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UC3842 Current Mode PWM Controller Specs, Datasheet

  • Contents

UC3842 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.

 

This blog will provide you the detailed information of UC3845, the PWM controller about its pinout, features, applications, equivalents, where and how to use this device, etc.


Catalog

UC3842 Pinout

UC3842 Features

UC3842 Parameters

UC3842 Absolute Maximum Ratings

UC3842 Functional Block Diagram

UC3842 Equivalents

Where to use UC3842 IC

How to use UC3842 IC

UC3842 Applications

UC3842 Package

Component Datasheet


UC3842 Pinout

UC3842-pinout

 

Note: UC3842 IC also comes in 14-Pin, 16-Pin, and 20-Pin packages. This article covers only the 8-Pin version of the IC.

Pin Number Pin Name Description
1 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.
2 VFB (Voltage Feedback) It is an input to the error amplifier inside the IC. The difference in voltage level is supplied to this pin
3 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
4 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.
5 Ground Connected to the ground of the circuit
6 Output This pin outputs the PWM signal based on the feedback provided and we can use this to switch the power electronic device.
7 Vcc Supply voltage for the IC (Nominal 11V)
8 VREF Reference voltage based on which the PWM signal is produced.

UC3842 Features

  • Optimized for off-line and DC-to-DC converters

  • Low start-up current (< 1 mA)

  • Automatic feedforward compensation

  • Pulse-by-pulse current limiting

  • Enhanced load-response characteristics

  • Undervoltage lockout with hysteresis

  • Double-pulse suppression

  • High-current totem-pole output

  • Internally trimmed bandgap reference

  • Up to 500-kHz operation

  • Error amplifier with low output resistance


UC3842 Parameters

Topology Boost, Buck, Buck-Boost, Flyback, Forward
Control method Peak Current Mode
VCC (Min) (V) 16
VCC (Max) (V) 28
Duty cycle (Max) (%) 100
UVLO thresholds on/off (V) 16/10
Frequency (Max) (kHz) 500
Operating temperature range (C) 0 to 70
Gate drive (Typ) (A) 1
Features Adjustable Switching Frequency, Current Limiting, Dead Time Control, Error Amplifier, Multi-topology
Rating Catalog

UC3842 Absolute Maximum Ratings

UC3842-Absolute-Maximum-Ratings


UC3842 Functional Block Diagram

UC3842 Block Diagram, Toggle

UC3842 Functional Block Diagram (Toggle)


UC3842 Equivalents

Part Number Description Manufacturer
UC3842ANG4 POWER CIRCUITS 30-V, 1A, 500KHz current mode PWM controller with 16V/10V UVLO 100% duty cycle, 0°C to 70°C 8-PDIP 0 to 70 Texas Instruments
UC3842N POWER CIRCUITS 1A SWITCHING CONTROLLER, 500kHz SWITCHING FREQ-MAX, PDIP8, 0.300 INCH, MINI, DIP-8 STMicroelectronics
CS-3842BN8 POWER CIRCUITS Switching Controller, Current-mode, 1A, 500kHz Switching Freq-Max, BIPolar, PDIP8, Cherry Semiconductor Corporation
IP3842AJ POWER CIRCUITS 1A SWITCHING CONTROLLER, 500kHz SWITCHING FREQ-MAX, CDIP8, CERAMIC, DIP-8 TT Electronics Power and Hybrid / Semelab Limited
UC3842AN POWER CIRCUITS 1A SWITCHING CONTROLLER, 500kHz SWITCHING FREQ-MAX, PDIP8, PLASTIC, DIP-8 Motorola Mobility LLC
UC3842AN2 POWER CIRCUITS 1A SWITCHING CONTROLLER, 500kHz SWITCHING FREQ-MAX, PDIP8, PLASTIC, DIP-8 ON Semiconductor
UC3842BNG POWER CIRCUITS High Performance Current Mode PWM Controller, 8 LEAD PDIP, 50-TUBE ON Semiconductor
CS3842BGN8 POWER CIRCUITS 1A SWITCHING CONTROLLER, PDIP8, 0.300 INCH, PLASTIC, MS-001, DIP-8 ON Semiconductor
UC3842NG4 POWER CIRCUITS Single ended 500KHz current mode PWM controller with 16V/10V UVLO 100% duty cycle, 0C to 70C 8-PDIP 0 to 70 Texas Instruments

Where to use UC3842 IC

The UC3842 IC is a current mode PWM controller, which means that it can be used to provide constant current by varying the output voltage to the load. This IC features a trimmed oscillator for precise duty cycle control, a temperature-compensated reference, a high gain error amplifier, a current sensing comparator, and a high current totem pole output for power MOSFET operation.

 

UC3842 can be used to regulate or limit current in applications such as SMPS, RPS, DC-DC Converters, Line voltage regulators, etc. So if you're looking for an IC to produce PWM signals to control a power switch based on the current flowing through the circuit, this IC might be the right choice for you.


How to use UC3842 IC

It’s pretty simple to use UC3842 in a circuit. Down below is a sample circuit diagram from UC3845 datasheet.

uc3842-application-circuit

UC3842 Application Circuit

 

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


UC3842 Applications

  • SMPS (Switch Mode Power Supplies) circuits

  • DC-DC converter circuits

  • Electronics power supply

  • Battery drain circuit

  • Load machines


UC3842 Package

UC3842-Package


Component Datasheet

UC3842 Datasheet


FAQ

  • How does UC3842 work?

The use of the UC3842 in a circuit is fairly straightforward because it only requires a few components. The IC's output pin is connected to the gate driver circuit of the to-be-switched Power switch. The VFB (Voltage feedback) pin serves as feedback for controlling the PWM signal.

 

  • What is UC3842?

UC 843 is basically a current mode Pulse Width Modulation (PWM) controller having fixed frequency.

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