| ??? 12/22/04 16:38 Read: times |
#83630 - I see no way Responding to: ???'s previous message |
Robert said:
Question is, can anyone see any way I can get it working by just changing capacitor values? or do I need to mod my PCB's (ouch)? It confuses me a bit, that there are two types of circuits recommended, one with and one without current limiting resistor. And it confuses me a bit, that this resistor is such high. Such high current limiting resistors would only make sense in combination with very very tiny crystals, where the maximum drive level is well beyond 1mW. The bigger the quartz the higher the allowed drive level and the lower the needed current limiting resistor. In most built-in pierce oscillators some sort of current limiting resistor is already implemented on die as poly-silicon resistor or similar, so that an additional resistor is not needed. But if a manufacturer indeed recommends the use of a current limiting resistor, then this should be a serious warning to you, to follow this well ment suggestion! The only way to avoid this current limiting resistor would be the use a very very big crystal, but this would demand making changes of PCB also, right? By simply changing burden capacitances drive level can be a bit manipulated. But the danger is too high, that start-up reserve is going lost then. Kai |
| Topic | Author | Date |
| A little O/T help with UART Crystal | 01/01/70 00:00 | |
| Rethink | 01/01/70 00:00 | |
| Using current limiting resistor? | 01/01/70 00:00 | |
| Track cuts x200 | 01/01/70 00:00 | |
| I see no way | 01/01/70 00:00 | |
| full chip numbers | 01/01/70 00:00 | |
| Rp is missing with TI's chip! | 01/01/70 00:00 | |
| Thanks Kai | 01/01/70 00:00 | |
| Linear operation | 01/01/70 00:00 | |
| Resolution - I think..... | 01/01/70 00:00 | |
| Part Numbers | 01/01/70 00:00 | |
| the resistor | 01/01/70 00:00 | |
Both: Limiting and phase shifting | 01/01/70 00:00 | |
| Crystal oscillator reference. | 01/01/70 00:00 | |
| Thanks. | 01/01/70 00:00 |