UCC39002: Power up logic when modules have current limit Hiccup mode

Mitchell Kary

Part Number: UCC39002
Other Parts Discussed in Thread: UCC29002

Hi,

I am using the UCC39002 evaluation board to control two +12V bricks. If the two bricks have a current limit with a 100ms retry are started up with close to a full load, then what prevents one module from entering a current limit hiccup mode which in turn forces the full current to the other module which also enters hiccup mode? This is the situation I have now at startup. The sharing is fine at 70% to 80% of full load and startup is fine. At loads greater than this, I enter into a perpetual hiccup current limit which only seems to resolve it self after I remove the load and power up again.

Thanks,

Mitch

over 7 years ago

0 John Griffin1 over 7 years ago

TI__Mastermind 34465 points

Hello Michael,
The UCC39002 has a startup logic which disables current sharing and the load share module is forced to share maximum current.
It sounds like in your situation this results in overcurrent of the +12V supplies.
The UCC39002/1 does not disable the load sharing at startup so you should try using this part.
Or you could increase the soft start time of the +12V supplies so the system is gradually eased into the max load at startup.

Regards
John

0 Mitchell Kary over 7 years ago in reply to John Griffin1

Intellectual 630 points

Hi John,

WE are using the evaluation board which has the PDIP packages. I do not see the /1 option for this package. The 29002/1 is not a PDIP. is the UCC39002/1 available as a sample?

0 John Griffin1 over 7 years ago in reply to Mitchell Kary

TI__Mastermind 34465 points

Hi Mitchell,
As you say the UCC29002/1 is not available in DIP package but for your testing it is possible to solder the surface mount package into the DIP solder pads.
It looks like you can get samples of this part here:
store.ti.com/.../1.aspx

Regards
John

0 Mitchell Kary over 7 years ago in reply to John Griffin1

Intellectual 630 points

John,

My mistake I just realized the evaluation board has a SOIC so I can use the 29002/1. I just ordered some to try. I will post the result of whether this prevented the current limit hiccup mode from occurring. As to your other suggestion, unfortunately the bricks to be controlled do not have a soft start option. They are standard 1/8 style bricks with only Vin, enable and output/sense pins.

0 John Griffin1 over 6 years ago in reply to Mitchell Kary

TI__Mastermind 34465 points

Hi Mitchell,
Since there has been no new information in over 3 weeks I will go ahead and close this post.
Please open a new post if you have any other issues
Regards
John

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UCC39002: Power up logic when modules have current limit Hiccup mode