Tool/software: WEBENCH® Design Tools
I would like to understand why the Power Designer chose two 3W resistors in parallel for Rsense in my design. ...seems like way more power than necessary.
The tool lists the total Rsense power dissipation as approx. 0.6W (2 x 0.3W). The peak current is listed as approx 24A (avg 20A). Pd = 24A^2 * 0.0015ohms = 0.9W peak power
Why does the tool suggest two 3W resistors (total=6W) for a predicted average power dissipation of 0.6W?
Hi Paul,
As per datasheet eqn 22 , currently minimum power rating for sense resistor is kept as VcsMax^2 / Rsense, and some margin over it.
For shared design, total sense resistor is 1.5 mOhm, which constitutes to 4.48W from above eqn. For each resistor it would be 2.24W and with some margin it will be 3W. Please let us know if this helps.
On second query, currently EVM uses two Rsense resistors and this seem to reflect in WEBENCH schematic as well. But this is not necessary if high power and current rating resistor is available. Hope this helps.
EVM: http://www.ti.com/lit/ug/slvu828a/slvu828a.pdf
Best Regards,
Bhushan
