OB2268 Datasheet PDF - Liteon

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OB2268
Liteon

Part Number OB2268
Description (OB2268 / OB2269) Current Mode PWM Controller
Page 12 Pages


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GENERAL DESCRIPTION
OB2268/9 is a highly integrated current mode PWM
control IC optimized for high performance, low
standby power and cost effective offline flyback
converter applications in above 20W power level.
PWM switching frequency at normal operation is
externally programmable and trimmed to tight range.
At no load or light load condition, the IC operates in
extended ‘burst mode’ to minimize switching loss.
Lower standby power and higher conversion
efficiency is thus achieved.
www.DataSheVet4DUD.colmow startup current and low operating current
contribute to a reliable power on startup design with
OB2268/9. A large value resistor could thus be used
in the startup circuit to minimize the standby power.
The internal slope compensation improves system
large signal stability and reduces the possible sub-
harmonic oscillation at high PWM duty cycle output.
Leading-edge blanking on current sense input
removes the signal glitch due to snubber circuit diode
reverse recovery. and greatly reduces the external
component count and system cost in the design.
OB2268/9 offers complete protection coverage with
automatic self-recovery feature including Cycle-by-
Cycle current limiting (OCP), over load protection
(OLP), over temperature protection (OTP), VDD
over voltage protection (OVP) and under voltage
lockout (UVLO). The Gate-drive output is clamped
to maximum 18V to protect the power MOSFET.
Excellent EMI performance is achieved with On-
Bright proprietary frequency shuffling technique
(OB2269 only) together with soft switching control at
the totem pole gate drive output.
The tone energy at below 20KHZ is minimized in
operation. Consequently, audio noise performance is
greatly improved.
OB2268
OB2269
Current Mode PWM Controller
OB2268/9 is offered in SOP-8 and DIP-8 packages.
FEATURES
Extended Burst Mode Control For Improved
Efficiency and Minimum Standby Power Design
Audio Noise Free Operation
External Programmable PWM Switching
Frequency
Internal Synchronized Slope Compensation
Low VIN/VDD Startup Current(4uA) and Low
Operating Current (2.3mA)
Leading Edge Blanking on Current Sense Input
Complete Protection Coverage With Auto Self-
Recovery
o External Programmable Over Temperature
Protection (OTP)
o With or Without On-chip VDD OVP for
Output Over Voltage Protection.
o Under Voltage Lockout with Hysteresis
(UVLO)
o Gate Output Maximum Voltage Clamp (18V)
o Line Compensated Cycle-by-Cycle Over-
current Threshold Setting For Constant Output
Current Limiting Over Universal Input Voltage
Range (OCP)
o Over Load Protection. (OLP)
On-Bright Proprietary Frequency Shuffling
Technology for Improved EMI Performance
(OB2269 only)
APPLICATIONS
Offline AC/DC flyback converter for
Laptop Power Adaptor
PC/TV/Set-Top Box Power Supplies
Open-frame SMPS
Battery Charger
TYPICAL APPLICATION
©On-Bright Electronics
A Liteon Semiconductor Company
-1-
Confidential
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GENERAL INFORMATION
Pin Configuration
The OB2268/9 is offered in DIP and SOP packages
shown as below.
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Ordering Information
Part Number Description
OB2268AP
No Frequency Shuffling,
DIP8, Pb-free
OB2268APV No Frequency Shuffling,
DIP8, Pb-free and no OVP
OB2269CP
With Frequency Shuffling,
SOP8, Pb-free
OB2269CPV With Frequency Shuffling,
SOP8, Pb-free and no OVP
OB2268
OB2269
Current Mode PWM Controller
Package Dissipation Rating
Package
DIP8
SOP8
RθJA (°C/W)
90
150
Absolute Maximum Ratings
Parameter
VDD Input Voltage
VIN Input Voltage
Value
36 V
36 V
VDD Clamp Continuous Current
VFB Input Voltage
VSENSE Input Voltage to Sense
Pin
10 mA
-0.3 to 7V
-0.3 to 7V
VRT Input Voltage to RT Pin
VRI Input Voltage to RI Pin
Min/Max Operating Junction
Temperature TJ
Min/Max Storage Temperature
-0.3 to 7V
-0.3 to 7V
-20 to 150 oC
-55 to 150 oC
Tstg
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.
©On-Bright Electronics
A Liteon Semiconductor Company
-2-
Confidential
V2.1



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Marking Information
OB2268
OB2269
Current Mode PWM Controller
www.DataSheet4U.com
TERMINAL ASSIGNMENTS
Pin Num Pin Name
1 GND
2 FB
3 VIN
4 RI
5 RT
6 SENSE
7 VDD
8 GATE
I/O Description
P Ground
I Feedback input pin. PWM duty cycle is determined by voltage level into this
pin and current-sense signal level at Pin 6.
I Connected through a large value resistor to rectified line input for Start up
chip supply and line voltage sensing.
I Internal Oscillator frequency setting pin. A resistor connected between RI
and GND sets the PWM frequency.
I Temperature sensing input pin. Connected through a NTC resistor to GND.
Once the voltage of the RT pin drops below a fixed limit of 1.05V, PWM
output will be disabled.
I Current sense input pin. Connected to MOSFET current sensing resistor
node.
P DC power supply pin.
O Totem-pole gate drive output for power MOSFET.
©On-Bright Electronics
A Liteon Semiconductor Company
-3-
Confidential
V2.1



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BLOCK DIAGRAM
www.DataSheet4U.com
OB2268
OB2269
Current Mode PWM Controller
©On-Bright Electronics
A Liteon Semiconductor Company
-4-
Confidential
V2.1



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