LM62440-Q1: SW node rise time dependency with resistor value

Hello Rahil,

Rahil Ajani said:

To maximize efficiency, 0 Ω is chosen for this example. Under most circumstances, selecting an RBOOT resistor value above 100 Ω is undesirable since the resulting small improvement in EMI is not enough to justify further decreased efficiency.

Yes, I understand it. However, customer would like to use 1kohm to mitigate EMI as much as possible. Thus, provinding the graph and formula is highly appreciated.

Thanks,

Kento

Hello Rahil,

Understood that over 700ohms do not slow down the rise time from 12ns. I will tell this to my customer.

Thanks,

Kento

Hi Rahil,

Regarding the 12ns SW rise time, do you have any graph you can provide for efficiency like the graph below?

Or, do you have any equation to calculate switching loss based on the rise time?

Thanks,

Kento

Hi Kento, 

I will ask the team if we have any data on this to share. 

Regards,

Rahil

Hello Rahil,

Any updates on it?

Thanks,

Kento

Hello Rahil,

I found a good documentation to calculate the efficiency.

An Accurate Approach for Calculating the Efficiency of a Synchronous Buck Conver

Customer wants to calculate the efficiency based on this equation, but they cannot find enough information for the calculation in the datasheet.

They need the following parameters. Could you please contact to design/simulation team to check the following information?

Turn-on time: tr (when R=1kohm)

Turn-off time: toff (when R=1kohm)

Output charge: Qoss

Reverse recovery charge: Qrr

deadtime: tdr, tdf

Thanks,

Kento

OK. Thanks!

Reagrds,

Kento