National Semiconductor LM3151, LM3152, LM3153 Technical data

October 17, 2008

LM3151/LM3152/LM3153
SIMPLE SWITCHER® CONTROLLER, 42V Synchronous
Step-Down

LM3151/LM3152/LM3153 SIMPLE SWITCHER

General Description

The LM3151/2/3 SIMPLE SWITCHER® Controller is an easy
to use and simplified step down power controller capable of
providing up to 12A of output current in a typical application.
Operating with an input voltage range of 6V-42V, the
LM3151/2/3 features a fixed output voltage of 3.3V, and fea­tures switching frequencies of 250 kHz, 500 kHz, and 750
kHz. The synchronous architecture provides for highly effi­cient designs. The LM3151/2/3 controller employs a Constant
On-Time (COT) architecture with a proprietary Emulated Rip­ple Mode (ERM) control that allows for the use of low ESR
output capacitors, which reduces overall solution size and
output voltage ripple. The Constant On-Time (COT) regula­tion architecture allows for fast transient response and re­quires no loop compensation, which reduces external com­ponent count and reduces design complexity.

Fault protection features such as thermal shutdown, under­voltage lockout, over-voltage protection, short-circuit protec­tion, current limit, and output voltage pre-bias startup allow for
a reliable and robust solution.

The LM3151/2/3 SIMPLE SWITCHER® concept provides for
an easy to use complete design using a minimum number of
external components and National’s WEBENCH® online de­sign tool. WEBENCH® provides design support for every step
of the design process and includes features such as external
component calculation with a new MOSFET selector, electri­cal simulation, thermal simulation, and Build-It boards for
prototyping.

Features

PowerWise® step-down controller

■

6V to 42V Wide input voltage range

■

Fixed output voltage of 3.3V

■

Fixed switching frequencies of 250 kHz/500 kHz/750 kHz

■

No loop compensation required

■

Fully WEBENCH® enabled

■

Low external component count

■

Constant On-Time control

■

Ultra-Fast transient response

■

Stable with low ESR capacitors

■

Output voltage pre-bias startup

■

Valley current limit

■

Programmable soft-start

■

Typical Applications

Telecom

■

Networking Equipment

■

Routers

■

Security Surveillance

■

Power Modules

■

®

CONTROLLER, 42V Synchronous Step-Down

Typical Application

30053201

SIMPLE SWITCHER® is a registered trademark of National Semiconductor Corporation

© 2008 National Semiconductor Corporation 300532 www.national.com

Connection Diagram

LM3151/LM3152/LM3153

Pin Descriptions

Pin Name Description Function

1 VCC

2 VIN Input Supply Voltage

3 EN Enable

4 FB Feedback

5,9 SGND Signal Ground

6 SS Soft-Start

7,8 N/C Not Connected

10 SW Switch Node

11 HG

12 BST

13 LG Low-Side Gate Drive

14 PGND Power Ground

EP EP Exposed Pad

Supply Voltage for

FET Drivers

High-Side Gate

Drive

Connection for

Bootstrap Capacitor

Nominally regulated to 5.95V. Connect a 1 µF to 2.2 µF decoupling capacitor from this
pin to ground.

Supply pin to the device. Nominal input range is 6V to 42V. See ordering information
for Vin limitations.

To enable the IC apply a logic high signal to this pin greater than 1.26V typical or leave
floating. To disable the part, ground the EN pin.

Internally connected to the resistor divider network which sets the fixed output voltage.
This pin also senses the output voltage faults such a over-voltage and short circuit
conditions.

Ground for all internal bias and reference circuitry. Should be connected to PGND at a
single point.

An internal 7.7 µA current source charges an external capacitor to provide the soft-start
function.

Internally not electrically connected. These pins may be left unconnected or connected
to ground.

Switch pin of controller and high-gate driver lower supply rail. A boost capacitor is also
connected between this pin and BST pin

Gate drive signal to the high-side NMOS switch. The high-side gate driver voltage is
supplied by the differential voltage between the BST pin and SW pin.

High-gate driver upper supply rail. Connect a 0.33 µF-0.47 µF capacitor from SW pin to
this pin. An internal diode charges the capacitor during the high-side switch off-time. Do
not connect to an external supply rail.

Gate drive signal to the low-side NMOS switch. The low-side gate driver voltage is
supplied by VCC.

Synchronous rectifier MOSFET source connection. Tie to power ground plane. Should
be tied to SGND at a single point.

Exposed die attach pad should be connected directly to SGND. Also used to help
dissipate heat out of the IC.

eTSSOP-14

30053202

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Ordering Information

LM3151/LM3152/LM3153

Order Number Package Type NSC Package

Drawing

LM3151MH-3.3

LM3151MHE-3.3 250 Units in Tape and

LM3151MHX-3.3 2500 Units in Tape and

LM3152MH-3.3

LM3152MHE-3.3 250 Units in Tape and

LM3152MHX-3.3 2500 Units in Tape and

LM3153MH-3.3

LM3153MHE-3.3 250 Units in Tape and

LM3153MHX-3.3 2500 Units in Tape and

LM3151MH-2.5

LM3151MHE-2.5

LM3151MHX-2.5

LM3152MH-2.5

LM3152MHX-2.5

LM3153MH-2.5

LM3153MHX-2.5

LM3151MH-5.0

LM3151MHX-5.0

LM3152MH-5.0

LM3152MHX-5.0

LM3153MH-5.0

LM3153MHX-5.0

eTSSOP-14 MXA14A 6V - 42V 3.3V 250KHz

eTSSOP-14 MXA14A 6V - 33V 3.3V 500KHz

eTSSOP-14 MXA14A 8V - 18V 3.3V 750KHz

eTSSOP-14 MXA14A

eTSSOP-14 MXA14A

Input

Voltage

Range

*

* 500KHzLM3152MHE-2.5

* 750KHzLM3153MHE-2.5

*

* 500KHzLM3152MHE-5.0

* 750KHzLM3153MHE-5.0

Output

Voltage

2.5V

5.0V

Switching

Frequency

250KHz

250KHzLM3151MHE-5.0

Supplied As

94 Units per Anti-Static

Tube

Reel

Reel

94 Units per Anti-Static

Tube

Reel

Reel

94 Units per Anti-Static

Tube

Reel

Reel

*Coming Soon

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Absolute Maximum Ratings (Note 1)

If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/

All Other Inputs to GND -0.3V to 7V
ESD Rating (Note 2) 2kV
Storage Temperature Range -65°C to +150°C

Distributors for availability and specifications.

VIN to GND -0.3V to 47V
SW to GND -3V to 47V
BST to SW -0.3V to 7V
BST to GND -0.3V to 52V

LM3151/LM3152/LM3153

Electrical Characteristics Limits in standard type are for T

Operating Ratings (Note 1)

V

IN

Junction Temperature Range (TJ)

EN 0V to 5V

= 25°C only; limits in boldface type apply over the

J

−40°C to + 125°C

junction temperature (TJ) range of -40°C to +125°C. Minimum and Maximum limits are guaranteed through test, design, or statistical
correlation. Typical values represent the most likely parametric norm at TJ = 25°C, and are provided for reference purposes only.
Unless otherwise stated the following conditions apply: VIN = 18V.

Symbol Parameter Conditions Min Typ Max Units

Start-Up Regulator, VCC

V

CC

VIN - V

I

VCCL

VCC

UVLO

V

CC-UVLO-HYS

t

CC-UVLO-D

I

IN

I

IN-SD

CC

VIN - VCC Dropout Voltage

VCC Current Limit (Note 3) VCC = 0V 65 100

VCC Under-voltage Lockout threshold
(UVLO)

VCC UVLO Hysteresis

VCC UVLO Filter Delay

Input Operating Current No Switching

Input Operating Current, Device
Shutdown

C

= 1 µF, 0 mA to 40 mA 5.65 5.95 6.25

VCC

I

= 2 mA, Vin = 5.5V 40

VCC

I

= 30 mA, Vin = 5.5V 330

VCC

VCC Increasing

VCC Decreasing

4.75 5.1 5.40

475

3

3.6 5.2

VEN = 0V

32 55

GATE Drive

I

Q-BST

R

DS-HG-Pull-Up

R

DS-HG-Pull-Down

R

DS-LG-Pull-Up

R

DS-LG-Pull-Down

Boost Pin Leakage

HG Drive Pull–Up On-Resistance

HG Drive Pull–Down On-Resistance

LG Drive Pull–Up On-Resistance

LG Drive Pull–Down On-Resistance

V

– VSW = 6V 2

BST

IHG Source = 200 mA 5

IHG Sink = 200 mA 3.4

ILG Source = 200 mA 3.4

ILG Sink = 200 mA 2

Soft-Start

I

SS

I

SS-DIS

SS Pin Source Current

SS Pin Discharge Current

VSS = 0V 5.9 7.7 9.5

200

Current Limit

V

CL

Current Limit Voltage Threshold

175 200 225

ON/OFF Timer

t

ON-MIN

t

OFF

ON Timer Minimum Pulse Width

OFF Timer Minimum Pulse Width

200

370 525

Enable Input

V

V

EN-HYS

EN

EN Pin Input Threshold Trip Point

EN Pin threshold Hysteresis

VEN Rising 1.14 1.20 1.26

VEN Falling 120

6V to 42V

V

mV

mA

V

mV

µs

mA

µA

nA

Ω

Ω

Ω

Ω

mA

µA

mV

ns

ns

V

mV

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Symbol Parameter Conditions Min Typ Max Units

Boost Diode

I

= 2 mA 0.7

V

f

Forward Voltage

BST

I

= 30 mA 1

BST

V

V

Thermal Characteristics

T

SD

θ

JA

Thermal Shutdown Rising 165 °C

Thermal Shutdown Hysteresis Falling 15 °C

Junction to Ambient

4 Layer JEDEC Printed Circuit
Board, 9 Vias, No Air Flow

2 Layer JEDEC Printed Circuit

40

140

°C/W

Board. No Air Flow

θ

JC

Junction to Case No Air Flow

4

°C/W

3.3V Output Option

Symbol Parameter Conditions Min Typ Max Units

V

V

OUT-OV

OUT

Output Voltage

Output Voltage Over-Voltage Threshold

3.234 3.3 3.366

3.83 4.00 4.17

V

V

LM3151-3.3 42

V

IN-MAX

Maximum Input Voltage (Note 4)

VLM3152-3.3 33

LM3153-3.3 18

LM3151-3.3 6

V

IN-MIN

Minimum Input Voltage (Note 4)

VLM3152-3.3 6

LM3153-3.3 8

LM3151-3.3, RON = 115 kΩ

f

S

Switching Frequency

LM3152-3.3, RON = 51 kΩ

LM3153-3.3, RON = 32 kΩ

LM3151-3.3, RON = 115 kΩ

t

ON

On-Time

LM3152-3.3, RON = 51 kΩ

LM3153-3.3, RON = 32 kΩ

R

FB

FB Resistance to Ground

250

500

750

730

400

330

566

kHz

ns

kΩ

LM3151/LM3152/LM3153

Note 1: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for which the device is

intended to be functional, but does not guarantee specific performance limits. For guaranteed specifications and conditions, see the Electrical Characteristics.

Note 2: The human body model is a 100 pF capacitor discharged through a 1.5 kΩ resistor into each pin. Test Method is per JESD-22-A114.

Note 3: VCC provides self bias for the internal gate drive and control circuits. Device thermal limitations limit external loading.

Note 4: The input voltage range is dependent on minimum on-time, off-time, and therefore frequency, and is also affected by optimized MOSFET selection.

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Simplified Block Diagram

LM3151/LM3152/LM3153

30053203

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