• State
  • Locked Locked
  • Replies 3 replies
  • Subscribers 63 subscribers
  • Views 276 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.

TPS63900: input current limit

Connie Lu1
Intellectual 2130 points
Part Number: TPS63900

Hi team,

My customer's supply seems to be current limiting on a board with TPS63900. The input current seems to be around 80 mA when the convertor appears to brown-out.

If they have Rcfg1 set to 36.5Kohms, Rcfg2 set to 0 ohms,  Rcfg3 is set to 0 ohms. This gives Vout = 3.3V

Sel = High

So shouldn’t they be getting unlimited current limiting on the input?

For the output it should be typical 1.45 A peak switching current limit. Is this correct? (1.33 to 1.6 A)

Thanks,

Connie

  • 0
    TI__Mastermind 32350 points

    Hi   Connie,

    correct, in customer's application, TPS63900 will work without input current limit and a 1.45A(typical) peak switching current limit.

    BTW , how did you get the value of 80mA, with a multimeter or oscilloscope?

    if measurment with a multimeter, it should be a RMS value but not a instantaneous one. then, it is possible that peak switching current limit triggered and converter brown-out altough input current is a small one.

    Regards

    Tao

  • 0 in reply to Tao Zhang
    TI__Intellectual 2130 points

    Hi Tao,

    Let me check with the customer on the measurement of 80mA.

    Fyi, I forgot to mention that the UVLO is set to around 1.8V.

    At an input voltage of 2.2V, the VCORE_EN signal is at a high enough level to enable the buck-boost. So the device browning out is not due it being disabled by the UVLO circuit.

    They start the board up at a higher input voltage like 4.5V the VOUT is then 3.3V as desired. Then on a bench top supply they start dropping the input voltage (i.e. as would happen on an actual battery) to see how low they can get the input voltage. The target for this design is to be able run to down from the initial 4.5V down to the 2.2V when the battery reaches the end of its operational curve.

  • 0 in reply to Connie Lu1
    TI__Mastermind 32350 points

    Hi   Connie,

    ok, it is better you can help to share waveforms during the unnormal working.

    Regards

    Tao