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OB2353
Low Power Off Line SMPS Switcher Freq Shuffling
GENERAL DESCRIPTION
OB2353 combines a dedicated current mode PWM
controller with integrated high voltage power
MOSFET .It is optimized for high performance
low standby power and cost effective offline flyback
converter applications in sub 10W range.
OB2353 PWM frequency operates in the fixed and
trimmed . At no load or light load the frequency is
internal adjusted, the IC operates in Extended ‘burst
mode’ to minimize switching loss. Lower standby
power and higher conversion efficiency is thus
achieved.
VDD low startup current and low operating current
contribute to a reliable power on startup design with
OB2353. 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(CS) input
removes the signal glitch due to snubber circuit diode
reverse recovery and thus greatly reduces the external
component count and system cost in the design.
OB2353 offers complete protection coverage with
automatic self-recovery feature including Cycle-by-
Cycle current limiting (OCP), over load protection
(OLP), VDD over voltage clamp and under voltage
lockout (UVLO). Excellent EMI performance is
achieved with On-Bright proprietary frequency
shuffling technique together with soft switching
control at the totem pole gate drive output.
The tone energy at below 20KHZ is minimized in the
www.DdaetasiSghneeat4nUd.caoumdio noise is eliminated during operation.
OB2353 is offered in SOP-8 package.
FEATURES
Optimized for sub 10W Applications
Single Chip 650V Sense FET Power Switch for
Package.
Soft Start with 4mS
Frequency shuffling for EMI
Extended Burst Mode Control For Improved
Efficiency and Minimum Standby Power Design
Audio Noise Free Operation
Fixed 50KHZ Switching Frequency
Internal Synchronized Slope Compensation
Low VDD Startup Current and Low Operating
Current
Leading Edge Blanking on Current Sense Input
Good Protection Coverage With Auto Self-
Recovery
o VDD Over Voltage Clamp and Under Voltage
Lockout with Hysteresis (UVLO)
o On-Bright Proprietary Line Input Compensated
Cycle-by-Cycle Over-current Threshold Setting
For Constant Output Power Limiting Over
Universal Input Voltage Range.
o Overload Protection (OLP).
o Over voltage Protection(OVP)
APPLICATIONS
Offline AC/DC flyback converter for
Battery Charger
PDA power supplies
Digital Cameras
Power Adaptor
Set-Top Box Power Supplies
Open-frame SMPS
TYPICAL APPLICATION
©On-Bright Electronics
-1-
Confidential
OB_DOC_DS_5301

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OB2353
Low Power Off Line SMPS Switcher Freq Shuffling
GENERAL INFORMATION
Pin Configuration
The OB2353 is offered in SOP8 package, shown as
below.
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Ordering Information
Part Number Description
OB2353CP SOP8, Pb-free
OB2353CP/A SOP8,Pb-free,Tape&Reel
Package Dissipation Rating
RθJA
SOP8
(°C/W)
150
Absolute Maximum Ratings
Parameter
Drain Input Voltage
VDD Input Voltage
VDD-G Input Voltage
VDD Input DC Current
VFB Input Voltage
VSENSE Input Voltage to Sense
Pin
Min/Max Operating Junction
Temperature TJ
Min/Max Storage Temperature
Tstg
Lead Temperature (Soldering,
10secs)
Value
650V
32 V
32 V
10mA
-0.3 to 7V
-0.3 to 7V
-20 to 150 oC
-55 to 160 oC
260 oC
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
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Marking Information
OB2353
Low Power Off Line SMPS Switcher Freq Shuffling
X: C for SOP8;
P: Pb-free Package;
Y: Year Code (0-9)
WW: Week Code (1-52)
s: Optional Internal Code
TERMINAL ASSIGNMENTS
Pin Name
GND
FB
I/O
P
I
www.DaVtaDShDee-Gt4U.com P
SENSE
I
VDD
P
Drain
P
Description
Ground
Feedback input pin. The PWM duty cycle is determined by voltage level into this pin and
the current-sense signal at Pin 3.
Power Supply specially for Internal Gate Driver
Current sense input pin.
Chip DC power supply pin.
The Drain pin is designed to connect directly to the primary lead of the transformer and
is capable of switching a maximum of 650V
©On-Bright Electronics
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BLOCK DIAGRAM
OB2353
Low Power Off Line SMPS Switcher Freq Shuffling
www.DataSheet4U.com
©On-Bright Electronics
-4-
Confidential
OB_DOC_DS_5301

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OB2353
Low Power Off Line SMPS Switcher Freq Shuffling
ELECTRICAL CHARACTERISTICS
(TA = 25OC if not otherwise noted)
Symbol
Parameter
Test Conditions
Min Typ Max Unit
Supply Voltage (VDD)
I_VDD_Startup VDD Start up
VDD =14.5V,Measure
5 20 uA
Current
Leakage current into VDD
I_VDD_Operation Operation Current VDD=16V, VFB=3V
1.6 mA
UVLO(ON)
VDD Under
8.7 9.7 10.7 V
Voltage Lockout
Enter
UVLO(OFF)
VDD Under
14.9 15.9 16.9 V
Voltage Lockout
Exit (Recovery)
OVP(ON)
Over voltage
VDD=16V,CS=0V,FB=3V 28.5 30 31.5 V
protection
Ramp up VDD until gate
voltage
clock is off
VDD_Clamp
VDD Zener Clamp IDD = 10 mA
Voltage
31 32 33 V
Feedback Input Section(FB Pin)
VFB_Open
VFB Open Loop
Voltage
IFB_Short
FB pin short
circuit current
VTH_0D
Zero Duty Cycle
FB Threshold
Voltage
VTH_PL
Power Limiting
FB Threshold
Voltage
Short FB pin to GND and
measure current
VDD=16V
5.4 5.7 6.0 V
1.45 mA
0.8 V
3.7 V
TD_PL
Power limiting
Debounce Time
50 mSec
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Input Impedance
4 Kohm
Current Sense Input(Sense Pin)
Soft start time
4 ms
T_blanking
Leading edge
270 ns
blanking time
ZSENSE_IN
TD_OC
Input Impedance
Over Current
Detection and
From Over Current Occurs
till the Gatedrive output start
40
120
Kohm
nSec
Control Delay
to turn off
VTH_OC
Internal Current
Limiting
FB=3.3V
VDD=16V
0.72 0.77 0.82 V
Threshold Voltage
Oscillator
FOSC
f_Temp
f_VDD
Normal Oscillation
Frequency
Frequency
Temperature
Stability
Frequency Voltage
Stability
VDD = 16V
VDD = 16V
VDD = 16-20V
45 50 55 KHZ
5%
5%
©On-Bright Electronics
-5-
Confidential
OB_DOC_DS_5301