Moteur de recherche de fiches techniques de composants électroniques |
|
UC2577T-ADJ Fiches technique(PDF) 6 Page - Texas Instruments |
|
UC2577T-ADJ Fiches technique(HTML) 6 Page - Texas Instruments |
6 / 8 page UC2577-ADJ 3. Compensation Network (RC, CC) and Output Capacitor (COUT) Selection The compensation network consists of resistor RC and capacitor CC which form a simple pole-zero network and stabilize the regulator. The values of RC and CC depend upon the voltage gain of the regulator, ILOADmax, the in- ductor L, and output capacitance COUT. A procedure to calculate and select the values for RC, CC, and COUT which ensures stability is described below. It should be noted, however, that this may not result in optimum com- pensation. To guarantee optimum compensation a stand- ard procedure for testing loop stability is recommended, such as measuring VOUT transient responses to pulsing ILOAD. A. Calculate the maximum value for RC. RC ≤ 750 • ILOADmax • VOUT2 VINmin 2 Select a resistor less than or equal to this value, not to exceed 3k Ω. B. Calculate the minimum value for COUT using the fol- lowing two equations. COUT ≥ 0.19 • L • RC • ILOADmax VINmin • VOUT and COUT ≥ VINmin • RC • (VINmin + (3.74 • 105 • L)) 487,800 • VOUT3 The larger of these two values is the minimum value that ensures stability. C. Calculate the minimum value of CC. CC ≥ 58.5 • VOUT2 • COUT RC 2 • VINmin The compensation capacitor is also used in the soft start function of the regulator. When the input voltage is ap- plied to the part, the switch duty cycle is increased slowly at a rate defined by the compensation capacitor and the soft start current, thus eliminating high input currents. Without the soft start circuitry, the switch duty cycle would instantly rise to about 90% and draw large currents from the input supply. For proper soft starting, the value for CC should be equal or greater than 0.22 µF. Figure 6 lists several types of aluminum electrolytic ca- pacitors which could be used for the output filter. Use the following parameters to select the capacitor. Working Voltage (WVDC): Choose a capacitor with a working voltage at least 20% higher than the regulator output voltage. Ripple Current: This is the maximum RMS value of cur- rent that charges the capacitor during each switching cy- cle. For step-up and flyback regulators, the formula for ripple current is: IRIPPLErms = ILOADmax • Dmax 1 − Dmax Choose a capacitor that is rated at least 50% higher than this value at 52kHz. Equivalent Series Resistance (ESR): This is the primary cause of output ripple voltage, and it also affects the val- ues of RC and CC needed to stabilize the regulator. As a result, the preceding calculations for CC and RC are only valid if the ESR does not exceed the maximum value specified by the following equations. ESR ≤ 0.01 • 15V IRIPPLE(P−P) and ≤ 8.7 • 10−3 • VIN ILOADmax where IRIPPLE(P−P ) = 1.15 • ILOADmax 1 − Dmax Select a capacitor with an ESR, at 52kHz, that is less than or equal to the lower value calculated. Most electro- lytic capacitors specify ESR at 120kHz which is 15% to 30% higher than at 52kHz. Also, note that ESR increases by a factor of 2 when operating at −20°C. In general, low values of ESR are achieved by using large value capacitors (C ≥ 470µF), and capacitors with high WVDC, or by paralleling smaller value capacitors. Inductor Code Manufacturer’s Part Number AIE Pulse Renco L47 415 - 0932 PE - 53112 RL2442 L68 415 - 0931 PE - 92114 RL2443 L100 415 - 0930 PE - 92108 RL2444 L150 415 - 0953 PE - 53113 RL1954 L220 415 - 0922 PE - 52626 RL1953 L330 415 - 0926 PE - 52627 RL1952 L470 415 - 0927 PE - 53114 RL1951 L680 415 - 0928 PE - 52629 RL1950 H150 415 - 0936 PE - 53115 RL2445 H220 430 - 0636 PE - 53116 RL2446 H330 430 - 0635 PE - 53117 RL2447 H470 430 - 0634 PE - 53118 RL1961 H680 415 - 0935 PE - 53119 RL1960 H1000 415 - 0934 PE - 53120 RL1959 H1500 415 - 0933 PE - 53121 RL1958 H2200 415 - 0945 PE - 53122 RL2448 AIE Magnetics, Div. Vernitron Corp., (813)347-2181 2801 72nd Street North, St. Petersburg, FL 33710 Pulse Engineering, (619)674-8100 12220 World Trade Drive, San Diego, CA 92128 Renco Electronics, Inc., (516)586-5566 60 Jeffryn Blvd. East, Deer Park, NY 11729 Figure 5. Table of Standardized Inductors and Manufacturer’s Part Numbers APPLICATIONS INFORMATION (cont.) 6 |
Numéro de pièce similaire - UC2577T-ADJ |
|
Description similaire - UC2577T-ADJ |
|
|
Lien URL |
Politique de confidentialité |
ALLDATASHEET.FR |
ALLDATASHEET vous a-t-il été utile ? [ DONATE ] |
À propos de Alldatasheet | Publicité | Contactez-nous | Politique de confidentialité | Echange de liens | Fabricants All Rights Reserved©Alldatasheet.com |
Russian : Alldatasheetru.com | Korean : Alldatasheet.co.kr | Spanish : Alldatasheet.es | French : Alldatasheet.fr | Italian : Alldatasheetit.com Portuguese : Alldatasheetpt.com | Polish : Alldatasheet.pl | Vietnamese : Alldatasheet.vn Indian : Alldatasheet.in | Mexican : Alldatasheet.com.mx | British : Alldatasheet.co.uk | New Zealand : Alldatasheet.co.nz |
Family Site : ic2ic.com |
icmetro.com |