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
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Confidential
OB_DOC_DS_5301
