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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

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  • \$\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

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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.

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