What is a reasonable value to use as the capacitance a I2C device adds to a bus if so is not stated in the datasheet?

With this value I intend on calculating the pull-up resistors to eventually use in a PCB.

I need to append to the bus the following devices:

L3G4200D gyroscope

LIS331DLH accelerometer

HMC5883L compass

  • \$\begingroup\$ What is the device? I am amazed that it would not tell you the SDA / SCL load capacitances. I2C specifies no more than a total load of 400pF across the entire bus, so you could design around that. \$\endgroup\$
    – stefandz
    Aug 14, 2015 at 14:22
  • \$\begingroup\$ 3 devices, actually: L3G4200D gyroscope, LIS331DLH accelerometer and a HMC5883L compass, and the only thing said about it in any of the datasheets are 2 2k2 pull-up resistors added in the compass application notes... \$\endgroup\$ Aug 14, 2015 at 14:25
  • \$\begingroup\$ And not one tells you its load capacitance? Please put links to the datasheets in the original question text. \$\endgroup\$
    – stefandz
    Aug 14, 2015 at 14:26
  • \$\begingroup\$ That's actually my second question around here, só I appreciate any more tips to write better :) Thanks! \$\endgroup\$ Aug 14, 2015 at 14:33
  • \$\begingroup\$ I will tell you what I would do. In practice. I would use 2.2k pullups on I2C and then check it during bring-up. \$\endgroup\$
    – user57037
    Aug 15, 2015 at 3:03

1 Answer 1


Since none of the three of those datasheets give any details on data line capacitive loading, design around a total bus capacitance of 400pF (the maximum allowed within the I2C spec). Obviously, once you have a prototype PCB up, use a scope to check the signal waveforms and adjust the pullups appropriately.


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.