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TCA9509: About V_OL-V_ILC, V_ILC, I_ILC, R_ILC that are not described in TCA9617B

Noriyuki Takahashi
Genius 10980 points
Part Number: TCA9509
Other Parts Discussed in Thread: TCA9517A, , TCA9617B

Hi team

Customer is wondering the characteristics, V_OL-V_ILC, V_ILC, I_ILC, R_ILC that are not described in TCA9617B, but are described in TCA9509, PCA9803 and TCA9517A.

Actually they already used TCA9617B. And they consider to use TCA9509, PCA9803 and TCA9517A for other projects. But they are not sure  V_OL-V_ILC, V_ILC, I_ILC, R_ILC  and what they need to take care about when they use TCA9509, PCA9803 and TCA9517A. What design considerations are required for these VILC, IILC, RILC, and other specifications, or should they be reflected in the circuit, etc.?

Regards,

Noriyuki Takahashi

  • 0
    Guru 316690 points

    Different devices can have different architectures. The limitations of the TCA0617B's B-side I/Os are described in section 8.1 of the datasheet; also see VIL in the electrical characteristics.

  • 0 in reply to Clemens Ladisch
    TI__Genius 10980 points

    Clemens,

    The understanding of Vol - VILC and VIL as attached is correct?   Although, in this exmaple, I don't care about VIL as SDAA, SCLA and SDDAB, SCLB is less than 0.3 × VCCA and 0.3 × VCCB.


    tca9517a.pptx

    Regards,

    Noriyuki Takahashi

  • 0 in reply to Noriyuki Takahashi
    TI__Guru 72771 points

    Noriyuki-san,

    Slide 1 is correct in the sense that the I2C target (what you call the slave)  needs to drive the B side of TCA9517A below 0.45V (ViLc of TCA9517A). However on A side, the VoL does not need to be 0.47V, it would need to be below the ViL set by the I2C standard or the minimum set by the I2C controller. 

    On slide 2, the I2C Controller's VoL only needs to be below ViLA of the TCA9517A device which is set to 30% of VccA. VoLB will be a typical value of 0.52V based on the datasheet (this is affected by the B side pull up resistor though). 

    -Bobby

  • 0 in reply to BOBBY
    TI__Genius 10980 points

    Bobby,

    Thanks, then how should we consider about VOL – VILc = 70mV typ on the schematic?

    I am not sure how to deal with this.

    Regards,

    Noriyuki Takahashi

  • +1 in reply to Noriyuki Takahashi
    TI__Guru 72771 points

    VoL-ViLc is just the typical VoL on B side minus the typical hysteresis value on B side when the static offset on B side is active. This basically just tells you the noise margin from VoLB and ViLc. 

    -Bobby

  • 0 in reply to BOBBY
    TI__Genius 10980 points

    Bobby

    Thanks. I think your presentaion is helpful to understand why VILC is needed for I2C buffer.

    https://training.ti.com/i2c-technical-deep-dive-japan-2018

    Regards,

    Noriyuki Takahashi

  • 0 in reply to Noriyuki Takahashi
    TI__Genius 10980 points

    Bobby,

    Please let me confirm two things about TCA9509.

    1. In case of TCA9509, the static offset voltage is on A-side and the voltage is 0.2V(typ) at the condition of 1.2V < VCCA ≤ (VCCB – 1 V). So the Vol of A-side is also 0.2V(typ) and VILC is 0.15V(typ). So Vol of A-side should not be lower than VILC.   Is this understanding correct?

    2. I think my understaning above is correct and pull-up resistors are not required on A-side to adjust Vol, but it seems that Vol of A-side needs to be adjusted by pull-up resistors according to the P.13 of the datasheet as below. How should I understand this? 

    Regards,

    Noriyuki Takahashi

  • 0 in reply to Noriyuki Takahashi
    TI__Guru 72771 points
    Noriyuki Takahashi said:
    1. In case of TCA9509, the static offset voltage is on A-side and the voltage is 0.2V(typ) at the condition of 1.2V < VCCA ≤ (VCCB – 1 V). So the Vol of A-side is also 0.2V(typ) and VILC is 0.15V(typ). So Vol of A-side should not be lower than VILC.   Is this understanding correct?

    The devices on A side should drive below the ViLc of 0.15V. We suggest not having any series resistors on A side of TCA9509 and to also not use external pull ups since this would make it harder for the devices on A side to drive below the ViLc. \

    Noriyuki Takahashi said:
    2. I think my understaning above is correct and pull-up resistors are not required on A-side to adjust Vol, but it seems that Vol of A-side needs to be adjusted by pull-up resistors according to the P.13 of the datasheet as below. How should I understand this? 

    Having lower VoLs is better in I2C generally speaking, you shouldn't be trying to raise the VoL by adding pull up resistors.

    -Bobby

  • 0 in reply to BOBBY
    TI__Genius 10980 points

    Bobby, 

    BOBBY said:
    The devices on A side should drive below the ViLc of 0.15V.

    Is this a typo? I wanted to confirm Vol of TCA9509 A-side should not go below Vilc. 

    Regards,

    Noriyuki Takahashi

  • +1 in reply to Noriyuki Takahashi
    TI__Guru 72771 points

    Devices external on A side should drive below 0.15V. The TCA9509 A side is designed to not drive  below ViLc when B side sees a low.

    -Bobby