Datasheet > LM3687

LM3687

更新时间： 2024-11-15 04:44:23

品牌	Logo	应用领域
美国国家半导体 - NSC		转换器稳压器
页数	文件大小	规格书
22页	623K
描述
Step-Down DC-DC Converter with Integrated Low Dropout Regulator and Startup Mode

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LM3687 数据手册

December 4, 2007

LM3687

Step-Down DC-DC Converter with Integrated Low Dropout

Regulator and Startup Mode

General Description

Features

The LM3687 is a step-down DC-DC converter with an inte-

grated low dropout Linear Regulator optimized for powering

ultra-low voltage circuits from a single Li-Ion cell or 3 cell

NiMH/NiCd batteries. It provides a dual output with fixed out-

put voltages and combined load current up to 750mA in post

regulation mode or 1100mA in independent mode of opera-

tion, over an input voltage range from 2.7V to 5.5V. There are

several different fixed output voltage combinations available

(refer to table 'Voltage Options').

DC-DC Converter:

750mA maximum load capability

■

1.8MHz PWM fixed switching frequency (typ.)

Automatic PFM/PWM mode switching

27µA typ. Quiescent Current

Internal synchronous rectification for high efficiency

Internal soft start

Dual Rail Linear Regulator:

The Linear Regulator being driven from the fixed output volt-

age of the buck converter (post regulation) translates to high

efficiency.

Startup Mode

■

Load transients < 25mVpeak typ.

Line transients < 1mVpeak typ.

The device offers superior features and performance for mo-

bile phones and similar portable applications with complex

power management systems. Automatic intelligent switching

between PWM low-noise and PFM low-current mode offers

improved efficiency over the full load current range. During

full-power operation, a fixed-frequency 1.8MHz (typ.) PWM

mode drives loads from ~80mA to 750mA max. Hysteretic

PFM mode extends the battery life through reduction of the

quiescent current during light loads and system standby.

Very Low Dropout Voltage: 82mV typ. at 350mA load

current

0.7V ≤ V_{IN_LIN}≤ 4.5V

■

10µA typical I_Qfrom V_{IN_LIN}

350mA maximum load capability

Combined Common Features:

65µA typical Quiescent Current from V_BATTif both

regulators are enabled

■

The LM3687 also features internal protection against over-

temperature, current overload and under-voltage conditions.

750mA maximum combined load capability in post

regulation setup (DC-DC 400mA + Linear Regulator

350mA)

■

Two enable pins allow the separate operation of either the

DC-DC or the Linear Regulator alone or both. If the power

input voltage for the Linear Regulator V_{IN_LIN}is not sufficiently

high (e.g. the DC-DC converter is not enabled or starting up)

a startup LDO supplies the Linear Regulator Output from

V_BATTfor 50mA rated load current (Startup Mode). If V_{IN_LIN}

is at the required voltage level, the startup LDO is deactivated

and the main regulator provides 350mA output current. In

shutdown mode (Enable pins pulled low) the device turns off

and reduces battery consumption to 0.1µA (typ.).

1100mA maximum total load capability in independent

mode of operation (DC-DC: 750mA, Linear Regulator:

350mA)

■

Operates from a single Li-Ion cell or 3 cell NiMH/NiCd

batteries

■

Only four tiny surface-mount external components

required (one inductor, three ceramic capacitors)

■

Small 9-bump micro SMD package

■

The LM3687 is available in a tiny, lead-free (NO PB) 9-bump

micro SMD package. A high switching frequency of 1.8MHz

(typ.) allows the use of tiny surface-mount components. Only

four external components -one inductor and three ceramic

capacitors- are required.

Over-temperature, current overload and under-voltage

protection

Applications

Mobile Phones

■

Hand-Held Radios

Personal Digital Assistants

Palm-top PCs

Portable Instruments

Battery Powered Devices

202101

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与LM3687相关器件

型号	品牌	获取价格	描述	数据表
LM3687TL-1812	NSC	获取价格	Step-Down DC-DC Converter with Integrated Low Dropout Regulator and Startup Mode
LM3687TL-1812/NOPB	TI	获取价格	具有集成低压降稳压器和启动模式的降压直流/直流转换器 \| YZR \| 9
LM3687TL-1813	NSC	获取价格	Step-Down DC-DC Converter with Integrated Low Dropout Regulator and Startup Mode
LM3687TL-1815	NSC	获取价格	Step-Down DC-DC Converter with Integrated Low Dropout Regulator and Startup Mode
LM3687TL-1815/NOPB	TI	获取价格	具有集成低压降稳压器和启动模式的降压直流/直流转换器 \| YZR \| 9 \| -30 to
LM3687TLX-1812	NSC	获取价格	Step-Down DC-DC Converter with Integrated Low Dropout Regulator and Startup Mode
LM3687TLX-1812/NOPB	TI	获取价格	Step-Down DC-DC Converter with Integrated Low Dropout Regulator and Startup Mode 9-DSBGA
LM3687TLX-1813	NSC	获取价格	Step-Down DC-DC Converter with Integrated Low Dropout Regulator and Startup Mode
LM3687TLX-1815	NSC	获取价格	Step-Down DC-DC Converter with Integrated Low Dropout Regulator and Startup Mode
LM368H-10	NSC	获取价格	LM368-5.0 and LM368-10 Precision Voltage References

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