UCC2808-2: Repeated fault analysis

Alon Druker

Part Number: UCC2808-2
Other Parts Discussed in Thread: UCC2808A-2Q1, UCC2808A-2

I'm using the UCC2808-2 in a push-pull topology 50% D.C . The chip powered by 9.5v power supply specified for it only . There is no voltage surges of any kind , and the chip drives 2 mosfet drivers so

there is no load on the outputs .It seems that in the history our engineers had failures on this chip and they add a series resistor of 20 ohm on it's VDD input mayabe because the thought that

there is a problem with the VDD power but i checked it and i didnt found any problem .I my self encounered some fails with this chip in the last months . The failure is that the outputs dosnt operate and

there is no oscilation on the RC and i measured the current through the VDD pin and its 5 mA .I checked the Data Sheet and so to my suprised that its recommended junction temp is 85 and

"junction=ambient " ???? .I want to know if its real data ( junction temp) or a mistake in data sheet ? . I think that the failure apeared in our design because of the high ambient temp (8 7 ambient )

I have another question , I saw that there is an automotive version of this chip that is UCC2808A-2Q1 and this chip is defined -40 to 125 ambient . I want to know what is the diffrent between them that

makes it more high temp resistant ?

Thanks

over 8 years ago

0 Peter Meaney over 8 years ago

TI__Mastermind 31580 points

Hi Alon,

Sorry about the delay in responding to your questions. I suggest you return the failed IC's for analysis through your local TI contact. I have asked one of our application engineers to respond to your questions.

Regards

Peter

0 Wangxin Huang over 8 years ago

TI__Intellectual 1550 points

Hi Alon,

It meant ambient temp rather than junction temp. 87C Ambient temp exceed max recommended operating range of UCC2808-2. Can you lower the ambient temp to see where the part starts switching?

For the UCC2808A-2Q1, I compared it against UCC2808A-2, they are functionally equivalent. So I think the auto-qualified version either has tightened the parametric spec by silicon modification or through screening during ATE test.

Regards,
Wangxin

0 Alon Druker over 8 years ago in reply to Wangxin Huang

Prodigy 20 points

Hi ,

The damaged parts do'nt work at all (even in room temperature) .

Is it possible that the temperature data that is wrriten in the data sheet (junction temp 85 celsius)

not wrriten by mistake and the chip has a problem at working high temperatures ?

Best regards

Alon

0 Wangxin Huang over 8 years ago in reply to Alon Druker

TI__Intellectual 1550 points

Alon,

I don't think 85C junction temperature makes sense for an IC. Can you please share your schematic either here or email me at w-huang3@ti.com?

Regards,
Wangxin

0 alon druker over 8 years ago in reply to Wangxin Huang

Prodigy 30 points

Hi , here is the relevant schematic .

Do you think that there is an error in data sheet refering to 85 c junction temperature ?

Regarads

Alon

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UCC2808-2: Repeated fault analysis