電荷泵解決更高的電壓應(yīng)用

　　在最基本的形式中，電荷泵是一種產(chǎn)生大于其工作電壓的電壓的電路。傳統(tǒng)上，電荷泵被認(rèn)為具有有限的電壓能力，提供性能，被視為在低壓差LDO和開(kāi)關(guān)調(diào)節(jié)器之間的距離填補(bǔ)利基。盡管如此，還是有一些好處使它們對(duì)某些應(yīng)用程序具有吸引力。例如，電荷泵提供更高的效率和良好的熱管理，并有靈活性，以提高電壓，降壓，或反轉(zhuǎn)輸入電壓。由于電荷泵使用電容器來(lái)存儲(chǔ)和傳遞能量，所以電荷泵也很簡(jiǎn)單，不需要電感，它的成本更高，輸出噪聲更高，輸出電流能力也常常降低。

　　隨著工藝技術(shù)的進(jìn)步，制造商已經(jīng)提高了這些設(shè)備的輸入電壓能力。集成電荷泵電路現(xiàn)在能夠驅(qū)動(dòng)低噪聲高壓運(yùn)算放大器（運(yùn)放）。它們也可以用來(lái)從一個(gè)電源提供雙極電源到高壓雙軌高壓運(yùn)放。它們可以產(chǎn)生足夠的功率來(lái)驅(qū)動(dòng)用于背光LCD面板的白光LED。

　　為了解決各種需要高電壓無(wú)電感的應(yīng)用需求，供應(yīng)商包括線性技術(shù)和集成，其中，已經(jīng)準(zhǔn)備好一系列的電荷泵。由于電荷泵輸出沒(méi)有得到很好的調(diào)節(jié)，一些供應(yīng)商提供調(diào)節(jié)電荷泵，這是集成片上低壓差穩(wěn)壓器（LDO）的副產(chǎn)品。

　　Typical examples

　　Linear Technology， for example， has developed two high voltage inverting monolithic charge pump ICs， the LTC3260 and LTC3261， for these applications.1 The LTC3261 is a high voltage inverting charge pump that can deliver up to 100 mA of output current， while the LTC3260 is an inverting charge pump that includes on-chip both positive and negative LDO regulators that can source up to 50 mA output current each.

　　The negative LDO post regulator is powered from the inverting charge pump output. The positive and negative LDO output voltages can be adjusted down to 1.2 and -1.2 V， respectively， using external resistor dividers. Both devices operate over a wide input voltage range of 4.5 to 32 V.

　　A typical application circuit generating ±12 V from a 15 V input is illustrated in Figure 1. As shown， it uses a few external resistors and ceramic capacitors for stability. Plus， the LTC3260 IC features soft-start circuitry to prevent excessive current flow during startup， and incorporates short circuit and thermal protection. The part comes in a low-profile 14-lead DFN package and a 16-lead MSOP package， both with a backside thermal pad. Operating junction temperature for the device is –40° to +125°C.