Tool/software: WEBENCH® Design Tools
Hi,
i'm use LM2733 device with help of webench simulation and the next parameters:
- Vin = 5V
- Vout = 28V
- Iload = 0.1A
- Vdiode = 0.3-0.36V (MBR140SFTIG)
in the simulation, webench recommend to use inductor 12uH and when i was tried to approved that value, i could not successes. maybe i missing somethings, according to the datasheet:
Lmin = V*(Dt/Di) = (Vin-Vsw)*((Ton(max)*D.C.)/Di)
Ton(max) = 1/(1.15[MHz]) = 0.87[us]
Vsw = Rds(on)*IL(avg) = 0/48[ohm] * 0.1[A] = 0.048[V]
D.C. = (Vout +Vdiode-Vin)/(Vout +Vdiode-Vsw) = (28+0.3-5)/(28+0.3-0.048) = 82.472%
and then:
Lmin = (5-0.048)*((0.00000087*0.82472)/0.1) = 28.355[uH]
and it's seems that when Iload will decrease, the Lmin will increase meaningfully.
please your good help.
best regards,
Itzik Mizrahi
