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TVS Selection for ESD on 3.3V and 5V Lines

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tiwari.sachin

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I am using the following diodes for ESD proection of IO for some pins of MCU

There are some ESD Diodes for 3.3V and some on 5V (USB VBus and some external inputs that are 5V)

I am using the following parts


No. Make Ordering code Voltage
1 Nexperia PESD3V3V1BCZF 3.3 V
2 Nexperia PESD5V0X1BL 5V


My doubt is... Can we really use a 3V3 TVS on 3.3V line. and 5V TVS for 5V line. Wouldn’t it just conduct at that voltage and give false results.

My test requirements are for 8KV
 

Hi,

reading datasheet helps:
here the 3V3 datasheet values.
Reverse stand off voltage: 3.3V
Breakdown voltage 5.5V typ
Clamp voltage 8.9V

Klaus
 

KlausST said:
Hi,

reading datasheet helps:
here the 3V3 datasheet values.
Reverse stand off voltage: 3.3V
Breakdown voltage 5.5V typ
Clamp voltage 8.9V

Klaus
Click to expand...

I am working at 3.3V (MCU IO). Is it feasible to use TVS that has working voltage mentioned at 3.3V or should i be selecting working voltage a bit higher than 3.3V.

Using exact 3.3V working voltage dint work but using 5V working voltage at 3.3v did
 

Hi,

I am working at 3.3V (MCU IO). Is it feasible to use TVS that has working voltage mentioned at 3.3V
Click to expand...
Yes. This is why it is called "working voltage".

Using exact 3.3V working voltage dint work but using 5V working voltage at 3.3v did
Click to expand...
What does this mean? Give a useful description. What happened?

Klaus
 

I was using PESD3V3V1BCZF on a 3V3 line for the sch below and it dint work and was always showing 0V at output. Changing/Replacing it to PESD5V0X1BL it all worked fine. After that i am little skeptical about working voltage concept.

FEED SWITCH.png
 

Side remark, both diodes are bidirectional types, thus they aren't best choice for unipolar IO port protection.
 

Hi,

I was using PESD3V3V1BCZF on a 3V3 line for the sch below and it dint work and was always showing 0V at output.
Click to expand...
I find it not likely that the TVS in this configuration becomes short circuit.
Bad soldering, overheat? Mechanical stress? PCB quality problem?

Klaus
 

I did try the same on usb VBus line. A TVS (unidirectional) with 5V Working voltage dint work while one with 5.5V did.

It was a bit strange behaviour.

I had put a USB bootloader code via JTAG and when I connected USB, it enumarated

When I loaded the USB Virtual COM code, it didnot


Note: The code had no bugs

Finally after about 2days of trying, i finally decided to remove the TVS and it worked.
 

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