mcu: 8bit MC9S08SC4
function : dc motor control current about 1A
the shell: PCB ground and Motor negative connected with the metal casing directly,Half of the shell is metal half plastic。
phenomenon: 1: when +15kv air dischage at the metal shell,the mcu reset. distance between the discharge point and mcu is about 6cm.
2: solder a wire on the metal shell. Hung it above the mcu about 3cm. then +15kv air discharge at the wire,the mcu breakdown.
breakdown mcu phenomenon:
I use a LDO to supply the mcu power;normally the voltage should be 5v, because of the breakdown mcu,it is 1v. if I replace the old with new one,the LDO voltage return to normal 5v.
operation procedure:1:bring generator electrode close to the discharge point until 3mm ,then switch on ,arc appears .
2:the devece is placed on the horizontal coupling plane directly.
help1: operation procedure is correct?
help2: layout suggestion to prevent ESD damage to the mcu.Especially radiated interference.the