AM335X Touch screen controller ESD protection

Peng Liu50174

Hi,

We are using AM335X TSC to connect to 5-wire resistive touch screen.

There are TVS and series ferrite beads before the TSC signals AIN0~AIN4 input. But when running 15K air discharge on the touch screen surface, the AM335X TSC port got damaged, some pins among AIN0~AIN4 are damaged to shorted to ground, and VDDA_ADC pin is damaged to shorted to ground too.

so the question is whether AM335X TSC port has internal ESD protection circuit, if it has, what is the ESD protection charateristics (clamp voltage and maximum current).

In additional, is there TI recommended external ESD protection circuit/component for AM335X TSC?

Thanks,

Peng

over 9 years ago

0 Biser Gatchev-XID over 9 years ago

TI__Guru**** 393215 points

Hi,

AM335X does not have internal ESD protection on its AINx pins. These pins operate at 1.8V levels, so external protection will need to clamp the ESD pulse to +1.8V + 0.3V = 2.1V maximum.

0 Alex Kupchik66 over 9 years ago in reply to Biser Gatchev-XID

Prodigy 175 points

Hi Biser,

Peng points out they already have TVS diodes and ferrite beads for an ESD protection. I believe we have been seeing a similar failure when running 15K air discharge. I wondering if there are any additional tips or recommendations TI can provide.

Alex

0 Biser Gatchev-XID over 9 years ago in reply to Alex Kupchik66

TI__Guru**** 393215 points

There are no additional recommendations. This is board-dependent, so what you should do is try to figure out and eliminate the path through which the ESD noise couples into the device. This can be both through ADC inputs or through the main oscillator, if crystal is used.

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AM335X Touch screen controller ESD protection