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UC2842 Current-Mode PWM Controller

The UC2842 is a fixed frequency current-mode PWM controller. This IC is specially designed for Off-Line and DC to DC converter applications with minimum external components. The UC2842 IC offers a variety of package options, temperature range options, choice of maximum duty cycle, and choice of turn-on and turnoff thresholds and hysteresis ranges.


Note: This IC also comes in 14-Pin, 16-Pin, and 20-Pin packages. This article covers only the 8-Pin version of the IC.


Pin Description UC2842 IC

Pin Number

Pin Name



COMP (Comparator)

It is an output pin that outputs low impedance 1MHz signal based on the difference between the set and current-voltage. It is normally connected to the voltage feedback pin of the IC through a resistor and capacitor.


VFB (Voltage Feedback)

It is an input to the error amplifier inside the IC. The difference in voltage level is supplied to this pin


Current Sense

A shunt resistor is used to monitor the current through the circuit, and the voltage across it is provided as a feedback to the current sense pin


RT/CT (Timing Resistor/ Timing Capacitor)

The IC has an internal oscillator which can be set using an external resistor and capacitor connected to this pin.



Connected to the ground of the circuit



This pin outputs the PWM signal based on the feedback provided, and we can use this to switch the power electronic device.



Supply voltage for the IC (Nominal 11V)



Reference voltage based on which the PWM signal is produced.


UC2842 Specifications

  • Current-Mode PWM controller
  • Operating Voltage: 12V to 28V
  • Output pin current: 200 mA
  • Switching Frequency: 500 kHz
  • Duty Cycle - Max: 100 %
  • Operating Supply Current:25 mA
  • Optimized for Off-line and DC-to-DC Converters
  • High-Current Totem-Pole Output


Note: Complete Technical Details can be found at the UC2842 datasheet given at the end of this page.


Equivalent/Substitute for UC2842: UC3843, UC2842, UC3844

Alternatives PWM controller IC:  SG2524


Where to use the UC2842 PWM Controller IC:

Both UC2842-series devices and UC3842-series devices are almost the same. The primary difference between these two series devices is the ambient operating temperature range. The UC2842-series devices operate between –40°C and 85°C, and the UC3842-series devices operate between 0°C and 70°C. Other differences between members of these series are the UVLO thresholds and maximum duty cycle ranges.

So if you are looking for a PWM Controller IC that has a wide temperature range and can work in extremely cold or hot conditions, then this IC might be the right choice for you.


How to use UC2842 IC

Using UC2842 in a circuit is very simple as it requires a minimum number of components. A sample application circuit from the UC2842 datasheet is shown below.

UC2842 Application Circuit

The input voltage to the VCC pin should be 12V to 28V. The output pin of the IC is connected to the gate driver circuit of the Power switch which is to be switched. The VFB (Voltage feedback) pin acts as feedback based on which the PWM signal is controlled. A shunt resistor is used to monitor the change in current in the circuit, and then this difference voltage across the shunt is provided to the feedback pin. VREF is used to provide charging current to the oscillator timing capacitor through the timing resistor. It is important for reference stability that VREF is bypassed to GROUND with a ceramic capacitor connected as close to the pin as possible.


Applications of UC2842:

  • SMPS (Switch Mode Power Supplies) circuits
  • DC-DC converter circuits
  • Electronics power supply
  • Battery drain circuit
  • Load machines


2D-Model of UC2842:

Dimensions for UC2842 IC is given below. These dimensions are for the 8-Pin GDIP package. If you are using a different package IC, please refer to the UC2842 datasheet.

UC2842 Dimensions

Component Datasheet

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