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?
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?
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.