It is true teh Rja of 180°C for SOIC package is just massive....
CHi Winsu,
TPS73801 LDO datasheet shows how to calculate PD in last section. It's a 1A SOT-223 device. If you ever read it, it almost seems to deliberately/thought-provokingly end abruptly at the result of Tj +Tamb is 121°C for only 500mA out and Vin - Vout only 3V, Tamb 50°C. It's almost funny how it chooses to end, like a cliffhanger... It really made me see how top of datasheet specs in normal, not maximum, operating section of e.g. 1A out, x Watts PD are extremely relative and can be limiting in one's goals.
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Hi again,
Further to the above - and bearing in mind I'm a just a 'learn-as-you-go' hobbyist, so everything I try to study or make is always about lengthy learning curves and getting something 'wrong' first time around (... and if I were honest: second and third and nth time around...) for me - when I did some low voltage, low current SEPIC calculations, the choice of transistor was several iterations (...) as a few whose various power specs seemed matched to and/or far greater to needs went over PD/Tj max.
What's your boost converter going to be enclosed in? Could you add a heatsink, or a (little or large) fan for forced cooling?
I wonder if the Onsemi design tool is calculating correctly. Curiously the displayed switching losses are increasing with decreasing switching frequency, although duty cycle and peak current remain constant.
Hello! Please tell me where you can see how to correctly calculate the conductivity of partial discharges and switching partial discharges. Thank you.Hi Winsu,
I think you know how to do these PD conduction and PD switching calculations already, but still.
MOSFET power losses and how they affect power-supply efficiency
That 7ns and 0.2ns is fascinating.
Pages 2 and 3 might indicate something about where those times are obtained from in PRACTICAL CONSIDERATIONS IN HIGH PERFORMANCE MOSFET, IGBT and MCT GATE DRIVE CIRCUITS - gate charge graph where switching on, rising current and falling voltage overlap and switching off opposite direction Ids and Vds overlap can be calculated from nC graph and device capacitances in datasheets. Toshiba (Toshiba Semicon) usually have some interesting app. notes on several topics, including switching losses, etc. This one attached complements the Unitrode (pause for joy, typed application notes from yesteryear employee tracking software) 'Practical Considerations...' one. Unitrode (TI) have a good few application notes about SMPS.
I wonder if the 7 ns and 0.2 ns are not specific to the NPN switch in that IC... You could write to AD to ask where those numbers come from as a last resort.
Good luck.
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