 |
Electronic Components Datasheet Search |
|
|
Electronic Components Datasheet Search |
|
LT3506IFE-PBF Datasheet(PDF) 8 Page - Linear Technology |
|
||||||||||||||||||||||||||||||
LT3506IFE-PBF Datasheet(HTML) 8 Page - Linear Technology |
|
|
8 / 24 page  LT3506/LT3506A 3506afb APPLICATIO S I FOR ATIO FB Resistor Network The output voltage is programmed with a resistor divider between the output and the FB pin. Choose the 1% resis- tors according to: R1 = R2(VOUT/0.8 – 1) The parallel combination of R1 and R2 should be 10k or less to avoid bias current errors. Reference designators refer to the Block Diagram in Figure 2. Input Voltage Range The minimum input voltage is determined by either the LT3506’s minimum operating voltage of ~3.6V, or by its maximum duty cycle. The duty cycle is the fraction of time that the internal switch is on and is determined by the input and output voltages: DC = (VOUT + VD)/(VIN – VSW + VD) where VD is the forward voltage drop of the catch diode (~0.4V) and VSW is the voltage drop of the internal switch (~0.3V at maximum load). This leads to a minimum input voltage of: VIN(MIN) = (VOUT + VD)/DCMAX - VD + VSW with DCMAX = 0.89 (0.78 for the LT3506A). A more detailed analysis includes inductor loss and the dependence of the diode and switch drop on operating current. A common application where the maximum duty cycle limits the input voltage range is the conversion of 5V to 3.3V. The maximum load current that the LT3506 can deliver at 3.3V depends on the accuracy of the 5V input supply. With a low loss inductor (DCR less than 80m W), the LT3506 can deliver 1.2A for VIN > 4.7V and 1.6A for VIN > 4.85V. The maximum input voltage is determined by the absolute maximum ratings of the VIN and BOOST pins and by the minimum duty cycle DCMIN = 0.08 (0.15 for the LT3506A): VIN(MAX) = (VOUT + VD)/DCMIN – VD + VSW. This limits the maximum input voltage to ~21V with VOUT = 1.2V and ~15V with VOUT = 0.8V. For the LT3506A the maximum input voltage is ~8V with VOUT=0.8V. Note that this is a restriction on the operating input voltage; the circuit will tolerate transient inputs up to the absolute maximum rating. Inductor Selection and Maximum Output Current A good first choice for the inductor value is: L = 2 • (VOUT + VD) for the LT3506 L = (VOUT + VD) for the LT3506A where VD is the voltage drop of the catch diode (~0.4V) and L is in μH. With this value the maximum load current will be ~1.6A, independent of input voltage. The inductor’s RMS current rating must be greater than your maximum loadcurrentanditssaturationcurrentshouldbeabout30% higher.Tokeepefficiencyhigh,theseriesresistance(DCR) should be less than 0.1 W. Table 1 lists several vendors and types that are suitable. Of course, such a simple design guide will not always result in the optimum inductor for your application. A larger value provides a slightly higher maximum load current, and will reduce the output volt- age ripple. If your load is lower than 1.6A, then you can decrease the value of the inductor and operate with higher ripple current. This allows you to use a physically smaller inductor, or one with a lower DCR resulting in higher ef- ficiency. Be aware that if the inductance differs from the simple rule above, then the maximum load current will depend on input voltage. 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. Also, low inductance may result in dis- continuous mode operation, which may be acceptable, but further reduces maximum load current. For details of maximum output current and discontinuous mode opera- tion, see Linear Technology Application Note 44. Finally, for duty cycles greater than 50%(VOUT/VIN < 0.5), there is a minimum inductance required to avoid subharmonic oscillations. See Application Note 19 for detailed informa- tiononsubharmonicoscillations.Thefollowingdiscussion assumes continuous inductor current. |
Similar Part No. - LT3506IFE-PBF |
|
Similar Description - LT3506IFE-PBF |
|
|
|
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
