 |
Moteur de recherche de fiches techniques de composants électroniques |
|
|
Moteur de recherche de fiches techniques de composants électroniques |
|
FAN5602 Fiches technique(PDF) 9 Page - Fairchild Semiconductor |
|
||||||||||||||||||||||||||||||
FAN5602 Fiches technique(HTML) 9 Page - Fairchild Semiconductor |
|
|
9 / 13 page  © 2005 Fairchild Semiconductor Corporation www.fairchildsemi.com FAN5602 Rev. 1.5.3 9 Functional Description FAN5602 is a high-efficiency, low-noise switched capaci- tor DC/DC converter capable of step-up and step-down operations. It has seven built-in switch configurations. Based on the ratio of the input voltage to the output volt- age, the FAN5602 automatically reconfigures the switch to achieve the highest efficiency. The regulation of the output is achieved by a linear regulation loop, which modulates the on-resistance of the power transistors so that the amount of charge transferred from the input to the flying capacitor at each clock cycle is controlled and is equal to the charge needed by the load. The current spike is reduced to minimum. At light load, the FAN5602 automatically switches to Pulse Frequency Modulation (PFM) mode to save power. The regulation at PFM mode is achieved by skipping pulses. Linear Regulation Loop The FAN5602 operates at constant frequency at load higher than 10mA. The linear regulation loop consisting of power transistors, feedback (resistor divider), and error amplifier is used to realize the regulation of the out- put voltage and to reduce the current spike. The error amplifier takes feedback and reference as inputs and generates the error voltage signal. The error voltage sig- nal is then used as the gate voltage of the power transis- tor and modulates the on-resistance of the power transistor and, therefore, the charge transferred from the input to the output is controlled and the regulation of the output is realized. Since the charge transfer is controlled, the FAN5602 has a small ESR spike. Switch Array Switch Configurations The FAN5602 has seven built-in switch configurations, including 1:1, 3:2, 2:1 and 3:1 for step-down and 2:3, 1:2 and 1:3 for step-up. When 1.5 x VOUT > VIN > VOUT, the 1:1 mode shown in Figure 21 is used. In this mode, the internal oscillator is turned off. The power transistors connecting the input and the output become pass transistors and their gate voltages are controlled by the linear regulation loop, the rest of power transistors are turned off. In this mode, the FAN5602 operates exactly like a low dropout (LDO) regu- lator and the ripple of the output is in the micro-volt range. When 1.5 x VIN > VOUT > VIN, the 2:3 mode (step-up) shown in Figure 22 is used. In the charging phase, two flying capacitors are placed in series and each capacitor is charged to a half of the input voltage. In pumping phase, the flying capacitors are placed in parallel. The input is connected to the bottom the capacitors so that the top of the capacitors is boosted to a voltage that equals VIN/2 + VIN, i.e., 3/2 x VIN. By connecting the top of the capacitors to the output, one can ideally charge the output to 3/2 x VIN. If 3/2 x VIN is higher than the needed VOUT, the linear regulation loop adjusts the on- resistance to drop some voltage. Boosting the voltage of the top of the capacitors to 3/2 x VIN by connecting VIN the bottom of the capacitors, boosts the power efficiency 3/2 times. In 2:3 mode, the ideal power efficiency is VOUT/1.5 x VIN. For example, if VIN = 2V, VOUT = 2 x VIN = 4V, the ideal power efficiency is 100%. When 2 x VIN > VOUT > 1.5 x VIN, the 1:2 mode (step-up) shown in Figure 23 is used. Both in the charging phase and in pumping phase, two flying capacitors are placed in parallel. In charging phase, the capacitors are charged to the input voltage. In the pumping phase, the input volt- age is placed to the bottom of the capacitors. The top of the capacitors is boosted to 2 x VIN. By connecting the top of the capacitors to the output, one can ideally charge the output to 2 x VIN. Boosting the voltage on the top of the capacitors to 2VIN boosts the power efficiency 2 times. In 1:2 mode, the ideal power efficiency is VOUT/2 x VIN. For example, VIN = 2V, VOUT = 2 x VIN = 4V, the ideal power efficiency is 100%. When 3 x VIN > VOUT > 2 x VIN, the 1:3 mode (step-up) shown in Figure 24 is used. In charging phase, two flying capacitors are placed in parallel and each is charged to VIN. In the pumping phase, the two flying capacitors are placed in series and the input is connected to the bottom of the series connected capacitors. The top of the series connected capacitors is boosted to 3 x VIN. The ideal power efficiency is boosted 3 times and is equal to VOUT/ 3VIN. For example, VIN = 1V, VOUT = 3 x VIN = 3V, the ideal power efficiency is 100%. By connecting the output to the top of the series connected capacitors, one can charge the output to 3 x VIN. The internal logic in the FAN5602 monitors the input and the output compares them, and automatically selects the switch configuration to achieve the highest efficiency. The step-down modes 3:2, 2:1, and 3:1 can be under- stood by reversing the function of VIN and VOUT in the above discussion. The built-in modes improve power efficiency and extend the battery life. For example, if VOUT = 5V, mode 1:2 needs a minimum VIN = 2.5V. By built-in 1:3 mode, the minimum battery voltage is extended to 1.7V. |
Numéro de pièce similaire - FAN5602 |
|
Description similaire - FAN5602 |
|
|
|
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 |
French ▼
English
Chinese
German
Japanese
Russian
Korean
Spanish
French
Italian
Portuguese
Polish
Vietnamese
Indian
Mexican
British
New Zealand
