POWER STAGE CALCULATIONS

Please refer to the LT16810 datasheet for many of these calculations.

Contents

Some Constants

Vin = 15; %volts
Vout = [3.3 5];%volts

FB Resistor Network

Referring to scott's original circuit, we have to reset the value of the divider.

$R1 = R2(\frac{V_{out}}{0.970} = 1)$

Originally it was:

R1 = [620e3 866e3];
R2 = [243e3 200e3];
VoutOrig = (R1./R2+1)*0.970

% Let's reset for 3.3 and 5. Let's keep R2
R1new = [1e6 1e6];
R2new = [412e3 243e3];
VoutNew = (R1new./R2new+1)*0.970

% Determine the quiescent current
Iq = (1.7e-6 + (VoutNew/(R1new+R2new))*(VoutNew/Vin)*(1/.8) ) * 1e6 %uA

VoutOrig =

    3.4449    5.1701


VoutNew =

    3.3244    4.9618


Iq =

    2.5503    2.9691

Inductor Selection

This a simple suggestion for where to start based on sampling frequency

fsw = 0.200; %MHz
Vout
L = (Vout + Vswbot)/fsw

Vout =

    3.3000    5.0000


L =

   17.2500   25.7500

Max Frequency of Switching

% First some supporting variables.
Vswbot = 0.15;
Vswtop = 0.3;
tonmin = 45e-9;
fswmax = Vout;

%The resulting operating frequencies (MHz) are

fswmax = ( Vout + Vswbot) ./ (tonmin * (Vin - Vswtop + Vswbot))*1e-6

%

fswmax =

    5.1627    7.7067


Published with MATLAB® R2013b