Tool/software:
Good day,
I've been looking at the calculations for the application examples for the LM2578A.
For the buck converter application, everything mostly checks out. There is a discrepancy if the value is calculated directly, but on page 22 (RS-232 Line Drive Example), it's stated that "a larger output capacitor than this theoretical value should be used since electrolytics have poor high frequency performance. Experience has shown that a value from 5 to 10 times the calculated value should be used." Applying this to the example makes the given value in the example make sense.
However, for the rest of the examples, I have not been getting similar luck.
Buck with Boosted Output Current p16
In this example, R3 is given as 0.05 Ohms instead of the 0.15 Ohms previously calculated. The datasheet says "Component values are selected as outlined for the buck regulator with a discontuity factor of 10%, with the addition of R4 and R5." Yet there is no explanation for this changed value.
Other values that aren't consistent are R4/R5/C2.
R4 and R5 use Vbe and Bf of the output transistor, in this case, a D45. The Vsat is the saturation voltage of the LM2578A found on pg3, 1.4V.
Using these values, I've not come close to the calculated values.
Even the output capacitor, C2, is different.
Inverting Regulator
In this example, R3 is even smaller at 0.01Ohms. Is there something key I'm missing?
I appreciate the assistance in advance.
