• State Resolved
  • Locked Locked
  • Replies 1 reply
  • Subscribers 63 subscribers
  • Views 629 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.

TPS40200: Failure to self recover from "Hiccup" mode

Eric Duhamel
Prodigy 10 points
Other Parts Discussed in Thread: TPS40200

I am using a TPS40200 to supply 27.2V @ 1.65A from a 37V input.  When I increase the load to a point were over current protection circuit trips, the parts enters the "Hiccup" mode as described in the data sheet.  The problem is when I remove the load the part still remains in "Hiccup" mode and cannot self recover.  I need to remove the input power and let everything "drain down" and reset in order for the part to startup again and achieve proper regulation.  When the part is in "Hiccup" mode the output is a very ripply 8V or so.  What can I do to help the part self recover.  How sensitive is the compensation network?  And is it posible to vary the output voltage on the fly by pulling on the Feedback resistor divider? 

Please help!  :-) 

Thanks.

Eric

Sr. EE at Medtronic in Littleton MA

  • 0
    TI__Genius 17240 points

    Hi Eric,

    If the part stucked in the hiccup mode after the load is removed, there are some possiblities.

    (1) When the part restarts with pre-biased output voltage, it will not go through the normal soft-start. When the output voltage is higher than target value, the COMP voltage will be at the minimum. Once the output volage is lower than the target value, the COMP is supposed to rise quickly to force the output voltage follow the reference. However, the error amplifier has relatively weak sourcing current ability of 250 uA, which may cause delay and overshoot on COMP. As a result, there might be a rush current to charge the output capacitor.

    You may try to increase the overcurrent limit to see whether the part can get off hiccup. If it is the reason, higher overcurrent limit is one solution, or you can modify the compensation RC. Using bigger R, smaller C to lower down the requirement for sourcing current.

    (2) Do you have RC filter between VDD and ISNS pin as shown in Figure 30 of the datasheet? Another possible reason is the retry after OC fault may cause voltage dip on VIN and ISNS. But somehow VDD is not seeing the dip due to the trace impedance between VIN and VDD. Therefore, the large voltage drop between VDD and ISNS triggers OC by mistake. You may check the waveform of VIN, VDD pin and ISNS pin to see whether it is the case.

    Regards,

    Na