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PDF MP3397 Data sheet ( Hoja de datos )
| Número de pieza | MP3397 | |
| Descripción | 4-String Max 350mA/String White LED Driver | |
| Fabricantes | MPS | |
| Logotipo |  |
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Hay una vista previa y un enlace de descarga de MP3397 (archivo pdf) en la parte inferior de esta página. Total 16 Páginas | ||
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The Future of Analog IC Technology
DESCRIPTION
The MP3397 is a step-up controller with 4
current channels designed to drive WLED
arrays for large-size LCD-panel backlighting
applications. The MP3397 is flexible, and can
expand the number of LED channels with two
or more MP3397s in parallel operating from a
single inductive power source.
The MP3397 uses current-mode fixed-
frequency architecture. An external resistor sets
the switching frequency. This signal drives an
external MOSFET to boost up the output
voltage from 5V to a 28V input supply. The
MP3397 regulates the current in each LED
string to the programmed value set by an
external current-setting resistor.
The MP3397 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. The dimming
PWM signal can be generated internally and
the dimming frequency is programmed by an
external setting capacitor.
MP3397
Step-Up, 4-String
Max 350mA/String White LED Driver
FEATURES
4-String, Max 350mA/String at 10% DPWM
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
16-pin TSSOP，SOIC Package
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.
MP3397 Rev. 1.01
www.MonolithicPower.com
9/4/2012
MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited.
© 2012 MPS. All Rights Reserved.
1
1 page  
MP3397—4-STRING, MAX 350mA/STRING WHITE LED DRIVER
ELECTRICAL CHARACTERISTICS (continued)
VIN =12V, VEN = 5V, TA = 25°C, unless otherwise noted.
Parameters
Symbol Condition
Min Typ
LEDX Regulation Voltage
VLEDX ILED=180mA
390
PROTECTION
OVP(Over Voltage Protection)
Threshold
OVP UVLO threshold
LEDX UVLO Threshold
LEDX Over Voltage Threshold
Thermal Shutdown Threshold
VOVP_OV
VOVP_UV
VLEDX_UV
VLEDX_OV
TST
Rising Edge
Step-up Converter Fails
1.20 1.23
50 70
156 196
5.8 6.3
150
Notes:
5) Matching is defined as the difference of the maximum to minimum current divided by 2 times average currents.
Max
1.26
90
236
6.8
Units
mV
V
mV
mV
V
°C
MP3397 Rev. 1.01
www.MonolithicPower.com
9/4/2012
MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited.
© 2012 MPS. All Rights Reserved.
5
5 Page 
MP3397—4-STRING, MAX 350mA/STRING WHITE LED DRIVER
APPLICATION INFORMATION
Selecting the Switching Frequency
Set the switching frequency of the step-up
converter from 150kHz to 500kHz for most
applications. An oscillator resistor on OSC pin
sets the internal oscillator frequency for the step-
up converter according to the equation:
fSW(kHz)
62100
ROSC(k)
For ROSC=330kΩ, the switching frequency is set
to 188kHz.
Setting the LED Current
The LED string currents are identical and set
through the current setting resistor on the ISET
pin.
ILED (mA )
790 1.23V
(RSET +0.4)k
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
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 MP3397 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, larger-
value inductors have 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 MP3397 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
MP3397 Rev. 1.01
www.MonolithicPower.com
9/4/2012
MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited.
© 2012 MPS. All Rights Reserved.
11
11 Page | ||
| Páginas | Total 16 Páginas | |
| PDF Descargar | [ Datasheet MP3397.PDF ] | |
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