LM5164: IC failure above 48V

Steven Shenker

Part Number: LM5164

Tool/software:

Hi there,

We have a 12V 1A 680 kHz design based on Webench which fails above 48V (we have tested this a few times). Our schematic looks like:

I can share our PCB layout with you but I am fairly confident that it is correct as I have done a similar LM5164 design before but at a lower switching frequency (300kHz).

Below are scopes of the Output Voltage taken at different input voltage of 42V 44V and 46V (left to right) and light load of <0.05A. You can see a large increase in output ripple.

We would appreciate your advice as to what could cause this behaviour. I am concerned that it could be the value of Rr since this value is related to the input voltage.

Thanks in advance,

Steven

11 months ago

0 David Baba 11 months ago

TI__Mastermind 40040 points

Hello Steven,

Can you share your schematic please.

Thanks.

David.

0 Steven Shenker 11 months ago in reply to David Baba

Intellectual 930 points

Hi David,

Please see the below. EN_REMOTE is connected to 3.3V when applied on. Thanks.

0 David Baba 11 months ago in reply to Steven Shenker

TI__Mastermind 40040 points

Thanks for sharing Steven,

The ripple voltage on VOUT is expected to increase as the device goes into light load operation. I would double check your design to make sure you have optimal ripple voltage at the feedback node by using the calculator spreadsheet. put your requirement into the sheet, select typeIII ripple injection and use the values suggested therein.

LM5163-LM5164DESIGN-CALC Calculation tool | TI.com

Hope this helps.

David.

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LM5164: IC failure above 48V