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TPS23758: Power consumption on the DC-DC controller

Part Number: TPS23758 Hi, Do we have a power consumption number of TPS23758 when an output load is 5V/13W for reference? Do we have a recommended max ambient operating temp of TPS23758? or a curve showing ambient temp vs TPS23758 PD Thanks.

Hello Hector, The TPS23758EVM-080 shows the load regulation and efficiency. The load regulation shows the specific output voltage at the related output current, so you can calculate the exact output power. Then you can use the efficiency to calculate the input power and the power lost in the system. The datasheet specifies a max temperature before thermal shutdown on page 9. Can you list a specific metric you want graphed against temperature? Pages 10-13 show graphs that list different parameters tested against temp. If this post answers your question, please indicate so by marking this thread as resolved. Thank you. Regards, Michael P. Applications Engineer customer organization

Hi Michael, Thanks for your information. I can estimate power loss by input power and efficiency. However, the power loss includes other components in the PD like transformer. What I want is to get power loss on TPS23758 only so that I can use thermal resistance to estimate Tj. Our system consumes 7.9W input power, the case temp of TPS23758 is 101C and ambient temp is around 80C. Do you suggest TPS23758 operates when Tj is over 125C but lower than Turnoff temperature? In other words, we can use TPS23758 without encountering the reliability issue or damages if Tj is lower than Turnoff temp (I know parameters will be affected by temp)? Thanks.

Hi Michael, Thanks for your information. I can estimate power loss by input power and efficiency. However, the power loss includes other components in the PD like transformer. What I want is to get power loss on TPS23758 only so that I can use thermal resistance to estimate Tj. Our system consumes 7.9W input power, the case temp of TPS23758 is 101C and ambient temp is around 80C. Do you suggest TPS23758 operates when Tj is over 125C but lower than Turnoff temperature? In other words, we can use TPS23758 without encountering the reliability issue or damages if Tj is lower than Turnoff temp (I know parameters will be affected by temp)? Thanks.

Hector, I understand now you want Tj. The following application note details how to calculate Tj and other thermal parameters for our IC's: <secret URL>/lit/an/spra953c/spra953c.pdf As specified in the datasheet, –40°C to 125°C is the Junction temperature range. If this post answers your question, please indicate so by marking this thread as resolved. Thank you. Regards, Michael P. Applications Engineer customer organization

Michael, I understand how to calculate Tj using thermal resistance. Is it diffcult to know TPS23758 power consumption becasue of internal MOS ? Thanks Hector

Hello Hector, The power consumption of the IC is discussed in this other post. Since they already discuss it, I just attach the link: <secret URL>/support/power-management/f/196/t/820034?TPS23755-TPS23755-IC-Power-Dissipation-Calculation The calculation includes an assumption about the power loss through the internal FET gate because the direct gate capacitance cannot be measured. However, we can estimate the power loss through there because all the power for the gate is coming from VCC so that is how we calculate it. If this post answers your question, please indicate so by marking this thread as resolved. Thank you. Regards, Michael P. Applications Engineer customer organization

Hi Michael, The calculation shown in <secret URL>/support/power-management/f/196/t/820034?TPS23755-TPS23755-IC-Power-Dissipation-Calculation The power dissipated by the IC will be the power at the pass FET (IRTN*IRTN*RDSon) and the power to drive the gate of the switching FET (VCC*ICC) and conduction loss of the switching FET (RDSonFET*Irms*Irms). Can we ignore switching loss of the switching FET ?

Hello Hector, Yes that is correct. If this post answers your question, please indicate so by marking this thread as resolved. Thank you. Regards, Michael P. Applications Engineer customer organization

Hi Michael, Here is current measurment of the switching MOS in TPS23758. Calculated conduction loss of the MOS is 0.08W. Total power loss of TPS23758 would be too low to match case temperture measurment on TPS23758 itself. Why can we ignore switching loss of the switching MOS ? Thanks.

Hello Hector, The switching loss is estimated by the power to drive the gate of the switching FET (VCC*ICC). The traditional way to calculate the switching loss is not possible with the FET internal to the part. If this post answers your question, please indicate so by marking this thread as resolved. Thank you. Regards, Michael P. Applications Engineer customer organization