KA7541

www.fairchildsemi.com KA7541 Simple Ballast Controller Features Internal soft start Flexible soft start frequency No lamp protection Trimmed 1.5% internal bandgap reference Under voltage lock out with 1.8V of hysteresis Totem pole output with high state clamp Low start up and operating current Descriptions The KA7541 provides simple and high performance electronic ballast control functions. KA7541 is optimized for electronic ballast requiring a minimum board area, reduced component count and low power dissipation. Internal soft start circuitry eliminates the need for an external soft start PTC resistor. The initial soft start switching frequency and soft start time can be adjusted depending on the types of lamps. Protection circuitry has also been added to prevent burning out of switches in no lamp condition. output gate drive circuit clamps power MOSFET gate voltage irrespective of supply voltage 8-DIP 1 8-SOP 1 Rev. 1.0.3 ©2001 Fairchild Semiconductor Corporation KA7541 Internal Block Diagram UVLO 2V Ref CS 0.22µF 2.5µA 1 − + Vref VZ Ict + + 3V 8Ict 1V + + − + Vref 2kΩ IS SQ Oscilator R latch Current mirror Frequency divider F.D IC Oscilator Internal bias IH Ik = IS / 6 1.8V + − 8 VCC UVLO 9.5V VCC Ct 180pF 2 7 OUT 1 VCC RS 22kΩ 30kΩ 3 3pF 6 OUT 2 Ldet 40kΩ 4 5pF 2V − + Shut down signal IH = Ik × (Vref − VSS) / Vref IS = Vref / RS 5 GND Absolute Maximum Ratings Parameter Supply voltage Peak drive output current Drive output cl...