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Determine the value of pull-up resistor

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davyzhu

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Hello all,

I found there are several values of pull-up resistor, for example 1k, 3.3k, 4.7k. Is the value of resistor proportional to the VCC? Or it related to other parameters, such as current?

Regards,

DAVY
 

2 days ago forum had something about I2C bus pull-up resistors.
Your question is very general as in different situations different values are used. For example, pretty common on address busses, multiplexed address/data buses are 10kΩ resistor networks.
As for low speed digital inputs one will use 4k7 -10k. but higs speed digital counters will be fitted with 1k. Generally speaking the higher speed the lower the value..
 

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    davyzhu

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To some extent, it should be dependent on the current allowed at the output port... it's dangerous if the current sinking into the microP is high
 

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