Product details


Topology Boost, Flyback, Forward Control method Current VCC (Min) (V) 12 VCC (Max) (V) 28 Duty cycle (Max) (%) 100 UVLO thresholds on/off (V) 16/10 Frequency (Max) (kHz) 500 Operating temperature range (C) -55 to 125 Gate drive (Typ) (A) 1 Features Error Amplifier, Multi-topology Rating Catalog, Military open-in-new Find other PWM controllers & resonant controllers

Package | Pins | Size

CDIP (JG) 8 64 mm² 9.6 x 6.67 CFP (W) 14 55 mm² 9.2 x 6.39 LCCC (FK) 20 79 mm² 8.89 x 8.89 open-in-new Find other PWM controllers & resonant controllers


  • 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

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The UCx84x series of control integrated circuits provide the features that are necessary to implement off-line or DC-to-DC fixed-frequency current-mode control schemes, with a minimum number of external components. The internally implemented circuits include an undervoltage lockout (UVLO), featuring a start-up current of less than 1 mA, and a precision reference trimmed for accuracy at the error amplifier input. Other internal circuits include logic to ensure latched operation, a pulse-width modulation (PWM) comparator that also provides current-limit control, and a totem-pole output stage that is designed to source or sink high-peak current. The output stage, suitable for driving N-channel MOSFETs, is low when it is in the off state.

The UCx84x family offers a variety of package options, temperature range options, choice of maximum duty cycle, and choice of turnon and turnoff thresholds and hysteresis ranges. Devices with higher turnon or turnoff hysteresis are ideal choices for off-line power supplies, while the devices with a narrower hysteresis range are suited for DC-DC applications. The UC184x devices are specified for operation from –55°C to 125°C, the UC284x series is specified for operation from –40°C to 85°C, and the UC384x series is specified for operation from 0°C to 70°C.

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Technical documentation

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Type Title Date
* Datasheet UCx84x Current-Mode PWM Controllers datasheet (Rev. F) Apr. 28, 2020
* SMD UC1842 SMD 5962-86704 Jun. 21, 2016
Application note Understanding Inverting Buck-Boost Power Stages in Switch Mode Power Supplies (Rev. B) Mar. 12, 2019
Application note UCC38C42 Family of High-Speed BiCMOS Current-Mode PWM Controllers Feb. 07, 2002
Application note Conditioning a Switch-mode Power Supply Current Signal Using TI Op Amps Mar. 23, 2000
Application note DN-26 UC3842A Low-Cost Start-up and Fault Protection Circuit Sep. 05, 1999
Application note DN-27 UC1842/UC1842A Family - Summary of Functional Differences Sep. 05, 1999
Application note DN-29 UC3842A Family - Frequency Foldback Technique Provides Protection Sep. 05, 1999
Application note DN-30 Programmable Electronic Circuit Breaker Sep. 05, 1999
Application note DN-40 The Effects of Oscillator Discharge Current Variations on Maximum Duty Sep. 05, 1999
Application note DN-42A Design Considerations for Transitioning from UC3842 to the New UCC3802 Sep. 05, 1999
Application note DN-62 Switching Power Supply Topology Voltage Mode vs. Current Mode Sep. 05, 1999
Application note DN-65 Considerations in Powering BiCMOS ICs Sep. 05, 1999
Application note DN-89 Comparing the UC3842, UCC3802, and UCC3809 Primary Side PWM Controllers Sep. 05, 1999
Application note Modeling, Analysis and Compensation of the Current-Mode Converter Sep. 05, 1999
Application note U-100A UC3842/3/4/5 Provides Low-Cost Current-Mode Control Sep. 05, 1999
Application note U-111, Practical Considerations in Current Mode Power Supplies Sep. 05, 1999

Design & development

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Design tools & simulation

SLUM522.ZIP (4 KB) - PSpice Model
SLVM049.ZIP (101 KB) - PSpice Model

CAD/CAE symbols

Package Pins Download
CDIP (JG) 8 View options
CFP (W) 14 View options
LCCC (FK) 20 View options

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