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DRV104 ramp signal

Oswald Mesidor
Prodigy 40 points
Other Parts Discussed in Thread: DRV104

I'm using the DRV104 to drive a solenoid valve. I took some plots with no load and some with load. Attached are the plots and the schematic.

There is a ramp on start up before the delay and I would like to know why the output is doing that?


 
  
  
  
  
  
  
  
  
  
  
  
  
 
 
 


 

24VDC 50% Duty Load and No Load.zip
  • 0
    TI__Genius 9975 points

    Hello Oswald Mesidor,

    Thank you for the oscilloscope plots, they will be helpful in figuring out the situation in your circuit. The schematic is, however, not included. Could you please try sending the schematic again and indicate the node where your oscilloscope probe is placed?

    Thank you and best regards,

    Jose

  • 0 in reply to Jose Duenas
    Prodigy 40 points

    Hi Jose,

    The probe was placed between TP1 and ground. This test was done with a solenoid valve. This morning I ran a resistive load the ramp was still there on start up. After that the ramp was gone and the PWM signal was clean.

     

    Is it normal to have the ramp there during start up and during PWM (No load and load)?

    DRV104 Schematic.doc
  • 0 in reply to Oswald Mesidor
    TI__Genius 9975 points

    Hello Oswald Mesidor,

    No, it is not normal to have the ramp shown in the scope captures you sent in your first forum post.

    Could you please capture another set of oscilloscope plots this time connecting three probes simultaneously?

    One probe should be connected to TP1 and the ground clip should be connected as physically close as possible to pin 11 of the DRV104.

    The second probe should be connected  directly to pin 8 of the DRV104 and the ground clip should be connected as physically close as possible to pin 11 of the DRV104.

    The third probe should be connected directly to pin 14 of the DRV104 and the ground clip should be connected as physically close as possible to pin 11 of the DRV104. This channel should be set to 1 V/div.

    Please attach the acquired plots similarly to the first forum on this thread.

    Thank you and best regards,

    Jose

  • 0 in reply to Jose Duenas
    Prodigy 40 points

    Hi Jose,

    I took the data that you requested. After reviewing the data, it appeared that the power supply was causing the ramp. I re-ran the test with the power supply already on with a switch between the power supply and DRV104. The ramp was gone.

    The only thing that I'm seeing now is the PWM still has some ramping taking place with the solenoid valve. With resistive load there's no ramp. Please let me know if the DRV104 is OK for inductive load with that ramp?

  • 0 in reply to Jose Duenas
    Prodigy 40 points

    Hi Jose,

    I took the data that you requested. After reviewing the data, we noticed that the power supply was causing the ramp. I added a switch inline with the power supply and when the switch was flipped the ramp was gone.

    The only thing that I'm seeing now is the PWM signal is showing a small ramp with inductive load but not with resistive load. Is that OK with the DRV104 when a solenoid valve is connected to it?

    Thanks,

    Oswald

     

    24VDC 50% Duty PS already on with switch.zip
  • 0 in reply to Oswald Mesidor
    TI__Genius 9975 points

    Hello Oswald,

    Thanks for taking the data and sending the oscilloscope plots. I am glad that you found the source of the initial ramp.

    The small ramp with inductive load must be caused by the interaction of the inductive load with the resistance of the traces connecting the power supply to pins 8 and 9 of the DRV104 and pins 6 and 7 to the load.

    There is no issue for the DRV104 caused by that small ramp.

    Best regards,

    Jose