LM25119: Operation frequency

Zoe Ko

Part Number: LM25119

Hi team,

The LM25119 max switching frequency is 750KHz as the datasheet mentioned.

But we would like to know if we always operate at around 918KHz.

The chip may have risk of the damage and could you provide some direction to us for what may result in the risk of the damage?

Thank you!

0 Qian Chen over 4 years ago

Hi Zoe,

The chip damage risk is very low. The main concern is some performance may not meet spec.

I would suggest to set Fsw at 750kHz.

If you have to set Fsw to 918kHz, can you explain a little bit?

Thanks

Qian

0 user6224372 over 4 years ago in reply to Qian Chen

Hi Qian ,

I know the max switching frequency is 750KHz as the datasheet mentioned .

But I use a wrong RT resistance value (24.9 ohm) , that make frequency at 918KHZ .

Because I need to make a risk evaluation report .

so I need to know , when I set Fsw to 918KHZ , the LM25119 circuit which part will be affected (Ex : MOSFET or CHOCK ... ) ?

Thanks you !

0 Qian Chen over 4 years ago in reply to user6224372

Hi Zoe,

What's Vin and Vout in your application?

Below potential risk I can think of.

1. The switch loss is large and may cause thermal problem on MOSFET and Inductor.

2. The PWM off time is close to minimum off time (320ns typical, 430ns maximum).

Thanks

Qian

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