• State Resolved
  • Locked Locked
  • Replies 3 replies
  • Subscribers 64 subscribers
  • Views 435 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.

TPS54060A based DC/DC converter

Manoj Tyagi
Prodigy 110 points
Other Parts Discussed in Thread: TPS54160

Hi,

i have designed a DC-DC converter with input ranging from 8V to 48V and providing 5V output at 0.5A load current. Webench design suggested me a design which shows that top resistor used for UVLO condition is 105kohm & Bottom resistor is 22.1kohm.

This seems OK when 8V is ok but when input is at 48V the EN pin will be connected to a voltage higher than its absolute maximum ratings.

Plz clear this confusion, it seems webench is not able to take care of absolute max ratings in this case.

rgds

webench_design_3810016_33_264396959.pdf
  • 0
    TI__Guru**** 191445 points

    As long as EN is pulled up to a high voltage with a high impedance it is acceptable.  From the TPS54160 datasheet (which has the same EN circuit internally):

    Do not place a low-impedance voltage source with greater than 5 V directly on the EN pin.  Do not place a capacitor directly on the EN pin if V EN > 5 V when using a voltage divider to adjust the start and stop voltage. The node voltage, (see Figure 30) must remain equal to or less than 5.8 V. The zener diode can sink up to 100μA.  The EN pin voltage can be greater than 5 V if the VIN voltage source has a high impedance and does not source more than 100 μA into the EN pin.
  • 0 in reply to JohnTucker
    Prodigy 110 points

    OK, the pin can sink current upto 100 micro ampere but in this case with input voltage of 48volt, the source current is around 400 micro amp.SO this condition is not met.

    plz clarify.

  • 0 in reply to Manoj Tyagi
    TI__Guru**** 191445 points

    For that resistor divider, I calculate an EN pin voltage of 6.701 V at Vin = 48 V and 90 uA EN current.  That is within the limit.