TPS92641: External NFETs Selection

Takashi Yamaguchi

Part Number: TPS92641

Hi team,

The d/s doesn't describe how to calculate the power loss of the High-side / Low Side FETs. Could you tell me the equations?

Regards,

Yamaguchi

over 6 years ago

0 Tuan Tran74 over 6 years ago

TI__Mastermind 18890 points

Hi Yamaguchi-san,

We currently do not have the equations for this.

Thanks Tuan

0 Takashi Yamaguchi over 6 years ago in reply to Tuan Tran74

TI__Genius 13270 points

Hi Tuan-san,

I described below the equation of FET loss of a general synchronous rectification IC. Is this equation applicable to the TPS92641?

-High side FET

Pcond(H)=Io^2*Rds

Psw(H)=1/2*Vin*Io*(trise+tfall)*Fsw

Pcoss(H)=1/2*Coss*Vin^2**Fsw

Ploss_total(H)=Pcond(H)+Psw(H)+Pcoss(H)

-Low side FET

Pcond(L)=Io^2*Rds

Pdead(L)=Io*VF*(TD-LH+TD-HL)*Fsw

Pcoss(L)=1/2*Coss*Vin^2*Fsw

PQrr(L)=Qrr*Vin*Fsw

Ploss_total(L)=Pcond(L)+Pdead(L)+Pcoss(L)+PQrr(L)

Regards,

Yamaguchi

0 Tuan Tran74 over 6 years ago in reply to Takashi Yamaguchi

TI__Mastermind 18890 points

Hi Takashi-san,

Your equations does not take into account ripple current in the inductor. Please see the following if you need more exact equations for general buck regulator MosFET loss calculations.

http://www.ti.com/lit/an/slyt664/slyt664.pdf

Thanks Tuan

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TPS92641: External NFETs Selection