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UC3842 Series Datasheet

UC3842

PWM Controllers

The UC384xB family of control ICs provides the nec-essary features to implement off-line or DC to DC fixed frequency current mode control schemes witha minimal external parts count. Internally imple-mented circuits include a trimmed scillator for pre-cise DUTY CYCLE CONTROL under voltage lock-out featuring start-up current less than 0.5mA, a pre-cision reference trimmed for accuracy at the error amp input, logic to insure latched operation.

UC3842 Data sheet.pdf

UC3842 Pin Configuration and Function

Pin No	Function	Description
1	COMP	This pin is the Error Amplifier output and is made available for loop compensation.
2	Vfb	This is the inverting input of the Error Amplifier. It is normally connected to the switchingpower supply output through a resistor divider
3	ISENSE	A voltage proportional to inductor current is connected to this input. The PWM uses thisinformation to terminate the output switch conduction
4	Rt/Ct	The oscillator frequency and maximum Output duty cycle are programmed by connectingresistor RT to Vref and cpacitor CT to ground. Operation to 500kHz is possible
5	GROUND	This pin is the combined control circuitry and power ground
6	OUTPUT	This output directly drives the gate of a power MOSFET. Peak currents up to 1A are sourcedand sunk by this pin.
7	Vcc	This pin is the positive supply of the control IC.
8	Vref	This is the reference output. It provides charging current for capacitor CT through resistor RT