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PDF MP3394 Data sheet ( Hoja de datos )
| Número de pieza | MP3394 | |
| Descripción | 4-String Max 200mA/String White LED Driver | |
| Fabricantes | MPS | |
| Logotipo |  |
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The Future of Analog IC Technology
MP3394
Step-up, 4-String
Max 200mA/String White LED Driver
DESCRIPTION
The MP3394 is a step-up controller with 4-
channel current sources designed for driving
the WLED arrays for large size LCD panel
backlighting applications. The MP3394 is
flexible for extending LED channels with two or
more MP3394s in parallel while operating from
a single inductor power source.
The MP3394 uses current mode, fixed
frequency architecture. The switching frequency
is programmable by an external frequency
setting resistor. It drives an external MOSFET
to boost up the output voltage from a 5V to 28V
input supply. The MP3394 regulates the current
in each LED string to the programmed value set
by an external current setting resistor.
The MP3394 applies 4 internal current sources
for current balance and the current matching
can achieve 2.5% regulation accuracy between
strings. Its low 350mV regulation voltage on
LED current sources reduces power loss and
improves efficiency.
PWM dimming is implemented with external
PWM input signal or DC input signal. The
dimming PWM signal can be generated
internally and the dimming frequency is
programmed by an external setting capacitor.
TYPICAL APPLICATION
VIN
5V~28V
CIN
L1
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, SOIC20 Package
APPLICATIONS
• Desktop LCD Flat Panel Displays
• 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.
D1
COUT
Enable
DIMMING
CVCC
15 VIN
16 VCC
C RCOMP
COMP 1 COMP
GATE 14
ISENSE 13
2 EN
MP33945 OSC
GND 4
R OSC
OVP 12
RBOSC
7 BOSC
C BOSC
LED1 11
LED2 10
RSET
3 DBRT
6 ISET
LED3 9
LED4 8
M1
RSENSE
R1
R2
MP3394 Rev. 1.07
www.MonolithicPower.com
3/21/2013
MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited.
© 2013 MPS. All Rights Reserved.
1
1 page  
MP3394—4-STRING, MAX 200mA/STRING WHITE LED DRIVER
PIN FUNCTIONS
TSSOP16EP
&SOIC16
1
SOIC20
1
Name Description
COMP
Step-up Converter Compensation Pin. This pin is used to compensate the
regulation control loop. Connect a ceramic capacitor from COMP to GND.
2 2 EN Enable Control Input. Do not let this pin float.
Brightness Control Input. To use external PWM dimming mode, apply a
PWM signal on this pin for brightness control. To use DC input PWM
3 3 DBRT dimming mode, apply a DC voltage range from 0.2V to 1.2V on this pin
linearly to set the internal dimming duty cycle from 0% to 100%. The MP3394
has positive dimming polarity on DBRT.
4 5 GND Ground.
Switching Frequency Set. Connect a resistor between OSC and GND to set
5
7
OSC
the step-up converter switching frequency. The voltage at this pin is
regulated to 1.23V. The clock frequency is proportional to the current
sourced from this pin.
LED Current Set. Tie a current setting resistor from this pin to ground to
6
8
ISET
program the current in each LED string. This pin voltage is regulated to
1.23V. The LED current is proportional to the current through the ISET
resistor.
Dimming Repetition Set. This is the timing pin for the oscillator to set the
dimming frequency. To use DC input PWM dimming mode, connect a
7
9
BOSC
capacitor from this pin to GND to set the internal dimming frequency. A saw-
tooth waveform is generated on this pin. To use external PWM dimming
mode, connect a resistor from this pin to GND, and apply the PWM signal on
DBRT pin.
8
10
LED4
LED String 4 Current Input. This pin is the open-drain output of an internal
dimming control switch. Connect the LED String 4 cathode to this pin.
9
11
LED3
LED String 3 Current Input. This pin is the open-drain output of an internal
dimming control switch. Connect the LED String 3 cathode to this pin.
10
12
LED2
LED String 2 Current Input. This pin is the open-drain output of an internal
dimming control switch. Connect the LED String 2 cathode to this pin.
11
13
LED1
LED String 1 Current Input. This pin is the open-drain output of an internal
dimming control switch. Connect the LED String 1 cathode to this pin.
Over-voltage Protection Input. Connect a resistor divider from output to this
12 14 OVP pin to program the OVP threshold. When this pin voltage reaches 1.23V, the
MP3394 triggers Over Voltage Protection mode.
MP3394 Rev. 1.07
www.MonolithicPower.com
3/21/2013
MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited.
© 2013 MPS. All Rights Reserved.
5
5 Page 
MP3394—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 150kHz 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) = 62100 / ROSC（kΩ）
For ROSC=330kΩ, the switching frequency is set
to 188 kHz.
Setting the LED Current
The LED string currents are identical and set
through the current setting resistor on the ISET
pin.
ILED(mA) = 790 x 1.23V / (RSET+0.4)(kΩ)
For RSET=7.68kΩ, the LED current is set to
120mA. The ISET pin can not be open.
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
high frequency switching current from passing
through the input. Ceramic capacitors with X5R
or X7R dielectrics are highly recommended
because of their low ESR and small temperature
coefficients. For most applications, a 4.7μF
ceramic capacitor paralleled a 220uF electrolytic
capacitor is sufficient.
Selecting the Inductor and Current Sensing
Resistor
The inductor is required to force the 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. The minimum
value of inductor is selected to ensure that the
boost converter works in continuous conduction
mode for high efficiency and good EMI
performance.
Calculate the required inductance value by the
equation:
L
≥
η × VOUT ×
2 × fSW
D × (1− D)2
× ILOAD
D = 1− VIN
VOUT
Where VIN and VOUT is the input and output
voltage, fSW is the switching frequency, ILOAD is
the LED load current, and η is the efficiency.
The switch 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 should be 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 MP3394 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)
4. Gate source charge QGS and gate drain
charge QGD
5. Total gate charge, QG
MP3394 Rev. 1.07
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 MP3394.PDF ] | |
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