• 状态
  • 回复 3 回复
  • 订户 16 订户
  • 视图 55 视图
  • 用户 0 会员在此处
选项
选项
相关

TCA9517: Different Pull-up Voltage on SCLB/SDAB vs. VCCB

Benedikt Auer
Prodigy 10 points

Part Number: TCA9517

Hello TI-Team,

we want to use the TCA9517 and have a question regarding the voltage levels.

Is it allowed to use a different pull-up voltage for SCLB/SDAB than the supply voltage VCCB?

In our design:

  • VCCB (= PWR_1 in picture) is supplied separately
  • Pull-ups on SCLB/SDAB (= PWR_2 in picture) use a different voltage
  • We are planning to use two separate 3.3V rails with different power-up sequences. 3.3V pull-up Voltage ramps up before VCCB supply. The current for the pull upvoltage is only <40mA this is why we want to use a different supply 
  • Additionally, we are considering using 5V for VCCB (PWR_1) as an alternative option

Our power-up sequence is:

Option 1: 1.8V (VCCA) => PWR_2 (pull-up voltage for SCLB/SDAB) => PWR_1 (VCCB)

Option 2: 1.8V (VCCA)  => PWR_1 (VCCB) => PWR_2 (pull-up voltage for SCLB/SDAB)

Is this configuration valid, or are there any concerns we might have overlooked?

Thank you for your support.

Best regards,

Benedikt

TCA9517_different-VCCB.png

  • 0
    TI__Mastermind 39765 points

    Hello, we have received your case and the investigation will take some time. Thank you for your patience.

  • 0 回复 Eirwen
    TI__Mastermind 39765 points

    SCLB/SDAB is Connected to VCCB through a pull-up resistor in datasheet.

  • 0 回复 Eirwen
    Prodigy 10 points


    Hi Eirwen,
    Thank you for your reply. Sorry if I'm in the wrong forum but it was the only one i could choose when I created this thread.

    We saw this in the datasheet. But the datasheet also mention:

    Page 1:

    Page 3:

    So we are not sure if the inputs are completely separated from the VCCB supply voltage. If they are separated it should possible to connect a different voltage source to VCCB. Or do I miss something?  Is there internally something that would connect SCLB/SDAB to VCCB. Because, in the case of VCCA, it is explicitly stated that the voltage is used only as a reference.

    Best regards, Benedikt