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DRV104: In a Master/Slave configuration

Mike Tierney
Prodigy 60 points
Part Number: DRV104

I am debugging a PCA where there are four DRV104s that control four separate valves. The configuration is similar to Figure 15 in the DRV104 datasheet with the exception there is a third slave. It appears that the Master's input must be turned ON in order for the slaves to become functional. Can you confirm if this is the case? If this is the case it is really unwanted behavior in this design, and an explicit warning should have been given in the datasheet. In this application the valves are operated independently and should not depend on whether the Master is ON or not. However, it is desirable not to have audible beat frequencies at times when multiple valves are powered on.

  • 0
    TI__Expert 3460 points

    Hi Mike,

    Thanks for the question. To clarify, it sounds like you want the DRV104s to act independently, but also want to use the master/slave configuration when multiple switches are on to eliminate the beat frequencies?

    You are correct when saying that in order to use the DRV104 in slave mode, you will need at least one master. It's also true that the DRV104s have an internal pull-up on the Master pin to default the device to function as a master. Could you explore the option of using some type of control that would could change a DRV104 from master to slave when there are multiple devices active?

  • 0 in reply to Harry Kennedy1
    Prodigy 60 points

    Hi Harry,

    Thanks for the response and the idea. The problem I see with that approach is that the timing specification for the SYNC transition is so loose that output contention could occur on the transition which at best would be an EMI event and at worse could shorten the life the part. I think it was an oversight for TI not to specify that in order for a Master to perform as a master it had to be selected ON and Driving.
  • 0 in reply to Mike Tierney
    TI__Expert 3460 points
    Good point Mike,

    I'm sorry we were not able to arrive to a solution.