ESD Protection Basics - TVS Diode Selection & Routing - Phil's Lab #75
ฝัง
- เผยแพร่เมื่อ 14 พ.ค. 2024
- Basics of ESD protection in hardware and PCB designs, TVS diode basics and relevant parameters, layout and routing guidelines, as well as an example on how to select a TVS diode for a specific application.
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[TIMESTAMPS]
00:00 Introduction
00:36 Altium Designer Free Trial
01:00 ESD Protection Basics
02:33 TVS Diode Operation
03:19 TVS Diode Parameters
03:46 Uni- vs Bidirectional
04:59 Number of Channels
05:23 Working Voltage
05:52 Clamping Voltage
06:39 Capacitance
07:56 IEC 61000-4-2 Rating
08:28 Schematic & PCB Layout Guidelines
10:56 Example: Choosing a Suitable TVS Diode
14:02 Outro
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What golden times we live in where awesome people like you give this knowledge to us for free. Thank you very much Phil!
Thank you for watching, Paul!
agree!
One parameter to check on, particularly for high-speed/low capacitance diodes, is if they have a snapback voltage spec. When one of these diodes is triggered by an ESD event, it won't reset until the voltage falls below the snapback voltage. For instance, if you want to have ESD protection on a data line and a 3.3v rail you might decide to use the high speed diode for both lines to simplify the BOM. However, the snapback voltage may be 2.7v so if it is triggered on the rail it won't reset, i.e., it goes into latch-up, short circuits the rail and bad things may happen. On the data line, the diode will reset when the data line toggles low. Search term: esd diode "snapback"
If I may point out, shuffling across the carpet is the finest form of locomotion, and is designed to keep TVS diode manufacturers in business. Thanks for another excellent episode!
Indeed :D
Thank you!
"ESD Protection Basics" is a great idea for a series.
Thanks for sharing !
Thanks!
10:01 why a TVS diode on the power supply input if any "ESD" is gonna see that massive 2u2 MLCC capacitor? The diode could serve to clamp the maximum supply voltage and offer some minimal protection to over-voltage until it burns up due to the power dissipation. For ESD I would think the capacitance on that rail would suffice.
That's true - a (~ >=0.1uF) cap is usually enough for ESD protection on power rails. However, adding a suitable (larger body/power rating than shown in this video) TVS diode can help - as you said - with clamping the max. supply voltage. Quite a numer of app notes do suggest placing suitable TVS diodes also on the power lines.
This channel is a hidden gem that will positively become a staple in little time. Congratulations on producing stellar content sir
Great... I highly appreciate this kind of content, which most other channels tend to rarely talk about, but still of highly practical (professional) importance!
Thank you!
The most informative video about TVS/ESD suppression! Many thanks dear Phil
Thanks so much Phil - thrilled you've addressed this important area. Really hoping you can do a back-to-back video on power filtering, then your followers can safely design circuits for the real world. I'd love to see your take on common and differential mode EMI filtering (on both power and data lines), and when to use discrete components vs integrated eFuse IC's
Thank you very much, Dan! Definitely will be making a video or two on power filtering in the (hopefully near) future.
Thanks again Phil for one more great video. I didn't care about the position of the ESD to my designs. I will take care of it next version!
absolutley awesome, premium content, and its for free, just crazy, love it!
this is what ive been searching the whole time. big thanks
why on earth we do not find such amazing lecturer like this guy?
It is worth attending. thank you, sir.
Your style of explaining is extremely easy to understand, have you / could you do a video on EMI / EMC filtering on the connector / PCB please? Excellent video as always!
Hi Phil, it would be awesome if you had a "interfacing PCBs with mains" series - like how to chose rectifier diodes, filtering etc, especially for high power PCBs like driving motors. Thanks for the awesome information as always!
Excellent video Phill.. waiting for your High speed design course
Phil... you're the man! I already know most of this but it feels great to hear it from another source. When I got started as a PCB designer back in the early 2000s I was all on my own. Now I have your channel as a great reference to keep me plugged in to fellow designers.
Thank you very much, Jason - glad we have a little community of like-minded people here :)
Very informative content as usual. Thanks for posting
Thanks, Nilanjan!
Fantastic!! I had just figured out that the microprocessor board I am laying out needed some ESD protection. And then this video happened!!
Thanks, Isaac - glad to hear that it could help out with your latest board!
Excellent video, demystified it for sure!
Glad to hear that, thanks!
Great video tutorial 👍❤thank you for sharing your knowledge and experience 🇵🇭🙂
Brilliant as always
Great Video, Well explained, now i will use them also for my designs
Thank you!
You can run in to problems as you get close to the clamping voltage as they start to conduct below this. This current can cause heating if the clamping voltage is too close to the maximum voltage on that net. So finding a TVS diode that will clamp low enough but not too low can be quite hard.
I have seen designs where the TVS diode in series with a diode or zener to up the trip voltage. But the diodes or zeners are not fast enough so affectively take the TVS out of circuit. Also a low value resistor a few ohms can help if the current pulse is expected to be large.
Have you done any lightning testing, that really puts your TVS diodes under strain. Had one where we kept seeing little flashes of light during the tests inside the box. On the third or forth strike the little flash was followed by a bang and a TVS diode exited stage left at a vast rate of knots.
nice! one spec that’s worth mentioning is the reverse bias leakage current, which could be detrimental to high impedance sources or receive networks (like an ADC)
While your video focused on electrostatic discharges, during connector handling, there's also the point that signal lines can be subject to transient voltage spikes during operation.
It's advisable to consider where the energy absorbed by your suppression devices is delivered to. Dumping directly into ground isn't always a good idea.
I have, in my past designs, separated the equipment casing from signal ground (often not completely, resistive and other networks can be used) then routed the suppression devices to low-impedance traces which are bonded to the chassis or case internal shielding coating (for plastics).
The aim is to prevent large injections of current under transient voltage application from affecting the signal ground and upsetting system operation. This is of particular importance to systems running at voltages of 3.3V and below.
Thank you for these interesting and helpful videos !
Thanks for watching!
Excellent info short sharp and clear 🙂
Thanks, Steve!
Very interesting and informative. Thanks for sharing.
Thanks!
Good info, fast. Very nice.
Thanks for watching, Gregory!
Great video as usual Phil!
Thank you!
I stumbled across your channel a few months back, I have found its content to be brilliant, informative & very understandable. I’ve not done any circuit / pcb design other than playing around with a 555 timer IC and a bit of veroboard when I was much younger. But you have inspired me to download KiCAD & have a go at trying to build a few simple circuits, I’m building up to ordering a PCB in the near future. Could I ask, would the TVS diodes offer any protection to indirect lighting strikes or is this beyond their capacity?
Thank you very much, David. Glad to hear the videos have inspired you zo try out KiCad! Hope all goes will with your PCB designs and orders.
W.r.t. your TVS question - to a certain extent, yes, TVS diodes will offer protection to indirect lightning strikes. However, as also not covered in this 'basics' video, you have to ensure adequate power ratings and so on.
For more info, in particular for aviation, this is a good read: www.google.com/url?sa=t&source=web&rct=j&url=www.microsemi.com/document-portal/doc_download/14682-micronote-127-lightning-protection-for-aircraft-electrical-systems&ved=2ahUKEwjc6o6ez4j6AhVqSfEDHcuAAIQQFnoECCsQAQ&usg=AOvVaw3Ya0EK8fU5ELqXRS-TsOpW
@@PhilsLab Thank you Phil, I’m sure the first PCB will be a disaster but I will look on it as a learning opportunity and hopefully the second one will be ok. I suspected looking at the data sheets, there would be a capacity rating. I look forward to reading the article you provided, keep up the great work...
Thank you very much Phil!
Thanks for watching :)
top tips -thank you
Great video as always, thank you for that.
Would you also protect the CC lines of the USB-C connector?
Hi Phil, this is a neat and good content about ESD diodes, thank you for that!
My request is please do a video on how to design Pi filters from scratch.
Thank you! That's a future video for sure!
Thanks for this educational video! I've always placed a slow fuse (cartridge or poly) in front of the TVS diode. My intention with that is that in case there's a spike that persists for some time and/or, the more likely scenario, where the user plugs in a wrong power supply with a greater voltage, then the fuse would save the diode from burning up shunting all that current. I'd rather replace a fuse cartridge than a SMD diode.
Great video!!
Please do a tutorial on filter design also.
Thanks, will do!
Great video.
Thanks!
As a complete novice - I wondered - wouldn't the unidirectional TVS diode (D100) placed on the power input in the PCB layout example be destroyed during a reverse polarity event? Wouldn't a bi-directional TVS diode be better here just to protect the PCB from stupid? xD nvm I asked too soon and you addressed this point exactly. Thank you so much for your high quality content, you're a bloody legend as far as the common parlance here goes.
Yes, it would burn up. I know first hand. oops
Brilliant
Thanks for another awesome video! Would you mind recommending if one should use uni-directionals or bi-directional TVS diodes for SD-Card Readers? Also, do input devices like tactile buttons need TVS protection diodes?
Nice overview. Except for USB, I tend to forget EMI and reverse-bias protection when designing circuits... until something stupid happens. lol
A video on Surge Suppression would be great as well (eg. using MOVs, spark gaps, TVS diodes, etc.). Probably not as relevant for (most) strictly DC circuits, although I find myself working a lot with line AC (either building my own power supplies, or for doing industrial control stuff for my CNC machine).
Thanks, Jacob. Will try to cover surge suppression in a future video as well.
this video is great! thankyou! btw is it possible to have a video to talk about ESD with chassis earth? for example, the case is in metal and how to layout the pcb
Thanks! I'm planning on making a video on chassis connections, grounding, etc. around April.
Great video on ESD protection.(TVS diode)👍
If possible please Can you also make video ferrite beads?
Thank you, Madhav. Yes, I've been wanting to make a video on ferrite beads for quite some time - will be in a (near) future video.
Golden content as always! How do you deal with not having the TLP value? Do you just use the maximum rating value?
Thanks! Yeah, either by maximum rating, digging a little deeper into manufacturer's files/models, or simply using the TVS diode with the smallest possible clamping voltage.
What about snapback voltage, Phil?
Hi Phil. As always thanks for making such good videos.
We are working on a small electrical cart with the supply voltage of 48 Volts. The motor used for the cart creates 60 Amps current in back-EMF. How can we select a suitable TVS diode for reverse EMF protection circuit?
The diodes described in this video would die very quickly in that environment. Take a look at the SMDJ48CA or 5.0SMDJ diodes made by just about everyone. The key is the pulse power rating of the device. An SMD (not surface mount device, this is a part numbering thing done by Littlefuse, Vishay, and so on) component can handle a pulse of 3kW for around 1000us all day long. If you know the rise and fall times of your back EMF you can derate accordingly (maybe you need a bigger part, or multiple in parallel). Look at the datasheet for any of these devices and you will see a table that shows the peak power handling of the device over the time of the transient.
FWIW- Those part numbers are like this SM [A,B,C,D (Power rating and size)] J [ Working Voltage ] [A for unidirectional CA for bidirectional]. So an SMDJ48CA is a 48V, D rated bidirectional devices. An SMAJ5A is a 5V unidirectional A rated device... and so on. The 5.0 or 3.0 you sometimes see is a higher power device crammed into a smaller package.
The BI-directional diode works in most of the cases, and you don't need to choose the polarity at all. Unless you are manually mounting the diode, and you are not able to know if the diode is soldered well to the trace, because either direction is open, in that case, uni-directional is better choice, because you can use the diode mode to measure its forward biased voltage, and that's will tell you whether the diode is soldered well.
If you have a fairly high impedance input (gpio/ADC/opamp kinda deal) could you put a resistor before the tvs diode to reduce the current it'd have to deal with, rise times all that kinda deal? Or is it still better to have that after the tvs?
great video, though it does make me want to redo the circuit board I ordered last week...
I'm waiting for your new course on udemy Phil
Is power dissipation a concern? If so is there a rule of thumb to go by?
How do I check if the ESD bidireccional diode has gone bad?
Is this similar/different to having 2 diodes, 1 to Vcc and 1 to ground?
Don't a lot of MUCs have that(diodes to ground and Vcc) at least on IO pins for ESD?
If they used TVS Diodes, then could you have 3.3v ICs with 12v IO tolerance?
Hi Phil, I have a question on the order of esd as connector esd filter and IC.
I have seen that the resistor element of the filter is put before the esd to also limit the energy going into the esd while still serving same purpose electrically. Is this is a good practice?
I meant this question for a data line
Awesome videos
Are the thicker red DC wires some of your own best practices or is it a Altium feature?
Altium allows you to add color to certain nets. Its called custom net colors. In the schematic go to View -> Set Net Color -> choose your favorite color. Its useful for things like DDR where you have a ton of address and data lines. It make seeing it easier in the PCB view.
As I understood, you are trying to give (9V-12V-->3.3V) to microcontroller ? and protecting the circuit using TVS diode + pi-filter.
We can also use this type of protection ( TVS+ reverse polarity diode+ pi-filter) between 5V SMPS and Microcontroller board for EMI/EMC issue ?
what is the role of pi-filter here ?
where we can ask a problem in details any linkedln profile or website you have?
Phil I love you if you reply to this you'll make my little nerd heart
Haha here's your reply :D
What is the rule about using ferrite beads? Is there any real benefit of using FB at 5V input of PDN?
I know it can filter out HF noise coupled to the VBUS line (USB cable, especially unshielded can act as an antenna for sub-ghz range), but what's the aim? Is it included to protect from this or to prevent HF noise getting out of the board?
Hey Phil, what about the power ratings of a TVS diode?
Hi , should the TVS be connected to GND or to EARTH (in the case where the casing is EARTHed ?)
Will you keep putting out courses on fedevel, or will you use the new TH-cam Learning platform for new courses?
Hi, I have a DC motor operating at 24 VDC @20amp. On the supply line a surge voltage of +/-250VDC for 500msec is getting generated. In such case how to select the TVS diode? Also if current is also an important factor right?
Is there a parameter for the diode that says how long after a high-voltage pulse the line can stay high? Or is that something that has to be calculated based on the filter network?
The signal line can stay high forever, the diode is going to shunt the excess voltage to current. When the transient disappears, the voltage will settle back to whatever the voltage was. I saw a comment in here about snapback. I have been doing DO-160 lightning testing for years and never seen an interface get latched up by lightning. Im not saying it cant happen, but i havent seen it.
Thanks for a nice video. I see that you showed ESD protection for LDO regulator and I went back to check the design I'm currently working on. In datasheet of the LDO that I use (AP2112K-3.3) it says ESD (Machine Model) 400V and ESD (Human Body Model) 4000V under Absolute Maximum Ratings. Does that mean that I don't need to add TVS diode?
If your goal is to save money or you just dont have the room on the PCB, skip the diode and use the built in ESD diode. Personally, i think its worth adding additional protection. I dont know why, but i just dont trust the IC manufacturers with this. It seems sus that this tiny IC has enough room for the IC and a reasonably large ESD diode. Your mileage may vary, but it never hurts to make a design more robust.
The esd diode integrated into the ic must be second line of protection and you gotta put an external tvs diode for full protection
I work in an industry where we use M12A 5 pin connectors on all of our equipment and have a need for this. I wonder if there is any way to integrate this into a connector or something similar?
Hi Phil, how can I stop the noise from an ili9341 display from seeping into my audio projects?
What if the clammping voltage is less than the operating voltage. The diode will be activated when it exceeds the clammping voltage or when it exceeds the operating voltage?. For example this diode PESD5V0C1ULS-QYL
I was expecting to hear something about the power rating, how do we choose that? When I was looking recently I saw values 500W to 5000W. How could somebody predict how much power the ESD event will have?
If I connect the cathodes of two TVS unidirectional diodes with the same values, will it be a bidirectional TVS diode?
I have learned that from you; where did you learn it from?
OK, so the ESD current goes into ground, but what if there is no ground? i.e I am holding the PCB in my hand? Where will the energy be dissipated in that case?
How is this different from a zener diode?
Are those TVS diodes kind of Zener diodes?
Why does the working voltage matter when it is only the clamp voltage that really matters?
Very useful educational video. Thank you.... also I have a question. What is the difference between zener diode and ESD protection diode in this case? When think about functionality both behave same.
Maybe the functionality is similar but the construction is specialized for that purpose. ESD diode might not have a very well set voltage level, or the votlage level might vary a lot with the current. A Zener might have a slow response time, making it almost useless for protection.
why J100 a 3 pin connector and not 2?
For all other connectors I'm using either 3- or 4-pin. Adding an additional 3-pin instead of a 2-pin makes me need fewer unique components, as well as cable harnesses.
I think you meant capacitance decreases rise/fall steepness not rise/fall times.
👍🙏❤
Think ESD design on a PCB is complicated? Then modern CMOS processes are 10x more complex. Primary and secondary protection, cross-domains, HBM, MM, CBM, antenna diodes, latchup...
Oh, and in high data rate I/O they couple ESD protection via a T-coil to reduce capacitive loading.
First!!!
I literally can’t concentrate on what you are saying you’ve got stunning look jesus