| ??? 09/20/06 19:04 Read: times Msg Score: +1 +1 Informative |
#124712 - Some answers Responding to: ???'s previous message |
Ertan said:
Are ADuCs more suscaptable then the competitors parts(ti msc1210 or silabs parts). Hardly. And even if, you can filter the noise down to any level you need. Ertan said:
the reset is as recomended by the adi: the reset pin is pulled down to the gnd by a 100k resistor. 2 years ago when i first used an aduc 834 in one of my designs they recomenden pulling down the reset pin to the gorund by a resistor. Unfortunately, what the manufacturers recommend in their datasheets is crap sometimes! Do never use this simple RC-reset if you are designing a professional board. Why? Because, the RC-reset does not show any brown-out (undervoltage) detection!!! It's only "good" to provide a power-on reset, if at all, and this only if Vcc rises sufficiently fast! I highly recommend to use a proper reset supervisory chip, like the MAX1232, for instance, also containing an internal watchdog. Ertan said:
i wonder weather the designers are satisfied by the noise immunity of the aduc84x. It has nothing to do with the microcontroller, but with your power supply! Your power supply must be able to suppress the bad effects of bursts and surges. Or by other words, you must never see the bursts at the output of 5V regulator! I guess you will see here spikes when having a look with your scope? Do you have a scope? Did you have a look at supply pins during the burst test? Ertan said:
There is a 220V/12V transformer placed on the power supply board. the regulator is a standart 7805. there is a 100uF/25V electrolitic and a 10uF tantalium plus a 100nF ceramic capacitor placed before 7805. What about the main storage cap behind the rectifier? Big enough? Use at least 470µF, better 1000µF, even if supply current of micro board is rather small. Or is the 100µF cap your storage cap, finally? Another trap: When connecting the micro board to a device having contact to ground (protection earth), the rectifier diodes can be damaged by the bursts due to the interwinding capacitance of transformer, acting like a short circuit and resulting in all the bursts voltage dropping across the pj-junctions of rectifier diodes. To avoid damage, connect 10...47nF caps across each rectifier diode. Ertan said:
we applied a burst signal form 200v to 2000v at 5kHz Was something else connected to the micro board during the burst test? Kai |
| Topic | Author | Date |
| aduc 848 noise immunity | 01/01/70 00:00 | |
| Reset. | 01/01/70 00:00 | |
| reset configuration | 01/01/70 00:00 | |
| It is unreasonable to compare | 01/01/70 00:00 | |
| is aduc84x fragile? | 01/01/70 00:00 | |
| re;fragile | 01/01/70 00:00 | |
| how long are the traces | 01/01/70 00:00 | |
| by pass caps | 01/01/70 00:00 | |
| sounds as if | 01/01/70 00:00 | |
| by pass caps | 01/01/70 00:00 | |
| I'd say so | 01/01/70 00:00 | |
| oops 0.5mm will be 0.5cm | 01/01/70 00:00 | |
| Where?? | 01/01/70 00:00 | |
| burst signal | 01/01/70 00:00 | |
| re:burst test | 01/01/70 00:00 | |
Exactly, that's the point! | 01/01/70 00:00 | |
| Some answers | 01/01/70 00:00 |