I'm currently designing a circuit to convert a 24V (±30%) to supply a 3,3V IC used to monitor currents. I need to use the LT1073 which has the following diagram.
The operations of the component and its applications are well-explained in the datasheet. According to the circuit example, I should place a 100uH inductor and a Schottky-Diode at the switch. As far as my understanding goes, the Schottky-Diode is needed to block the discharge of current from going to the ground to allow the current to flow into the load. Is this correct?
This is how the circuit is supposed to be connected
According to the example, I need to put an inductor of 100uH. But what if this isn't possible and I need to pick a smaller inductor? What do I need to consider?
The datasheet mentions:
To operate as an efficient energy transfer element, the inductor must fulfill three require-ments. First, the inductance must be low enough for the inductor to store adequate energy under the worst-case condition of minimum input voltage and switch ON time. The inductance must also be high enough so that maxi-mum current ratings of the LT1073 and inductor are not exceeded at the other worst-case condition of maximum input voltage and ON time. Additionally, the inductor core must be able to store the required flux, i.e., it must not saturate.
And then the datasheet goes on with some formulas that I can't really understand.
(1) Pl = (Vout + Vd - Vin) * (IOut), where Vd is the diode drop(0.5V for IN5818 Schottky) (2) PL = 1/2 * L * iPeak^2 *fOsc
These formulas raised a few questions:
- Where does IOut flows?
- How can I get fOsc?
I would really appreciate it if someone could give some tips or answers to my questions. Thanks in advance!