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Número de pieza | MP1488 | |
Descripción | 800mA Fixed Frequency White LED Driver | |
Fabricantes | MPS | |
Logotipo | ||
Hay una vista previa y un enlace de descarga de MP1488 (archivo pdf) en la parte inferior de esta página. Total 8 Páginas | ||
No Preview Available ! MP1488
800mA Fixed Frequency
White LED Driver
The Future of Analog IC Technology
MPS CONFIDENTIAL AND PROPRIETARY INFORMATION – INTERNAL USE ONLY
DESCRIPTION
The MP1488 is a step-up converter designed for
driving up to 27 WLEDs (9 strings of 3 WLEDs
each) from a 5V system rail. The MP1488 uses a
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 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 MP1488 includes under-voltage lockout,
current limiting and thermal overload protection
preventing damage in the event of an output
overload.
The MP1488 is available in a small 6-pin TSOT23
package.
FEATURES
• 2.5V to 6V Input Voltage Range
• On Board Power MOSFET
• Drives up to 27 White LEDs at 5V Input
• Up to 92% Efficiency
• Over 1MHz Fixed Switching Frequency
• Open Load Shutdown
• Low 104mV Feedback Voltage
• Soft-Start/PWM Dimming
• UVLO, Thermal Shutdown
• Internal 800mA Current Limit
• Available in a TSOT23-6 Package
APPLICATIONS
• Cell Phones
• Handheld Computers and PDAs
• Digital Still Cameras
• Small LCD Displays
“MPS” and “The Future of Analog IC Technology” are Registered Trademarks of
Monolithic Power Systems, Inc.
TYPICAL APPLICATION
IN SW
EN EN MP1488 OV
GND
FB
Efficiency vs
Input Voltage
100
IOUT=100mA
90
IOUT=180mA
80
70
60
50
4.0
4.5 5.0 5.5
INPUT VOLTAGE (V)
6.0
MP1488 Rev. 0.9
4/7/2008
www.MonolithicPower.com
MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited.
© 2008 MPS. All Rights Reserved.
1
1 page MP1488 – 800mA, FIXED FREQUENCY WHITE LED DRIVER
MPS CONFIDENTIAL AND PROPRIETARY INFORMATION – INTERNAL USE ONLY
APPLICATION INFORMATION
OFF ON
IN
EN
GND
SW
OV
FB
Figure 2—Circuit for Driving 27 WLEDs
A typical application circuit is provided in Figure
2. The 27 white LEDs can be driven from a
voltage supply range of 4V to 6V at a total
output current of 180mA. A 2.2µF output
capacitor is sufficient for most applications but
up to 1µF may be used. A 10µH inductor with
low DCR (inductor resistance) is recommended
to improve efficiency. A 4.7µF ceramic
capacitor is recommended for the input
capacitance in the real system. Schottky diodes
with fast recovery and a low forward voltage are
recommended. Schottky diodes with a 500mA
rating are sufficient for the MP1488. The
switching characteristics during normal
operation can be seen in Figure 3. The MP1488
has internal soft-start to limit the amount of
current through the IN pin at startup and to also
limit the amount of overshoot on the output. The
current limit is increased by a fourth every 40µs
giving a total soft-start time of 120µs.
Figure 3—Steady State Operation
Figure 4 shows the startup behavior of the
MP1488. The ramped voltage added to the
current sense amplifier reduces the current
output as the duty cycle increases. As more
LEDs are added, the output voltage rises but
the current that can be delivered to the load is
reduced as well.
MP1488 Rev. 0.9
4/7/2008
www.MonolithicPower.com
MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited.
© 2008 MPS. All Rights Reserved.
5
5 Page |
Páginas | Total 8 Páginas | |
PDF Descargar | [ Datasheet MP1488.PDF ] |
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