| ??? 04/23/10 14:07 Modified: 04/23/10 14:18 Read: times |
#175324 - Design for an industrial environment! Responding to: ???'s previous message |
Manish said:
Solid ground plane, please guide so as to what portion needs a ground plane only the micon part or what as there is limitation for using max double sided borad only so I feel this point difficult to implement but if sensitive areas are known I hope this can be done there Everything should have a solid ground plane, the faster the circuitry the more demanding. Even with a double sided board a solid ground plane can be implemented in many applications, as shown in the following example board: 
(Take care, for clarity the many vias connecting the ground fills with the solid ground plane of both sides aren't shown!) Manish said:
it will be very difficult to route all those signal at edge when most of them are getting out from direct pins of IC’s Who says that all the signals shall be connected directly to the micro? That's just the point: They shall not be connected directly to the microcontroller! Create a boundary of drivers or buffers or filters or protection circuitry, or what else is needed, right where the cables enter the pcb. Keep everything insane to this point, so that no interference is able to reach the micro and other sensitive parts of the circuitry. Remember, that a microcontroller is a highly dynamically running thing. There is a UART running inside all the time, PCAs, charge pumps for the flash memory programming voltages, a Pierce oscillator, a watchdog and whatsoever. Even the least glitch reaching the microcontroller on any port line can make the micro running ill, stopping or even destroy it. Latch-up and lock-up can be the consequences. In a rough industrial environment you must consider "burst", "surge" and "esd" as well. You must consider switching noise from relays, hum from big transformers and ground loops. Now you come with a "kitchen table" design and wonder that your circuit isn't running properly. But this is no surprise at all, if you don't design your application to withstand the interferences of an industrial environment. It's simple to make a microcontroller work somehow, but it can be very difficult to make it work in a dirty environment. Protection circuitry, buffers, drivers, filters, shields can consume much more board space than the naked microcontroller circuit itself... Kai Klaas |
