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PDF MP3393EY Data sheet ( Hoja de datos )
| Número de pieza | MP3393EY | |
| Descripción | 8-String Step-Up White LED Driver | |
| Fabricantes | MPS | |
| Logotipo |  |
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The Future of Analog IC Technology
DESCRIPTION
The MP3393 is a step-up controller with 8
current channel sources designed to power
WLED backlights for large LCD panels.
The MP3393 uses current-mode fixed-frequency
architecture. It drives an external MOSFET to
boost the output voltage. The switching frequency
is programmable by an external setting resistor.
The MP3393 integrates a constant-current control
circuit to regulate the current in each LED string
to the value set by an external current feedback
resistor. Current matching can achieve 1.2%
regulation accuracy between strings. Its low
202mV regulation voltage reduces power loss
and improves efficiency.
The MP3393 includes protections including
under-voltage lockout, LED open/short protection,
and thermal shutdown. The fault flag pin indicates
the statuses of all fault signals.
The MP3393 can be daisy-chained to expand
the number of LED channels. It is available in
TSSOP28EP and SOIC28 packages.
MP3393
8-String Step-Up White LED Driver
with External Transistor
FEATURES
• 9V-to-32V Input Voltage Range
• Drives 8 Channels of LED strings
• Internal Constant-Current Control
• Maximum Channel Current Over 350mA
• 1.2% Current Matching Accuracy Between
Strings
• Programmable Switching Frequency
• Analog Dimming and External PWM
Dimming
• Open and Short LED Protection
• Programmable Over-Voltage Protection
• Fault Output Flag
• Thermal Shutdown
• Extendable LED Channels that Share One
Power Stage Set
• TSSOP28EP and SOIC28 Packages
APPLICATIONS
• Flat Panel Video Displays
• LCD TVs and Monitors
All MPS parts are lead-free and adhere to the RoHS directive. For MPS green
status, please visit MPS website under Quality Assurance.
“MPS” and “The Future of Analog IC Technology” are Registered Trademarks of
Monolithic Power Systems, Inc.
MP3393 Rev. 1.05
www.MonolithicPower.com
3/26/2013
MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited.
© 2013 MPS. All Rights Reserved.
1
1 page  
MP3393—8-STRING WHITE LED DRIVER WITH STEP-UP CONTROLLER
ELECTRICAL CHARACTERISTICS (continued)
VIN =12V, VEN = 5V, TA = +25°C, unless otherwise noted.
Parameters
Symbol Condition
PROTECTION
OVP Over Voltage Threshold
OVP UVLO threshold
CTLx UVLO Threshold
CTLx Over Voltage Threshold
Thermal Shutdown Threshold
FF Pull Down Resistance
VFAULT Pull Down Current
VFAULT Blocking-Off Voltage
(with Respect to VIN)
VOVP_OV
VOVP_UV
VCTL_UV
VCTL_OV
TST
RFF
IFAULT
VFAULT
Rising Edge
Step-up Converter Fails
VIN =24V, VIN-VFAULT
Min Typ Max Units
1.20
50
180
6
40
5
1.23
70
210
6.4
150
22
55
5.5
1.26
90
240
6.8
70
6
V
mV
mV
V
℃
Ω
μA
V
MP3393 Rev. 1.05
www.MonolithicPower.com
3/26/2013
MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited.
© 2013 MPS. All Rights Reserved.
5
5 Page 
MP3393—8-STRING WHITE LED DRIVER WITH STEP-UP CONTROLLER
OPERATION
The MP3393 is a step-up controller with 8
internal constant current control circuit to regulate
an array of 8 strings of white LEDs. It employs
peak-current mode with programmable operation
frequency. Refer to the block diagram in Figure 1
for some of the operational details.
Internal 10V Regulator
The MP3393 has an internal linear regulator,
VCC. When VIN exceeds 10V, this regulator
provides a 10V power supply for the internal
MOSFET switch gate driver and the internal
control circuitry. The VCC voltage drops to 0V
when the chip shuts down. The MP3393 features
under-voltage lockout that disables the chip until
VCC exceeds the UVLO threshold. The UVLO
hysteresis is approximately 400mV.
System Startup
When the MP3393 is enabled, the chip monitors
the OVP pin to see whether the Schottky diode is
connected and whether the boost output is
shorted to GND. The chip is disabled if the OVP
voltage drops below 70mV. The MP3393 also
checks for other safety limits, including under-
voltage, over-voltage, and over-temperature
conditions. If the device functions within normal
working parameters, it boosts the output voltage
with an internal soft-start.
The start-up sequence consists of establishing
the input voltage and the PWM dimming signal
before the enable signal.
Step-up Converter
The device’s operating frequency is
programmable from 100kHz to 500kHz through
an external set resistor on the OSC pin. This
customizable frequency is helpful to optimize
external components for size and efficiency.
At the beginning of each cycle, the internal clock
turns on the external MOSFET. The addition of a
stabilizing ramp at the output of the current-sent
amplifier prevents sub-harmonic oscillations at
duty cycles greater than 50%; the output is fed
into the PWM comparator. When this voltage
reaches the output voltage level of the error
amplifier (VCOMP), the external MOSFET turns off.
The voltage at the output of the internal error
amplifier is the amplified difference between the
320mV reference voltage and the feedback
voltage. The converter automatically chooses the
lowest active CTLx pin voltage to provide the bus
voltage to power all the LED arrays.
If the feedback voltage drops below the 300mV
reference, the output of the error amplifier
increases. This results in more current flowing
through the power FET, thus increasing the
power delivered to the output. In this way it forms
a closed loop to regulate the output voltage.
Internal Accurate Constant Current Control
The MP3393 employs an internal current-control
circuit to provide accurate constant current
regulation. The FBx pin detects the LED current
and provides the signal to the current-control
circuit. The CTLx pin controls the external PNP
transistor to accurately regulate the LED current.
Both features improve thermal performance for
high-current LED applications.
Dimming Control
The MP3393 provides both analog dimming
mode and external PWM dimming mode. For
analog dimming mode, apply a 0.4V-to-1.5V DC
signal on the PWM pin to linearly program the
LED current from 0% to 100%. For PWM
dimming, apply an external PWM signal: The
brightness of the LED array is proportional to the
duty cycle of the external PWM signal. Use a
PWM frequency range from 50Hz to 2kHz.
Open-String Protection
The MP3393 uses over-voltage protection (OVP)
to provide open string protection: If one or more
strings are open, then the voltage on the
respective CTLx pin is low and the IC keeps
raising the output voltage until it reaches the
OVP threshold. The part can then discern the
open strings and shut down it because their
CTLx pin voltages are less than 210mV. Once
the part finishes determining the open strings, the
remaining LED strings force the output voltage
back into tight regulation. The string with the
highest voltage drop is the feedback string that
regulates the output voltage.
The MP3393 always tries to light at least one
string: If all strings in use are open, the MP3393
shuts down the step-up converter. The open
MP3393 Rev. 1.05
www.MonolithicPower.com
3/26/2013
MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited.
© 2013 MPS. All Rights Reserved.
11
11 Page | ||
| Páginas | Total 19 Páginas | |
| PDF Descargar | [ Datasheet MP3393EY.PDF ] | |
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