Moteur de recherche de fiches techniques de composants électroniques |
|
RT5047B Fiches technique(PDF) 11 Page - Richtek Technology Corporation |
|
RT5047B Fiches technique(HTML) 11 Page - Richtek Technology Corporation |
11 / 17 page RT5047B Copyright © 2017 Richtek Technology Corporation. All rights reserved. is a registered trademark of Richtek Technology Corporation. DS5047B-00 November 2017 www.richtek.com 11 Application Information Boost Converter/Linear Regulator The 5047B integrates a current-mode boost converter and linear regulator. Use the SEL pin to control the LNB voltage and the boost converter track is at least greater 800mV than the LNB voltage. The boost converter is high efficiency PWM architecture with 700kHz operation frequency. The linear regulator has the capability to source current up to 550mA during continuous operation. All the loop compensation, current sensing, and slope compensation functions are provided internally. The RT5047B has current limiting on the boost converter and the LNB output to protect the IC against short circuits. The internal MOSFET will turn off when the LX current is higher than 3A cycle-by-cycle. The LNB output will turn off when the output current higher than the 550mA and 6ms and turn-on after 1800ms automatically. Input Capacitor Selection The input capacitor reduces voltage spikes from the input supply and minimizes noise injection to the converter. A 30 F capacitance is sufficient for most applications. Nevertheless, a higher or lower value may be used depending on the noise level from the input supply and the input current to the converter. Note that the voltage rating of the input capacitor must be greater than the maximum input voltage. Inductor Selection The inductance depends on the maximum input current. As a general rule, the inductor ripple current range is 20% to 40% of the maximum input current. If 40% is selected as an example, the inductor ripple current can be calculated according to the following equations : OUT OUT(MAX) IN(MAX) IN RIPPLE IN(MAX) VI I = V I = 0.4 I where η is the efficiency of the converter, IIN(MAX) is the maximum input current, and IRIPPLE is the inductor ripple current. The input peak current can then be obtained by adding the maximum input current with half of the inductor ripple current as shown in the following equation : IPEAK = 1.2 x IIN(MAX) note that the saturated current of the inductor must be greater than IPEAK. The inductance can eventually be determined according to the following equation : 2 2 IN OUT IN OUT OUT(MAX) OSC η V V V L 0.4 V I f where fOSC is the switching frequency. For better system performance, a shielded inductor is preferred to avoid EMI problems. Boost Output Capacitor Selection The RT5047B boost regulator is internally compensated and relies on the inductor and output capacitor value for overall loop stability. The output capacitor is in the 30 F to 50F range with a low ESR, as strongly recommended. The voltage rating on this capacitor should be in the 25V to 35V range since it is connected to the boost VOUT rail. The output ripple voltage is an important index for estimating chip performance. This portion consists of two parts. One is the product of the inductor current with the ESR of the output capacitor, while the other part is formed by the charging and discharging process of the output capacitor. As shown in Figure 1, VOUT1 can be evaluated based on the ideal energy equalization. According to the definition of Q, the Q value can be calculated as the following equation : IN L OUT IN L OUT IN OUT OUT1 OUT OSC 1 1 1 Q = I I I I I I 2 2 2 V 1 = C V Vf where fOSC is the switching frequency and IL is the inductor ripple current. Bring COUT to the left side to estimate the value of VOUT1 according to the following equation : OUT OUT1 OUT OSC DI V = Cf |
Numéro de pièce similaire - RT5047B |
|
Description similaire - RT5047B |
|
|
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 |