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Hot!Recommended ESD Suppression Diode for My Microcontroller?

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michelle_bax_19
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2019/07/22 08:25:14 (permalink)
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Recommended ESD Suppression Diode for My Microcontroller?

I am using at89s8253 and would like to add ESD protection diodes. I have 2 main questions:
1. Does my microcontroller have internal protection? If so, what kind and what are the specs?
2. I also want to add external ESD suppression diodes. What are recommendations on which ones work best with at89s8253?
 
Thanks in advance!
#1

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    NKurzman
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    Re: Recommended ESD Suppression Diode for My Microcontroller? 2019/07/22 14:47:04 (permalink)
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    1. Probably, check the Data sheet.
    2.  ESD suppression diodes are Not tailored to the CPU.  What is Your Vcc, and are the pins for Analog or Digital?
    If Analog, what range or voltage.
    #2
    michelle_bax_19
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    Re: Recommended ESD Suppression Diode for My Microcontroller? 2019/07/23 06:20:37 (permalink)
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    The datasheet doesn't have a single thing about internal ESD protection, that's why I'm asking on this forum... hoping someone who has had a similar problem can help out.
     
    My criteria for the diodes is: standoff voltage > 5.5 V and clamping voltage < 6.6 V. But, I can't find any that have clamping voltage < 6.6 AND standoff voltage that is close to 5.5 (like 6 or 7 V), which means I have to trade off standoff voltage being close to 5.5 for a clamping voltage less than 6.6 V. One of the engineers brought up that sometimes a clamping voltage 1 or 2 volts higher than the absolute maximum rating of the MCU is fine, since there are often times internal protection at the pins. Hence, coming full circle, why I have these 2 questions. Any thoughts would be appreciated.
    #3
    Antipodean
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    Re: Recommended ESD Suppression Diode for My Microcontroller? 2019/07/23 06:34:40 (permalink)
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    michelle_bax_19
    The datasheet doesn't have a single thing about internal ESD protection, that's why I'm asking on this forum... hoping someone who has had a similar problem can help out.

     
    So what do you expect the internal diodes from any and every I/O pin to Vdd and Vss do then? After all they are the reason for the absolute maximum ratings spec of no higher than Vdd+0.3V and no lowewr then Vss-0.3V
     
    michelle_bax_19
    My criteria for the diodes is: standoff voltage > 5.5 V and clamping voltage < 6.6 V. But, I can't find any that have clamping voltage < 6.6 AND standoff voltage that is close to 5.5 (like 6 or 7 V), which means I have to trade off standoff voltage being close to 5.5 for a clamping voltage less than 6.6 V. One of the engineers brought up that sometimes a clamping voltage 1 or 2 volts higher than the absolute maximum rating of the MCU is fine, since there are often times internal protection at the pins. Hence, coming full circle, why I have these 2 questions. Any thoughts would be appreciated.



    I don't think they can make TVS diodes to that tight a spec. You will need to use higher voltage ones if you really must go to 5.5V and have current limiting and clamping networks between there and the I/O pins.

    Do not use my alias in your message body when replying, your message will disappear ...

    Alan
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    michelle_bax_19
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    Re: Recommended ESD Suppression Diode for My Microcontroller? 2019/07/23 06:44:01 (permalink)
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    Well, as a first time student intern with no prior experience, I wouldn't have any knowledge to know that there are internal diodes at the I/O pins for the MCU that serve as that function. As I mentioned, one of the engineers proposed the idea that there may be extra protection in addition to the +0.5, hence why I'm seeking out advice from more experienced people on this forum to see if that's the case, which you have provided. 
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    NKurzman
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    Re: Recommended ESD Suppression Diode for My Microcontroller? 2019/07/23 06:57:58 (permalink)
    +1 (1)
    Are you looking for these perfect components, or ones that will work.
    There is no perfect part. You are an engineer, you will have the engineer was solution.
    If you look at the input High you will see you can get a little clipping, and it will work fine for digital inputs. For rail to rail analog you can’t.
    So you need diodes resistors capacitors and maybe even A ferrite bead.

    All CMOS Circus tend to have ESD diodes.
    If the data sheet does not list them then people in a user forum can not help.

    Additional you are not at the official support channel for Atmel. Microchip bought them but has not merged the forums yet.
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    michelle_bax_19
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    Re: Recommended ESD Suppression Diode for My Microcontroller? 2019/07/23 07:01:57 (permalink)
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    Just ones that work. I realized long time ago there's no perfect diode, so anything that will work is good. Thank you for your helpful suggestions NKurzman, I will look more into it.
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    NKurzman
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    Re: Recommended ESD Suppression Diode for My Microcontroller? 2019/07/23 07:15:51 (permalink)
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    You still have not said what Vcc is or if they are analog or digital.
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    michelle_bax_19
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    Re: Recommended ESD Suppression Diode for My Microcontroller? 2019/07/23 07:17:07 (permalink)
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    Vcc is +5 and pins digital
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    Antipodean
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    Re: Recommended ESD Suppression Diode for My Microcontroller? 2019/07/23 07:37:35 (permalink)
    +1 (1)
    OK, I had a look at the datasheet (at http://ww1.microchip.com/downloads/en/devicedoc/doc3286.pdf ) and I can see why you have some confusion, they don't show a typical port pin schematic the way Microchip does for PIC devices, which do show the ESD diodes.
     
    Normally once a device is in circuit, and with appropriate resistors or other protective items on I/O pins, then handling a PCB while your body is attached to ground through an appropriate grounding strap is normally sufficient. If other protection is required on inputs then that should be designed in against established design requirements for the system in question.
     
    Have a look at https://www.bourns.com/markets/consumer/consumer-electronic-equipment-applications and
    https://www.analog.com/en/search.html?q=esd for application notes.
     

    Do not use my alias in your message body when replying, your message will disappear ...

    Alan
    #10
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