OB2638

GENERAL DESCRIPTION

OB2638 is a highly integrated Quasi-Resonant(QR) controller with adaptive multi-mode regulation, optimized for high performance, low standby power consumption and wide output voltage range PD adapter solutions, together with PD secondary controller, such as OB2613. The controller is integrated 105V low dropout regulator (LDO) and is as well compatible with cost effective offline flyback converter applications covering a wide output range.

At normal load condition, it operates in QR mode in high line input voltage. To minimize switching loss, the maximum switching frequency in QR mode is internally limited to 82 KHz. When the loading goes low, it operates in PFM mode with valley switching for high power conversion efficiency. When the load is very small, the IC operates in ‘Extended Burst Mode’ to minimize the standby power loss. Additionally, in the low line input voltage, the IC operates in fixed frequency (65KHz) CCM mode at the heavy loading. As a result, high conversion efficiency can be achieved in the whole loading range.

VCC low startup current and low operating current contribute to a reliable power on startup and low standby design.

OB2638 offers complete protection coverage  including cycle-by-cycle current limiting (OCP), over load protection (OLP), over temperature protection (OTP), output short(SCP), output and VDD over voltage protection.  Excellent EMI performance is achieved with On-Bright proprietary frequency shuffling technique.

The tone energy at below 22KHz is minimized to avoid audio noise during operation.

OB2638 is offered in SOP8 package.

FEATURES

■   Multi-Mode Operation

100KHz maximum operation frequency in CCM mode @ Peak Load in low line voltage

82KHz maximum clamping frequency in QR mode @ Full Load in high line voltage

65KHz minimum clamping frequency in CCM mode @ Heavy Load in low line voltage

Valley switching operation @ Green mode

Burst Mode @ Light Load & No Load

■   Very wide range of supply voltage

■   Integrated 105V low dropout regulator(LDO)

■   Low operating current at light/no load

■   Internal OCP compensation for universal line voltage

■   Extended burst mode control for improved efficiency and low standby power

■   Power on soft start reducing MOSFET Vds stress

■   Frequency shuffling for EMI

■   Audio noise free operation

■   Comprehensive protection coverage

o   VDD under voltage lockout with hysteresis (UVLO)       

o   Cycle-by-cycle over current protection (OCP) with auto-recovery

o   Overload protection (OLP) with auto-recovery

o   Over temperature protection (OTP) with latch shut down

o   VDD over voltage protection with latch shut down

o   Output over voltage protection with latch shut down

o   Output short protection (SCP) with auto-recovery

o   Output diode short protection with auto-recovery

APPLICATIONS

Offline AC/DC flyback converter for

■   PD adapters

■   Wide output range adapters

TYPICAL APPLICATION