盛群新发表***启动电压的升压型DC/DC转换器 -- HT77XX

3/14/2005

HT77XX为盛群半导体推出的高效率升压型DC/DC转换器，利用CMOS制程以及PFM (Pulse Frequency Modulation) 技术，呈现低功耗及低噪音的***特性。藉由整合一低阻抗的功率晶体管，HT77XX仅需外接电感、电容及二极管等三个组件，就可以组成一个效***达85%的DC/DC转换电路，是低成本及省面积的升压解决方案。

本系列产品提供2.7V、3V、3.3V、3.7V及5V等五种输出电压，的特色是启动电压低至0.6V，再加上仅4微安的消耗电流 (IDD2)，使得HT77XX可以有效地延长电池寿命，广泛地应用于单颗或多颗碱性、锂离子及镍氢电池供电的手持式装置。

在封装方面提供有小巧的TO-92、SOT-89及SOT-25，其中SOT-25封装更增加关机功能，在此省电模式下，静态电流可进一步降至0.5微安培。

HT77XX -- PFM Step-up DC/DC Converter

General Description

The HT77XX series is a set of PFM step-up DC/DC converter with high efficiency and low ripple. The series features extremely low start-up voltage and high output voltage accuracy. They require only three external components to provide a fixed output voltage of 2.7V, 3.0V, 3.3V, 3.7V or 5.0V. CMOS technology ensures ultra low supply current and makes them ideal for battery-operated applications powered from one or more cells.

The HT77XX consists of an oscillator, a PFM control circuit, a driver transistor, a reference voltage unit, and a high speed comparator. They employ pulse frequency modulation (PFM) for minimum supply current and ripple at light output loading. These devices are available in space saving TO-92, SOT-89 and SOT-25 packages. For SOT-25 package, it also build-in a chip enable function to reduce power consumption during shutdown mode.