[time-nuts] PICTIC II ready-made?

shalimr9 at gmail.com shalimr9 at gmail.com
Sat Apr 28 22:22:16 UTC 2012


By the way, Actel is now part of Microsemi, with all that it entails.

Didier KO4BB

Sent from my BlackBerry Wireless thingy while I do other things...

-----Original Message-----
From: Jim Lux <jimlux at earthlink.net>
Sender: time-nuts-bounces at febo.com
Date: Sat, 28 Apr 2012 14:19:40 
To: <time-nuts at febo.com>
Reply-To: Discussion of precise time and frequency measurement
	<time-nuts at febo.com>
Subject: Re: [time-nuts] PICTIC II ready-made?

On 4/28/12 12:10 PM, shalimr9 at gmail.com wrote:
> I have not studied CPLDs but Actel has the only true Flash based FPGAs. The flash cells directly control the FPGA fabric. As such, they are mostly immune to Single Event Upset that plagues just about any other FPGA technology, and there is no configuration step at power up.


mmmm..  the flash contents can still be lost(although Actel claims that 
their flash is pretty neutron and alpha particle immune.. but heavy 
ions?)..  the Actel anti-fuse parts, like the AX and RTAX series, have 
logic that can't be changed.  We use a lot of the Actel flash parts 
(ProASIC3) for prototyping, then burn it to an rtax for final.

I think there's a similar path for the 54SX parts (i.e. a reprogrammable 
version and an antifuse OTP part)


Here's what was in a Brookhaven report about using FPGAs in PHENIX

The Actel FPGAs do not have SRAM configuration memory so they are immune 
to this form of upset.  FLASH memories exhibit dissipation of the charge 
on the floating gate after 20kRad of integrated dose.  The dissipation 
is not permanent damage and is remediated by reprogramming the device. 
Flash memories also displayed SEE problems during programming during 
radiation exposure that included gate punch-through, a destructive 
effect.  These types of SEEs are avoided by not programming the FLASH 
under radiation exposure conditions, namely during machine operation.


Practically speaking 20kRad is a fairly decent dose (it's a typical 
design requirement for a trip to Mars or for GEO).. you pick up about a 
kRad/year

In LEO it's a lot lower (otherwise astronauts in ISS would die).

Around Jupiter it's a lot higher (typical design requirements for Europa 
missions and such are 1 MRad)

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