LM5034: The maximum duty

Rock Shao

Expert 2995 points

Part Number: LM5034

Hi Team,

The datasheet shows the maximum duty at 76% when the UVLO pin =1.3V,

but the waveforms show only 68%. Please help to check this problem of the LM5034. thanks.

over 2 years ago

0 Hong Huang over 2 years ago

TI__Guru 74115 points

Hi,

Typical is 76%, min is smaller, you need to consider about -15% in a design.

0 jason.tsai over 2 years ago

Prodigy 20 points

-15%? What?

0 jason.tsai over 2 years ago

Prodigy 20 points

Big error -15%? What?

0 Hong Huang over 2 years ago in reply to jason.tsai

TI__Guru 74115 points

Hi,

The typical duty 76%, the worst can be as low as 65%. So -15% variation compared to typical 76%.

0 Rock Shao over 2 years ago in reply to Hong Huang

Expert 2995 points

Hi Hong,

Has any document or application note to explain the LM5034 max duty? Thanks,

0 Hong Huang over 2 years ago in reply to Rock Shao

TI__Guru 74115 points

Hi,

No other documents t explain the max duty but the datasheet. Basically it looks your transformer turns ratios need to adjust to adapt the Dmax variation.

0 Rock Shao over 2 years ago in reply to Hong Huang

Expert 2995 points

Will you remark on the -15% variation compared to the typical 76% in the LM5034 datasheet? thanks.

0 Hong Huang over 2 years ago in reply to Rock Shao

TI__Guru 74115 points

Hi，

Typical 76%, min 64.6%

0 sean over 2 years ago in reply to Hong Huang

Prodigy 10 points

The error of LM5034 is so large, it is too unreasonable, how do you know the minimum duty 64.6%, is there any proof information?

0 Yao Chin Hung over 2 years ago in reply to Hong Huang

Prodigy 10 points

The error range is so wide??

0 Hong Huang over 2 years ago in reply to Yao Chin Hung

TI__Guru 74115 points

Hi,

it is from the IC design and at worst case. 68% in your case is about -10%, so quite reasonable. you need to make transformer turns ratios with enough margin.

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LM5034: The maximum duty