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PDF MP3394S Data sheet ( Hoja de datos )
| Número de pieza | MP3394S | |
| Descripción | 4-String Max 200mA/String White LED Driver | |
| Fabricantes | MPS | |
| Logotipo |  |
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The Future of Analog IC Technology
MP3394S
Step-Up, 4-String
Max 200mA/String White LED Driver
DESCRIPTION
The MP3394S is a step-up controller with 4
current channels. It’s designed to drive WLED
arrays for large-size LCD-panel backlighting
applications. The MP3394S is flexible, and can
expand the number of LED channels with 1 or 2
MP3394S in parallel operating from a single
inductive power source.
The MP3394S uses an architecture of current –
mode and fixed operation frequency The
frequency is programmable by an external
frequency-setting resistor. MP3394S 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
programmed value set by an external current-
setting resistor.
The MP3394S 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 and
improves efficiency.
An external PWM input signal or DC input
signal controls PWM dimming. In DC-input
dimming mode, the dimming PWM signal can
be generated internally and the dimming
frequency is programmed by an external setting
capacitor.
FEATURES
• 4-String, Max 200mA/String WLED Driver
• 5V to 28V Input Voltage Range
• 2.5% Current Matching Accuracy Between
Strings
• Programmable Switching Frequency
• PWM or DC Input Burst PWM Dimming
• Open and Short LED Protection
• Programmable Over-Voltage Protection
• Cascading Capability with a Single Power
Source
• Under-Voltage Lockout
• Thermal Shutdown
• TSSOP16EP, SOIC16 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 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
5V to 28V
CIN
L1
MP3394S
Enable
DIMMING
VIN
15
CVCC
VCC
16
CCOMPRCOMP 1 COMP
EN
2
ROSC
OSC
5
RBOSC
BOSC
7
CBOSC
RSET
DBRT
3
ISET
6
GATE
14
ISENSE
13
GND
4
OVP
12
LED1
11
LED2
10
LED3
9
LED4
8
D1
COUT
R1
M1
R2
RSENSE
MP3394S Rev. 1.03
www.MonolithicPower.com
3/21/2013
MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited.
© 2013 MPS. All Rights Reserved.
1
1 page  
MP3394S—4-STRING, MAX 200mA/STRING WHITE LED DRIVER
TYPICAL PERFORMANCE CHARACTERISTICS
VIN = 12V, 10LEDs in series 4 strings, 120mA/string, unless otherwise noted.
Efficiency vs. VIN
Steady State
VIN Power On
100
95
90 VSW
85 20V/div.
80
75 VOUT
70
65
20V/VdiIvN.
10V/div.
60
55
IINDUCTOR
1A/div.
50
5 10 15 20 25 30
VSW
20V/div.
VOUT
20V/div.
VIN
10V/div.
ILED
500mA/div.
EN Power On
VSW
20V/div.
VOUT
20V/div.
VEN
5A/div.
ILED
500mA/div.
VSW
20V/div.
VOUT
20V/div.
VBOSC
1V/div.
ILED
500mA/div.
VSW
20V/div.
VOUT
20V/div.
VPWMI
5V/div.
ILED
500mA/div.
Open LED Protection
Open all LED string at working
Open LED Protection
Open one LED string at working
Short LED Protection
Short VOUT to LEDx at working
VSW
20V/div.
VOUT
20V/div.
ILED
500mA/div.
VSW
20V/div.
VOUT
20V/div.
ILED
500mA/div.
VSW
20V/div.
VOUT
20V/div.
VLED1
20V/div.
ILED
500mA/div.
MP3394S Rev. 1.03
www.MonolithicPower.com
3/21/2013
MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited.
© 2013 MPS. All Rights Reserved.
5
5 Page 
MP3394S—4-STRING, MAX 200mA/STRING WHITE LED DRIVER
APPLICATION INFORMATION
Selecting the Switching Frequency
The switching frequency of the step-up converter
is recommended from 100kHz to 500kHz for
most of application. An oscillator resistor on OSC
pin sets the internal oscillator frequency for the
step-up converter according to the equation:
fSW(kHz)
=
69190
ROSC(kΩ)
For ROSC=374kΩ, the switching frequency is set
to 185 kHz.
Setting the LED Current
The LED string currents are identical and set
through the current setting resistor on the ISET
pin. The ISET pin can not be open.
ILED(mA)
=
800
(RSET
×1.22V
+ 0.5)kΩ
Selecting the Input Capacitor
The input capacitor reduces the surge current
drawn from the input supply and the switching
noise from the device. The input capacitor
impedance at the switching frequency should be
less than the input source impedance to prevent
the high-frequency switching current from
passing through to the input. Use ceramic
capacitors with X5R or X7R dielectrics for their
low ESR and small temperature coefficients. For
most applications, use a 4.7μF ceramic capacitor
in parallel with a 220µF electrolytic capacitor.
Selecting the Inductor and Current Sensing
Resistor
The MP3394S requires an inductor to supply a
higher output voltage while being driven by the
input voltage. A larger value inductor results in
less ripple current, resulting in lower peak
inductor current and reducing stress on the
internal N-channel MOSFET. However, the larger
value inductor has a larger physical size, higher
series resistance, and lower saturation current.
Choose an inductor that does not saturate under
the worst-case load conditions. Select the
minimum inductor value to ensure that the boost
converter works in continuous conduction mode
with high efficiency and good EMI performance.
Calculate the required inductance value using the
equation:
L
≥
η × VOUT ×
2 × fSW
D × (1− D)2
× ILOAD
D = 1− VIN
VOUT
Where VIN and VOUT are the input and output
voltages, fSW is the switching frequency, ILOAD is
the LED load current, and η is the efficiency.
The switching current is usually used for the peak
current mode control. In order to avoid hitting the
current limit, the voltage across the sensing
resistor RSENSE must measure less than 80% of
the worst-case current-limit voltage, VSENSE.
RSENSE
=
0.8 × VSENSE
IL(PEAK)
IL(PEAK)
=
VOUT × ILOAD
ηVIN
+
VIN × (VOUT -VIN )
2 × L × fSW × VOUT
Where IL(PEAK) is the peak value of the inductor
current. VSENSE is shown in Figure 3.
Vsense vs. Duty Cycle
500
400
300
200
100
0 0 10 20 30 40 50 60 70 80 90100
DUTY CYCLE (%)
Figure 3—VSENSE vs Duty Cycle
Selecting the Power MOSFET
The MP3394S is capable of driving a wide variety
of N-channel power MOSFETS. The critical
parameters of selection of a MOSFET are:
1. Maximum drain-to-source voltage, VDS(MAX)
2. Maximum current, ID(MAX)
3. On-resistance, RDS(ON)
MP3394S Rev. 1.03
www.MonolithicPower.com
3/21/2013
MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited.
© 2013 MPS. All Rights Reserved.
11
11 Page | ||
| Páginas | Total 17 Páginas | |
| PDF Descargar | [ Datasheet MP3394S.PDF ] | |
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