• Resolved

TCA9803: Master position in system sequence

Part Number: TCA9803

Dear Whomever it concerns!

My plan is to use a series connection of two TCA9803. See attached picture below.

Interface C is between MCU (bus master) and B-side of one TCA9803. MCU and TCA9803 are supplied with the same VCC +3V3. Corresponding to

10.2.2 Buffering Without Level-Shifting but reversed electrical circuit structure.

In this case I belive I can control the enable signal from the MCU even if it is on the "wrong" side.

Is this correct understood?

Then I have interface B that is across a 1m cable between the two TCA9803.

At last there is my sensor at interface A.

Interface A will have a need of a thight controlled 3.35V+- 0.05

The tolerances of the voltages on the main PCB and the voltage drop across the wire will cause two  different voltage levels.

Therefore I thought of selecting the TCA9803.

Is the TCA9803 the best solution for this case?

The complete solution is an adjusted 10.2.4 Series Device Use Case

Bus master is to the right. Enable signal from the right TCA9803 is connected to the bus master. The right bus master VCCA and VCCB is connected to the same supply 3V3 +-10%.

The left TCA 9803 is interfacing the sensor. The sensor has an internal pull-up and this makes it impossible to use the set-up defined in the datasheet.

I assume that the direction of not critical.

What are the drawbacks with my approach?

Best regards Anders

  • Hi Anders,

    Interesting application! You should be OK to use the MCU to control the enable line - there isn't really a "wrong" side in this case since both VCCA and VCCB share the same voltage. It is OK to connect the "A" and "B" sides together as well. At first look, then, I don't see any reasons for concern. I'll continue to think this over and see if there are any details we are overlooking, though, and get back to you tomorrow.

    Regards,
    Max
  • In reply to Max Robertson:

    Anders,

    Just wanted to confirm there are no issues with this planned approach. Please feel free to contact us if you have further questions or if you would like us to check over your schematic once it is available.

    Max