| ??? 01/16/10 15:38 Read: times |
#172513 - Indeed, a very poor design!!! Responding to: ???'s previous message |
Gopal said:
Moreover this capacitor is charged from a +12V DC while the ADC is driven from a 5V regulator. That seemed a poor design but I wanted a hint on what exactly is wrong and yes your answer is very helpful. Oops! This means, that some inputs of multiplexer are overdriven all the time? Indeed, this is a very poor design, because some ADCs behave very strange if the input multiplexer is overdriven. Even if it is only a neighbour channel that is overdriven, this can upset the AD-conversion of a channel with regular level!! Better, to feed the pots from the ADC's 5V-supply. Or, put at least a resistor in parallel to this cap, to form a voltage divider which prevents the input of ADC from being overdriven all the time. Adding only a protection diode might not be enough, as it cannot prevent the input from being overdriven. Kai Klaas |
| Topic | Author | Date |
| ADC0809 problem | 01/01/70 00:00 | |
| Is the very same ADC chip in both cases? | 01/01/70 00:00 | |
| From time to time... | 01/01/70 00:00 | |
| Datasheet read, same hardware | 01/01/70 00:00 | |
| Define 1000000000% | 01/01/70 00:00 | |
| Thoughts... | 01/01/70 00:00 | |
| Solved partially | 01/01/70 00:00 | |
| So the cap did help? | 01/01/70 00:00 | |
| RE: That cap did help? | 01/01/70 00:00 | |
| The input multiplexer is damaged! | 01/01/70 00:00 | |
| Discharge diode | 01/01/70 00:00 | |
| RE: The input multiplexer is damaged | 01/01/70 00:00 | |
| Indeed, a very poor design!!! | 01/01/70 00:00 | |
RE: Indeed, a very poor design!!! | 01/01/70 00:00 |