I need to design a buck converter with the following parameters:
- Vin = 53V
- Vout = 50V
- Iout = 4A
The LT8645 or LT8646 seem to be a good choice. However, in the DS, there is no exemple of a circuit with an output power of 200W (maximum is around 100W).
I've used LTpowerCAD to estimate the power dissipation of the device. The software says that the efficiency at full load would be better than 97.5% with the LT864 dissipating:
- Pd=1.17W @f=200kHz -> Tj=Tamb+20°C @Oj=17°C/W (temperature is OK)
In the DS, you only mention 95% efficiency @12Vin and @5Vout. In this worst case I would have:
- Pd=200W*0.5%=10W -> Tj=Tamb+170°C @Oj=17°C/W (temperature is not OK)
How is the power and the efficiency calculated by LTpowerCAD ? There is no data in the datasheet that could help me check these results. Can I trust them ?
Thanks for your time,