Current-Mode PWM Controller - UC3843

UC3843 (ACTIVE)

Current-Mode PWM Controller

Recommended alternative parts

  • UCC28700  - The device has SIMILAR FUNCTIONALITY but is not functionally equivalent to the compared device.   Next Generation Current Mode PWM with Primary-Side Regulation for Flyback
  • UCC28710  - The device has SIMILAR FUNCTIONALITY but is not functionally equivalent to the compared device.   Next Generation Current Mode PWM with Primary-Side Regulation for Flyback

Description

The UC1842/3/4/5 family of control devices provides the necessary features to implement off-line or dc-to-dc fixed frequency current mode control schemes with a minimal external parts count. Internally implemented circuits include under-voltage lockout featuring start up current less than 1 mA, a precision reference trimmed for accuracy at the error amp input, logic to insure latched operation, a PWM comparator which also provides current limit control, and a totem pole output stage designed to source or sink high peak current. The output stage, suitable for driving N-Channel MOSFETs, is low in the off state.

Differences between members of this family are the under-voltage lockout thresholds and maximum duty cycle ranges. The UC1842 and UC1844 have UVLO thresholds of 16 VON and 10 VOFF, ideally suited to off-line applications. The corresponding thresholds for the UC1843 and UC1845 are 8.4 V and 7.6 V. The UC1842 and UC1843 can operate to duty cycles approaching 100%. A range of zero to 50% is obtained by the UC1844 and UC1845 by the addition of an internal toggle flip flop which blanks the output off every other clock cycle.

Features

  • Optimized For Off-line and DC-to-DC Converters
  • Low Start-Up Current (<1 mA)
  • Automatic Feed ForwardCompensation
  • Pulse-by-Pulse Current Limiting
  • Enhanced Load Response Characteristics
  • Under-Voltage Lockout With Hysteresis
  • Double Pulse Suppression
  • High Current Totem Pole Output
  • Internally Trimmed Bandgap Reference
  • 500-kHz Operation
  • Low RO Error Amp

View more

Parametrics Compare all products in PWM and Resonant Controller

 
Topology
Control Method
Duty Cycle (Max) (%)
Frequency (Max) (kHz)
UVLO Thresholds On/Off (V)
Regulated Outputs (#)
Special Features
Rating
Operating Temperature Range (C)
Pin/Package
UC3843 UC1843 UC2843
Boost
Buck
Flyback
Forward    
Boost
Flyback
Forward    
Boost
Flyback
Forward    
Current     Current     Current    
100     100     100    
450     450     450    
8.4/7.6     8.4/7.6     8.4/7.6    
1     1     1    
Error Amplifier     Error Amplifier     Error Amplifier    
Military     Military     Military    
0 to 70     -55 to 125     -40 to 85    
14SOIC
8PDIP
8SOIC    
14CFP
20LCCC
8CDIP    
14SOIC
8PDIP
8SOIC    

Other qualified versions of UC3843

Version Part Number Definition
Military UC1843 QML certified for Military and Defense Applications
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