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PCA9546A: PCA9546A power remove LTC2616

Blindu Marcel
Intellectual 315 points
Part Number: PCA9546A
Other Parts Discussed in Thread: SN74LV4066A

Hi,

I want to use 4 IC I2C DAC LTC2616 using the same I2C of the microcontroller. 

In order to save power consumption I will place a power switch for each one VCC Power.

This is the comment form the datasheet of LTC2616 "The VCC power should not be removed 
from the LTC2606/LTC2616/LTC2626 when the I2C bus is active to avoid 
loading the I2C bus lines through the internal ESD protection diodes."

Can I use PCA9546A for this purpose in order to be able to eliminate the power of the IC LTC2616?

Case of use:

  • One I2C of microcontroller connect to the port I2C of the 4 IC LTC2616
  • 4 Power switches for the VCC of the LTC2616

I attach a block diagram from my system:

  • Power Diagram


  • Possible communications diagram

If PCA9546A isn't a good fit which IC might fit in my application.
  • +1
    Guru 297570 points

    Yes; an I²C switch like the PCA9546A can disconnect the I²C lines. You could also use plain switches like the SN74LV4066A; the only difference is that the latter need separate signals to control them (but you might already have them for the power lines).

  • 0 in reply to Clemens Ladisch
    Intellectual 315 points

    If I understand you, I need to put 2 IC SN74LV4066A? One for SCL and another for the SDA signal and short 1A, 2A, 3A and 4A and take its corresponding output 1B, 2B, 3B and 4B to each IC LTC2616?

  • +1 in reply to Blindu Marcel
    TI__Mastermind 37453 points

    Hi Blindu,

    PCA9546A will work for your application to switch between 4 different I2C lines via I2C control. 

    Clemens' suggestion of using SN74LV4066A will work, but will need separate signals to control the enable-inputs (C). 

    Blindu Marcel said:
    If I understand you, I need to put 2 IC SN74LV4066A? One for SCL and another for the SDA signal and short 1A, 2A, 3A and 4A and take its corresponding output 1B, 2B, 3B and 4B to each IC LTC2616?

    Your understanding is correct here. You will need a total of 2 x SN74LV4066A to accomplish your desired use case. Short the A-channel and take corresponding outputs 1B - 4B to each of the LTC2616 IC's for SDA, and the a separate 4066A for the SCL line. 

    Regards,

    Tyler

  • 0 in reply to Tyler Townsend
    Intellectual 315 points

    Hi again,

    I see that PCA9546A are allow Voltage-Level Translation.

    We can use PCA9546A to change level from 3.3V signals (SDA and SCL) to 5V signals (SD0...SD3 & SC0...SC3) powering PCA9546A at 3.3V or we need to power at 5V?

  • +1 in reply to Blindu Marcel
    TI__Mastermind 37453 points

    Hi Blindu,

    You can power the device to 3.3V. 

    In order for the device to act as a voltage translator, the Vpass voltage must be equal to or lower than the lowest bus voltage. According to figure 9-2 in the datasheet, since lowest bus voltage for your design is 3.3V, VCC needs to be below ~4.6V. So powering PCA9546A with 3.3V is fine for your application. 

    Regards,

    Tyler