C
Christian Walter
- Jan 1, 1970
- 0
Hello,
I just wanted to ask the more experienced people here for some advice. I
am currently working on a redesign of an existing board and I want to
improve some ESD aspects of the board because we had some problems in
this area in the past. The system is built from two components where the
PCB in questions contains some micro controllers and a USB equipment and
the other PCB is the power supply unit and contains additional internal
modules.
I have to protect some I/O ports and an USB interface. I have chosen to
use a TVS Diode Array (Littlefuse SP0502BA). I have chosen to place the
diode array as near as possible to the I/O connectors of the system.
What I am unsure about is whether to connect the common pins of the
diode array. My first choice would be to use the earthing because if I
connect it directly to the ground plane any discharge current will take
the path from the I/O connector over the diode. From there to the ground
plane and the PCB FCC connector cable to the power supply board and then
to earthing. In my opinion this can cause some signal and system
stability problems although the device on the PCB will not be damaged.
Does anybody support this claim?
The next question I would like to ask what you people think about spark
gaps as a cheap alternative ESD protection for onboard I/O ports. That
is I would add add a signal layer which surround the PCB connections
using a very short distance (maybe 8 thou which is easily doable in a
manufacturing house) and connect this to plane to the earthing. This
would effectively limit the voltage to maybe 1-2kV.
What I have also read is that a small guard ring at the edges of the PCB
(connected to ground) can help to improve ESD performance. Has anybody
used and tried this?
I would be very grateful for some advice because I am still a bit new in
the field. Another question is how I can verify my ESD protection
without having to go to a special laboratory because of costs.
Kind regards,
Christian Walter
I just wanted to ask the more experienced people here for some advice. I
am currently working on a redesign of an existing board and I want to
improve some ESD aspects of the board because we had some problems in
this area in the past. The system is built from two components where the
PCB in questions contains some micro controllers and a USB equipment and
the other PCB is the power supply unit and contains additional internal
modules.
I have to protect some I/O ports and an USB interface. I have chosen to
use a TVS Diode Array (Littlefuse SP0502BA). I have chosen to place the
diode array as near as possible to the I/O connectors of the system.
What I am unsure about is whether to connect the common pins of the
diode array. My first choice would be to use the earthing because if I
connect it directly to the ground plane any discharge current will take
the path from the I/O connector over the diode. From there to the ground
plane and the PCB FCC connector cable to the power supply board and then
to earthing. In my opinion this can cause some signal and system
stability problems although the device on the PCB will not be damaged.
Does anybody support this claim?
The next question I would like to ask what you people think about spark
gaps as a cheap alternative ESD protection for onboard I/O ports. That
is I would add add a signal layer which surround the PCB connections
using a very short distance (maybe 8 thou which is easily doable in a
manufacturing house) and connect this to plane to the earthing. This
would effectively limit the voltage to maybe 1-2kV.
What I have also read is that a small guard ring at the edges of the PCB
(connected to ground) can help to improve ESD performance. Has anybody
used and tried this?
I would be very grateful for some advice because I am still a bit new in
the field. Another question is how I can verify my ESD protection
without having to go to a special laboratory because of costs.
Kind regards,
Christian Walter