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LTC3125 Datasheet(PDF) 11 Page - Linear Technology |
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LTC3125 Datasheet(HTML) 11 Page - Linear Technology |
11 / 18 page LTC3125 11 3125fa APPLICATIONS INFORMATION power losses compared to cheaper powdered iron types, improving efficiency. The inductor should have low DCR (DC resistance of the windings) to reduce the I2R power losses, and must be able to support the peak inductor current without saturating. Molded chokes and some chip inductors usually do not have enough core area to support the peak inductor currents of 1.8A seen on the LTC3125. To minimize radiated noise, use a shielded inductor. See Table 1 for suggested components and suppliers. Table 1. Recommended Inductors VENDOR PART/STYLE Coilcraft (847) 639-6400 www.coilcraft.com LPO2506 LPS4012, LPS4018 MSS6122 MSS4020 MOS6020 DS1605, DO1608 Coiltronics www.cooperet.com SD52, SD53, SD3114, SD3118 Murata (714) 852-2001 www.murata.com LQH55D Sumida (847) 956-0666 www.sumida CDH40D11 Taiyo-Yuden www.t-yuden.com NP04SB NR3015 NR4018 TDK (847) 803-6100 www.component.tdk.com VLP, LTF VLF, VLCF Wurth (201) 785-8800 www.we-online.com WE-TPC Type S, M, MH, MS Output and Input Capacitor Selection When selecting output capacitors for large pulsed loads, the magnitude and duration of the pulsing current, together with the ripple voltage specification, determine the choice of the output capacitor. Both the ESR of the capacitor and the charge stored in the capacitor each cycle contribute to the output voltage ripple. The ripple due to the charge is approximately: VRIPPLE (mV)= IPULSE –ISTANDBY ()•t ON COUT where IPULSE and tON are the peak current and on time during transmission burst and ISTANDBY is the current in standby mode. The above is a worst-case approximation assuming all the pulsing energy comes from the output capacitor. The ripple due to the capacitor ESR is: VRIPPLE_ESR = (IPULSE – ISTANDBY) • ESR Low ESR and high capacitance are critical to maintain low output voltage ripple. Typically, two low profile 2200μF parallel Vishay TANTAMOUNT ® tantalum, low ESR capaci- tors are used. The capacitor has less than 40m Ω ESR. These capacitors can be used in parallel for even larger capacitance values. For applications requiring very high capacitance, the GS, GS2 and GW series from Cap-XX, the BestCapTM series from AVX and PowerStor® Aerogel Capacitors from Cooper all offer very high capacitance and low ESR in various package options. Table 2 shows a list of several reservoir capacitor manufacturers. Multilayer ceramic capacitors are an excellent choice for input decoupling of the step-up converter as they have extremely low ESR and are available in small footprints. Input capacitors should be located as close as possible to the device. While a 10μF input capacitor is sufficient for most applications, larger values may be used to re- duce input current ripple without limitations. Consult the manufacturers directly for detailed information on their selection of ceramic capacitors. Although ceramic capaci- tors are recommended, low ESR tantalum capacitors may be used as well. Table 2. Capacitor Vendor Information SUPPLIER PHONE WEBSITE Vishay (402) 563-6866 www.vishay.com AVX (803) 448-9411 www.avxcorp.com Cooper Bussman (516) 998-4100 www.cooperbussman.com Cap-XX (843) 267-0720 www.cap-xx-com Panasonic (800) 394-2112 www.panasonic.com |
Similar Part No. - LTC3125_15 |
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Similar Description - LTC3125_15 |
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