OB3370N Datasheet PDF - On-Bright

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OB3370N
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Part Number OB3370N
Description Cost Effective LED Controller
Page 10 Pages


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OB3370N
Cost Effective LED Controller
GENERAL DESCRIPTION
OB3370N is a high integrated and cost effective
Light Emitting Diode (LED) driver optimized for
LCD monitor and LCD TV backlight application.
The OB3370N operates in voltage mode boost
topology with fixed frequency 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 200mV, the error is amplified to control the
pulse width of the power switch thus to regulate
the current flowing the LED.
It offers both internal burst and external low
frequency PWM (LPWM) dimming methods for a
wide range of dimming control.
OB3370N integrates under voltage lockout (VCC
UVLO) and output over voltage protections that
prevent the damage in the event of abnormal
conditions. The output voltage level is monitored
through OVP pin and it turns off the converter if an
over voltage condition is present due to an open
circuit condition.
The OB3370N is available in SOP-8 Packages.
Product Specification
FEATURES
„ Voltage Mode PWM Controller
„ Flexible Dimming Mode Control:
| Internal burst dimming control
| External burst (LPWM) dimming control
„ 0-2V DC voltage direct dimming control
without external circuits
„ Output Over Voltage Protections
„ Under Voltage Lockout
„ Soft Start
APPLICATIONS
„ LCD Monitor
„ LCD TV
„ Flat panel display
TYPICAL APPLICATION
Figure1. OB3370N Typical Application Schematic
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OB3370N
Cost Effective LED Controller
Absolute Maximum Ratings
Parameter
VDD 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
7V
-0.7V to
VDD + 0.3V
-20~ 85
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
VDD Voltage
Burst Dimming Frequency
Value
4.5V to 5.5V
100Hz to 1KHz
Package Thermal Characteristics
Parameter
Thermal Resistance θJA
(SOP)
Value
85/W
Ordering Information
Part Number
OB3370NCP
OB3370NCPA
Description
SOP8, pb-free in tube
SOP8, pb-free in T&R
Package Marking Information
©On-Bright Electronics
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Pin Configuration
OB3370N
Cost Effective LED Controller
1 DIM
2 OVP
3 FB
4 VDD
BF/DMOD 8
CMP 7
GND 6
GATE 5
Terminal Assignment
Number Pin Name
1 DIM
2 OVP
3 FB
4 VDD
5 GATE
6 GND
7 CMP
8 BF/DMOD
I/O Pin Function
Input
Dimming signal input. Digital PWM signal input for external
PWM dimming mode or 0V-2V DC voltage input to adjust
duty cycle for internal burst dimming mode.
Input
Output Over Voltage Protection — Signal input. Connect
OVP to an external output voltage divider. The detection
threshold for voltage limiting at OVP is 2V (typical).
Input
Feedback signal input. An external current sensing resistor
is connected in series between LED strings and ground,
The voltage signal is fed back to pin FB (error amplifier
input). The reference voltage for current regulation is 0.2V
(typical).
P
Output
DC power supply pin. A decoupling capacitor to ground must
be placed close to this pin to minimize the switching noise.
Gate drive output for power MOSFET.
P Ground.
Loop compensation. Connecting a capacitor or a series RC
I/O network from CMP to ground to compensate the control
loop.
Dimming mode selection and Internal PWM dimming
frequency setting:
I/O z Connected to GND to set external LPWM dimming mode
z Connect an external capacitor to GND to set internal burst
dimming mode. The burst mode frequency is determined by
the external capacitor
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Functional Block Diagram
OVP
2.0V
OVP
+ Comparator
_
OSC
300KHz
0.2V
+
EA
_
OB3370N
Cost Effective LED Controller
VDD
UVLO
Voltage &
Current
Reference
+
_
PWM
Comparator
Logic
Control
Dimming
Control
Gate Drive
GATE
GND
FB CMP
Figure2. OB3370N Functional Block Diagram
DIM BF/DMOD
©On-Bright Electronics
Confidential
-4-
OB_DOC_DS_3370NA0



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