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I/O Protection

M

M Ihsan Baig

Jan 1, 1970
0
I am designing a data acquisition circuit. The I/O's are TTL
compatible, the I/O's get damaged when ever a high voltage spike(50 V,
100us) hits the I/O's. Is there any any I/O protection circuit which I
could use to guard against high voltage spikes.
Thanks,
Beg
 
J

Jan Panteltje

Jan 1, 1970
0
I am designing a data acquisition circuit. The I/O's are TTL
compatible, the I/O's get damaged when ever a high voltage spike(50 V,
100us) hits the I/O's. Is there any any I/O protection circuit which I
could use to guard against high voltage spikes.
Thanks,
Beg

Several exist for example:
Optocoupler.
Transorb.
 
S

Spehro Pefhany

Jan 1, 1970
0
I am designing a data acquisition circuit. The I/O's are TTL
compatible, the I/O's get damaged when ever a high voltage spike(50 V,
100us) hits the I/O's. Is there any any I/O protection circuit which I
could use to guard against high voltage spikes.
Thanks,
Beg

Digital or analog? A series resistor and a clamp into a CMOS input
will take care of some really severe transients on digital lines. If
you like living dangerously, just the series resistor might be okay
(probably you'll want a pullup or pulldown on the input in either
case).


Best regards,
Spehro Pefhany
 
E

Eeyore

Jan 1, 1970
0
M said:
I am designing a data acquisition circuit. The I/O's are TTL
compatible, the I/O's get damaged when ever a high voltage spike(50 V,
100us) hits the I/O's. Is there any any I/O protection circuit which I
could use to guard against high voltage spikes.

Lots of possibilities. Diode clamps to the supply rails is the most obvious and
simplest one.

Graham
 
W

whit3rd

Jan 1, 1970
0
I am designing a data acquisition circuit. The I/O's are TTL
compatible... Is there any any I/O protection circuit

For modest spikes, MC1489A is a common Schmitt trigger inverter
that has no problem with +/- 20V input (and responds to TTL levels).
That's about as robust as a cheap IC gets, you can add discrete
components
to go to higher tolerances (diode clamp to ground, transzorb or
zener, even fuses and spark gaps).
 
R

Rich Grise

Jan 1, 1970
0
I am designing a data acquisition circuit. The I/O's are TTL compatible,
the I/O's get damaged when ever a high voltage spike(50 V, 100us) hits the
I/O's. Is there any any I/O protection circuit which I could use to guard
against high voltage spikes. Thanks,

I've always just used reverse-biased diodes to the rails, with optionally
a small (maybe 100 ohms) resistor or a small choke.

That's how they do it in video games, and I've never seen one fail at the
inputs. (I used to fix video games.)

Cheers!
Rich
 
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