摘要：MAX5073是一款可工作于降壓或升壓模式的雙路轉(zhuǎn)換器。作為雙路降壓轉(zhuǎn)換器工作時(shí)，該器件兩路輸出可分別提供高達(dá)2A和1A的輸出電流。該參考設(shè)計(jì)主要說(shuō)明MAX5073作為降壓轉(zhuǎn)換器、工作于2MHz開關(guān)頻率的應(yīng)用。高開關(guān)頻率允許使用更小尺寸的無(wú)源元件，并工作在汽車應(yīng)用中AM波段以外的頻率。
本文給出了采用MAX5073雙通道降壓型轉(zhuǎn)換器、工作于2MHz開關(guān)頻率下的詳細(xì)參考設(shè)計(jì)。該設(shè)計(jì)可用于電路板空間受限的應(yīng)用，因?yàn)檩^高的開關(guān)頻率允許采用更小尺寸的無(wú)源元件。此外，該電源解決方案可用于汽車電子(帶有拋負(fù)載保護(hù))，即需要開關(guān)頻率工作在AM調(diào)頻波段以外的產(chǎn)品。例如，汽車儀表盤和信息娛樂(lè)系統(tǒng)。
該參考設(shè)計(jì)的關(guān)鍵規(guī)格在下面列出，并給出了應(yīng)用所需的詳細(xì)原理圖(圖1)及材料清單(表1)。
規(guī)格
輸入電壓：5.5V至16V
第1路轉(zhuǎn)換器輸出電壓 = 3.3V/2A (最大值)
第2路轉(zhuǎn)換器輸出電壓 = 2.5V/1A (最大值)
每路轉(zhuǎn)換器的開關(guān)頻率(fSW) = 2MHz
環(huán)境溫度(TA) = -40°C至+85°C
圖1. MAX5073參考設(shè)計(jì)
表1. 材料清單
| Designator | Value | Description | Part | Footprint | Manufacturer | Quantity |
| C1 | 100µF/35V | Capacitor | EEVFK1V101P | 8mm x 10.2mm | Panasonic | 1 |
| C2, C3, C4, C17, C18 | 0.1µF/25V | Capacitors | GRM188R71E104KA01D | 603 | Murata | 5 |
| C5, C6, C7 | 22µF/6.3V | Capacitors | GRM31CR60J226KE19 | 1206 | Murata | 2 |
| C8, C9 | 10µF/25V | Capacitors | GRM31CR61E106KA12 | 1206 | Murata | 1 |
| C10, C12 | 2.2nF | Capacitors | GRM188R71H222JA01 | 603 | Murata | 2 |
| C11 | 560pF | Capacitor | GRM188R71H561KA01 | 603 | Murata | 1 |
| C13, C14 | 22pF | Capacitors | GRM1885C1H220JA01 | 603 | Murata | 2 |
| C15 | 1nF | Capacitor | GRM18871H102KA01 | 603 | Murata | 1 |
| C16 | 4.7µF/6.3V | Capacitor | GRM188R60J475KE19B | 603 | Murata | 1 |
| C19 | 0.22µF/10V | Capacitor | GRM188R71A224KA01 | 603 | Murata | 1 |
| C20 | 0.01µF | Capacitor | GRM188R71H103KA01J | 603 | Murata | 1 |
| D1, D2 | 30V, 500mA | Schottky diodes | MBR0530 | SOD123 | ON Semiconductor | 2 |
| D3 | 40V, 3A | Schottky diode | MBRS340 | SMC | ON Semiconductor | 1 |
| D4 | 40V, 2A | Schottky diode | MBRS240 | SMB | ON Semiconductor | 1 |
| L1, L2 | 4.7µH | Inductors | IHLP2525-CZ | 6.86mm x 6.47mm x 3.18mm | Vishay | 1 |
| R1, R11 | 100kΩ | Resistors | SMD, 1%, 0.125W | 603 | Vishay | 2 |
| R2 | 6.8Ω | Resistor | SMD, 1%, 0.125W | 603 | Vishay | 1 |
| R3 | 4.7Ω | Resistor | SMD, 1%, 0.125W | 603 | Vishay | 1 |
| R4, R8, R10 | 1.18kΩ | Resistors | SMD, 1%, 0.125W | 603 | Vishay | 3 |
| R5, R9 | 27.4kΩ | Resistors | SMD, 1%, 0.125W | 603 | Vishay | 2 |
| R6 | 10kΩ | Resistor | SMD, 1%, 0.125W | 603 | Vishay | 1 |
| R7 | 12.7kΩ | Resistor | SMD, 1%, 0.125W | 603 | Vishay | 1 |
| R12 | 2.2Ω | Resistor | SMD, 1%, 0.125W | 603 | Vishay | 1 |
| R13 | 6.19kΩ | Resistor | SMD, 1%, 0.125W | 603 | Vishay | 1 |
| R14 | 8.76kΩ | Resistor | SMD, 1%, 0.125W | 603 | Vishay | 1 |
| U1 | MAX5073 | Dual buck converter | MAX5073ETI+ | 32-TQFN_EP (5mm x 5mm) | Maxim | 1 |
實(shí)際測(cè)量電路獲得的數(shù)據(jù)給出了器件的效率指標(biāo)，詳細(xì)內(nèi)容參見表2和表3。
表2. VOUT2禁止時(shí)的效率指標(biāo)
fSW = 2MHz、LOUT = 4.7µH、COUT = 22µF/6.3V (陶瓷電容)
| VIN (V) | IIN (A) | VOUT1 (V) | IOUT1 (A) | Efficiency (%) |
| 14.007 | 0.065732 | 3.3371 | 0.1018 | 36.8973371 |
| 14.010 | 0.183690 | 3.3339 | 0.5122 | 66.3542117 |
| 14.005 | 0.267750 | 3.3321 | 0.8032 | 71.3722082 |
| 14.007 | 0.329490 | 3.3309 | 1.0112 | 72.9812485 |
| 14.005 | 0.449290 | 3.3298 | 1.4007 | 74.1230723 |
| 14.002 | 0.584520 | 3.3281 | 1.8203 | 74.0201375 |
| 14.001 | 0.650260 | 3.3267 | 2.0150 | 73.6279304 |
表3. VOUT1禁止時(shí)的效率指標(biāo)
fSW = 2MHz、LOUT = 4.7µH、COUT = 22µF/6.3V (陶瓷電容)
| VIN (V) | IIN (A) | VOUT2 (V) | IOUT2 (A) | Efficiency (%) |
| 14.008 | 0.044533 | 2.5350 | 0.1075 | 43.6845979 |
| 14.008 | 0.067144 | 2.5337 | 0.2049 | 55.1967881 |
| 14.003 | 0.087638 | 2.5337 | 0.3010 | 62.1452787 |
| 14.004 | 0.109076 | 2.5337 | 0.4003 | 66.3986847 |
| 14.005 | 0.133680 | 2.5337 | 0.5122 | 69.3178710 |
| 14.005 | 0.155350 | 2.5338 | 0.6097 | 71.0058542 |
| 14.008 | 0.255976 | 2.5334 | 1.0001 | 70.6597037 |
在穩(wěn)定性方面，圖2和圖3所示為每路輸出的波特圖，詳細(xì)說(shuō)明了每路輸出的增益和相位。
圖2. 3.3V/1.4A VOUTPUT波特圖
圖3. 2.5V/0.6A VOUTPUT波特圖