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# TPS57140

Other Parts Discussed in Thread: TPS54140, TPS57140-Q1, TPS54240

I am having issues with the Switcher pro software not opening, and the online version does not have the TPS57140 listed.  It appears as though the TPS54140 might be the non-automotive version of this part, in which case, can i substitute it in switcher pro to find my surrounding components?

Thanks

• Hi Eric,

The TPS54140 model can be used for component selection with the TPS57140-Q1.

Best Regards,
Anthony

• Thank you Anthony,

It looks like the TPS57140 (or the 54140) cant run at 2.5Mhz while regulating from 16V to 8.25V, but it looks like the TPS54240 can.  is that correct?

• I like to know how to calculate  tps57140 max power dissiapation ?

• I would recommend using webench.  Let that tool calculate the power dissipation.

• what is the max power rating of TPS57140?
• It is not directly specified. It is limited by maximum operating junction temperature. Tj max = Ta + Pdiss * theta J-A .
So Pdiss max = ( 150 - Ta max) / theta J-A. Theta J-A is given in section 6.4 Thermal Information. It is for a JEDEC standard coupon. It is useful for comparison purposes. Your actual PCB may have better or worse performance. You can use that equation to get an estimate.
• Hi John
Thanks for the Information and when I calculate Pdiss max = ( 150 - Ta max) / theta J-A.
Pdiss_max = (150-25)/61.5 = 2.03 W.
My actual power Dissipation for Vin = 12V and I_Load = 0.795 A, P= 12 V* 0.795 A = 9.54W.

I must calculating something wrong please give me an example so I can see what kind of Max power the TPS57140 can handle

Thanks

• Hi John
Thanks for the Information and when I calculate Pdiss max = ( 150 - Ta max) / theta J-A.
Pdiss_max = (150-25)/61.5 = 2.03 W.
My actual power Dissipation for Vin = 12V and I_Load = 0.795 A, P= 12 V* 0.795 A = 9.54W.

I must calculating something wrong please give me an example so I can see what kind of Max power the TPS57140 can handle

Thanks

• Hi John
Thanks for the Information and when I calculate Pdiss max = ( 150 - Ta max) / theta J-A.
Pdiss_max = (150-25)/61.5 = 2.03 W.
My actual power Dissipation for Vin = 12V and I_Load = 0.795 A, P= 12 V* 0.795 A = 9.54W.

I must calculating something wrong please give me an example so I can see what kind of Max power the TPS57140 can handle

Thanks
• What you are calculating is not a real parameter. As a first order estimate, Pdiss = (Vin * Iin) - (Vout * Iout) - ((Iout^2) * DCR) wher DCR is the inductor series resistance. There are some other losses, but they are small compared to the above. If you do not know Iin, you can estimate it from the efficiency Iin = (Vout * Iout) / (Vin * eff) or Pdiss = (Vout * Iout) * ( 1/eff - 1) - ((Iout^2) * DCR).

You can estimate efficiency from one of the datasheet graphs close to your application.
• John,

What is the  Pmax for the TPS57140 at 85C

this what I calculated for Pdiss

is this right?

• Pdiss = (Vi *Ii) -(Vo*Io) - Io^2*DCR
Pdiss= (12*1.5) - (7*0.795) - (0.795)^2 * (0.045) = 12.4 w
• John,
This what I calculated for Pdiss = (Vi *Ii) -(Vo*Io) - Io^2*DCR
Pdiss= (12*1.5) - (7*0.795) - (0.795)^2 * (0.045) = 12.4 w
Is this right?
What is the Pmax for the TPS57140
Thanks
• That can't be right.  For a buck converter Iin should be much less than Iout.  Why don't you run your design in webench and let it calculate the power dissipation?

• I don't know how to do it on the Webench. please tell me what is the Pmax for TPS57140
Thanks
• John,
What is P mat that TPS57140 can Handel
this what I got from webench for Vi = 12 Vo =7, Io = 1A I got
Pdiss = 0.58W
Po = 7W
what is
Pmax= ?

Thanks
• I like to kwon What is the Pmax for TPS57140

Thanks
• There is not really a Pmax...The limiting factor is Tj .  Does this make sense to you or do you need additional explanation?

• Pmax = (150 - Ta max) / Theta j-a. Theta j-a from the datasheet is based on JEDEC standard coupon. It is for comparison purposes only. Your actual Theta j-a should be better for your actual pcb.