2 Input Capacitor Selection C in A 100 m F 25 V aluminium electrolytic

2 input capacitor selection c in a 100 m f 25 v

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2. Input Capacitor Selection (C in ) A 100 m F, 25 V aluminium electrolytic capacitor located near to the input and ground pins provides sufficient bypassing. 3. Catch Diode Selection (D1) A. Since the diode maximum peak current exceeds the regulator maximum load current the catch diode current rating must be at least 1.2 times greater than the maximum load current. For a robust design the diode should have a current rating equal to the maximum current limit of the LM2576 to be able to withstand a continuous output short B. The reverse voltage rating of the diode should be at least 1.25 times the maximum input voltage. 3. Catch Diode Selection (D1) A. For this example the current rating of the diode is 3.0 A. B. Use a 20 V 1N5820 Schottky diode, or any of the suggested fast recovery diodes shown in Table 1. 4. Inductor Selection (L1) A. According to the required working conditions, select the correct inductor value using the selection guide from Figures 18 to 22 . B. From the appropriate inductor selection guide, identify the inductance region intersected by the Maximum Input Voltage line and the Maximum Load Current line. Each region is identified by an inductance value and an inductor code. C. Select an appropriate inductor from the several different manufacturers part numbers listed in Table 2. The designer must realize that the inductor current rating must be higher than the maximum peak current flowing through the inductor. This maximum peak current can be calculated as follows : where t on is the “on” time of the power switch and For additional information about the inductor, see the inductor section in the “Application Hints” section of this data sheet. I p(max) + I Load(max) ) ǒ V in –V out Ǔ t on 2L t on + V out V in x 1.0 f osc 4. Inductor Selection (L1) A. Use the inductor selection guide shown in Figures 19. B. From the selection guide, the inductance area intersected by the 15 V line and 3.0 A line is L100. C. Inductor value required is 100 m H. From Table 2 , choose an inductor from any of the listed manufacturers.
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LM2576 11 Procedure (Fixed Output Voltage Version) (continued) In order to simplify the switching regulator design, a step−by−step design procedure and some examples are provided. Procedure Example 5. Output Capacitor Selection (C out ) A. Since the LM2576 is a forward−mode switching regulator with voltage mode control, its open loop 2−pole−1−zero frequency characteristic has the dominant pole−pair determined by the output capacitor and inductor values. For stable operation and an acceptable ripple voltage, (approximately 1% of the output voltage) a value between 680 m F and 2000 m F is recommended. B. Due to the fact that the higher voltage electrolytic capacitors generally have lower ESR (Equivalent Series Resistance) numbers, the output capacitor’s voltage rating should be at least 1.5 times greater than the output voltage. For a 5.0 V regulator, a rating at least 8.0 V is appropriate, and a 10 V or 16 V rating is recommended.
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  • Spring '19
  • Margaret Earle
  • Switched-mode power supply, Vout

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