LM2645MTDNOPB National Semiconductor, LM2645MTDNOPB Datasheet

LM2645MTDNOPB

Manufacturer Part Number

LM2645MTDNOPB

Description

TSSOP48

Manufacturer

National Semiconductor

Datasheet

1.LM2645MTDNOPB.pdf (20 pages)

Specifications of LM2645MTDNOPB

Date_code

10+

Current page: 1 of 20
Download datasheet (912Kb)

LM2645

Advanced Two-Phase Switching Controller With Two

Linear Outputs

General Description

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.

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.

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.

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.

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.

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.

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.

DS200159

Features

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

n TSSOP package

SWITCHING SECTION

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

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

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

LINEAR SECTION

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

n Output UVP for adjustable linear regulator

n Fixed 3.3V/50mA output rail

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

adjustable outputs

PNP pass transistor

2% initial tolerance of set voltage

www.national.com

April 2005

Related parts for LM2645MTDNOPB

Related keywords

LM2645MTDNOPB datasheet
LM2645MTDNOPB data sheet
LM2645MTDNOPB pdf datasheet
LM2645MTDNOPB component
LM2645MTDNOPB part
LM2645MTDNOPB distributor
LM2645MTDNOPB RoHS
LM2645MTDNOPB datasheet download