• State TI Thinks Resolved
  • Locked Locked
  • Replies 1 reply
  • Answers 1 answer
  • Subscribers 33 subscribers
  • Views 232 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

TCA6408A: VCCp unpowered while VCCi powered.

Paul Venginickal
Prodigy 160 points
Part Number: TCA6408A

I have a design where VCCi will be +3.3V and VCCp will be +1.8V.  Often, VCCp will be unpowered, and the peripheral connected to the GPIO ports connected to VCCp will be unpowered.  VCCi will be powered, and there are other peripherals on the +3.3V I2C bus that need to be working.

Is this a problem?  Will the TCA6408A hold the I2C bus if VCCp is not powered?  Will having VCCi on while VCCp is off damage the device?

After turing VCCp on, will issuing a reset to the TCA6408A clear up any issues?  

Is there another part that is more suited to my needs?

Thank You

Paul

  • 0
    TI__Mastermind 47278 points

    HI Paul,

    Paul Venginickal said:
    Is there another part that is more suited to my needs?

    I don't think damage is the major concern when powering VCCI and leaving VCCP unpowered. 

    Generally with the TCA64xx series of devices, we recommend that VCCP be powered first before VCCI in order to prevent SDA from being stuck low. In the case that the I2C bus does get stuck low, we recommend a power-on reset of the device. 

    Paul Venginickal said:

    Is there another part that is more suited to my needs?

    If the SDA bus is stuck low from VCCI being powered first then VCCP, a device RESET would help to fix this issue (power-off VCCI below POR threshold, and power up again). Usually in application, we also recommend that VCCI and /RESET pin be tied together, /RESET connected to VCCI via pull-up resistor. 

    ...

    If you don't want to deal with the POR circuitry in these devices, you can upgrade to the TCAL64xx in which this issue was cleared up, however, the TCAL version supply voltage is only operational up to a VCC of 3.6V recommended operating conditions.

    Regards,

    Tyler