 |
Electronic Components Datasheet Search |
|
|
Electronic Components Datasheet Search |
|
LT1767EMS8-1.8 Datasheet(PDF) 8 Page - Linear Technology |
|
||||||||||||||||||||||||||||||
LT1767EMS8-1.8 Datasheet(HTML) 8 Page - Linear Technology |
|
|
8 / 16 page  8 LT1767/LT1767-1.8/ LT1767-2.5/LT1767-3.3/LT1767-5 sn1767 1767fas APPLICATIONS INFORMATION Figure 3. Output Ripple Voltage Waveform and reduces the current at which discontinuous operation occurs. The following formula gives maximum output current for continuous mode operation, implying that the peak to peak ripple (2x the term on the right) is less than the maximum switch current. Continuous Mode IOUT MAX () = IP − () − () ()( )( ) VV V Lf V OUT IN OUT IN 2 Discontinuous operation occurs when I V Lf OUT DIS OUT () () ()( ) = 2 For VIN = 8V, VOUT = 5V and L = 3.3µH, I A OUT MAX () − =− () − () ()( )() =− = 15 58 5 2 3 3 10 1 25 10 8 15 0 23 1 27 66 . .• . • .. . Note that the worst case (minimum output current avail- able) condition is at the maximum input voltage. For the same circuit at 15V, maximum output current would be only 1.1A. When choosing an inductor, consider maximum load current, core and copper losses, allowable component height, output voltage ripple, EMI, fault current in the inductor, saturation, and of course, cost. The following procedure is suggested as a way of handling these some- what complicated and conflicting requirements. 1. Choose a value in microhenries from the graphs of maximum load current. Choosing a small inductor with lighter loads may result in discontinuous mode of operation, but the LT1767 is designed to work well in either mode. Assume that the average inductor current is equal to load current and decide whether or not the inductor must withstand continuous fault conditions. If maxi- mum load current is 0.5A, for instance, a 0.5A inductor may not survive a continuous 2A overload condition. Also, the instantaneous application of input or release from shutdown, at high input voltages, may cause INDUCTOR CHOICE AND MAXIMUM OUTPUT CURRENT Maximum output current for a buck converter is equal to the maximum switch rating (IP) minus one half peak to peak inductor current. In past designs, the maximum switch current has been reduced by the introduction of slope compensation. Slope compensation is required at duty cycles above 50% to prevent an affect called subharmonic oscillation (see Application Note 19 for details). The LT1767 has a new circuit technique that maintains a constant switch current rating at all duty cycles. (Patent Pending) For most applications, the output inductor will be in the 1 µH to 10µH range. Lower values are chosen to reduce the physical size of the inductor, higher values allow higher output currents due to reduced peak to peak ripple current, Table 2. Surface Mount Solid Tantalum Capacitor ESR and Ripple Current E Case Size ESR (Max, Ω) Ripple Current (A) AVX TPS, Sprague 593D 0.1 to 0.3 0.7 to 1.1 AVX TAJ 0.7 to 0.9 0.4 D Case Size AVX TPS, Sprague 593D 0.1 to 0.3 0.7 to 1.1 C Case Size AVX TPS 0.2 (typ) 0.5 (typ) Figure 3 shows a comparison of output ripple for a ceramic and tantalum capacitor at 200mA ripple current. VOUT USING 47µF, 0.1Ω TANTALUM CAPACITOR (10mV/DIV) 0.2 µs/DIV 1767 F03 VOUT USING 2.2µF CERAMIC CAPACITOR (10mV/DIV) VSW (5V/DIV) |
Similar Part No. - LT1767EMS8-1.8 |
|
Similar Description - LT1767EMS8-1.8 |
|
|
|
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
