新型LM557x和LM2557x的SIMPLE SWITCHER降壓穩壓器產品具有各種所需功能,使用最少數量的外部組件可以實現高效的高壓降壓穩壓器。 新型穩壓器工作的輸入電壓最高可達75V,并可提供高達3A的連續輸出電流。已獲專利的仿電流模式結構在不能由傳統電流模式控制進行編址的低占空比應用下，提供了出色的負載瞬態響應?？烧{工作頻率為50 kHz到1 MHz，可實現業界領先的動態范圍。為了減少EMI，一個頻率同步的引腳允許此系列的多重IC實現自同步或與外部時鐘同步。新的穩壓器具有逐周期電流限制、短路保護和熱關機功能，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的可調開關頻率 • 可調的軟啟動 • 各種輸出電流 o 0.5A （LM5574和LM25574） o 1.5A （LM5575和LM25575） o 3.0A （LM5576和LM25576） • 仿電流模式結構 o 出色的瞬態響應 o 超短的占空比 o 降低噪聲敏感度 WEBENCH®設計優化程序 利用美國國家半導體的WEBENCH®在線設計環境，工程師可以在將尺寸和效率達到最優化的同時縮短產品上市時間并確保設計質量。每一個新款開關穩壓器都具有頻率可調和外部補償的特性，以滿足設計工程師對于產品性能、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]