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TCA9800: Need SDAB and SCLB spec for Voh

aarmutat
Intellectual 2971 points
Part Number: TCA9800

Hi, Please look at TCA9800 datasheet Figure 18.  In this usage the TCA9800 SDAB and SCLB pins drive the '9715 SDAA and SCLA pins via the internal current sources in the '9800 to generate a logic HI at the the '9517 pins.  The designer must be certain that these current sources will pull up the '9517 SDAA and SCLA pins to a voltage that is at least the Vih MIN spec of the '9517, which is Vcca * 0.7V.  I'm sure the '9800 meets this requirement; however, there is no spec in the '9800 datasheet that states it will.  What is the MIN guaranteed Voh at 100uA (or some other reasonable load current) for the SDAB and SCLB pins of the TCA980x?  Please add this to the datasheet for completeness. If I'm missing something and this information is already in the datasheet, please help me locate it.

Thanks, Andy

  • 0
    TI__Guru 73891 points
    Hey Andy,


    VoH is typically not a spec used in I2C because the pull up resistor drives the line high passively. Our Device on B side will drive the bus to VccB assuming no other NFETs are driving the bus low.

    Though, there is not a VoH spec in the datasheet, the application curves give rise times for given capacitance loads on page 22. Remember rise time references the time for signal to go from 30% of Vcc to 70% of Vcc as spec'd by the I2C standard. This means B side will drive the signal to atleast 70% of VccB given a specific load capacitance.


    Thanks,

    -Bobby