Re: 4420 driver ICs

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: Jan Wagner <jwagner-at-cc.hut.fi> 


On Thu, 1 Apr 2004, Tesla list wrote:
 > Umm im not sure what you mean...The input to the 4420?Or the MOSFET?The
 > input to the 4420 is connected to the antenna...

Relying heavily on the chip's ESD protection to handle it, right? ;-)

I mean it seems a bit odd, with potentially 100V... x kV antenna signals
going directly to the 4420 input pin. Now OTOH the 4420 datasheet shows
internal protection diodes, so maybe your setup actually _does_ have
some chances of working properly (?) :)

To be on the safe side I'd probably add a 18V zener diode accross the
chips Vdd and ground, and a very small 6.8V zener between the input pin
and ground, so that the circuit is better protected from the kilovolts. Oh
and a 100ohm..1kOhm resistor in series with the antenna, on the tc4420
side.

good luck,
  - Jan

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