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How to resolve spikes on GND tracks in ESD

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bluetoooth

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ESD

Hi boys.I have problem with ESD.There are spikes only on GND tracks.I use transils for ESD protection but they didn't work because i can't find reference for this voltage.
Have U any idea how solve this problem?
 

Re: ESD

I looked up a datasheet for a transils and it shows a response time in the 10's to 100's of microseconds. This is more of an EOS event not ESD.

HBM ESD is over in ~750ns with a rise time of 2-10ns.

MM ESD is even faster and CDM ESD can be over in <10ns.

I do not believe a transil can respond fast enough for these transient events.

You need to provide some more information for us to help you.

Please describe your failure signature better and what part/process you are using.

I'm not sure what you mean by "spikes only on GND tracks".

Dr.Prof
 

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    bluetoooth

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Re: ESD

I have PCB with mega128 AVR and FTDI chip.The communication is OK in normal state but when i test the response on ESD signal /2kV/ ,i measure on GND track spikes witch reset AVR or FTDI.
I tried to use transils for ESD protection of this signal.When i test the response on GND plane i see noisy signal. Signal looks like signal when i don't use transils..
Are there transils working or is there other problem?
 

Re: ESD

Transils don't have the necessary response time to absorb the ESD event. Therefore your GND voltage is rising from the charge injected by the ESD event. I suspect your other parts are being reset because ground rises in response to ESD. I'm assuming it is a positive zap to the GND pin/trace.

You may want to try an MOV instead of a transil. Varistors respond faster than transils.

I'm aware of a company (www.littlefues.com) that has a set of varistors that can respond in the nanosecond time frame. They make surface mount version that are small and compact. These are used in conjunction with on-chip protection to provide two levels of ESD protection.

Dr. Prof
 

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