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TCA9509 - Which side of the device has offset, A-side or B-side ?

Kawai
Guru 19785 points

Other Parts Discussed in Thread: TCA9509, TCA9517

Hi Team,

In the datasheet, it says that A-side bus would have the offset from ground. However, looking at the waveform information (Figure 5), B-side seems to have the offset. Which is the true description ?

Best Regards,

Kawai

  • 0
    TI__Expert 5140 points
    Kawai-san,

    Thank you for the question,

    The TCA9509 does not have a static voltage offset on the B-side of the device, the unique thing about our 9509 device is that it contains a current source on the A-side which causes the operation shown in those waveforms. That pedestal you are seeing on the B-side is due to the parallel combination of slave devices pulling down on the SDA line.

    Thanks,
    Siby
  • 0 in reply to Siby James
    Guru 19785 points

    Hello Siby-san,

    Please allow me to clarify. Doesn't this Figure 5 show that B-side of TCA9509 has a offset for VOL ? I thought this waveform is for A-side instead of B-side.

    I have been supporting TCA9517 and this figure seems to be exactly the same with the one on TCA9517 datasheet. However, TCA9517 has a opposite spec compared to TCA9509 that VILC is on B-side of the device.

    Thanks in advance.

    Best Regards,

    Kawai

  • 0 in reply to Kawai
    TI__Expert 5140 points

    Kawai-san, 

    You're analysis of the differences between TCA9509 and TCA9517 is correct. You can think of them of opposites almost.

    TCA9517 has a static voltage offset on the B side while TCA9509 has a current source on the A-side.

    This can be attributed to the flipped waveforms.

    Thanks,

    Siby