HokieEE
Newbie level 2
Hi folks,
First time post.
I searched the site for threads relating to my issue, but I could not find one that really answered my question. Please forgive me if I missed a relevant thread.
My design is a small (1"x1") wireless transceiver that is designed as a watch (also designed the enclosure or 3D printing) for simple detection and transmission of data. It contains a pic 18F microcontroller and RF chip with printed antenna, and is 4 layers with internal GND and 3.3V. Cell battery will be face up, and the most of the SMD circuitry, including microcontroller and TX will be face down towards the bottom of the enclosure.
My questions are:
1. With ample application notes on ESD diodes, TVS, etc, I understand the concept of ESD protection when there is a clear GND or case ground, like the metallic case of a mp3 player or cell phone. In my case, my board will not be grounded to the skin, so what protection do I need from ESD, and where will this voltage arc? In short, I am inserting my TVS between my uc nets and GND, but if GND is just another net floating above the skin, will bidirectional diodes relative to this GND net be effective?
2. Do I need to shield my circuitry with copper tape on the inside of the enclosure and treat that like a normal ESD protection rail/ case ground? I was hoping to avoid this but it would be better than shot chips. I do have some small screws that will hold a lid on the watch. Would it be advantageous to tap into these and use the user's skin as ground?
3. With the printed antenna, where would this TVS diode be placed to protect the transmitter? Near the transmitter or near the antenna feed past the match circuit and balun?
Thanks in advance for the help. Any and all is appreciated.
First time post.
I searched the site for threads relating to my issue, but I could not find one that really answered my question. Please forgive me if I missed a relevant thread.
My design is a small (1"x1") wireless transceiver that is designed as a watch (also designed the enclosure or 3D printing) for simple detection and transmission of data. It contains a pic 18F microcontroller and RF chip with printed antenna, and is 4 layers with internal GND and 3.3V. Cell battery will be face up, and the most of the SMD circuitry, including microcontroller and TX will be face down towards the bottom of the enclosure.
My questions are:
1. With ample application notes on ESD diodes, TVS, etc, I understand the concept of ESD protection when there is a clear GND or case ground, like the metallic case of a mp3 player or cell phone. In my case, my board will not be grounded to the skin, so what protection do I need from ESD, and where will this voltage arc? In short, I am inserting my TVS between my uc nets and GND, but if GND is just another net floating above the skin, will bidirectional diodes relative to this GND net be effective?
2. Do I need to shield my circuitry with copper tape on the inside of the enclosure and treat that like a normal ESD protection rail/ case ground? I was hoping to avoid this but it would be better than shot chips. I do have some small screws that will hold a lid on the watch. Would it be advantageous to tap into these and use the user's skin as ground?
3. With the printed antenna, where would this TVS diode be placed to protect the transmitter? Near the transmitter or near the antenna feed past the match circuit and balun?
Thanks in advance for the help. Any and all is appreciated.