Problems understanding I2C pullup calculation

by Scott Anderson   Last Updated June 16, 2018 10:25 AM

I have been trying to read about I2C pullups such that I can select an appropriate pullup resistor for an EEPROM (24LC02B-I/P) which I want to use as serial ROM to drive some 7-segment displays.

Despite the advice in this 'AddOhms' video I still am curious about how you actually calculate a pullup and a caulcated pullup range, but this TI document baffles me totally in section 2. Below are some specific questions:

  1. Why does Rp(min) take an output low voltage from Vcc?

  2. It talks of bus capacitance: the only reference I can find on the datasheet of the EEPROM is to pin capacitance (10 picofarads)- is this one and the same?

  3. How comes T(r) is the rise time between Vol and not V = 0, or some median between Vol and V = 0? I was under the impression Vol was a determined V output maximum but necessarily the actual value.
  4. How comes the calculations deal with output low/high for strong pullup and input low/high for weak pullup?

Sorry if these questions seem diverse and broad, I am just struggling with the concept generally and getting a bit frustrated with it



Related Questions


Open Drain Output to Microcontroller?

Updated October 17, 2017 04:25 AM


Open Collector/Drain vs Push pull

Updated December 23, 2016 08:10 AM

Open Drain Serial TX output on Arduino

Updated June 19, 2017 10:25 AM