ESD Circuit 2

[loosy]

Can somebody help me find a good circuit for ESD. Trying to protect the circuitry I have from any ESD through hands for the heart rate.<br>
<br>
<br>
Thank you

 

[ChrisW]

Do you need to know 'the human body model' ie how much static you will get, or how to prevent static damaging your circuit?

 

[loosy]

Chris,<br>
<br>
Thank you for your response. I need to know a circuit to prevent static from damaging the electronics.<br>
<br>
<br>
Thank you

 

[DareDevil]

Try useing hi-speed switching diodes back to back to protect your inputs to the CCT'S also decoupling Capacitors will ground out some of the static.<br>
<br>
All the best <br>
<br>
Steve Lloyd (GW0JQT)

 

[ronhotchkiss]

I agree with DareDevil. Just keep an eye on the operating voltage of your circuit (do not set the clamp voltage to low). A few zeners, transzorbs or MOVs in parallel with some caps to filter the circuit should do the trick.

 

[wzkbrown]

Look in latest Electronic Component News (ECN).&nbsp;&nbsp;Some ICs were advertized just for this purpose.<br>The Human Body Model may not be adequate for your needs.&nbsp;&nbsp;Static is strong and sneaky.<br>k

 

[wzkbrown]

I found SEMTEC supplies chips in many configurations.<br>k

 

[Rip]

You may want to explore using something like the Fairchild FDV301N digital FET as an input buffer. It has an input zener clamp they claim will withstand the 6KV Human Body Model. Pre-conditioning the gate with a small R/C circuit should buy you additional protection depending on how much signal attenuation/delay you can afford.<br>Rip

 

[MDMarcel]

How about simulations for the different stress models of ESD??? Any idea guys/gals???

 

You can protect your circuit from Transorb i.e. Transient Voltage Suppressor. As ESD has pulse width of the order of 5nS so energy content is very less so transorb will work perfectly upto 15KV ESD.


Regards
Bhanwar Lal Bishnoi
B.E.(Electronics)
M.B.M.Engineering College Jodhpur (Rajasthan) India

 

[melone]

Unfortunately, transorbs are fairly expensive. A simple resistor to ground, and a capacitor to ground will do the trick. C = 0.1uF and R=1K will effectively kill your ESD and will only cost you about 1.5 cents per circuit.

If the 1K pulls down your circuit too much, then you can either increase R or eliminate it completely. The purpose of the R is to help eliminate the energy in the spike, while the C shunts the current. Try it out, you should be happy with the results.

For simulation, PSpice works very well. Finding a circuit that describes the &quot;Human Body Model&quot; for ESD are all over the place. I will take a look around and see if I have one handy.

Good Luck and keep us posted!

 

[MDMarcel]

Melone,
About that PSPICE Simulation can you recommend a site for a tutorial. I dont have any experience using it. Thanks!
As well as the HBM model.

 

[melone]

I don't know of any sites off the top of my head, and it will take some digging at work to find the human body model, but I can find it. Once I do, I can throw something to together in a couple of hours and email it to you. I will let you know when I find something.

 

[MDMarcel]

Hi Melone!

Can PSPICE be used to simulate radiated EMI?
Thanks!

 

[melone]

I am not sure. I know that you can work in the frequency domain, and deal with harmonics, but I have never actually tried it before.

 

[Lewish]

On a cardiac monitor we used 5.6Kohm resistor in the lead, with a 0.1uF capacitor to ground on the board side of the resistor. This is sufficient to absorb the pulse from a heart defibrilator. There are sometimes also gas-discharge tubes used in parallel, but are always necessary.

 

[CIRCUITMAG]

If using surface mount and space is an issue, try using a BAT54S. These are a SOT-23 with 2 fast schottkies in series. And of course, it's always best to add a series resistance to the signal line. Good luck.

 

[MDMarcel]

Melone, Thanks!

 

[melone]

Did it work? What was your final solution?

 

[MDMarcel]

Hi Melone,

Since the PSICE Im currently using is only a Student Demo Version... the library was limited. the only result I got based from the circuit model I inputed was a Discharge (Transient Analysis) event. Thanks again!