DESCRIPTION
KA3842/43/44/45 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 UC3842A(AM) and UC3844A(AM) have UVLO thresholds of 16 V (on) and 10 V (off).
The corresponding thresholds for the UC3843A(AM)/45A(AM) are 8.4V (on) and 7.6V
(off). The UC3842A(AM) and UC3843A(AM) can operate within 100% duty cycle. The
UC3844A(AM) and UC3845A(AM) can operate within 50% duty cycle.
The UC384XA(AM) has Start-Up Current 0.17mA (typ).

FEATURES
• Low Start-Up and Operating Current
• High Current Totem Pole Output
• Undervoltage Lockout With Hysteresis
• Operating Frequency Up To 300KHz (384XA)
500KHz (384XAM