In my application, I am looking to use TLV755P. The requirements are as follows:
- 3.3Vin
- 1.8Vout
- 300mA peak output
- Output is modulated - typical on-time is 200us with four pulses every 500ms; duty cycle can be as high as 5%
- Pd,peak = 450mW, 5ms max
- Pd,avg = 23mw (D < 5%)
- Board will have 4 or 6 layers with multiple ground layers
- T,PCB,max = 85C (doesn't rise significantly during on time)
I am trying to determine the thermal viability of the SON and SOT-23 packages. I have a general idea of how Rja and Rjb are characterized and how they differ from one another. I also see from one of our app notes that the Rja of the SOT-23 package of TLV755P can be much improved on a well-designed board. Without the ability to measure Rjb on the application PCB, it's my understanding that an analysis using Rja makes more sense. However, both the SOT and SON Rja values from the datasheet lead to the disqualifications of these devices from the application (Tj > 125C).
I'm looking for a sanity check here. Do you see any issue using this TLV755P in this application? Further, do you have any guidance on how to conduct a meaningful thermal analysis with the information available?
Thanks,
Brian