 |
Electronic Components Datasheet Search |
|
|
Electronic Components Datasheet Search |
|
LT1432 Datasheet(PDF) 11 Page - Linear Technology |
|
||||||||||||||||||||||||||||||
LT1432 Datasheet(HTML) 11 Page - Linear Technology |
|
|
11 / 28 page  11 LT1432 S APPLICATI I FOR ATIO 50mV/DIV 1A/DIV 0 0 0.5A/DIV 0.2A RMS. Theoretically the output capacitor size would be minimized by using one which just met this ripple current, but in practice, this would yield such high output ripple voltage that an additional output filter would have to be added. A better solution in the case of buck converters is usually just to increase the size of the output capacitor to meet output ripple voltage requirements. Figure 8 shows output ripple voltage at the top and switch current below. Peak-to-peak ripple voltage is 80mV. This implies an output capacitor effective series resistance (ESR) of 80mV/0.7A = 0.11 Ω. Capacitor ESR varies sig- nificantly with temperature, increasing at low tempera- tures, so be sure to check ESR ratings at the lowest expected operating temperature. Ripple voltage can be reduced by increasing the inductor value, but this has rapidly diminishing returns because of typical size re- straints. Figure 9 shows diode current under normal load condi- tions of 2A, and with the output shorted. Current limit has been set at 3A. Average diode current at IOUT = 2A is only about 1A because of duty cycle considerations. Under short circuit conditions, duty cycle is nearly 100% for the diode (switch duty cycle is near zero), and diode average current is nearly 3A. Designs which must tolerate continu- ous short circuit conditions should be checked carefully for diode heating. Foldback current limiting can be used if necessary. Figure 10 shows inductor current (0.5A/DIV) with a 2A and 100mA load. Average inductor current is always equal to output current, but it is obvious that with 100mA load, inductor current drops to zero for part of the switching cycle, indicating dicontinuous mode. When selecting an inductor, keep in mind that RMS current determines copper losses, peak-to-peak current determines core loss, and peak current must be calculated to avoid core satura- tion. Also, remember that during short circuit conditions, inductor current will increase to the full current limit value. Inductor failure is normally caused by overheating of the winding insulation with resultant turn-to-turn shorts. Foldback current limiting will be helpful. 0 1A/DIV 1A/DIV 0 Figure 8. Output Ripple Current 5 µs/DIV Figure 9. Diode Current 5 µs/DIV 5 µs/DIV Figure 10. Inductor Current |
Similar Part No. - LT1432_15 |
|
Similar Description - LT1432_15 |
|
|
Link URL |
| Privacy Policy |
| ALLDATASHEET.COM |
| Does ALLDATASHEET help your business so far? [ DONATE ] |
About Alldatasheet | Advertisement | Datasheet Upload | Contact us | Privacy Policy | Link Exchange | Manufacturer List 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 |
English ▼
English
Chinese
German
Japanese
Russian
Korean
Spanish
French
Italian
Portuguese
Polish
Vietnamese
Indian
Mexican
British
New Zealand
