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TCA9617A: IIC signal rise time

Kailyn Chen
Genius 9560 points
Part Number: TCA9617A


Hello，

Two question need your help:

1. What's the start point of IIC signa rise time ?   A point or B point in figure 10? 

or use the waveform no pedestal overshoot?

2.  Usually, signal rise time is 10%--90% stable high level, is this definition also suitable for IIC signal? if not, please give me the corrective IIC signal rise time measure method.

base on follow AC and DC definition,  it is 10%~90% rise time.

3. The third question is how to get VILMAX  and VIH MIN value if we use TR and TF formula to calculate TR and TF?  measure the actual waveform or quote from DC table VILMAX=0.8V, VIH  MIN=5*1.05*0.7=3.675V?

Best regards

Kailyn 

  • +1
    TI__Guru* 78091 points
    Kailyn Chen said:

    1. What's the start point of IIC signa rise time ?   A point or B point in figure 10? 

    or use the waveform no pedestal overshoot?

    I2C uses the definition of 30% to 70% of Vcc for rise time. This pedastal usually doesn't fit within the 30% definition.

    Kailyn Chen said:

    2.  Usually, signal rise time is 10%--90% stable high level, is this definition also suitable for IIC signal? if not, please give me the corrective IIC signal rise time measure method.

    base on follow AC and DC definition,  it is 10%~90% rise time.

    I2C standard states it is from 30% to 70% of Vcc.

    Kailyn Chen said:
    3. The third question is how to get VILMAX  and VIH MIN value if we use TR and TF formula to calculate TR and TF?  measure the actual waveform or quote from DC table VILMAX=0.8V, VIH  MIN=5*1.05*0.7=3.675V?

    I'm not sure I follow. TCA9617 doesn't use a ViH level. It only looks at ViL/ViLc to determine a low (if the signal is above ViL/VILc then it turns off it's open drain driver). ViH in I2C is only used for I2C target devices and the high signal is generated by the external pull up resistor. 

    -Bobby