• State Resolved
  • Locked Locked
  • Replies 7 replies
  • Subscribers 50 subscribers
  • Views 1331 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

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.

Inquiry regarding suggested minimum load impedance on XTR300

Atsushi Okui
Genius 4015 points
Other Parts Discussed in Thread: XTR300, XTR300EVM

Hello, all

Now we have one inquiry regarding suggested minimum load impedance on XTR300 from our customer.

Please refer to the item below, and feedback us with your comment.

Now we are using this device based on the configuration which is described on datasheet page 17 "Figure 39. Standard Circuit Configuration".

The voltage applied into power supply is V+=+15V and V-=-15V.

On above usage, we found overshoot if RLOAD=10ohm, however this was not found if RLOAD=30ohm.

Please let us clarify how to find the suggested minimum load impedance on this device.

We thank you in advance for your information.

Best regards, 

  • 0
    TI__Guru 62065 points

    Hello,

    There is no minimum load resistance when the XTR300 is operating in current mode.  The XTR300 output can drive an output load ranging from 0 Ohms to Rload = (Vcc - Vis) / Iout.

    Please confirm that the overshoot is occuring in current output mode.  Any images you have of the output waveforms will be helpful.  Would you also please share the customer schematic showing all output loading during the test? 

  • 0 in reply to Collin Wells
    Genius 4015 points

    Hello, thank you for your prompt reply.

    The overshoot was occurred in current mode. Please see the waveform below;

    With regard to the schematic, we can send it to you. But this is a customer proprietary data.Please let me communicate with you directly via e-mail in order to have further proceed.

    We thank you once again for your information.

    Best regards,

  • 0 in reply to Atsushi Okui
    TI__Guru 62065 points

    Hello,

    I took some data today on the XTR300EVM and have confirmed that the results your customer is experiencing appear to be normal circuit behavior.  See below images, blue trace is input signal, magenta trace is output voltage across the load resistor, and yellow is the output current measured with a current probe at a gain of 10X.  Therefore 100mA on the scope is actually only 10mA.  So with an output current change of roughly 22.5mA, there is a worst-case overshoot of about 10mA.  This is not a standard 2nd order response with overshoot and ringing and has to do with the internal XTR300 circuitry.

    0 Ohms

    1 Ohms

    10 Ohms

    30 Ohms

    270 Ohms

  • 0 in reply to Collin Wells
    Expert 2440 points

    Hello Wells-san

    I have a question about your previous answer.

    XTR300 occurs overshoot at light loads.
    Is this the specification of XTR300?

    Is there a way to suppress the overshoot at light load?

    Best regards.

  • 0 in reply to Gk 110
    TI__Guru 62065 points

    Hello,

    While this is the expected behavior of the XTR300, we do not specify the behavior in the product datasheet.  To our knowledge there is no way to reduce the overshoot effects at light loads.

     

  • 0 in reply to Gk 110
    Expert 2440 points

    Hello,

    Thank you for your prompt reply.

    Although you mentioned not to occur overshoot at normal load , our customer have confirm to occur overshoot at 100Ω load.

    Please let me know why occur this issue as above?

    Best regards,

  • 0 in reply to Gk 110
    TI__Guru 62065 points

    Hello,

    This disagrees with the data I provided a few posts ago where the output overshoot is within a standard range once the output load is roughly 30 Ohms.  We took data using the XTR300 EVM with the default components.  This includes a 15Ohm series resistor and 10nF capacitor to GND on the output terminal. What type of output loading circuitry is your customer using? 

    You can see the schematic for the XTR300EVM in the User's Guide:  http://www.ti.com/lit/ug/sbou034a/sbou034a.pdf