LMR14030-Q1 Power loss

K.Hamamoto

Guru 12155 points

Other Parts Discussed in Thread: LMR14030, LMR12020

We are going to calculate the power loss of LMR14030.

The power loss is calculated by the sum of Pcond and Psw and Pq.

Pcond = Iout^2 x Rdson x Duty.

Psw = VIN x Iout x Fsw x Tr

Pq = VCC x Iq.

Should we need to add the internal boot diode loss(=Iboost x Vboost) to these sum?

Also could you give us the Tr or Tf parameter for that? (On the datasheet of LMR12020, it is mentioned 10ns. Can we use that?)

Regards,

Koji Hamamot

over 7 years ago

0 Arief Hernadi over 7 years ago

TI__Mastermind 23815 points

Hi,

Ideally yes, but unfortunately i do not know where to get the Iboost value. At no load condition, i think this losses is included in the VCC x Iq loss.
As for the rise and fall time, i will ask the application engineer if he has the value.
Also you need the dead time for the loss calculation also. This happen when both FET are off and the current goes to body diode of bottom FET
Pdeadtime = Vdiode x Iout x deadtime x Fsw

Thanks
-Arief

0 Arief Hernadi over 7 years ago in reply to Arief Hernadi

TI__Mastermind 23815 points

Sorry i just realized that this is a non-synchronous part. Therefore you need to include losses in the diode during the off time of the top side FET,
In this case, it should be Pdiode = Vdiode x Iout x Diode off time x Fsw
In addition to that you can use this part for synchronous if you worry about efficiency
www.ti.com/.../description

Thanks
-Arief