The 3842/43/44/45 are fixed frequency current mode PWM controller. They are specially designed for OFF−Line and DC to DC converter applications with a minimal external components. Internally implemented circuits include a trimmed oscillator for precise duty cycle control, a temperature compensated reference, high gain error amplifier, current sensing comparator, and a high current totempole output ideally suited for driving a power MOSFET. Protection circuitry includes built undervoltage lockout and current limiting. The 3842 and 3844 have UVLO thresholds of 16 V (on) and 10 V (off). The corresponding thresholds for the 3843/ 45 are 8.4V (on) and 7.6V (off). The 3842) and 3843 can operate within 100% duty cycle. The 3844 and 3845 can operate within 50% duty cycle. The 384X has Start-Up Current 0.17mA (typ).