Re: Using an oscillator in a rugged environment

Hi Alessandro,

> My doubts are the following:
> - is a good choise to connect directly the oscillator output to the
> FPGA pin or for this kind of environment is suggested to build a
> more reliable circuit around the oscillator ?

It would be best to have higher-frequency differential oscillator at,say, 32
or 64MHz, but basically, this should not be a huge problem.

> - is a good choise using the internal PLL ? Is it reliable in a
> rugged environment ? (I have chosen an external low frequency
> oscillator to reduce EMI emissions)

A colleague of mine is using a 33MHz single-ended clock in combination with
the Cyclone PLL to control train engine inverters by directly controlling
the gates of a few _big_ IGBTs that steer about 1000A over 3200V. So far it
has been working flawlessly. The PLL even filters out spikes in the clock
signal to some extent.

The only thing that happened was during a torture test when he directly put
the PCB with the Cyclone on it in in a 4500V electric field, with about 1"
between cathode and anode where the PLL stopped running. On the other hand,
as you can imagine, lots of other electronics on the board went weird under
this condition as well, and this situation _should_ never occur in trains.
BTW: once the field was removed, the PLL started running again as if
nothing had happened.

Best regards,



Ben

.

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