• State Resolved
  • Locked Locked
  • Replies 1 reply
  • Subscribers 62 subscribers
  • Views 1004 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.

LMZ20502: Resistor value calculation RFBB and RFBT for 3.3V VOUT for LMZ20502SILT

vinoth s1
Intellectual 660 points
Part Number: LMZ20502

We are using LMZ20502SILT to convert from 3.7V to 3.3V.

As per data sheet it is recommended to use RFBB = 53.2 kΩ and RFBT = 237 kΩ.

We cannot find 53.2KΩ of desired size we need (Size required: 0402).

So we need to change the Resistor value of RFBB and RFBT for 3.3V Vout.

SETTING THE OUTPUT VOLTAGE Formula in datasheet is as per below:

RFBB = 0.6 / (VOUT - 0.6)  . RFBT

When we calculate changing Resistor value of RFBT , it doesn't give the desired voltage.

With this formula if RFBB= 53.2K and RFBT = 237K the output is 3.272932 and not desired 3.3V.

We need to know how to calculate this combinational Resistor values for 3.3V Vout

  • 0
    TI__Guru**** 191445 points
    For the feed back resistors 53.2k and 237k, the calculated output voltage is indeed 3.272932 V. Most users would consider that close enough. *** value for RFBT, then solve for RFBB. You may need to use to resistors in series for your RFFB to get the precision you desire.