LM3409: Regarding the power dissipation calculation

Hello Gottapu, 

I recommend reviewing the following application note which provides a good guide for calculating losses in a buck converter.  

An Accurate Approach for Calculating the Efficiency of a Synchronous Buck Converter Using the MOSFET Plateau Voltage

The key ones to calculate are MOSFET conduction loss, MOSFET switching loss, Freewheel diode conduction loss, inductor losses, both conduction and switching, then bias losses (the power required for the IC, gate drive and other circuitry).

Thanks,

Jaron

Hi Jaron,

Thank you for your previous response and for providing the application note regarding the power dissipation of the LM3409. Upon reviewing the document, I noticed that the power dissipation calculation of buck IC only accounts for the losses contributed by the quiescent current.

Could you kindly confirm if this calculation provided in the above application note covers all IC losses? Specifically, we have observed that there is an internal regulator to generate the pulse voltage, and we would like to know if the losses related to that are included in the provided calculations.

Your clarification on this would be highly appreciated.

Thanks,

Gottapulithesh

Hi Gottapu, 

Yes the losses incurred on the internal regulator used to provide power to the MOSFET gate drive will be accounted for in section  2.1.3 Gate Drive Loss Calculation.

Thanks,

Jaron

Hi Jaron,

Thank you for your previous response, can you please provide efficiency graph for LM3409 with respective to

output voltage - 7.2V and output current - 2.3A

because we are using LM3409 in our application and to calculate the efficiency 

Regards 

Gottapu lithesh

Hi Gottapu, 

All of the efficiency graphs I have available to me are located on page 8 of the datasheet. 

Thanks,

Jaron

Hi Gottapu, 

Yes it is possible, please review datasheet section 9.1.2 Operation Near Dropout for more details.

Thanks,

Jaron