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PDF MP3398A Data sheet ( Hoja de datos )
| Número de pieza | MP3398A | |
| Descripción | White LED Controller | |
| Fabricantes | MPS | |
| Logotipo |  |
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The Future of Analog IC Technology
MP3398A
Step up, 4 strings, Max. 350mA/string
Analog and PWM dimming, White LED Controller
DESCRIPTION
The MP3398A is a step-up controller with 4
current channels, which is designed to drive
WLED arrays for large-size LCD-panel
backlighting applications. It is flexible to expand
the number of LED channels by two or more
ICs in parallel sharing a single inductive power
source.
The MP3398A uses peak-current mode with
fixed switching frequency. The frequency is
programmable by an external setting resistor.
The MP3398A drives an external MOSFET to
boost up the output voltage from a 5V to 28V
input supply. It regulates the current in each
LED string to the value set by an external
current-setting resistor.
The MP3398A applies 4 internal current
sources for current balance. The current
matching can achieve 2.5% regulation accuracy
between strings. Its low regulation voltage on
LED current sources reduces power loss.
The MP3398A can support both analog and
PWM dimming independently to meet the
different dimming-mode request. In addition,
rich protection modes are also integrated
including OCP, OTP, UVP, OVP, LED
short/open protection, inductor/diode short
protection.
The MP3398A is available in SOIC16,
TSSOP16-EP and SOIC20 packages.
FEATURES
• 4-String, Max 350mA/String WLED Driver
• 5V to 28V Input Voltage Range
• 2.5% Current Matching Accuracy Between
Strings
• Programmable Switching Frequency
• PWM and Analog Dimming Mode
• Cascading Capability with a Single Power
Source
• LED Open and Short LED Protection
• Programmable Over-Voltage Protection
• Recoverable Thermal Shutdown Protection
• Over Current Protection
• Inductor/Diode short Protection
• Under-Voltage Lockout
• SOIC16, TSSOP16-EP and SOIC20
Packages
APPLICATIONS
• Desktop LCD Flat Panel Displays
• Flat Panel Video Displays
• 2D/3D LCD TVs and Monitors
All MPS parts are lead-free, halogen 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.
TYPICAL APPLICATION
VIN
GND
L1
C1
15 VIN
GATE 14
C3
16
VCC
1
COMP
ISENSE 13
GND 4
R4
2
EN
MP3398A
12
OVP
C4 5
11
OSC
LED1
R5 7
ADIM
3
PWM
LED2 10
9
LED3
6 ISET
8
LED4
R3
D1
C2
R1
R2
VOUT
MP3398A Rev. 1.03
www.MonolithicPower.com
5/27/2015
MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited.
© 2015 MPS. All Rights Reserved.
1
1 page  
STEP UP, 4 STRINGS, MAX. 350MA/STRING ANALOG AND PWM DIMMING, WHITE LED CONTROLLER
TYPICAL CHARACTERISTICS
MP3398A Rev. 1.03
www.MonolithicPower.com
5/27/2015
MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited.
© 2015 MPS. All Rights Reserved.
5
5 Page 
STEP UP, 4 STRINGS, MAX. 350MA/STRING ANALOG AND PWM DIMMING, WHITE LED CONTROLLER
OPERATION
The MP3398A is a step-up converter with peak-
current mode. It employs 4 channels of current
sources to drive up to 4 strings of white LEDs.
Internal 6V Regulator
The MP3398A includes an internal linear
regulator (VCC). When VIN is greater than 6.5V,
this regulator outputs a 6V power supply to the
external MOSFET switch gate driver and the
internal control circuitry. The VCC voltage drops
to 0V when the chip shuts down. The MP3398A
features under-voltage lockout (UVLO). The
chip is disabled until VCC exceeds the UVLO
threshold. The UVLO hysteresis is
approximately 200mV.
System Startup
When enabled, the MP3398A checks the
topology connection first. The chip monitors the
over-voltage protection (OVP) pin to see if the
Schottky diode is not connected or if the boost
output is shorted to GND. An OVP voltage of
less than 75mV will disable the chip. The
MP3398A also checks other safety limits,
including UVLO and over-temperature
protection (OTP), over-current protection after
passing the OVP test. If all the protection tests
pass, the chip then starts boosting the step-up
converter with an internal soft-start.
It is recommended that the enable signal occurs
after the establishment of the input voltage and
PWM dimming signal during the start-up
sequence to avoid large inrush current.
Step-Up Converter
The converter operating frequency is
programmable (from 100kHz to 500kHz) with a
external resistor connected to the OSC pin.
This helps to optimize the size of external
components and the efficiency.
At the beginning of each switching cycle, the
internal clock turns on the external MOSFET (In
normal operation, the minimum turn on time is
200ns). A stabilizing ramp added to the output
of the current sense amplifier prevents sub-
harmonic oscillations for duty cycles greater
than 50 percent. This result is fed into the PWM
comparator. When this resulting voltage
reaches the output voltage of the error amplifier
(VCOMP) the external MOSFET turns off.
The output voltage of the internal error amplifier
is an amplified signal of the difference between
the reference voltage and the feedback voltage.
The converter automatically chooses the lowest
active LEDX pin voltage to provide a high-
enough bus voltage to power all the LED arrays.
If the feedback voltage drops below the
reference, the output of the error amplifier
increases. This results in more current flowing
through the MOSFET, thus increasing the
power delivered to the output. This forms a
closed loop that regulates the output voltage.
Under light-load operation, especially in the
case of VOUT ≈ VIN, the converter runs in
pulse-skipping mode where the MOSFET turns
on for a minimum on-time of approximately
200ns, and then the converter discharges the
power to the output for the remaining period.
The external MOSFET remains off until the
output voltage needs to be boosted again.
Dimming Control
The MP3398A provides two dimming methods:
PWM or analog dimming mode.
For PWM dimming, apply a PWM signal to
PWM pin. The LED current is chopped by this
PWM signal and the average LED current is
equal to Iset*D_dim where D_dim is the duty
cycle of PWM dimming signal and Iset is the
LED current amplitude.
For analog dimming, either a PWM signal or DC
signal can be applied to ADIM pin.
When a PWM signal is applied to ADIM pin, this
signal will be filtered by the internal RC filter.
The LED current amplitude is equal to
Iset*D_Dim where D_dim is the duty cycle of
PWM dimming signal and Iset is the LED
current amplitude. 20KHz or higher PWM signal
is recommended to get the better filtering
performance.
MP3398A Rev. 1.03
www.MonolithicPower.com
5/27/2015
MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited.
© 2015 MPS. All Rights Reserved.
11
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| Páginas | Total 19 Páginas | |
| PDF Descargar | [ Datasheet MP3398A.PDF ] | |
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