1. ADVANCED 8-PIN LOAD-SHARE CONTROLLER UCC39002 UCC29002 UCC29002/1
Jan 2007

2. What is Load Share? What is Load Share?
Provides equal distribution of the load current among parallel voltage-stabilized power supplies
Why parallel supplies?
High current/low voltage applications
Redundancy for enhanced reliability
Hot Swap capability
Distributed heat removal
Space and cost
Jan 2007

3. Why would you need a Controller?
Output impedance of power modules < 1mW
When connected in parallel, the supply with the highest Vout will supply the majority of the output current. Because the output R is so low, it doesn’t take a large difference in Vout for this to result in large current differences.
Current-limit mode
increased stress = decreased reliability
Jan 2007

4. The Concept
Basic concept of load-share controller: supply a voltage feedback loop
Iout of each module is accurately measured then compared to a current share bus
Vout is adjusted so each module delivers an equal amount of output current
Jan 2007

5. Improvements over the UC3902
Fully compliant with Intel SSI Specs
Server System Infrastructure
Power Supply and Chassis
Physical dimensions, wattage ratings, electromechanical interface parameters
Single connection between parallel modules
Scalable load share voltage independent of Rsense
High Accuracy, better than 1% at full load
High-side or low-side current sense capability
Hot-swap, Enable, Disconnect-at-Standby
BiCMOS
MSOP-8 package
5/16/2018

6. UCC39002, UCC29002, UCC29002/1 Start Up Logic LS driver disabled
ADJ amp sinks max current
Normal operation resumes when measured current >80%LS
Start up logic masked out in the UCC29002/1
Jan 2007

7. At start up, LS driver is disabled and ADJ amp is forced to sink MAX current
Starts in known state
Module forced full on to engage in sharing asap
Output of module adjusted high
At 80% of LS, ADJ amp reverts to normal
Jan 2007

8. UCC39002/UCC29002/ UCC290021
LS protection
5/16/2018

9. UCC39002/UCC29002/ UCC290021
Enable and Disconnect
5/16/2018