• State Resolved
  • Locked Locked
  • Replies 1 reply
  • Subscribers 63 subscribers
  • Views 67 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.

LM70880: Derating curves difference between the fixed vs the adj version (datasheet pg30)

Cosmin P
Intellectual 1690 points
Part Number: LM70880

Tool/software:

Hello,

Why are the pg30 power derating curves different between the fixed Vout vs he adjustable Vout versions - all conditions are same.
If they should not, which curve is valid?

maybe mixed with airflow info?

Thank you

  • +1
    TI__Guru 56345 points

    The fixed output voltage of 3.3V and 5V has a VCC voltage of 5V that drives the gate of the power FETs. At output voltages at 12V fixed or adjustable output, the VCC voltage is at 8V. Driving the FETs with a higher gate voltage will enhance the power FETs so that their RDSon values are lower than when the VCC voltage is at 5V. The higher RDSon values will contribute a higher power dissipation within the IC causing the junction temperature to be higher at a lower ambient temperature and hence the output current will derate to keep the junction temperature below the 150C spec.

    Ben