LM5145: LM5145 use as negative power rail regulator

Jiandong Liu

Part Number: LM5145
Other Parts Discussed in Thread: LM5146, LM5116

Hi Expert,

My customer want to use LM5145 to regulate negative power rails: input -75V, out put -5V to -60V adjustable, 2A output current. Do you think if it's practicable? And do you have some articles can guide customer to design this kind of negative power regulators? Thanks.

Regards,

Jared

over 4 years ago

0 Timothy Hegarty over 4 years ago

TI__Guru* 75852 points

Hi Jared,

Note that the voltage seen by the controlled in an inverting buck-boost (IBB) design is Vin + |-Vout| = 75V + 60V = 135V. This exceeds the ratings of the LM5145. If you can reduced the output voltage range, consider the LM5146 or LM5116 100V controllers.

See this app note for more detail on IBB designs: www.ti.com/lit/snva856

Regards,

Tim

0 Jiandong Liu over 4 years ago in reply to Timothy Hegarty

TI__Intellectual 1801 points

Hi Timothy,

Thanks for you reply. However, customer is using -75V input, not 75V, do you think the voltage stress is still 135V? And do you have some design guide of negative input to negative output, not positive input to negative output? Thanks.

Regards,

Jared.

+1 Timothy Hegarty over 4 years ago in reply to Jiandong Liu

TI__Guru* 75852 points

Hi Jared,

Please use the LM5146 100V controller for the -75V to -5 to -60V output at 2A.

See these links for more detail on negative Vin to negative Vout conversion:

https://e2e.ti.com/support/power-management/f/196/t/820019?tisearch=e2e-quicksearch&keymatch=negative%20input

https://e2e.ti.com/support/power-management/f/196/t/367158?Negative-input-negative-output-with-buck-converter

Regards,

Tim

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LM5145: LM5145 use as negative power rail regulator