SLUS223G April 1997 – July 2022 UC1842 , UC1843 , UC1844 , UC1845 , UC2842 , UC2843 , UC2844 , UC2845 , UC3842 , UC3843 , UC3844 , UC3845
PRODUCTION DATA
The high-current bipolar totem-pole output of the UCx84x devices sinks or sources up to 1-A peak of current. The OUTPUT pin can directly drive a MOSFET. The OUTPUT of the UCx842 and UCx843 devices switches at the same frequency as the oscillator and can operate near 100% duty cycle. In the UCx844 and UCx845 devices, the switching frequency of OUTPUT is one-half that of the oscillator due to an internal T flipflop. This limits the maximum duty cycle in the UCx844 and UCx845 to < 50%. Schottky diodes may be necessary on the OUTPUT pin to prevent overshoot and undershoot due to high impedance to the supply rail and to ground, respectively. A bleeder resistor, placed between the gate and the source of the MOSFET, should be used to prevent activating the power switch with extraneous leakage currents during undervoltage lockout. An external clamp circuit may be necessary to prevent overvoltage stress on the MOSFET gate when VCC exceeds the gate voltage rating.