[pacsat-dev] Re: Latchup Protection and Watchdog Parts

20 Jan 2023

      This I didn't know! Does anybody on the list know why the hardware 
watchdog wasn't working as expected on the RT-IHU?
Jonathan
On 1/19/23 17:43, Rich Gopstein wrote:
...
And - as long as I'm thinking about it, we had to disable the hardware 
watchdog on the RT-IHU to get it to run.  I don't recall if that 
changed, but if you get some RT-IHU boards, you might need to jumper 
the hardware WD disable.
Rich
On Thu, Jan 19, 2023 at 6:40 PM Rich Gopstein via pacsat-dev 
pacsat-dev@amsat.org wrote:
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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-- 
Jonathan Brandenburg
Radio Amateur Satellite Corporation
1-214-213-1066