Thanks a lot. I knw sg3524 is for voltage mode control. Actually i would like to use average current mode control as my buck converter feedback control. But i hav no experience in doing electronic project, i think it is better to start familiar with the PWM first so my friend recomend me try to use this sg3524. What u means 'pins 12&13 tied to drain'?? What difference if i connect it to Vin? My converter specification: input: 10-15V output: 5V switching freqquency: 100kHz output ripple: 1% As u say bootstrap circuitry is onboard, can u please kindly suggest me which PWM it is?