LM5116: LM5116

user1260659

Part Number: LM5116

I am developing a DC DC controller with input voltage ranges from 13V to 90V with output voltage of 12V. I have configured the board for about 3A load current. (LM5116MHX/NOPB)

I developed around 5 boards for testing. My observations were as follows:

Board gave only 3.9V output What might be the fault in these boards? is there any other parameters that i should verify? I have almost implemented the same circuit as that of LM5116 evaluation board

We used MOSFET FDMS86200 and BSC350N20NSFD and Bourns PM2120-560K-RC

Regards

H.J.Hamsaraj

over 7 years ago

0 Frank De Stasi over 7 years ago

TI__Guru 71935 points

Please provide your schematic and a view of your layout.

0 user1260659 over 7 years ago in reply to Frank De Stasi

Prodigy 170 points

SCH_LM5116.pdf

0 user1260659 over 7 years ago in reply to user1260659

Prodigy 170 points

PCB_LM5116.pdf

0 user1260659 over 7 years ago in reply to user1260659

Prodigy 170 points

I am developing a DC DC controller with input voltage ranges from 13V to 90V with output voltage of 12V. I have configured the board for about 3A load current. (LM5116MHX/NOPB)

I developed around 5 boards for testing. My observations were as follows:

Board gave only 3.9V output What might be the fault in these boards? is there any other parameters that i should verify? I have almost implemented the same circuit as that of LM5116 evaluation board

We used MOSFET FDMS86200 and BSC350N20NSFD and Bourns PM2120-560K-RC

Regards

H.J.Hamsaraj

0 David Baba over 7 years ago in reply to user1260659

TI__Mastermind 39900 points

Hello Hamsaraj,

Suggest we first fix the schematic.

Please see attached Quick Start calculator, I have entered in your specification, please follow all suggestion there in,

Please implement in your board and also please update your schematic to suit.

E2E LM5116_quickstart.xls

Also YOu need to make sure you are not violating the Toff min spec if you are trying to get the LM5116 to operate at Vin min.

Suggest reviewing link below to make sure you are not violating any specifications in the LM5116 datasheet.

Hope this helps?

David.

0 David Baba over 7 years ago in reply to David Baba

TI__Mastermind 39900 points

Hello Hamsaraj,

Sorry I forgot to post link regarding duty cycle max capability, if this is indeed your issue.

Hope this helps?

David.

0 Frank De Stasi over 7 years ago in reply to David Baba

TI__Guru 71935 points

I am closing tnis due to inactivity

0 user1260659 over 7 years ago in reply to Frank De Stasi

Prodigy 170 points

My observations were as follows input voltage ranges from 13V to 90V with output voltage of 12V. I have configured the board for about 3A load current. (LM5116MHX/NOPB) Board gave only 3.9V output What might be the fault in these We used MOSFET FDMS86200 and BSC350N20NSFD and Bourns PM2120-560K-RC
Regards
H.J.Hamsaraj

0 David Baba over 7 years ago in reply to user1260659

TI__Mastermind 39900 points

Hello Hamsaraj,

In general, a low Vout can be likely caused by the following.

1. Current limit engaging.

1a. Due to Noise on the current sense

2.a Due to real current reading on the CS pin

2a1. Can be due to cross conduction (layout)

2b. Due to wrong Rsense value for load current

2c due to Too much slope compensation

2. Instability

2a due to wrong compensation values

2b due to noise (Layout)

2c due to input filter interaction (Input filter undamped)

I believe we have discussed this design in the past? Is this the same design? If so, we had discussed that the likely cause was the layout. I believed at the time the layout was not ideal. I had made recommendations for you to fix the layout because the layout as it was, could very well cause you performance problems.

Have you fixed the layout since then, following all the recommendations I had made? If not, this is likely the cause of the issue.

If you wish me to re review your layout you can email me at the same email address as before.

David.Baba@ti.com

Hope this helps?

David.

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LM5116: LM5116