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