Part Number: TPS53515
Tool/software: WEBENCH® Design Tools
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Hello everyone,
I tried to calculate all components for my design because I am using a 3.3V for the input (i cannot use higher). The problem is that the simulation software is limited to a minimum of 4,5V input.
My calculation:
Choose the inductor:
L=3IoutMax*fsw*(VinMax-Vout*VOut)/(VinMax)
= 312*500k*3,3-0,8*0,8)/(3,3)
=303 nH ~ 330nH
For the peak I decide to use 30% of the maximum output current à 15,6A
IindPeak=Vtrip8*RDSon+1L*fSW*VinMax-VOut*VoutVinMax
IindPeak=10μ*Rtrip8*RDSon+1L*fSW*VinMax-VOut*VoutVinMax
IindPeak= 10μ*56,2k8*5,9m+1330n*500k*3,3-0,8*0,83,3=15,74 A
RTrip = 56,2kOhm
Calculation Rfbt / Rfbb for output voltage (Rfbb recommended between 1k and 20 k):
Rfbt=(Vout-0,6)/0,6*R2=(0,8-0,6)/0,6*10.2k= 3.4k kOhm
Mode operation : Skip à Rpgood = 150k on Mode pin
Choose switching frequency: Set to 479,17 kHz
(R5 (rf low) and R4(rf high))
R5 = 68,1k and R4 = 249k à frequency 478,18kHz
Vripple ? I am stuck because I am not sure of the IL Ripple, is it 30% of iL max ?
How can I calculation or dimenssion my by-pass capacitor ? in the schematic in copy I use the simulation for 5V input and then I modify the differents resistor/inductor and I keep the capacitor.
Please give me an answer soon ! Have a nice day.
Jordan