• State
  • Locked Locked
  • Replies 5 replies
  • Subscribers 31 subscribers
  • Views 1014 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

DRV120EVM Peak current

Luc Imbert
Prodigy 30 points
Other Parts Discussed in Thread: DRV120EVM, DRV110, DRV120

Hello,

Going through further tests of the DR120APWR on the DRV120EVM.

I am interested during the transcient of the valve activation to avoid current limiting. The valve I use is a 12V, 2.5W valve.This one does not exceed the rating of the DRV120EPWR.

To ensure that the current will not be limited I am adjusting the Rpeak. Through tests, I have noticed that the resistor value does not correspond to the graph in the specification document. For I am not limited in current for a resistor value between (62kohm and 80kohm), on the specification it is between 33.2kohm and 67.25kohm.

Would you have some information on the subject. 

Sincerely,

luc Imbert

  • 0
    TI__Guru** 114905 points
    Hi Luc,

    Our experts on the device have been notified. One on them is not available until next week, so response may be slow.
  • 0
    Prodigy 30 points

    At the time I had set the frequency under the advised minimum frequency, and was operating the device at 2kHz, could it be a reason for the difference in the resistor Rpeak value ?

    I also have another enquiry, on the datasheet provided there are no waveforms. I am wondering what will happen if the average current is higher than the max value specified by the specification. Assuming that the PWM is already set to the Dmin, how is the device going to react ? 

    In other words once the PWM is at the minimum duty and the current is still too high.

    Sincerely,

    Luc Imbert

  • 0 in reply to Luc Imbert
    TI__Genius 17380 points

    Luc,

    Sorry for the delay, I have been out of office. 

    It seems you are seeing that the IPEAK is not changing as a function of RPEAK between the range of 62kΩ and 80kΩ? What values of Rosc, Rpeak, and Ckeep? When you change Rpeak above 80kΩ, does the change occur? 

    Additionally, what do you mean by "I had set the frequency under the advised minimum frequency"? Is this in reference to the Rosc value? We have had a few customers report issues with audible noise when Rosc was set below 66.67kΩ, but this problem seems unrelated.

    For the third question, is your problem that the IHOLD value is too high for your application? When RHOLD is set high (250kΩ max), DMIN should be at it's lowest and IHOLD should be at it's lowest. If this is the issue, then I would recommend using the DRV110 and an external FET as you can change the value of the sense resistor to reduce the current further.

    Thanks,

    Kevin LaRosa

  • 0 in reply to Kevin LaRosa
    Prodigy 30 points

    Hello Mr LaRosa,

    This is the way the evaluation module is configured.

    Rosc = 1.8 Mohm
    Rpeak = 65 kohm
    Ckeep = 514 nF 
    Rhold = 225k

    freq = 2 kHz
    startup time = 40 ms 

    My aim is actually not to limit the current during the startup transcient. With Rosc at 1.8 Mohm the frequency in power save mode is 2kHz. This specific frequency is out of the advised range of the component datasheet. At this frequency in order to not limit the current the advised range (33 kohm to 67 kohm) does not produce the desired effect. The currewnt limit is lower than 250mA, by test i have found that the resistor values for which the current is limited at 250mA in my conditions are between ( 62kohm and 80kohm).
    When I change the value above 80kohm, the peak current decreases as it is supposed to.

    I do confirm audible noise, though it is not an issue for me.

    The last point concerning the hold current was due to the setup and has been resolved.

    Sincerely,

    Luc Imbert

  • 0 in reply to Luc Imbert
    TI__Genius 17380 points

    Hey Luc,

    There will always be a current limit to prevent damage to the DRV120 part and the connected solenoid. Even between 33.25 kΩ and 67.25 kΩ there is a current limit which should be 250 mA based on Figure 4. Are you finding that the actual current limit in this range for your application is coming out to less than 250 mA? If so, what current is it limiting at and does it vary between 33.25 kΩ and 67.25 kΩ or is it constant? Does changing the PWM frequency help? I don't think 2 kHz would be out of spec per say, since Rosc in equation (4) goes up to 2 MΩ, but some tuning may be necessary based on particular application. 

    If you need to have your IPEAK higher than 250 mA, the DRV110 with the external FET can handle larger current value.

    Thanks,

    Kevin LaRosa