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SS24 数据表(PDF) 6 Page - Monolithic Power Systems |
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SS24 数据表(HTML) 6 Page - Monolithic Power Systems |
6 / 11 page MP1591 – 2A, 32V, 330KHz STEP-DOWN CONVERTER MP1591 Rev. 2.3 www.MonolithicPower.com 6 9/27/2006 MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. © 2006 MPS. All Rights Reserved. The input capacitor value should be greater than 10µF. The capacitor can be electrolytic, tantalum or ceramic. However, since it absorbs the input switching current it requires an adequate ripple current rating. Its RMS current rating should be greater than approximately 1/2 of the DC load current. For insuring stable operation C1 should be placed as close to the IC as possible. Alternately, a smaller high quality ceramic 0.1µF capacitor may be placed closer to the IC and a larger capacitor placed farther away. If using this technique, it is recommended that the larger capacitor be a tantalum or electrolytic type. All ceramic capacitors should be placed close to the MP1591. Output Capacitor (C5) The output capacitor is required to maintain the DC output voltage. Low ESR capacitors are preferred to keep the output voltage ripple low. The characteristics of the output capacitor also affect the stability of the regulation control system. Ceramic, tantalum or low ESR electrolytic capacitors are recommended. In the case of ceramic capacitors, the impedance at the switching frequency is dominated by the capacitance, and so the output voltage ripple is mostly independent of the ESR. The output voltage ripple is estimated to be: 2 SW LC IN RIPPLE f f V 4 . 1 V ⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ × × ≅ Where VRIPPLE is the output ripple voltage, fLC is the resonant frequency of the LC filter, fSW is the switching frequency. In the case of tantalum or low-ESR electrolytic capacitors, the ESR dominates the impedance at the switching frequency, and so the output ripple is calculated as: ESR RIPPLE R I V × ∆ ≅ Where VRIPPLE is the output voltage ripple and RESR is the equivalent series resistance of the output capacitors. Output Rectifier Diode (D1) The output rectifier diode supplies the current to the inductor when the high-side switch is off. To reduce losses due to the diode forward voltage and recovery times, use a Schottky rectifier. Table 2 provides some recommended Schottky rectifiers based on the maximum input voltage and current rating. Table 2—Diode Selection Guide 2A Load Current 3A Load Current VIN (Max) Part Number Vendor Part Number Vendor 15V 30BQ15 4 B220 1 B320 1 SK23 6 SK33 1, 6 20V SR22 6 SS32 3 20BQ030 4 B330 1 B230 1 B340L 1 SK23 6 MBRD330 4, 5 SR23 3, 6 SK33 1, 6 30V SS23 2, 3 SS33 2, 3 21DQ04 4 B340L 1 MBRS240L 5 MBRS340 4 SK24 6 SK34 1, 6 34V SS24 2, 3 SS34 2, 3 Table 3 lists manufacturer’s websites. Table 3—Schottky Diode Manufacturers # Vendor Web Site 1 Diodes, Inc. www.diodes.com 2 Fairchild Semiconductor www.fairchildsemi.com 3 General Semiconductor www.gensemi.com 4 International Rectifier www.irf.com 5 On Semiconductor www.onsemi.com 6 Pan Jit International www.panjit.com.tw Choose a rectifier whose maximum reverse voltage rating is greater than the maximum input voltage, and whose current rating is greater than the maximum load current. |
类似零件编号 - SS24 |
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类似说明 - SS24 |
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