Product details


Share bus Differential Operating supply current (mA) 6 Operating supply (Min) (V) 2.7 Operating supply (Max) (V) 20 Features UVLO Operating temperature range (C) 0 to 70 open-in-new Find other Load share controllers

Package | Pins | Size

PDIP (P) 8 93 mm² 9.81 x 9.43 SOIC (D) 8 19 mm² 3.91 x 4.9 open-in-new Find other Load share controllers


  • 2.7-V to 20-V Operation
  • 8-Pin Package
  • Requires Minimum Number of External Components
  • Compatible with Existing Power Supply Designs
    Incorporating Remote Output Voltage Sensin
  • Differential Share Bus
  • Precision Current Sense Amplifier (40 Gain)
  • UVLO (Undervoltage Lockout) Circuitry
  • User Programmable Share Loop Compensation
    • Paralelled Power Supplies

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The UC3902 load share controller is an 8-pin device that balances the current drawn from independent, paralleled power supplies. Load sharing is accomplished by adjusting each supplies’ output current to a level proportional to the voltage on a share bus.

The master power supply, which is automatically designated as the supply that regulates to the highest voltage, drives the share bus with a voltage proportional to its output current. The UC3902 trims the output voltage of the other paralleled supplies so that they each support their share of the load current. Typically, each supply is designed for the same current level although that is not necessary for use with the UC3902. By appropriately scaling the current sense resistor, supplies with different output current capability can be paralleled with each supply providing the same percentage of their output current capability for a particular load.

A differential line is used for the share bus to maximize noise immunity and accommodate different voltage drops in each power converter’s ground return line. Trimming of each converter’s output voltage is accomplished by injecting a small current into the output voltage sense line, which requires a small resistance (typically 20 Ω to 100 Ω) to be inserted.

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Exact equivalent in functionality and parametrics to the compared device:
UCC29002 ACTIVE Advanced 8 pin load share controller, -40°C to 105°C This device has improved power efficiency and feature set.

Technical documentation

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Type Title Date
* Data sheet Load Share Controllers datasheet (Rev. E) Jul. 28, 2011
User guide UCC39002 Advanced Load-Share Controller User's Guide, HPA027A (Rev. A) Feb. 09, 2004
Application note U-163 The UC3902 Load Share Controller and its Performance in Distributed Power (Rev. A) Dec. 13, 2002

Design & development

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Hardware development

document-generic User guide

The UCC39002 is an advanced, high-performance load-share controller that provides all the necessary functions to parallel multiple independent power supplies or dc-to-dc modules. This load-share circuit is based upon the automatic master/slave architecture utilized in the UC3902 and UC3907 (...)

  • High accuracy, better than 1% current share error at full load
  • High-side current sensing
  • Ultra-low offset current sense amplifier
  • Single wire load-share bus
  • Intel® SSI load-share spcification compliant
  • Disconnect from load-share bus at stand-by
  • Load-share bus protection against shorts to GND or to the (...)

CAD/CAE symbols

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PDIP (P) 8 View options
SOIC (D) 8 View options

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