GENERAL DESCRIPTION
OB2502x is a high performance offline PSR power
switch for low power AC/DC charger and adapter
applications. It operates in primary-side sensing
and regulation. Consequently, opto-coupler and
TL431 could be eliminated. Proprietary Constant
Voltage (CV) and Constant Current (CC) control is
integrated as shown in the figure below.
In CC control, the current and output power setting
can be adjusted externally by the sense resistor
Rs at CS pin. In CV control, multi-mode operations
are utilized to achieve high performance and high
efficiency. In addition, good load regulation is
achieved by the built-in cable drop compensation.
Device operates in PFM in CC mode at large load
condition and it operates in PWM with frequency
reduction at light/medium load. The chip
consumes very low operation current. It achieves
less than 75mW standby power to meet strict
standby power standard.
OB2502x offers comprehensive protection
coverage with auto-recovery feature including
Cycle-by-Cycle current limiting, VDD over voltage
protection, feedback loop open protection, short
circuit protection, built-in leading edge blanking,
VDD under voltage lockout (UVLO), OTP etc.
OB2502x is offered in SOP8 packages.

FEATURES
 Primary-side sensing and regulation without
TL431 and opto-coupler
 High precision constant voltage and current
regulation at universal AC input
 Multi-mode PWM/PFM operation for efficiency
improving
 Integrated 2A/3A MOSFET
 Good dynamic response with synchronous
rectifier application
 Programmable CV and CC regulation
 Built-in primary winding inductance
compensation
 Programmable cable drop compensation
 No need for control loop compensation
 Audio noise free operation
 Built-in leading edge blanking (LEB)
 Ultra low start-up current and low operating
current
 Comprehensive protection coverage with
auto-recovery
 On-chip OTP
 VDD over voltage protection
 VDD under voltage lockout with
hysteresis (UVLO)
 Cycle-by-Cycle current limiting
 Feedback loop open protection
 Output short circuit protection

APPLICATIONS
Low Power AC/DC offline SMPS for
 Cell Phone Charger
 Digital Cameras Charger
 Small Power Adapter
 Auxiliary Power for PC, TV etc.
 Linear Regulator/RCC Replacement