TAS5805M: I2C Load capacitance

Hi George,

I'm taking a look into the load capacitance of the I2C pins. In the meantime can you tell me what the rise of the I2C signal is that you are seeing? In the datasheet we say that the max rise time should be 1000nS. 

Regards,

Robert Clifton

Hi Robert,

Thanks for reply. 

Customer is using fast mode which is 320kHz I2C speed, rise time should be lower than 300ns. And customer test result is 580ns.

George

Hi George,

Are there any other devices tied to the I2C line? I've been running my calculations and can't see how an 8pF capacitance is changing the time constant that much! 

Regards,

Robert Clifton

Hi Robert,

I don't think there's anything on the I2C line. How do you run those calculations? What's the capacitance value you used at I2C pin of TAS5805M?

8pF is the value of the pin capacitance of MCU side.

Thanks!

George

Hi George, 

The bus line capacitance is 400pF. That's how I was running my calculations. With that variable, you can derive the time constant and see that either there's somewhere else that's causing an increase in the time constant since you shouldn't be seeing a 580nS delay (with an ideal layout and system). 

Regards,

Robert Clifton