新型LM557x和LM2557x的SIMPLE SWITCHER降壓穩(wěn)壓器產(chǎn)品具有各種所需功能,使用最少數(shù)量的外部組件可以實(shí)現(xiàn)高效的高壓降壓穩(wěn)壓器。 新型穩(wěn)壓器工作的輸入電壓最高可達(dá)75V,并可提供高達(dá)3A的連續(xù)輸出電流。已獲專利的仿電流模式結(jié)構(gòu)在不能由傳統(tǒng)電流模式控制進(jìn)行編址的低占空比應(yīng)用下，提供了出色的負(fù)載瞬態(tài)響應(yīng)?？烧{(diào)工作頻率為50 kHz到1 MHz，可實(shí)現(xiàn)業(yè)界領(lǐng)先的動(dòng)態(tài)范圍。為了減少EMI，一個(gè)頻率同步的引腳允許此系列的多重IC實(shí)現(xiàn)自同步或與外部時(shí)鐘同步。新的穩(wěn)壓器具有逐周期電流限制、短路保護(hù)和熱關(guān)機(jī)功能，確保了其性能的魯棒性。 LM557x和LM2557x特性： • 6V至75V廣闊的電壓輸入范圍 • 50kHz到1MHz的可調(diào)開(kāi)關(guān)頻率 • 可調(diào)的軟啟動(dòng) • 各種輸出電流 o 0.5A （LM5574和LM25574） o 1.5A （LM5575和LM25575） o 3.0A （LM5576和LM25576） • 仿電流模式結(jié)構(gòu) o 出色的瞬態(tài)響應(yīng) o 超短的占空比 o 降低噪聲敏感度 WEBENCH®設(shè)計(jì)優(yōu)化程序 利用美國(guó)國(guó)家半導(dǎo)體的WEBENCH®在線設(shè)計(jì)環(huán)境，工程師可以在將尺寸和效率達(dá)到最優(yōu)化的同時(shí)縮短產(chǎn)品上市時(shí)間并確保設(shè)計(jì)質(zhì)量。每一個(gè)新款開(kāi)關(guān)穩(wěn)壓器都具有頻率可調(diào)和外部補(bǔ)償?shù)奶匦裕詽M足設(shè)計(jì)工程師對(duì)于產(chǎn)品性能、尺寸和集成度方面的要求。 original text： [COLOR=#708090]LM557x and LM2557x SIMPLE SWITCHER Regulators The new LM557x and LM2557x line of Simple Switcher buck regulators feature all of the functions necessary to implement an efficient, high-voltage buck regulator using a minimum of external components. The new regulators operate with an input voltage range up to 75V and deliver up to 3A of continuous output current. The patented emulated-current-mode architecture provides superior load transient response in low duty cycle applications that are not addressable by traditional current mode control. Operating frequency is adjustable from 50 kHz to 1 MHz, providing industry-leading dynamic range. To reduce EMI, a frequency synchronization pin allows multiple ICs from the family to self-synchronize or to synchronize to an external clock. The new regulators guarantee robustness with cycle-by-cycle current limit, short-circuit protection and thermal shut-down. LM557x and LM2557x Features: • Wide input voltage ranges from 6V to 75V • Adjustable switching frequencies between 50 kHz and 1 MHz • Adjustable soft-start • Various output currents o 0.5A （LM5574 and LM25574） o 1.5A （LM5575 and LM25575） o 3.0A （LM5576 and LM25576） • Emulated current mode architecture o Excellent transient response o Ultra-short duty cycle o Reduced noise sensitivity WEBENCH Design Optimizer Utilizing National‘s WEBENCH® online design environment, engineers can optimize for size and efficiency, while also realizing fast time-to-market and guaranteed design. Each of the new switching regulators features adjustable frequency and external compensation that enables the design engineer to “dial in” their performance, size and integration requirements. [/COLOR]