NSC LM2655MTCX-3.3, LM2655MTC-ADJ, LM2655MTC-3.3 Datasheet

February 2000

LM2655

2.5A High Efficiency Synchronous Switching Regulator

LM2655 2.5A High Efficiency Synchronous Switching Regulator

General Description

The LM2655 is a current-mode controlled PWM step-down switching regulator. It has the unique ability to operate in synchronous or asynchronous mode. This gives the designer flexibility to choose between the high efficiency of synchronous operation, or the low solution cost of asynchronous operation. Along with flexibility, the LM2655 offers high power density with the small footprint of a TSSOP-16 package.

High efficiency ( ternal low ON-resistance (33mΩ) MOSFET, and an external N-Channel MOSFET. This feature, together with its low quiescent current, makesthe LM2655 an ideal fit in portable applications.

Integrated in the LM2655 are all the power,control, and drive functions for asynchronous operation. In addition, a low-side driver output allows easy synchronous operation. The IC uses patented current sensing circuitry that eliminates the external current sensing resistor required by other currentmode DC-DC converters. A programmable soft-start feature limits start up current surges and provides a means of sequencing multiple power supplies.

>

90%) is obtained through the use of an in-

Typical Application

Features

n Ultra-high efficiency up to 96 n 4V to 14V input voltage range n Internal high-side MOSFET with low R n 300 kHz fixed frequency internal oscillator n Low-side drive for synchronous operation n Guaranteed less than 12 µA shutdown current n Patented current sensing for current mode control n Programmable soft-start n Input undervoltage lockout n Output overvoltage shutdown protection n Output undervoltage shutdown protection n Thermal Shutdown n 16-pin TSSOP package

%

= 0.033Ω

DS(ON)

Applications

n Hard disk drives n Internet appliances n TFT monitors n Computer peripherals n Battery powered devices

DS101284-29

Connection Diagram

LM2655

Block Diagram

16-Lead TSSOP (MTC)

DS101284-3

Top View

Order Number LM2655MTC-ADJ

See NS Package Number MTC16

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DS101284-4

Pin Description

Pin Name Function

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

MOSFET.

3-5 PV

6V 7AV

IN

CB

IN

8 SD(SS)

Main power supply input pin. Connected to the drain of the internal high-side MOSFET. Bootstrap capacitor connection for high-side gate drive. Input voltage for control and drive circuits. Shutdown control input, active low. This pin can also function as soft-start control pin.

Connect a capacitor from this pin to ground.

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 L

DELAY

A capacitor between this pin to ground sets the delay from when the output voltage

reaches 80%of its nominal to when the undervoltage latch protection is enabled. 12 LDR Low-side FET gate drive pin. 13 GND Power ground.

14-16 PV

IN

Main power supply input pin. Connected to the drain of the internal high-side MOSFET.

Ordering Information

LM2655

Supplied as 1000 units

Tape and Reel

Supplied as 3000 units,

Tape and Reel

LM2655MTC-3.3 LM2655MTCX-3.3

LM2655MTC-ADJ LM2655MTCX-ADJ

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Absolute Maximum Ratings (Note 1)

If Military/Aerospace specified devices are required,

LM2655

please contact the National Semiconductor Sales Office/ Distributors for availability and specifications.

Supply Voltage (PV Supply Voltage (AV

) 3.8V ≤ VIN≤ 14V

IN

) 4.0V ≤ VIN≤ 14V

IN

Feedback Pin Voltage -0.4V ≤ V V

Voltage, (Note 7) 7V

CB

C

Voltage 2.5V

SS

Comp Voltage 2.5V L

Voltage 2.5V

DELAY

LDR Voltage 5V V

, (Note 8) 14V

SW

LM2655-3.3 Electrical Characteristics

Specifications with standard typeface are for T Range.V

=

10V unless otherwise specified.

IN

Symbol Parameter Conditions

V

OUT

V

OUT

Output Voltage I

Output Voltage Line Regulation

Output Voltage Load Regulation

V

INUV

VINUndervoltage Lockout Threshold Voltage

V

UV_HYST

Hysteresis for the Input Undervoltage Lockout

I

(Note 9) Average Output Current

CL

Limit

=

J

LOAD

V I

LOAD

I

LOAD

V Rising Edge 3.8

V V

=

Power Dissipation (T

A

25˚C),

(Note 2)

TSSOP-16 Package θ

JA

140˚C/W

Power Dissapation 893mW

Lead Temperature

Vapor Phase (60 sec.) 215˚C

≤ 5V

FB

Infrared (15 sec.) 220˚C

ESD Susceptibility(Note 3)

Human Body Model(Note 4) 1kV Machine Model 200V

Operating Ratings (Note 1)

Storage Temperature Range −65˚C ≤ T Junction Temperature

Range −40˚C ≤ T

25˚C, and those in boldface type apply over full Operating Temperature

=

1.5 A 3.3

Typical

(Note 5)

Limit

(Note 6)

3.235/3.185

3.392/3.416

=

IN

=

IN

5V to 14V =

=

10V

1.5 A 100 mA to 2.5A

0.5

0.7

0.6

1.7

3.95

210 mV

IN OUT

=

5V

=

3.3V

3.3

≤ +150˚C

J

≤ +125˚C

J

Units

V(min)

V(max)

%

V(max)

V

%

(max)

%

(max)

V

A

LM2655-ADJ Electrical Characteristics

Specifications with standard typeface are for T Range.V

=

10V unless otherwise specified.

IN

Symbol Parameter Conditions

V

FB

V

OUT

Feedback Voltage I

Output Voltage Line Regulation

Output Voltage Load Regulation

V

INUV

VINUndervoltage Lockout Threshold Voltage

V

UV_HYST

Hysteresis for the Input Undervoltage Lockout

I

(Note 9) Average Output Current

CL

Limit

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=

25˚C, and those in boldface type apply over full Operating Temperature

J

=

1.5 A 1.238

LOAD

=

V

5V to 14V

IN

=

LOAD LOAD

IN

=

10V

1.5 A 100 mA to 2.5A

I I

V Rising Edge 3.8

=

V

5V

IN

=

OUT

3.3V

V

Typical

(Note 5)

Limit

(Note 6)

1.208/1.181

1.260/1.267

0.5

0.7

0.6

1.7

3.95

210 mV

3.3 A

Units

V

V(min)

V(max)

%

(max)

%

(max)

V

V(max)

All Output Voltage Versions Electrical Characteristics

Specifications with standard typeface are for T Range.V

=

10V unless otherwise specified.

IN

Symbol Parameter Conditions

I

Q

QSD

Quiescent Current Shutdown Pin Floating (Device On)

Quiescent Current in Shutdown Mode

R

DS(ON)

R

SW(ON)

Switch ON Resistance I

Switch On Resistance (MOSFET ON Resistance + Bonding Wire

Resistance) I V

L

BOOT

Switch Leakage Current 5 nA

Bootstrap Regulator

Voltage

G

M

Error Amplifier

Transconductance A

V

Error Amplifier Voltage

Gain I

EA_SOURCE

Error Amplifier Source

Current I

EA_SINK

V

EAH

Error Amplifier Sink Current VIN= 4V, VFB= 1.1*V

Error Amplifier Output

Swing Upper Limit V

EAL

Error Amplifier Output

Swing Lower Limit F

OSC

D

I

SS

V

MAX

OUTUV

Oscillator Frequency Measured at Switch Pin

Maximum Duty Cycle VIN=4V 95

Soft-Start Current Voltage at the SS Pin = 1.4V 11

V

Undervoltage

OUT

Lockout Threshold Voltage

V

OUTOV

Hysteresis for V

V

Overvoltage Lockout

OUT

OUTUV

Threshold Voltage

Hysteresis for V I

LDELAY__

SOURCE

I

SHUTDOWN

V

SHUTDOWN

LDELAY Pin Source

Current

Shutdown Pin Current Shutdown Pin Pulled Low 2.2

Shutdown Pin Threshold

OUTOV

Voltage

T

SD

Thermal Shutdown

Temperature T

SD_HYST

Thermal Shutdown

Hysteresis Temperature

=

25˚C, and those in boldface type apply over full Operating Temperature

J

Device Not Switching Shutdown Pin Pulled Low 7

= 1.5A 33

SWITCH

I

I C

VIN= 4V, VFB= .9*V

= 1.5A 72 mΩ

SWITCH

=1mA

BOOT

=tbd

BOOT

OUT,VCOMP

=

2V

OUT,VCOMP

=

2V VIN= 4V, VFB= .9*V

OUT,VCOMP

=

2V VIN= 4V, VFB= .9*V

OUT,VCOMP

=

2V

=4V

V

IN

Rising Edge 0.6

LM2655

Typical

(Note 6)

1.7

6.7

1250 µmho

100

40

80

2.70

1.25

300

81

5

108

5 5µA

165 ˚C

25 ˚C

Limit

(Note 5)

3

12/20

80

6.4

7.0

32/10

53/30

2.50/2.40

1.35/1.50

280/255 330/345

92

14

76 84

106 114

3.7/4.0

0.25

0.9

Units

mA

mA(max)

µA

µA(max)

mΩ

mΩ(max)

V

V(min)

V(max)

µA

µA(min)

µA

µA(min)

V

V(min)

V

V(max)

kHz

kHz(min)

kHz(max)

%

(min)

µA

µA(max)

%

V

%

V

OUT

%

V

OUT

%

V

%

V

%

V

OUT

%

V

OUT

%

V

µA

µA(max)

V

V(min)

V(max)

OUT

(min)

(max)

OUT OUT

(min)

(max)

OUT

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