TCA9544A: I2C Rise/Fall time measurement timing

DanS

Part Number: TCA9544A

I have a question on the measurement points for I2C rise/fall time of TCA9544A.

In the spec, it says the rise/fall time is between 0.3Vcc and 0.7Vcc.

I have captured the I2C waveform and the base of the waveform is at 517mV.

Is the rise time measured from 0.99V (=30% of Vcc) to 2.31V (=70% of Vcc) or from 1.352V (=0.517V+0.3[3.3V-0.517V]) to 2.465V (=0.517V+0.7[3.3V-0.517V])?

Thanks.

over 2 years ago

0 Clemens Ladisch over 2 years ago

Guru 323430 points

V_CC and the switching thresholds are measured relative to GND, i.e., 0 V.

0 DanS over 2 years ago in reply to Clemens Ladisch

Intellectual 420 points

Hi,

I understand the voltages are reference to 0V. My concern is the measurement position for the rise/fall time when the base of the signal is not at 0V. As shown in my capture waveform, the base of the signal is at 517mV. For TCA9544A specification, is the rise/fall time to be measured between 0.99V to 2.31V even if the base is not at 0V?