LM25149-Q1: Current Capability Assessment @2.2MHz

PY (Pengyu) Song

Expert 5860 points

Part Number: LM25149-Q1

Hi team,

What would be the maximum current LM25149-Q1 can output with Fsw = 2.2MHz (or close to 2MHz)?

Vin = battery level, nominal = 14V, max up to 18V functional.
Fsw = 2.2MHz.
Ta,max = 70C.

Can LM25149-Q1 support below application case with above Vin, Fsw and Ta conditions?

Vout = 3.3V/12A
Vout = 4V/11A

Thanks.

over 1 year ago

0 Colin Chen over 1 year ago

TI__Expert 6841 points

Hi Pengyou,

The output current of controller depends on parameter of mosfet you select.

For first question: generally no problem in 5A Io in this high Fsw;

Second question: LM25149-Q1 can support 20A-30A in Fsw=400k;

Thanks

Colin

0 PY (Pengyu) Song over 1 year ago in reply to Colin Chen

TI__Expert 5860 points

Hi Colin,

Thanks. Second question is asking what is max current LM25149-Q1 can support with the listed conditions, i.e. Vin = 14V-18V, Fsw = 2.2MHz & Ta,max = 70C.

Specifically datasheet has example with high current but with Fsw of 400kHz. How much degrading in terms of output current do we expect with increased Fsw from 400kHz to 2.2MHz?

0 Colin Chen over 1 year ago in reply to PY (Pengyu) Song

TI__Expert 6841 points

Hi PY,

The output current not only depends on controller, but also the parameter of mosfet you select. From below table we can see that the higher Fsw ,the higher the Iout, and more switching loss will be, this will cause mosfet thermal worse. Under same switching loss, you can treat Iout is inversely proportional to Fsw.

thanks

Colin

0 PY (Pengyu) Song over 1 year ago in reply to Colin Chen

TI__Expert 5860 points

Hi Colin,

Assuming external FETs are with low Ron low capacitance, can controller support Vin = 14V-18V, Fsw = 2.2MHz & Ta,max = 70C for Vout = 3.3V/12A and Vout = 4V/11A?

+1 Colin Chen over 1 year ago in reply to PY (Pengyu) Song

TI__Expert 6841 points

Hi PY,

I think such a condition may cause thermal too high and further leads to mos damaged. I suggest you can use two LM25149-Q1 configure for interleaved operation where both outputs are tied together to support such high Io in Fsw = 2.2MHz.

Thanks

Colin

0 PY (Pengyu) Song over 1 year ago in reply to Colin Chen

TI__Expert 5860 points

Hi Colin,

Thanks. So is there any way to estimate what is the maximum current or power the controller can handle? The design calculator doesn't seem to have this.

By the way, 2x LM25149-Q1 is considered not optimized.

0 Colin Chen over 1 year ago in reply to PY (Pengyu) Song

TI__Expert 6841 points

Hi PY,

You should take mosfet and layout as well as controller into consideration to estimate maximum current, not only focus on controller.

Colin

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LM25149-Q1: Current Capability Assessment @2.2MHz