J
John Larkin
Guest
The FAQ for this ADC is sort of terrifying:
http://www.analog.com/media/en/technical-documentation/frequently-asked-questions/AD779x_FAQ_Instru_Conv.pdf
Basically, the internal SPI state machine counts bits forever, and
deasserting CS doesn't initialize anything. If anything in the system
ever misses one clock, it's hosed forever after.
Furthermore, the ESD diodes are useless, because if they are ever
actually forward biased, the internal registers can be corrupted. That
includes the ESD diodes on the analog inputs.
We seem to be doing everything right but when it's cold, say -10C, the
SPI interface locks up maybe every 5 minutes, and only the 31-bit
reset sequence will fix it.
The obvious question is, why would anyone design such a nightmare? But
the more general question is, why are so many chips subject to bizarre
behavior when a little current flows into their ESD diodes? You'd
think that every semi house would have a mandatory ESD diode hazard
review for every product. This has been an industry problem for
decades now.
--
John Larkin Highland Technology, Inc
picosecond timing precision measurement
jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com
http://www.analog.com/media/en/technical-documentation/frequently-asked-questions/AD779x_FAQ_Instru_Conv.pdf
Basically, the internal SPI state machine counts bits forever, and
deasserting CS doesn't initialize anything. If anything in the system
ever misses one clock, it's hosed forever after.
Furthermore, the ESD diodes are useless, because if they are ever
actually forward biased, the internal registers can be corrupted. That
includes the ESD diodes on the analog inputs.
We seem to be doing everything right but when it's cold, say -10C, the
SPI interface locks up maybe every 5 minutes, and only the 31-bit
reset sequence will fix it.
The obvious question is, why would anyone design such a nightmare? But
the more general question is, why are so many chips subject to bizarre
behavior when a little current flows into their ESD diodes? You'd
think that every semi house would have a mandatory ESD diode hazard
review for every product. This has been an industry problem for
decades now.
--
John Larkin Highland Technology, Inc
picosecond timing precision measurement
jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com