Burns might remember the details (or Zach certainly would), but one of those parts was undersized for the RT-IHU and would cut out when we were transmitting with the ax5043.  I think we had to back down the xmit power in order for the device not to reset.

Rich


On Thu, Jan 19, 2023 at 5:46 PM Jonathan Brandenburg via pacsat-dev <pacsat-dev@amsat.org> wrote:
In last week's meeting, I noted I had been looking at the schematics for
Fox-1 and RT-IHU and found the circuits for the latchup protection and
watchdog functions. I admit this might be basic to some, but I'm finding
it fascinating! Anyway...

Since last week's meeting, I researched the parts used:

onsemi FPF2001 is a current limit switch used on both Fox-1 and half the
RT-IHU. It's obsolete, replaced by onsemi's FPF2000. But the FPF2000 is
listed as end-of-life. It's replacement part is the TI TPS22942.

MAX4995 is a current limit switch used on the other half of the. This
part looks good for new designs.


For the watchdog functionality, both Fox-1 and RT-IHU use the
STWD100NYWY3F chip. this parts looks good for new designs.


That's as far as I got. Next, I want to research the Fox-1 and RT-IHU
designs to determine the thresholds of the current limit switches. In
particular, I want to see if the TPS22942 is a suitable replacement,
assuming we have the same current requirements.

That's where I'm at,

Jonathan


--
Jonathan Brandenburg
Radio Amateur Satellite Corporation
1-214-213-1066


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