National Semiconductor LM3075 Technical data

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LM3075
High Efficiency, Synchronous Current Mode Buck
Controller

LM3075 High Efficiency, Synchronous Current Mode Buck Controller

September 2005

General Description

The LM3075 is a current mode control, synchronous buck
controller IC. Use of synchronous rectification and pulse­skipping operation at light load achieves high efficiency over
a wide load range. Fixed frequency operation can be ob­tained by disabling the pulse-skipping mode. Current mode
control assures excellent line and load regulation and a wide
loop bandwidth for fast response to load transients.

Current mode control can be achieved by either sensing
across the high side NFET or a sense resistor. The switching
frequency can be selected as either 200 kHz or 300 kHz
from an internal clock.

The LM3075 is available with an adjustable output in a
TSSOP-20 package.

Typical Application Circuit

Features

n Input voltage range of 4.5V-36V
n Current Mode Control
n Skip mode operation available
n Cycle by cycle current limit
n 1.24V

±

2% Reference

Applications

n Automotive Power Supplies
n Distributed Power Systems

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© 2005 National Semiconductor Corporation DS201623 www.national.com

Connection Diagram

LM3075

TOP VIEW

20-Lead TSSOP (MTC)

20162302

Ordering Information

Order Number Package Type NSC Package Drawing Supplied As

LM3075MTC TSSOP-20 MTC-20 73 Units per Anti-Static Tube

LM3075MTCX TSSOP-20 MTC-20 2500 Units on Tape and Reel

Pin Descriptions

LM3075 Pin # Name Function

1 VLIN5 5V linear regulator output

2 VIN Input voltage supply

3 EXT External power connection for VLIN5

4 FS Frequency select

5 EN Enable pin

6 FB Feedback pin

7 FPWM Forced PWM selection

8 COMP Compensation pin

9 SS Output enable / soft-start pin

10 AGND Analog ground

11 PGND Power ground

12 LDRV Low side gate drive

13 VDD Low side gate drive supply

14 CBOOT Bootstrap capacitor connection

15 HDRV High side gate drive

16 SW Switch node

17 CSL Current sense low

18 CSH Current sense high

19 ILIM Current limit threshold adjustment

20 PGOOD Power good flag

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LM3075

Absolute Maximum Ratings (Note 1)

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

Voltages from the indicated pins to GND:

VIN, ILIM, CSH −0.3V to 38V

SW, CSL −0.3 to (V

+ 0.3V)

IN

HDRV to SW −0.3V

HDRV to CBOOT +0.3V

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

Junction Temperature 150˚C

Lead Temperature (Soldering, 10
sec) 260˚C

ESD Rating (Note 2) 1.5kV

PGOOD, FB, VDD, EXT, EN −0.3V to +7V

COMP, SS, FPWM, FS −0.3V to (V

LIN5

Operating Ratings(Note 1)

+0.3)V

CBOOT -0.3V to +43V

CBOOT to SW −0.3V to 7V

LDRV −0.3V to (V

DD

+0.3V)

Electrical Characteristics Limits in standard type are for T

over the junction temperature T
sign, or statistical correlation. Typical values represent the most likely parametric norm at T
erence purposes only. Unless otherwise specified V

range of -40˚C to +125˚C. Minimum and Maximum limits are guaranteed through test, de-

J

= 12V.

IN

Junction Temperature −40˚C to +125˚C

VIN to GND 4.5V to 36V

EXT 6V Max

= 25˚C only, and limits in boldface type apply

J

= 25˚C, and are provided for ref-

J

Symbol Parameter Conditions Min Typ Max Unit

V

FB

Feedback pin voltage VIN= 4.5V to 36V 1.213 1.238 1.259 V

Load Regulation V

= 0.5V to 1.5V 0.04 %

COMP

Line Regulation VIN= 4.5V to 36V 0.04 %

I

Q

I

SD

V

LIN5

V

UVLO

V

UVLO_HYS

V

CL_OS

I

ILIM

I

SS_SRC

I

SS_SNK

V

SS_TO

V

OVP

V

OVP_HYS

POWERGOOD

V

PWR_GOOD

V

PWR_BAD

T

PGOOD

I

OL

I

OH

GATE DRIVE

Operating Quiescent current VIN= 4.5V to 36V 1.0 2 mA

Shutdown Quiescent current VEN=0V 60 100 µA

V

Output Voltage I

LIN5

V

Under Voltage

LIN5

= 0 to 25mA V

VLIN5

V

= 5.5V to 36V 4.7 5 5.3

IN

3.7 3.9 4.1 V

Lockout

V

Under Voltage

LIN5

0.2 V

Lockout Hysteresis

Current Limit Comparator

±

0.2 mV
Offset
(V

ILIM–VCSL

I

sink current 8.3 10 11.3 µA

LIM

Soft-Start Pin Source

)

VSS= 1.2V 1 2 3 µA

Current

Soft-Start Pin Sink Current VSS=2V 4 µA

Soft-Start Timeout

2V

Threshold

Over Voltage Protection

With respect to V

FB

105 111 117 %

Rising Threshold

Over Voltage Protection

With respect to V

FB

2.8 %

Hysteresis

PGOOD Rising Threshold 92.5 95.5 98.5 %

PGOOD Falling Threshold 87 90.5 95 %

PGOOD delay PGOOD pin de-asserting 10 µs

PGOOD Low Sink Current V

PGOOD High Leakage

V

= 0.4V 0.6 1mA

PGOOD

=5V 5 200 nA

PGOOD

Current

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Electrical Characteristics Limits in standard type are for T

over the junction temperature T

LM3075

or statistical correlation. Typical values represent the most likely parametric norm at T
purposes only. Unless otherwise specified V

Symbol Parameter Conditions Min Typ Max Unit

I

CBOOT

R

ds_on 1

C

BOOT

HDRV FET driver pull-up
On resistance

R

ds_on 2

HDRV FET driver pull-down
On resistance

R

ds_on 3

LDRV FET driver pull-up On
resistance

R

ds_on 4

LDRV FET driver pull-down
On resistance

OSCILLATOR

f

D

T

ON_MIN

OSC

MAX

Oscillator Frequency VFS=5V 255 300 330 kHz

Maximum Dutycycle VFB=1V 95.5 98 %

Minimum On Time 180 260 ns

ERROR AMPLIFIER

I

FB

I

COMP_SRC

Feedback pin bias current VFB= 1.5V 50 nA

COMP Output Source
Current

I

COMP_SNK

COMP Output Sink Current VFB= 1.5V

Gm Error Amplifier

Transconductance

A

VOL

V

SL

Error Amplifier Voltage Gain 1250 V/V

Slope Compensation
(referred to the internal
summing node)

A

CS

Current Sense Amplifier
Gain

LOGIC

V

IL

FS, /FPWM Pin Maximum
Low Level Input Level

V

IH

FS, /FPWM Pin Minimum
High Level Input Level

THERMAL SHUTDOWN

T

T

SD_HYS

SD

Thermal Shutdown 160 ˚C

Thermal Shutdown
Hysteresis

EXT

R

TH

EXT

EXT

EXT pin on resistance V

VLIN5 to EXT Switch Over
Rising Threshold

range of -40˚C to +125˚C. Minimum and Maximum limits are guaranteed through test, design,

J

= 12V. (Continued)

IN

Leakage Current V

V

=7V 10 nA

CBOOT

=0V 165 200 215

FS

VFB=1V

=1V

V

COMP

= 0.5V

V

COMP

= 0V 0.051 V/µs

V

FS

= 5V 0.076

V

FS

V

= 1.25V 4 5 6 V/V

COMP

=5V

EXT

=50mA

I

VLIN5

= 25˚C only, and limits in boldface type apply

J

= 25˚C, and are provided for reference

J

2.9 Ω

1.7 Ω

2.4 Ω

0.8 Ω

120 µA

110 µA

620 µmho

0.8 V

2 V

10 ˚C

4 Ω

4.6 V

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LM3075

Electrical Characteristics Limits in standard type are for T

over the junction temperature T
or statistical correlation. Typical values represent the most likely parametric norm at T
purposes only. Unless otherwise specified V

Note 1: Absolute maximum ratings indicate limits beyond which damage to the device may occur. Operating Range indicates conditions for which the device is
intended to be functional, but does not guarantee specfic performance limits. For guaranteed specifications and test conditions, see the Electrical Characteristics.
The guaranteed specifications apply only for the test conditions. Some performance characteristics may degrade when the device is not operated under the listed
test conditions.

Note 2: For testing purposes, ESD was applied using the human-body model, a 100pF capacitor discharged through a 1.5kΩ resistor.

range of -40˚C to +125˚C. Minimum and Maximum limits are guaranteed through test, design,

J

= 12V. (Continued)

IN

= 25˚C only, and limits in boldface type apply

J

= 25˚C, and are provided for reference

J

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Typical Performance Characteristics

LM3075

Efficiency (VIN= 12V to V

= 1.8V) Efficiency (VIN= 12V to V

OUT

OUT

= 3.3V)

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Efficiency (VIN= 12V to V

= 5V) Switching Frequency vs Temperature

OUT

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Error Amplifier Gm vs Temperature ILIM vs Temperature

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