LM50: I2C TR when operating at Standard Mode (100kHz)

Dillon Nichols

Part Number: LM5056

I'm communicating to the LM5056 via I2C at 100kHz. The LM5056 datasheet specifies a maximum rise time on the CLK or DAT lines as 300ns. This matches the I2C specification if operating in Fast Mode (400kHz), but I'm using Standard Mode (100kHz). My measured rise times are 900ns for DAT, 860ns for CLK which meet the I2C spec for standard mode. Is this acceptable for this part or do I need to meet 300ns even when operating at 100kHz? Screen captures of documents below:

over 3 years ago

0 Dillon Nichols over 3 years ago

Prodigy 30 points

0 Javier Contreras4 over 3 years ago in reply to Dillon Nichols

TI__Mastermind 26475 points

Dillion,

I need to look a little deeper but I would suggest going with the max limit on the datasheet. Is there any way you can remove any stray capacitance on that node or resistances that may be impacting the rise or fall times?

0 Dillon Nichols over 3 years ago in reply to Javier Contreras4

Prodigy 30 points

Thanks for the quick response, Javier. I can pull a stronger pull up on those I2C lines which should meet the 300ns timing. We noticed this late into the design cycle and would be best if we can move forward without that HW change and implement it in the future. But, we can make the HW change now if the datasheet value of 300ns is accurate for I2C Standard Mode.

0 Javier Contreras4 over 3 years ago in reply to Dillon Nichols

TI__Mastermind 26475 points

Dillion,

I looked into it and it was primarily designed for the 400kHz in mind.

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LM50: I2C TR when operating at Standard Mode (100kHz)