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PCA9548A: PCA9548 Driving Ability

Part Number: PCA9548A
Other Parts Discussed in Thread: TCA9803

Team,

I want to check with you if PCA9548 has driving ability, or only a MUX function when connected to master.

Background is, my customer is using PCA9548 as I2C salve together with other 4 I2C slaves. And PCA9548 has 8 slaves. When doing master device system design, does customer need to consider  4 I2C slaves+PCA9548, or need to consider 4 I2C slaves+PCA9548's 8 salves?

Below is the D/S PCA9548 diagram, seems that PCA9548 only acts as MUX without driving function:

Thanks! 

BR,

Qiang

  • The PCA9548A is a passive switch; the only pin that can actively output a signal is SDA.

    For the system design, you have to consider all bus segments and devices that are actually enabled. If only one of the PCA9548A's downstream channels is enabled at a time, then you have the other four slaves, the PCA9548A, and the one slave, i.e., 4+1+1.

    If the total capacitance is too large, you have to add buffers, e.g., TCA9803. (Please note that many buffers allow only one side to be connected to a MUX; for the TCA980x, this is the A side.)