OB2268 Datasheet – Current Mode PWM Controller
OB2268 overview
The OB2268 is a Current Mode PWM Controller made by Liteon, supplied in an SOP-8 and DIP-8 Type package. The absolute maximum ratings table on this page lists the 9 limits from the manufacturer's datasheet that must not be exceeded. This page brings together the OB2268 pinout and maximum ratings, with the full datasheet PDF to preview below or download.
OB2268/9 is a highly integrated current mode PWM control IC optimized for high performance, low standby power and cost effective offline flyback converter applications in above 20W power level.
PWM switching frequency at normal operation is externally programmable and trimmed to tight range. At no load or light load condition, the IC operates in extended ‘burst mode’ to minimize switching loss. Lower standby power and higher conversion efficiency is thus achieved.
startup current and low operating current contribute to a reliable power on startup design with OB2268/9. 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 input removes the signal glitch due to snubber circuit diode reverse recovery. and greatly reduces the external component count and system cost in the design.
OB2268/9 offers complete protection coverage with automatic self-recovery feature including Cycle-by- Cycle current limiting (OCP), over load protection (OLP), over temperature protection (OTP), VDD over voltage protection (OVP) and under voltage lockout (UVLO). The Gate-drive output is clamped to maximum 18V to protect the power MOSFET. Excellent EMI performance is achieved with On- Bright proprietary frequency shuffling technique (OB2269 only) together with soft switching control at the totem pole gate drive output. The tone energy at below 20KHZ is minimized in operation. Consequently, audio noise performance is greatly improved.
Datasheet
OB2268 features
- Extended Burst Mode Control For Improved Efficiency and Minimum Standby Power Design
- Audio Noise Free Operation
- External Programmable PWM Switching Frequency
- Internal Synchronized Slope Compensation
- Low VIN/VDD Startup Current (4uA) and Low Operating Current (2.3mA)
- Leading Edge Blanking on Current Sense Input.
- Complete Protection Coverage With Auto Self-recovery
- External Programmable Over Temperature Protection (OTP)
- With or Without On-chip VDD OVP for Output Over Voltage Protection.
- Under Voltage Lockout with Hysteresis (UVLO)
- Gate Output Maximum Voltage Clamp (18V)
- Line Compensated Cycle-by-Cycle Over- current Threshold Setting For Constant Output Current Limiting Over Universal Input Voltage Range (OCP)
- Over Load Protection. (OLP)
- On-Bright Proprietary Frequency Shuffling Technology for Improved EMI Performance (OB2269 only)
OB2268 pinout
| Name | Description |
|---|---|
| 1 | Ground |
| 2 | Feedback input pin. PWM duty cycle is determined by voltage level into this pin and current-sense signal level at Pin 6. |
| 3 | Connected through a large value resistor to rectified line input for Start up chip supply and line voltage sensing. |
| 4 | Internal Oscillator frequency setting pin. A resistor connected between RI and GND sets the PWM frequency. |
| 5 | Temperature sensing input pin. Connected through a NTC resistor to GND. Once the voltage of the RT pin drops below a fixed limit of 1.05V, PWM output will be disabled. |
| 6 | Current sense input pin. Connected to MOSFET current sensing resistor node. |
| 7 | DC power supply pin. |
| 8 | Totem-pole gate drive output for power MOSFET. |
Absolute maximum ratings
| Parameter | Value |
|---|---|
| VDD Input Voltage | 36 V |
| VIN Input Voltage | 36 V |
| VDD Clamp Continuous Current | 10 mA |
| VFB Input Voltage | -0.3 to 7V |
| VSENSE Input Voltage to Sense Pin | -0.3 to 7V |
| VRT Input Voltage to RT Pin | -0.3 to 7V |
| VRI Input Voltage to RI Pin | -0.3 to 7V |
| Min/Max Operating Junction Temperature TJ | -20 to 150 oC |
| Min/Max Storage Temperature Tstg | -55 to 150 oC |
OB2268 applications
- Laptop Power Adaptor
- PC/TV/Set-Top Box Power Supplies
- Open-frame SMPS
- Battery Charger
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