• State TI Thinks Resolved
  • Locked Locked
  • Replies 3 replies
  • Answers 1 answer
  • Subscribers 62 subscribers
  • Views 233 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.

TPS2662: current limit unexpected behaviour

Jan Bock
Intellectual 2395 points
Part Number: TPS2662

Hi Team, 

My customer encountered an unexpected behaviour for currentlimt function on TPS26625. 

He changed the RLim value from 30 kOhm (working setup) to 12kOhms set the current limit to 550mA. His testload is a potentiometer.

1 . At start-up: 31 ohm load connected to the output. Then 24V connected to the input. The current is limited to the 550mA. OK
2. During operation: The output is limited only when the load is equal to 31 ohms (approx. 760mA). This means: I can, for example, pull 700mA permanently. NOK
3 . During operation: After a fault, the current is no longer limited until 550mA.

thanks 

Jan

Thanks 

Jan

  • 0
    TI__Guru* 95881 points

    Hi Jan,

    Thanks for reaching out!

    Is the Iout current you measured before the Cout or after the Cout. ? Can you please share a test waveform of Vin, Vout, Iout and FLT in one scope shot as point in below.

    Best Regards, 

    Rakesh

  • 0 in reply to Rakesh
    TI__Intellectual 2395 points

    Hi Rakesh,

    find attached the measurments of  I = current in front of the Cap, Cout, Vin, Vout and /FLT

    Pictures:

    1. Current before Cout.
    2. Strom after Cout
    3. current limit (I before Cout)
    4. currentl limit without Cout

    As you can see in picture 1 the current has a freq. of 385kHz. In Pic 3 you can see the max. Peak of 1 A before the TPS limits the current. The input voltage of vin of 24V are generated by a flyback converter with 385kHz switching frequency.  When Cout is getting removed, the curicuit works as expected Pic 4.

    The customer thinks a a filter at the input could help. He will implement that. 

    Thanks 

    Jan  

  • 0 in reply to Jan Bock
    TI__Guru* 95881 points

    Hi Jan,

    Thanks for the measurements. The current limit loop in the eFuse devices is slow, so, the eFuse takes time to respond to the switching currents. Your approach is current. Stabilizing the input voltage helps

    Best Regards, Rakesh