 |
Electronic Components Datasheet Search |
|
|
Electronic Components Datasheet Search |
|
LCLT Datasheet(PDF) 11 Page - Linear Technology |
|
||||||||||||||||||||||||||||||
LCLT Datasheet(HTML) 11 Page - Linear Technology |
|
|
11 / 24 page  LT3502/LT3502A 11 3502fc Figure 2. Pulse Skip Occurs when Required On Time is Below 60ns VSW 20V/DIV VOUT 100mV/DIV 1μs/DIV VIN = 40V VOUT = 3.3V L = 6.8μH COUT = 10μF IOUT = 250mA 3502 F02 IL 500mA/DIV APPLICATIONS INFORMATION Inductor Selection and Maximum Output Current A good first choice for the inductor value is: L = 1.6(VOUT + VD) for the LT3502A L = 4.6(VOUT + VD) for the LT3502 where VD is the voltage drop of the catch diode (~0.4V) and L is in μH. With this value there will be no subharmonic oscillation for applications with 50% or greater duty cycle. The inductor’s RMS current rating must be greater than the maximum load current and its saturation current should be about 30% higher. For robust operation during fault conditions, the saturation current should be above 1.2A. To keep efficiency high, the series resistance (DCR) should be less than 0.1Ω. Table 1 lists several vendors and types that are suitable. There are several graphs in the Typical Performance Characteristics section of this data sheet that show the maximum load current as a function of input voltage and inductor value for several popular output voltages. Low inductance may result in discontinuous mode opera- tion, which is okay, but further reduces maximum load current. For details of the maximum output current and discontinuous mode operation, see Linear Technology Application Note 44. Figure 3. Pulse Skip with Large Load Current Will be Limited by the DA Valley Current Limit. Notice the Flat Inductor Valley Current and Reduced Switching Frequency off until the output voltage dips below the programmed value before it begins switching again (Figure 2). Provided that the load can tolerate the increased output voltage ripple and that the components have been properly selected, operation above VIN(MAX) is safe and will not damage the part. As the input voltage increases, the inductor current ramps up quicker, the number of skipped pulses increases and the output voltage ripple increases. For operation above VIN(MAX) the only component requirement is that the components be adequately rated for operation at the intended voltage levels. Inductor current may reach current limit when operating in pulse skip mode with small valued inductors. In this case, the LT3502/LT3502A will periodically reduce its frequency to keep the inductor valley current to 650mA (Figure 3). Peak inductor current is therefore peak current plus minimum switch delay: 900mA + VIN –VOUT L •60ns The part is robust enough to survive prolonged operation under these conditions as long as the peak inductor cur- rent does not exceed 1.2A. Inductor current saturation and junction temperature may further limit performance during this operating regime. VSW 20V/DIV VOUT 100mV/DIV 1μs/DIV VIN = 40V VOUT = 3.3V L = 6.8μH COUT = 10μF IOUT = 500mA 3502 F03 IL 500mA/DIV |
Similar Part No. - LCLT |
|
Similar Description - LCLT |
|
|
|
Link URL |
| Privacy Policy |
| ALLDATASHEET.NET |
| Does ALLDATASHEET help your business so far? [ DONATE ] |
About Alldatasheet | Advertisement | 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
