Other Parts Discussed in Thread: TPS54060, LMR16006, LMR14006,
Input voltage: 9-40V
Output voltage: 8V
Output current: max. 2A (typ.: 0.5-1.5A)
Webench recommends a 10µH inductor for this design. Changing the output current to 1A or 0.5A does not affect the inductance and only changes the recommended inductor's current rating.
The datasheet gives the following equation (p.20, Eq.10) to calculate the minimum output inductance:
L_min = [ (V_in_max - V_out) / (I_out * K_ind) ] * [ V_out / (V_in_max * f_sw) ]
Using the same input/output voltages as above, a switching frequency of 541kHz (as calculated by Webench) and K_ind = 0.4, this equation yields the following results:
For I_out = 2A: 14.79µH
For I_out = 1A: 29.57µH
For I_out = 0.5A: 59.15µH
The example design in the datasheet is apparently based on this equation with I_out = I_out_max. Therefore I would assume that it's save to set L_min = 14.8 uH and choose a 15uH inductor.
Either way, the calculated L_min does not match the Webench recommendation.
Why is that? Is it safe to choose components based on the Webench BOM or is the datasheet more accurate in this case?
Are the calculations based on I_out_max correct or is it necessary to choose an even higher inductance based on calculations for typical/minimal loads?