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lm3140-boost-calc.txt
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lm3140-boost-calc.txt
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280nm UVC LED
RVXD-280-SM-071005 / 1807-1021-1-ND
Vout = 8V (max) [7V nom]
Iout = 100mA (max)
ripple = 20%
Vin (min) = 3.0V
Vin (max) = 4.2V
fsw = 1.6MHz => Ts = .625 us = 625ns
Vout 1 Vout - Vin
------ ~= --- => D ~= ----------
Vin D Vout
Vout 1 Vout - (e)*Vin
------ ~= --- => D ~= -------------- where (e)=efficiency (90%)
Vin D Vout
(8-.9*3)/8 ~= 0.663 ~= 67%
dIpp = ripple * Iout = 20% * 100mA = 20mA
Vin(min) * Dmax * Ts 3 * .663 * .000000625
L = -------------------- = --------------------- =
2 * dIpp 2 * .02
------------------------------------------------------------
310nm UVB LED
Vout = 7V (nom?)
Iout = 40mA max
ripple = 20% (?)
Il(pp) = 80mA (?)
Vin(min) = 2.7
fsw = 1.6MHz => Ts = 625ns
dV = 250mV
Rd ~= 4 Ohm (?)
Vout - eff * Vin(min)
Dmax = --------------------- ~= 0.65
Vout
Vin(min) * Dmax * Ts
Lmin = -------------------- ~= 6.89 => L = 8.2 uH
2 * Il(pp)
Vout * Dmax
C2 >= ----------------- = 1.42
2 * fsw * Rd * dV
C1 = C2 = 2.2uF