| ??? 01/05/05 01:13 Read: times |
#84334 - AC loading Responding to: ???'s previous message |
John Terry said:
How is the capacitcance tied in with the time taken for the inputs to change? i presume the datasheet will show me the maximum capacitance for the timings specified? It takes time to charge (and discharge) a capacitor to a given voltage, so you can imagine that as you increase your capacitive loading, you necessarily increase the time it takes for the line to be driven to the final voltage level. Most data sheets still specify their timing into a 50 pF load, but read carefully to be sure! Data sheets also spec the input capacitance for each input pin. For most things I've looked at recently, the input capacitance tends to be between 3 pF and 8 pF. Of course, you can round this all off to 10 pF, which means that your output driver timing doesn't degrade unless driving more than five loads. By degrade I mean "get worse than data sheet max." When talking about timing analysis, always use the worst-case values. Does this make sense? -a |
| Topic | Author | Date |
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| bible time | 01/01/70 00:00 | |
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| AC analysis | 01/01/70 00:00 | |
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| new url | 01/01/70 00:00 | |
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| the link | 01/01/70 00:00 | |
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| old school | 01/01/70 00:00 | |
| ADC | 01/01/70 00:00 | |
| 1997 | 01/01/70 00:00 | |
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| true meaning of "Worst-Case" | 01/01/70 00:00 | |
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| Try this | 01/01/70 00:00 | |
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