OB2269AP datasheet(9/12 Pages) LITEON

9 / 12 page

©On-Bright Electronics

Confidential

A Liteon Semiconductor Company

- 9 -

V2.1

OB2268

OB2269

Current Mode PWM Controller

OB2268/9 Gate is connected to an external

MOSFET gate for power switch control. Too weak

the gate drive strength results in higher conduction

and switch loss of MOSFET while too strong gate

drive output compromises the EMI.

A good tradeoff is achieved through the built-in

totem pole gate design with right output strength

and dead time control. The low idle loss and good

EMI system design is easier to achieve with this

dedicated control scheme. An internal 18V clamp is

added for MOSFET gate protection at higher than

expected VDD input.

• Protection Controls

Good

system

reliability

achieved

with

OB2268/9’s rich protection features including

Cycle-by-Cycle current limiting (OCP), Over Load

Protection (OLP), over temperature protection

(OTP), on-chip VDD over voltage protection (OVP,

optional) and under voltage lockout.(UVLO).

The OCP threshold is input line voltage adjusted to

compensate the increased output current limit at

higher voltage caused by inherent Over-Current

sensing and control delay. A constant output power

limit is achieved with recommended reference

design on OB2268/9.

At overload condition when FB input voltage

exceeds power limit threshold value for more than

80mS, control circuit reacts to shut down the output

power MOSFET. Device restarts when VDD

voltage drops below UVLO limit.

Similarly, control circuit shuts down the power

MOSFET when an Over Temperature condition is

detected. OB2268/9 resumes the operation when

temperature drops below the hysteresis value.

VDD

supplied

with

transformer

auxiliary

winding output. It is clamped when VDD is higher

than 30V. The power MOSFET is shut down when

VDD drops below UVLO limit and device enters

power

start-up

sequence

thereafter.

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