LM5146: Suitable for my requirement or not ?

Gokul Karthik Sai Vamshi

Prodigy 90 points

Part Number: LM5146
Other Parts Discussed in Thread: LM5137F-Q1, LM5145

Tool/software:

Hello TI expert,

I wanted to design a high power buck converter with the following specifications.

Vin(min) = 48V

Vin(typical) = 58V

Vin(max) = 70V

Vout(constant) = 12V

Iout(peak) = 80A

Iout(continous) = 35-40amps

Power = 480W

As far as the first iteration is concerned i am not so specific about the efficiency, but would like to keep it at a minimum of 60%.

Could i have some guidance on this and if the decision of going with LM5146 is a good one or not for a synchronous non inverting buck converter. I would also like to know more about how I can select the parameters of the inductor being used and if i can follow the reference diagram given in the datasheet.

Any guidance would be helpful and appreciated.

Thank you.

11 months ago

0 Timothy Hegarty 11 months ago

TI__Guru 74312 points

Hello,

40A steady state and 80A transient is quite high for one phase. Take a look at the LM5137F-Q1, which is an 80V 2-phase controller. You could design it for 20A/phase DC, 40A/phase peak using 80V FETs. Go with Fsw < 250kHz to reduce switching losses (even though the inductors may be quite large).

Regards,

Tim

0 Gokul Karthik Sai Vamshi 11 months ago in reply to Timothy Hegarty

Prodigy 90 points

Hey Timothy, thanks for the reply. Since i already have LM5146 at my disposal going for another controller ic would be difficult. Then suppose that i am willing to compromise on the output current. (I am assuming that the 20A/phase DC, 40A/phase peak is by using LM5146).

The following is the circuit that ive found on TI Power Designer.

Can i use the circuit as it is and be good to go with assuming a vin max of 75V, output voltage of 12v(fixed) and output current is 15-20amps ?

TI Power Designer - LM5146 buck circuit

0 Timothy Hegarty 11 months ago in reply to Gokul Karthik Sai Vamshi

TI__Guru 74312 points

Hi Gokul,

The schematic you showed is similar to that for the LM5146 EVM (12V, 8A, 400kHz). We also have the LM5145 EVM (5V, 20A, 225kHz). If you exceed 20A, you likely need a 2-phase solution (depending on ambient temperature, airflow, etc.).

Regards

Tim

0 Gokul Karthik Sai Vamshi 11 months ago in reply to Timothy Hegarty

Prodigy 90 points

Hi Timothy,

Thank you for guiding me, would like to keep this thread open just in case i get stuck anywhere in my design process and need any help from you.

Regards,

Gokul.

0 Timothy Hegarty 11 months ago in reply to Gokul Karthik Sai Vamshi

TI__Guru 74312 points

No problem, thanks Gokul.

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LM5146: Suitable for my requirement or not ?