Datasheet > LM2645

LM2645

更新时间： 2024-11-23 00:01:07

品牌	Logo	应用领域
美国国家半导体 - NSC		开关控制器
页数	文件大小	规格书
21页	483K
描述
Advanced Two-Phase Switching Controller With Two Linear Outputs

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LM2645 数据手册

April 2001

LM2645

Advanced Two-Phase Switching Controller With Two

Linear Outputs

General Description

Features

The LM2645 is a feature-rich IC that combines two current

mode synchronous buck regulator controllers, an adjustable

linear regulator controller and a fixed 3.3V standby output

rail.

GENERAL

n 4.5V to 30V input range

n Power good function

n Input under-voltage lockout

n 10 µA Shutdown/Recycle for entire chip

n Thermal shutdown

The two switching regulator controllers operate 180˚ out of

phase. This feature reduces the input ripple RMS current,

thereby significantly reducing the required input capacitance.

The two switching regulator outputs can also be paralleled to

operate as a dual-phase regulator.

n TSSOP package

SWITCHING SECTION

n Two synchronous buck regulators for fixed 5V/3.3V or

adjustable outputs

The use of synchronous rectification and pulse-skip opera-

tion at light load achieves high efficiency over a wide load

range. Fixed-frequency operation can be obtained by dis-

abling the pulse-skip mode. The switching frequency of the

LM2645 is user selectable between 200 kHz or 300 kHz.

n Outputs adjustable from 1.3V to 5.5V

n 0.04% (typical) line and load regulation error

n Selectable switching frequency 200/300 kHz

n Two channels operating 180˚ out of phase

n Separate on/off for each channel

The first switching controller (Channel 1) features a fixed 5V

output, and the second switching controller controller (Chan-

nel 2) features a fixed 3.3V output. Both channels can also

be independently adjusted from 1.3 to 5.5V. The adjustable

linear regulator can be adjusted from 3.3V to 15V. An internal

5V rail is also available externally for driving bootstrap cir-

cuitry. This rail also serves as the input for an internal LDO

that provides the fixed 3.3V/50mA output rail.

n Separate Power Good signals

n Current mode control with or without sense resistor

n Adjustable cycle-by-cycle current limit

n Skip-mode operation available

n Negative current limit

n Separate soft start for each channel

n Output UVP and OVP

n Programmable output UVP delay

n Self discharge of output capacitors when turned off

Current-mode feedback control assures excellent line and

load regulation and a wide loop bandwidth for excellent

response to fast load transients. Current is sensed across

either the Vds of the top FET or across an external sense

resistor connected in series with the drain of the top FET.

Current limit is independently adjustable for each channel.

LINEAR SECTION

n Adjustable (3.3V to 15V) linear regulator with external

PNP pass transistor

The analog soft-start for the switching controllers uses an

innovative new approach. It is independent of the input

voltage which makes the soft-start behavior more predict-

able and controllable.

2% initial tolerance of set voltage

n Output UVP for adjustable linear regulator

n Fixed 3.3V/50mA output rail

Independant PGOOD signals monitor each of the switching

regulator outputs. The switching outputs have under-voltage

and over-voltage latch protection, while the output of the

external linear regulator has undervoltage latch protection.

The undervoltage latch can be disabled or adjustably de-

layed.

n Fixed 5V reference rail

Applications

n Notebook and sub-notebook computers

n Embedded computer systems

n Battery-powered instruments

n High end gaming systems

n Set-top boxes

n WebPAD

DS200159

www.national.com

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中文翻译

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与LM2645相关器件

型号	品牌	获取价格	描述	数据表
LM2645MTD	NSC	获取价格	Advanced Two-Phase Switching Controller With Two Linear Outputs
LM2647	NSC	获取价格	Dual Synchronous Buck Regulator Controller
LM2647	TI	获取价格	LM2647 Dual Synchronous Buck Regulator Controller
LM2647_15	TI	获取价格	LM2647 Dual Synchronous Buck Regulator Controller
LM2647LQ	NSC	获取价格	Dual Synchronous Buck Regulator Controller
LM2647LQ/NOPB	TI	获取价格	LM2647 Dual Synchronous Buck Regulator Controller
LM2647LQX	NSC	获取价格	Dual Synchronous Buck Regulator Controller
LM2647LQX/NOPB	TI	获取价格	Dual Synchronous Buck Regulator Controller 28-WQFN -5 to 125
LM2647MTC	NSC	获取价格	Dual Synchronous Buck Regulator Controller
LM2647MTC	TI	获取价格	DUAL SWITCHING CONTROLLER, 345kHz SWITCHING FREQ-MAX, PDSO28, TSSOP-28

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