| ??? 06/07/08 18:15 Read: times |
#155580 - It's just an array of schottky diodes, Erik Responding to: ???'s previous message |
arranged as 16 clamps to Vcc and GND and it's entirely passive. i.e. no power consumed from the supply other than what it dissipates from the signals.
Erik Malund said:
I like clamps Have a look at 74S1053
I would not use a 'S' chip Regular HC(T) chips can clamp 20mA either way and with the filter I suggested exceeding that is extremly unlikely. I recommend using a schmitt chip (e.g a -14) to handle the slower rise/fall time the cap introduces. I have no idea what the 'S' chip Richard suggest can clamp, but 20mA is more than sufficient when preceeded by 'my' filter. that series resistor should be valuable in limiting the voltage to legal levels I like the capacitor to reduce the risetime, clamps need a few nanoseconds to react, and I can visualize a heavy spike getting past that if no cap. Erik The advantages to using the Schottky clamps are (1) there are 16 of them in a single SO20 (among others) package and cheap (though DigiKey is very proud of them), and (2) they're Schottky diodes with a lower forward voltage than typical silicon diodes. They just provide another option, particularly if protecting the PISO register inputs is deemed necessary. No doubt the Schmidt-trigger is a good idea with switches, which can benefit from the RC-filter. RE |
