Termination Mode RH1020 RH1280 Devices Radiation Environment Ther

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Termination Mode RH1020 RH1280 Devices Radiation Environment Ther

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Termination Mode RH1020 RH1280 Devices Radiation Environment
There concern about Actel RH1020 RH1280 Field Programmable Gate Arrays (FPGA) space-flight, radiation-environment with MODE and/or pins left unterminated. trivial show that MODE must terminated GND. effects floating more difficult definitively assess. conclusion that must properly terminated reliable operation device.
meter. Programming security/probe fuse does eliminate need terminate mode pin.
MODE used control both state device (e.g., normal, programming, debug, outputs disabled, various test modes, etc.) operation with regular logic levels. device into various modes; when MODE logic state, commands shifted into internal registers DCLK (Data Clock) (Serial Data through proper sequencing. When MODE logic zero state, mode registers control path flip-flops directly held inactive state, guaranteeing that device normal operating mode. Note that there guarantee states these "configuration" registers power-up. effects floating MODE difficult predict because almost anything happen. example, state that device might into support board level test. this mode, device outputs tristated. Other examples possible modes include programming mode various device test modes. Incorrect configuration result functional failures and/or high currents which either damage pose serious reliability hazard hardware. effects damage device board must assessed specific basis. Testing shown that when MODE tied high, quite easy "latch-up" device with heavy ions. devices repeatedly drew excessive amounts current. probability having problem with unterminated MODE quite high. recommendations MODE terminate with hard jumper parallel with resistor. hard jumper protects against resistor failure. During prototyping debug stage hard jumper removed Silicon Explorer probing capability utilized. termination MODE each Actel device flight board should verified with
input supply used device programming (the Radiation-Hardened FPGAs' data sheet refers RH1020 RH1280 VCC). RECOMMENDED leave floating, since bounce around high voltage might device programming mode. operating radiation environment, there concern that unterminated leads charge various radiation cases this effect been observed. Under normal operating conditions (MODE high), signal used bias transistors peripheral control circuitry FPGA does directly access user-defined logic modules fuses array core. When device programming mode (MODE high), signal reach every module array core. MODE properly terminated, there risk that device could into programming mode functionality would lost. MODE tied properly terminated, then there risk damage peripheral control circuitry gate array. designed receive voltages exceeding VCC. Under normal operating conditions, signal used bias high voltage along with drain that FET. would break down lower bias voltages. Various tests analyses showed that radiation environment, single capable rupturing antifuse VDC, which corresponds electric field strength approximately MV/cm. Factors rupture will include electric field strength, oxide quality uniformity, parasitic junctions that biased. Internally, diode exists between signal. Under normal operating conditions (VPP tied high), this diode cannot forward-biased device will draw normal operating current outlined Actel FPGA Data Book. this diode becomes forward biased potential risk floats gets driven low), device will draw excessive current. Also, have found that most sensitive RH1020 RH1280.
2001 Actel Corporation
recommended that directly connected VCC. Additionally, should verified with meter that pins flight devices properly terminated.
above summary discussion shows effects unterminated MODE and/or pins Actel RH1020 RH1280 devices relative spaceflight use. trivial show that MODE must grounded this must done verified. unterminated more difficult definitively assess because occurrence number plausible failure scenarios. must connected directly. When operating outside space environment, these pins must also terminated ensure proper configuration device operation. Actel will guarantee long-term reliability devices that were always legal operating configuration. credible analysis been performed that would guarantee reliable operation parts that were always legal operating configuration.
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Termination Mode RH1020 RH1280 Devices Radiation Environment Ther

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