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ESD351: Designing Protection circuit using ESD351

Rushi Jariwala
Prodigy 20 points
Part Number: ESD351
Other Parts Discussed in Thread: TPD1E10B06-Q1, TVS0500

Hello, 

I am a beginner in the field of ESD protections and need the support of TI to choose the right ESD protection component and design the circuit. 

Setup:

An external signal comes as an input to a GPIO pin of the uC (F280049C). This signal is not a high-speed signal.  And there is a resistor divider from the connector pin to reduce the levels to 3.3V and then it is connected to the GPIO pin of the uC.

Application:

Automotive EVs (the external signal comes from the wiring harness)

Requirement: 

ESD protection for this GPIO pin. Now, I have gone through the ESD essential series from TI and I understand various IEC 61000 standards. But I am unable to design the ESD protection circuitry. Hence, I have posted down several questions below. 

1. I understand I need to qualify for IEC 61000-4-2 level 4. But I am not sure which level do I need to qualify for IEC 61000-4-5 surge protection. I could not find relevant information for it. With your experience, can you let me know what would be the level required for IEC 61000-4-5? 

2. I am planning to use ESD351. But it has only a 6A rating for an 8/20us surge. So, my plan was to use a series resistor between the conn pin and ESD351. This should reduce the current going into the ESD531 during higher surges. Is this a good idea? 

     a. Since, the resistor will see the higher voltage across it, what kind of resistor do I need to choose? 

     b. ESD351 has a clamping voltage of 6.5V at 16A. Will this 6.5V damage the GPIO pin or do I need to also add a series resistor between ESD351 and GPIO pin? 

So, will this arrangement work:

Conn Pin -> Resistor -> ESD351 -> Resistor -> GPIO pin

Or is there a better arrangement that is generally used? 

3. Another arrangement is to use a series resistor and then a Schottky protection diode to the supply rails. Which is a better protection design for this specific application - the TVS one or the Schottky one? 

4. Will the Schottky idea qualify for IEC standards? What are your thoughts on that?  

It would be nice if you can answer these questions in detail for better understanding. Thanks for your time. 

  • 0
    TI__Expert 8476 points

    Hello Rushi,

    Thanks for using E2E! Please see my answers to your questions below:

    1.) I will link some documents that go into IEC 61000-4-5 at the end of this answer. For data line surge protection, you will need to look at ratings with a 42 Ohm Req, which is what all of our surge ratings are spec'd at. ESD351 has a 6 A surge rating, so it can withstand a 252 V (peak) surge event. Please refer to Demystifying Surge Protection and our IEC 61000 Test papers for more details. There is also a Demystifying Surge Protection video series as well on our training page. 

    2.) If this is an automotive application, wouldn't you need an AEC Q101 qualified part? Here is all of our automotive qualified parts (Q1): https://www.ti.com/interface/circuit-protection/esd-protection-and-tvs-surge-diodes/products.html#p1498=Automotive . I would recommend TPD1E10B06-Q1 for automotive GPIO. With that being said, the series resistor would help reduce the effects of a surge event, granted it doesn't compromise signal integrity during normal operation. 

    a.) I am not sure on the different types of resistors, but you would at least need to have a resistor that matches the power rating of your desired protection. 

    b.) While the clamping voltage is higher than the abs max of the MC, that does not necessarily mean a transient voltage that is slightly higher will damage it. The abs max ratings on those devices are for constant DC voltages, not transients. The only way to find this out is to run a TLP curve on the GPIO pin and see what transient voltage it fails at. With that being said, another series resistor after the diode would add additional protection if your signal can handle it. 

    3.) While the Schottky steering method is another valid approach, you risk damaging other circuitry connected to that power rail as well as the power supply itself. Refer to page 23 of this document for a similar situation: https://www.ti.com/lit/ml/slyt562/slyt562.pdf 

    4.) No, since the diode isn't actually offering any protection, just steering.

    Let me know if you need any clarification on any of these items.

    Regards,

    Matt 

  • 0 in reply to Matt Smith3
    Prodigy 20 points

    Hi Matt, 

    Thanks for the detailed answer. Below are the follow-up questions: 

    1. As you mentioned, TPD1E10B06-Q1 is 6A rated and can sustain surges up to 252V peak with 42-ohm resistor. So, is it right to note that TPD1E10B06-Q1 cannot pass IEC 61000-4-5 level 1 (1kV) ? 

    2. I can use a series resistor between the connector pin and TPD1E10B06-Q1. In that case, the currents would reduce and that might help to pass the above standard. But in that case, is it better to use one single device like SMAJ5.0A or TVS0500? 

    3. What advantages I get in using TVS0500 vs SMAJ5.0A? 

    That's all for signal lines. Coming to power lines like 5V or 12V which go to the external wiring harness, 

    4. What would be the series resistor for IEC 61000-4-5 - is it 0 ohms or 10 ohms? I have gone through the documents that you suggested in your answer but I am not sure whats the correct coupling resistor to rate for? 

    5. Can you recommend a part for 5V supply protection? 

    Thanks

  • 0 in reply to Rushi Jariwala
    TI__Expert 8476 points

    Hi Rushi,

    1.) That's correct. This is mainly an ESD device, so the surge rating will not be as high. Also, IEC 61000-4-5 level 1 is 500 V. 

    2.) In general, it would be better to use a single device rather than two devices to save on board space/BOM cost. However, are you mainly focused on surge protection or ESD protection?

    3.) I believe TVS0500 is better than SMAJ5.0A. We have a couple of app notes highlighting the benefits of using the TVS family of devices compared to the SMA family here: https://www.ti.com/lit/an/slva979/slva979.pdf?ts=1621346096409&ref_url=https%253A%252F%252Fwww.ti.com%252Finterface%252Fcircuit-protection%252Fesd-protection-and-tvs-surge-diodes%252Ftechnical-documents.html

    https://www.ti.com/lit/an/slva930/slva930.pdf?ts=1621346109120&ref_url=https%253A%252F%252Fwww.ti.com%252Finterface%252Fcircuit-protection%252Fesd-protection-and-tvs-surge-diodes%252Ftechnical-documents.html 

    https://www.ti.com/lit/an/slvae53/slvae53.pdf?ts=1621346826876&ref_url=https%253A%252F%252Fwww.ti.com%252Finterface%252Fcircuit-protection%252Fesd-protection-and-tvs-surge-diodes%252Ftechnical-documents.html 

    One thing to note: neither of these devices are automotive qualified. 

    4.) The resistor in the test represent the characteristic impedance of the network in the user's application. There is a source impedance of 2 Ohms and then the coupling network impedance of either 0, 10, or 40 Ohms. For data lines, the coupling network impedance would be 40 Ohms, totaling 42 Ohms Req (refer to page 6 of the document). In your application, this resistor is already present by nature, so you would not need to add an additional resistor. 

    5.) For non-automotive, I would use TVS0500. For automotive, I would use TPD1E10B06-Q1 since we currently don't have any automotive TVS devices. 

    Regards,

    Matt Smith 

  • 0 in reply to Matt Smith3
    Prodigy 20 points

    Hi Matt, 

    Thanks for the answers. Just one question related to points 4 and 5. 

    There is a data line that comes to the connector pin and goes to the GPIO. But there is also a 5V supply line. For example, 5V input is given to the encoder and the output of the encoder goes to the uC. I understand the output of the encoder is a data line and the 40 ohm coupling impedance will be used. But what about the 5V which powers this encoder. Is that also counted as a data line or a low voltage supply line? 

    Also, I will be checking out the automotive-rated parts and using them. Thanks for pointing that out. 

  • 0 in reply to Rushi Jariwala
    TI__Expert 8476 points

    Hi Rushi,

    Generally, for power lines, surge would be applied with just the 2 Ohm source resistance, no other coupling. However, you will need to check if there is a certain surge requirement for your system. It can depend on many things like wire length, wire proximity, whether the wires exit the building, etc.

    Regards,

    Matt Smith