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OB3362F 데이터시트 PDF




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부품번호 OB3362F 기능
기능 4 Channels High Performance LED Driver
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OB3362F 데이터시트, 핀배열, 회로
OB3362F
4 Channels High Performance LED Driver
GENERAL DESCRIPTION
The OB3362F is a highly integrated and high
performance LED driver that optimized for LCD
backlight application. It integrates a boost driver
and 4 channels of current balancer that optimized
to drives multi LED arrays, and thus provides a
high performance LED backlight solution with
minimized BOM count.
The OB3362F contains a PWM boost driver which
uses current mode control and fixed frequency
operation. The operation frequency can be
programmed by setting external resistor value at
RI pin.
The OB3362F integrates 4 channels current
balancer with up to 200mA current capability per
channel and it can achieve 3% matching accuracy
among LED strings. The minimum voltage of
current source is regulated to as lower as 350mV,
which benefits the efficiency and improves the IC
thermal performance.
The OB3362F supports external PWM dimming
and internal burst dimming mode which allow
flexible control of the backlight luminance. The
LED current is directly modulated by external
PWM duty cycle when PWM dimming mode is
selected. The LED current can be adjusted by an
external DC voltage when internal burst dimming
mode is selected.
TYPICAL APPLICATION
FEATURES
„ 10V gate drive, better MOS compatibility
„ High Efficiency and Compact Size
„ 6V to 30V Input Voltage Range
„ 3% Matching Accuracy Between 4 LED
Strings Control Current
„ 100KHz~600KHz Operating Frequency
„ Internal/External PWM Dimming
„ Very Low Standby Power
„ Programmable Over Voltage Protection
„ Under Voltage Lockout(UVLO)
„ Open/Short LED Protection
„ Thermal Shutdown
APPLICATIONS
„ LCD Monitor
„ LCD TV
„ Flat panel display
OB3362F is offered in 16-pin ESOP/DIP
Figure1: OB3362F Typical Application Schematic
©On-Bright Electronics
Confidential
-1-
Preliminary Datasheet
OB_DOC_DS_3362F00




OB3362F pdf, 반도체, 판매, 대치품
Functional Block Diagram
VIN
OB3362F
4 Channels High Performance LED Driver
VCC
ENA
GND
RI
CMP
BF/DMOD
DIM
UVLO
LDO 10V
5V
Drive
OSC
CLK
S
+
-
- 350mV
EA
+
PWM
Control
Logic
+
- 1.2V
Dimming
Control
DIM
Feedback
Control
1.2V
+
-
Current
Control
GATE
CS
OVP
LED1
LED4
ISET
Figure2: OB3362F Functional Block Diagram
©On-Bright Electronics
Confidential
-4-
Preliminary Datasheet
OB_DOC_DS_3362F00

4페이지










OB3362F 전자부품, 판매, 대치품
OB3362F
4 Channels High Performance LED Driver
Function Description
General Operation
The OB3362F LED driver is designed for LCD
backlight system applications. It incorporates a
fixed frequency, current mode boost converter, a
10V regulator specially to power the gate driver,
dimming control circuits and 4 channels current
sources which regulate the current of LED array
made up by 4 LED strings. When enabled, the
converter boosts the output voltage to provide
sufficient headroom for the current sources to
regulate their respective string current. OB3362F
features programmable operation frequency
(100KHz to 600KHz) by setting the resistor on RI
pin which allows the trade-off between the
external components and the efficiency.
Internal burst and external PWM dimming modes
are provided to offer the flexible dimming control.
OB3362F offers comprehensive protection
features to protect the system in various fault
conditions. The open/short LED string protection
ensures that one or more LED strings fail do not
cause overall LED array out of function. The
cycle-by-cycle current limit function limits the
maximum current flowing through the external
power MOSFET. The over temperature protection
ensures that the system will not run into condition
of thermal runaway and blow up.
The principle of operation can be understood by
referring to the block diagram.
Internal 10V Regulator VCC and UVLO
The OB3362F includes an internal switching mode
regulator which is specially used to power the gate
driver. When the VIN is great than 10V, the
regulator generates a 10V supply. If VIN smaller
than 10V, the output of regulator can follow VIN
voltage until VIN drop below the UVLO voltage
threshold. The OB3362F also has an internal 5V
regulator to power the rest analog and logic
circuitry.
The OB3362F have Under Voltage Lockout
(UVLO) function. The chip is disabled when the
Vin is below the UVLO threshold (typically 5.2V)
and the hysteresis of UVLO is nearly 200mV.
Fixed-Frequency Boost converter
A fixed-frequency, current mode, boost converter
is built in and it automatically chooses the lowest
active LEDX voltage to regulate the output voltage.
The resulting error signal is amplified and
compared to the internal sensing current signal
plus the slope compensation to determine the
on-time of the switching MOSFET. The error
amplifier sources or sinks the current to the COMP
pin to adjust the required inductor current as the
load changes. The slope-compensation signal is
added to the current-sense signal to improve the
stability at high duty cycles.
The OB3362F has a gate driver which can provide
10V high level voltage (when VCC=10V), this can
greatly extend the select range of external power
MOSFET as well as increase the overall system
efficiency.
At light loads, the OB3362F automatically skips
some pulses to improve efficiency and also
prevent overcharging the output capacitor. In the
pulse-skipping mode, the inductor current ramps
up for a minimum on-time (typical 140ns), then
deliver the stored energy to the output. The switch
remains off until another pulse is needed to boost
the output voltage.
LED Current Sources
Maintaining uniform LED brightness and dimming
capability are critical for LCD backlighting
applications. The OB3362F is equipped with 4
matched current sources. These specialized
current sources are accurate to within 3%. All LED
full-scale currents are identical by setting through
the resistor at ISET pin (18mA < ILED < 200mA).
I LED
=
3000 ×
1.2V
RSET
The minimum voltage drop across each current
source is approximately 350mV. The low voltage
drop helps to reduce the dissipation while
maintaining sufficient compliance to control the
LED current within the required tolerances.
If any one channel out of the total 4 channels is not
used, the relative LEDX pin should be connected
to a voltage that higher than 5.5V to disable this
channel, the LEDX voltage must lower than 40V to
prevent IC be damaged.
All LEDX pins in use are measured and the lowest
voltage is extracted and fed into the step-up
converter’s error amplifier to regulate the step-up
converter’s output voltage.
Frequency Setting
The internal oscillator frequency is set by the
resistor on at RI pin as shown in the equation.
High frequency operation optimizes the regulator
for small component size at the expense of
efficiency due to increased switching losses. While
low frequency operation offers the better overall
efficiency, but requires larger components and
more PCB area.
FOSC
=
67850
RRI (kΩ)
©On-Bright Electronics
Confidential
-7-
Preliminary Datasheet
OB_DOC_DS_3362F00

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부품번호상세설명 및 기능제조사
OB3362F

4 Channels High Performance LED Driver

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