ESD protection

rf · Post by rf » Tue Jun 05, 2007 2:34 am

I didn't seen any protection from ESD in hardware implementation. What about ESD protection? There'a nothing to worry ? The USB connectors protect from ESD, or sth... ?

Thanks in advance. Cheers!

Post by **christian** » Thu Jun 07, 2007 2:33 pm

These circuits are designed to be as simple as possible. The AVR controller itself has some protection against ESD built-in. If you expect a hostile environment, you should add a dedicated ESD protection.

rf · Post by rf » Thu Jun 07, 2007 7:08 pm

Thanks for reply.

I'm a begginer, i didn't known that avr have some protection against ESD. Do you know how strong this protection is? The avr will survive ESD up to 15kv?

In Automator project i've seen the diode 1N4148, this is against ESD ?

Do you know how to design the ESD protection (or have some links to read)?

Thanks!

Post by **christian** » Thu Jun 07, 2007 8:05 pm

The 1N4148 in Automator is for decoupling, not for ESD protection.

Atmel should have a data sheet specifying ESD robustness of the chip. I have not found it in the standard device data sheet, though. They have diodes to V+ and GND on each pin.

Designing a REAL ESD protection is not easy. It's not only about choice of components and values, it's also the physics of the board (stray inductivities and capacities).

In practice, you should get away with the AVR's internal protection, especially since there are series resistors on D+ and D-. If you don't use a voltage regulator, you also need zener diodes which offer additional protection.