiting and thermal overload protection
preventing damage in the event of an output
overload. The MP3205 is available in a small
5-pin TSOT23 package.
EVALUATION BOARD REFERENCE
Board Number
Dimensions
EV3205DJ-00A
1.9”X x 1.8”Y x 0.4”Z
MP3205
1.3MHz Fixed Frequency
5 White LED Driver
FEATURES
• On Board Power MOSFET
• Drives up to 5 Series White LEDs
• Up to 87% Efficiency
• Over 1MHz Fixed Switching Frequency
• Low 104mV Feedback Voltage
• Soft-Start/PWM Dimming
• UVLO, Thermal Shutdown
• Internal Current Limit
• Available in a TSOT23-5 Package
APPLICATIONS
• Cell Phones
• Handheld Computers and PDAs
• Digital Still Cameras
• Small LCD Displays Application
“MPS” and “The Future of Analog IC Technology” are Trademarks of Monolithic
Power Systems, Inc.
TYPICAL APPLICATION
CMDSH-3
VIN
5V LED1
LED2
51
EN
4
2
IN SW
EN MP3205
GND
FB
3
LED3
LED4
LED5
MP3205-TAC-S01
Efficiency vs
LED Current
88
87 4 LEDs
86
85
84
83
82
5 LEDs
81
80
79
78
77
5
3 LEDs
VIN=3.6V
10 15
LED CURRENT (mA)
20
MP3205-EC01
MP3205 Rev. 1.3
7/13/2005
www.MonolithicPower.com
MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited.
© 2005 MPS. All Rights Reserved.
1
1 page  
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MP3205 – 1.3 MHz FIXED FREQUENCY 5 WHITE LED DRIVER
Setting the LED Current
The LED current is controlled by the feedback
resistor, R1, in Figure 2. The current through
the LEDs is given by the equation 104mV/R1.
Table 1 shows the selection of resistors for a
given LED current.
Table 1—ILED vs. R1
ILED (mA)
1
5
10
15
20
R1 (Ω)
104
20.8
10.4
6.93
5.2
Analog and Digital Dimming
There are three different ways to control dimming
for the MP3205 during normal operation. The first
way uses a DC voltage to control the feedback
voltage. This can be seen in Figure 6. As the DC
voltage increases, current starts flowing down R1,
R2 and R3. The loop will continue to regulate the
feedback voltage to 104mV. Thus the current has
to decrease through the LEDs by the same
amount of current as is being injected from the
DC voltage source. With a VDC from 0V to 2V, the
resistor values shown for R2 and R3 can control
the LED current from 0mA to 20mA.
VDC
signal used in Figure 7 should be 1KHz or
below due to the soft start function.
PWM
LED1
LED2
LED3
4
MP3205
EN FB
3
MP3205_F07_S01
Figure 7—PWM Dimming Control Using a
Logic Signal
If the PWM signal is above 1KHz, dimming can
be achieved by using the circuit shown in
Figure 8.
PWM
MP3205
FB
3
LED1
LED2
LED3
MP3205
FB
3
LED1
LED2
LED3
MP3205_F06_S01
Figure 6—Dimming Control Using a DC Voltage
Other applications need to use a logic signal to
do the dimming. This can be seen in Figure 7.
The PWM signal is applied to the EN pin of the
MP3205. The LEDs will switch between full load
to completely shut off. The average current
through the LEDs will increase proportionally to
the duty cycle of the PWM signal. The PWM
MP3205_F08_S01
Figure 8—Dimming Control Using a Filtered
PWM Signal
Layout Considerations
Careful attention must be paid to the PCB
board layout and component placement. Proper
layout of the high frequency switching path is
critical to prevent noise and electromagnetic
interference problems. Due to the high
frequency switching the length and area of all
the traces connected to the switch node should
be minimized. Refer to the evaluation board
EV3205DJ-00A for a sample layout of
theBMP3205.
MP3205 Rev. 1.3
7/13/2005
www.MonolithicPower.com
MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited.
© 2005 MPS. All Rights Reserved.
5
5 Page | ||
| Páginas | Total 6 Páginas | |
| PDF Descargar | [ Datasheet MP3205.PDF ] | |
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