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OB3350
Cost Effective LED Controller
GENERAL DESCRIPTION
OB3350 is a highly integrated and cost effective
Light Emitting Diode (LED) driver optimized for
LCD monitor and LCD TV backlighting application.
It provides a high performance LED backlight
solution with minimized BOM count.
The OB3350 contains a PWM boost driver which
uses current mode control and fixed frequency
operation to regulate the LED current. The LED
current is sensed through an external current
sense resistor. The voltage across the sensing
resistor is compared with reference level of 300mV,
the error is amplified to control the pulse width of
the power switch thus to regulate the current
flowing the LED.
The OB3350 offers external low frequency PWM
(LPWM) dimming method for a wide range of
dimming control.
The OB3350 offers comprehensive protection
such as power MOSFET over current protection
(OCP), output over voltage protection (OVP), IC
power supply under voltage lockout (UVLO), and
LED open protection.
FEATURES
Current Mode PWM Controller With Good
Dynamic Response
8V to 35V Input Voltage Range
External PWM Dimming Mode
Over Voltage Protection
Over Current Protection
Under Voltage Lockout (UVLO)
Thermal Shutdown
APPLICATIONS
LCD Monitor
LCD TV
Flat panel display
The OB3350 is offered in SOP-8 Packages.
TYPICAL APPLICATION
Figure1. OB3350 Typical Application Schematic
©On-Bright Electronics
Confidential
-1-
Preliminary datasheet
OB_DOC_DS_335000
Free Datasheet http://www.datasheetlist.com/

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OB3350
Cost Effective LED Controller
Absolute Maximum Ratings
Parameter
VIN Input Voltage to GND
I/O to GND
Operating Ambient Temp. TA
Operating Junction Temp. TJ
Min/Max Storage Temp. Tstg
Lead Temp. (10 Sec)
Value
-0.3V to 40V
-0.3V to 7V
-40 ~ 85
-40 ~ 150
-55 ~150
260
Note: Stresses beyond those listed under “absolute maximum
ratings” may cause permanent damage to the device. These
are stress ratings only, functional operation of the device at
these or any other conditions beyond those indicated under
“recommended operating conditions” is not implied. Exposure
to absolute maximum-rated conditions for extended periods
may affect device reliability.
Recommended Operating Range
Parameter
Vin Voltage
Burst Dimming Frequency
Value
8V to 35V
100Hz to 1KHz
Package Thermal Characteristics
Parameter
Thermal Resistance JA
(SOP)
Value
150 /W
Ordering Information
Part Number
Description
OB3350CP
SOP8, pb-free in tube
OB3350CPA
SOP8, pb-free in T&R
OB3350 X
X
X
Cost Effective LED Controller
Package
C:SOP8
Package Pb- free Packing
P:Pb-free
Blank:Tube
A: Taping
Package Marking Information
Y:Year Code
WW:Week Code(01-52)
ZZZ:Lot Code
C:SOP8 Package
P:Pb-free Package
S:Internal Code(Optional)
©On-Bright Electronics
Confidential
-2-
Preliminary datasheet
OB_DOC_DS_335000
Free Datasheet http://www.datasheetlist.com/

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OB3350
Cost Effective LED Controller
Pin Configuration
VIN
GATE
GND
CS
18
27
OB3350
36
45
PWM
OVP
COMP
FB
No. Name
1 VIN
2 GATE
3 GND
4 CS
5 FB
6 COMP
7 OVP
8 PWM
I/O
Power
I/O
GND
I/O
I/O
I/O
I/O
I/O
Pin Function
Power Supply Input
Gate Driver Output Pin
Ground
Current Sense Input
LED Current Feedback Input
Boost Converter Loop Compensation Pin
Over Voltage Protection Sense Input
External PWM Dimming Control
©On-Bright Electronics
Confidential
-3-
Preliminary datasheet
OB_DOC_DS_335000
Free Datasheet http://www.datasheetlist.com/

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Functional Block Diagram
OB3350
Cost Effective LED Controller
COMP
FB
CS
DIM
OSC
UVLO
Ramp
Adjust
Thermal
Shutdown
5V Reference
Soft-start
EA
Sense
Amplifer
S PW
M
PWM
Comparator
Vth_ovp
Control
Logic
Gate
Drive
DIM
Control
OVP
Figure2. OB3350 Functional Block Diagram
VIN
GATE
PWM
GND
©On-Bright Electronics
Confidential
-4-
Preliminary datasheet
OB_DOC_DS_335000
Free Datasheet http://www.datasheetlist.com/

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OB3350
Cost Effective LED Controller
Electrical Characteristics
VDDH=12V,PWM=5V, TA=25 , if not otherwise noted.
Parameter
Symbol
Conditions
Min Typ Max Units
Current Consumption
Input voltage range
Operating supply current
Stand by current
IVDD
IVDD _ STB
Vin=12V,PWM=5V no
load
PWM low >50ms sleep
mode
8
-
-
- 35
2.5 3
310 400
V
mA
uA
VDD UVLO
UVLO
UVLO Hysteresis
UVLO(ON)
UVLO(Hys)
6 78 V
500 mV
Soft start
Soft start slope
I sst _ slop
400 mV/mS
PWM Control
Operating frequency
Max duty cycle
PWM Input Threshold
FOSC
Dmax
PWM(high)
PWM(low)
High Level
Low Level
175 200 225 KHz
93 95 97 %
2.5 V
1.3 V
Error Amplifier
Reference voltage
Open loop voltage gain
Transconductance of EA
Vref _ ea
Am
Gm
Reference voltage at
non-inverting input
0.289
0.3
0.311 V
70 dB
80 100 120 uA/V
Output source current
I source
24 30 36 uA
Output sink current
I sin k
48 60 72 uA
Protection Threshold
OVP
OCP
VOVP OV
Vth_OCP
Threshold of output
over voltage
Threshold of over
current
protection
(duty=90%)
1.8
2.0 2.2
330
V
mV
OTP ON
TOTP _ ON
140 160 180
OTP OFF
TOTP _ OFF
120 140 160
Connect detect time
OVP UVLO threshold
Tdio
VOVP UV
Normal operation
System startup
1 mS
200 mV
100 mV
Gate Driver Output
Gate rise time
Trise 500pF load
-
40 80
ns
Gate fall time
T fall 500pF load
20 40
ns
©On-Bright Electronics
Confidential
-5-
Preliminary datasheet
OB_DOC_DS_335000
Free Datasheet http://www.datasheetlist.com/