Hi
I am planning to use : PCA9548A.
In that SDA/SCL is at 3.3V level and the SD0/SC0-SD7/SC7 is at 5V.Can you please suggest what could be the voltage level of VCC(3.3V or 5V)?
Regards,
Jenitt
Hi Jenitt,
The voltage that you choose as VCC depends on the Vpass voltage of the device. Here is a table that shows the correlation between Vpass and VCC:
In the datasheet section 9.2.1 explains how to size Vpass for any voltage translation set up. " In order for the PCA9548A to act as a voltage translator, the Vpass voltage must be equal to or lower than the lowest bus voltage. For example, if the main bus is running at 5 V and the downstream buses are 3.3 V and 2.7 V, Vpass must be equal to or below 2.7 V to effectively clamp the downstream bus voltages."
In your case your lowest voltages is 3.3V. So in order to achieve a Vpass of 3.3V or lower VCC must be 4.7V or lower. Just to be safe I would go with VCC <= 4.5V since that would give you a Vpass of 3V. In your system you can just connect VCC to the 3.3V rail since that would give you a Vpass around 2V which is significantly lower than your lowest bus voltage.
If this answered your question don't forget to hit the button. If you have any further questions let me know.
Best,
Chris
