I/O Line Protectors

Posted on Dec 2, 2012

A 5.1-V zener diode clamps positive-going transients, and a Schottky rectifier clamps negative-going transients. Th

I/O Line Protectors
Click here to download the full size of the above Circuit.

e Schottky rectifier has problems at both ends of the temperature scale. At 125°C (257°F), its leakage current can reach 50 when the input line is at 5 V. This leakage is not a big deal unless the input resistor has a value of 100 kfi or more. More troubling, at temperatures below -40°C (-40°F), the Schottky rectifier"s forward voltage rises to about 0.47 V, which is perilously close to the -0.50-V max spec that most HCMOS-type /iP"s inputs can tolerate. The third circuit, Fig. 20-3(c), uses two regular silicon rectifiers. One rectifier is connected in series with the input line, thereby isolating the " inputs from negative-going voltage spikes. The other rectifier is in series with a 5.1-V zener, which clamps positive-going transients.

Leave Comment

characters left:

New Circuits



Popular Circuits

telephone line loger
Electrical isolation for the I2C bus with optocouplers
Infrared circuits related resources
compressor microphone
Build your own PC interface
Complete SS Laser Power Supply Schematics
Controllable integrator F007 schematic