UCC2889 Off-line Power Supply Controller | TI.com


Off-line Power Supply Controller

Off-line Power Supply Controller - UCC2889


The UCC1889 controller is optimized for use as an off-line, low power, low voltage, regulated bias supply. The unique circuit topology utilized in this device can be visualized as two cascaded flyback converters, each operating in the discontinuous mode, and both driven from a single external power switch. The significant benefit of this approach is the ability to achieve voltage conversion ratios of 400V to 12V with no transformer and low internal losses.

The control algorithm utilized by the UCC1889 is to force the switch on time to be inversely proportional to the input line voltage while the switch off time is made inversely proportional to the output voltage. This action is automatically controlled by an internal feedback loop and reference. The cascaded configuration allows a voltage conversion from 400V to 12V to be achieved with a switch duty cycle greater than 10%. This topology also offers inherent short circuit protection since as the output voltage falls to zero, the switch off time approaches infinity.

The output voltage can be easily set to 12V or 18V. Moreover, it can be programmed for other output voltages less than 18V with a few additional components. An isolated version can be achieved with this topology as described further in Unitrode Application Note U-149.


  • Transformerless Off-line Applications
  • Ideal Primary-side Bias Supply
  • Efficient BiCMOS Design
  • Wide Input Range
  • Fixed or Adjustable Low Voltage Output
  • Uses Low Cost SMD Inductors
  • Short Circuit Protected
  • Optional Isolation Capability

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Parametrics Compare all products in PWM controllers & resonant controllers

Control method
VCC (Min) (V)
VCC (Max) (V)
Frequency (Max) (kHz)
UVLO thresholds on/off (V)
Duty cycle (Max) (%)
Gate drive (Typ) (A)
Operating temperature range (C)
Package Group
Package size: mm2:W x L (PKG)
UCC2889 UCC3889
Flyback     Flyback    
8.6     8.6    
9.3     9.3    
250     250    
8.4/6.3     8.4/6.3    
55     55    
0.2     0.2    
Error Amplifier
Green Mode
Light Load Efficiency
Soft Start    
Error Amplifier
Soft Start    
Catalog     Catalog    
-40 to 85     0 to 70    
PDIP | 8
SOIC | 8    
PDIP | 8
SOIC | 8    
See datasheet (PDIP)
8SOIC: 29 mm2: 6 x 4.9 (SOIC | 8)    
See datasheet (PDIP)
8SOIC: 29 mm2: 6 x 4.9 (SOIC | 8)