NSC LM2651MTCX-2.5, LM2651MTCX-1.8, LM2651MTC-2.5, LM2651MTC-1.8, LM2651MTCX-ADJ Datasheet

LM2651

1.5A High Efficiency Synchronous Switching Regulator

General Description

The LM2651 switching regulator provides high efficiency
power conversion over a 100:1 load range (1.5A to 15mA).
This feature makes the LM2651 an ideal fit in
battery-powered applications that demand long battery life in
both run and standby modes.

Synchronous rectification is used to achieve up to 97%effi­ciency.At light loads, the LM2651 enters a low power hyster­etic or “sleep” mode to keep the efficiency high. In many ap­plications, the efficiency still exceeds 80%at 15mA load. A
shutdown pin is available to disable the LM2651 and reduce
the supply current to less than 10µA.

The LM2651 containsa patented current sensing circuitry for
current mode control. This feature eliminates the external
current sensing resistor required by other current-mode
DC-DC converters.

The LM2651 has a 300 kHz fixed frequency internal oscilla­tor.The high oscillator frequency allows the use of extremely
small, low profile components.

A programmable soft-start feature limits current surges from
the input power supply at start up and provides a simple
means of sequencing multiple power supplies.

Other protection features include input undervoltage lockout,
current limiting, and thermal shutdown.

Features

n Ultra high efficiency up to 97

%

n High efficiency over a 1.5A to milliamperes load range
n 4V to 14V input voltage range
n 1.8V, 2.5V, 3.3V, or ADJ output voltage
n Internal MOSFET switch with low R

DS(on)

of 75mΩ

n 300kHz fixed frequency internal oscillator
n 7µA shutdown current
n Patented current sensing for current mode control
n Input undervoltage lockout
n Adjustable soft-start
n Current limit and thermal shutdown
n 16-pin TSSOP package

Applications

n Personal digital assistants (PDAs)
n Computer peripherals
n Battery-powered devices
n Handheld scanners
n High efficiency 5V conversion

Typical Application

DS100925-15

Efficiency vs Load Current

(V

IN

=

5V, V

OUT

=

3.3V)

DS100925-1

February 2000

LM2651 1.5A High Efficiency Synchronous Switching Regulator

© 2000 National Semiconductor Corporation DS100925 www.national.com

Connection Diagram

Ordering Information

V

OUT

Part Number

Package Type

NSC Package

Drawing

Supplied as 94 Units, Rail Supplied as 2.5k Units, Tape

and Reel

1.8 LM2651MTC-1.8 LM2651MTCX-1.8
TSSOP-16 MTC16

2.5 LM2651MTC-2.5 LM2651MTCX-2.5

3.3 LM2651MTC-3.3 LM2651MTCX-3.3

ADJ LM2651MTC-ADJ LM2651MTCX-ADJ

Pin Description

Pin Name Function

1, 2 SW Switched-node connection, which is connected with the source of the internal high-side

MOSFET.

3-5 VIN Main power supply pin.

6 VCB Bootstrap capacitor connection for high-side gate drive.
7 AVIN Input supply voltage for control and driver circuits.
8 SD(SS)

Shutdown control input, active low. This pin can also function as soft-start control pin. A
capacitor connected from this pin to ground sets the ramp time to full current output.

9 FB Output voltage feedback input. Connected to the output voltage.

10 COMP Compensation network connection. Connected to the output of the voltage error

amplifier.

11 NC No internal connection.
12-13 AGND Low-noise analog ground.
14-16 PGND Power ground.

16-Lead TSSOP (MTC)

DS100925-2

LM2651

www.national.com 2

Absolute Maximum Ratings (Note 1)

If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.

Input Voltage 15V
Feedback Pin Voltage −0.4V ≤ V

FB

≤ 5V

Power Dissipation (T

A

=

25˚C),

(Note 2)

893 mW

Junction Temperature Range −40˚C ≤ T

J

≤ +125˚C

Storage Temperature Range −65˚C to +150˚C
ESD Susceptibility

Human Body Model (Note 3) 1kV

Operating Ratings (Note 1)

Supply Voltage 4V ≤ V

IN

≤ 14V

Electrical Characteristics Specifications in standard type face are for T

J

=

25˚C and those with boldface

type apply over full operating junction temperature range. V

IN

=

10V unless otherwise specified.

LM2651-1.8 System Parameters

Symbol Parameter Conditions Typical Limit Units

V

OUT

Output Voltage I

LOAD

=

900 mA 1.8 1.761/1.719

1.836/1.854

V

V(min)

V(max)

V

OUT

Output Voltage Line
Regulation

V

IN

=

4V to 14V

I

LOAD

=

900 mA

0.2

%

V

OUT

Output Voltage Load
Regulation

I

LOAD

=

10 mA to 1.5A

V

IN

=

5V

1.3

%

V

OUT

Output Voltage Load
Regulation

I

LOAD

=

200 mA to 1.5A

V

IN

=

5V

0.3

%

V

HYST

Sleep Mode Output Voltage
Hysteresis

35 mV

LM2651-2.5 System Parameters

Symbol Parameter Conditions Typical Limit Units

V

OUT

Output Voltage I

LOAD

=

900 mA 2.5

2.43/2.388

2.574/2.575

V

V(min)

V(max)

V

OUT

Output Voltage Line
Regulation

V

IN

=

4V to 12V

I

LOAD

=

900 mA

0.2

%

V

OUT

Output Voltage Load
Regulation

I

LOAD

=

10 mA to 1.5A

V

IN

=

5V

1.3

%

V

OUT

Output Voltage Load
Regulation

I

LOAD

=

200 mA to 1.5A

V

IN

=

5V

0.3

%

V

HYST

Sleep Mode Output Voltage
Hysteresis

48 mV

LM2651-3.3 System Parameters

Symbol Parameter Conditions Typical Limit Units

V

OUT

Output Voltage I

LOAD

=

900 mA 3.3

3.265/3.201

3.379/3.399

V

V(min)

V(max)

V

OUT

Output Voltage Line
Regulation

V

IN

=

4V to 14V

I

LOAD

=

900 mA

0.2

%

V

OUT

Output Voltage Load
Regulation

I

LOAD

=

10 mA to 1.5A

V

IN

=

5V

1.3

%

V

OUT

Output Voltage Load
Regulation

I

LOAD

=

200 mA to 1.5A

V

IN

=

5V

0.3

%

LM2651

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