As discussed last night, I've completed some preliminary work on the radiation tolerant circuitry. That does bring up one question...
Bob, do you already have circuitry for watchdog protection and current limiting in the schematic / on the board? Or does that still have to be shoehorned into the board?
To refine the design I've prototyped, I need to know the anticipated/budgeted power requirements. The part I'm looking at for current limiting, MAX4995AAUT+T, can handle 600mA. If we derate that a bit (are we using 50%?) we can handle 300mA. That's quite a lot so I don't expect an issue with hitting max current except possibly the power amplifier and it's not clear to me if the power amplifier needs to be protected against latchup anyway. In our previous designs, we have a separate current limiter for each AX5043, the power amplifier, and the TMS570. (I think the LNAs are bundled with the AX5043 for the purposes of power limits and peripheral power requirements for TXCOs and such ). I don't think we'll need that many here but we'll probably need one for each voltage rail.
Do we have answers to some of the following questions or is some of still being determined:
1. What power output level are we using on the AX5043? Max current at 16dbm TX is 48 mA plus 6.5 mA for VHF receiver or 9.5 mA for UHF receive.
2. What LNAs are we using? Does each AX5043 have its own LNA? (I haven't looked for a schematic so tell me to go find it myself if it's in Github.)
3. What power amplifier are we using and what is the power output? (I still need to double-check a need for current limiter here.)
4. Do we have a characterization for the TMS570 configuration to know which subsystems will be active and thus have a power budget for the TMS570?
Thanks a lot!
Jonathan