LT1176-5_15 [Linear]

Step-Down Switching Regulator;


型号：	LT1176-5_15
厂家：	Linear
描述：	Step-Down Switching Regulator
文件：	总8页 (文件大小：146K)
中文：	中文翻译
下载：	下载PDF数据表文档文件

LT1176/LT1176-5

Step-Down

Switching Regulator

and all current limit components are included on the chip.

The topology is a classic positive buck configuration but

severaldesigninnovationsallowsthisdevicetobeusedas

apositive-to-negativeconverter,anegativeboostconverter,

and as a flyback converter. The switch output is specified

to swing below ground.

FEATURES

1.2A Onboard Switch

100kHz Switching Frequency

Excellent Dynamic Behavior

DIP and Surface Mount Packages

Only 8mA Quiescent Current

The LT1176 uses a true analog multiplier in the feedback

loop.Thismakesthedevicerespondnearlyinstantaneously

toinputvoltagefluctuationsandmakesloopgainindepen-

dent of input voltage. As a result, dynamic behavior of the

regulator is significantly improved over previous designs.

Preset 5V Output Available

Operates Up to 35V Input

Micropower Shutdown Mode

APPLICATIONS

On-chip pulse by pulse current limiting makes the LT1176

nearly bust proof for output overloads or shorts. The input

voltage range as a buck converter is 8V to 35V, but a self

boot feature allows input voltages as low as 5V in the

inverting and boost configurations.

Buck Converter with Output Voltage Range of

2.5V to 30V

Positive-to-Negative Converter

Negative Boost Converter

Multiple Output Buck Converter

The LT1176 is available in a low cost 8-lead DIP package

with frequency preset at 100kHz and current limit at 1.7A.

An adjustable output is offered as well as a preset 5V ver-

sion. For further design details and application help, see

the LT1074/LT1076 data sheet and Application Note 44.

DESCRIPTION

TheLT^®1176isa1Amonolithicbipolarswitchingregulator

which requires only a few external parts for normal opera-

tion. The power switch, all oscillator and control circuitry

L, LT, LTC, LTM, Linear Technology, SwitcherCAD and the Linear logo are registered

trademarks of Linear Technology Corporation. All other trademarks are the property of their

respective owners.

TYPICAL APPLICATION

Basic 5V Positive Buck Converter

5V Buck Converter Efficiency

L1*

100µH

L = 100µH ON MAGNETICS INC.

SIZE T-50 KOOL Mµ CORE

5V, 0.8A

10V T0 35V

LT1176-5

SENSE

= 10V

1N5819

= 20V

GND

470µF

25V

2.7k

100µF

0.01µF

*COILTRONICS #100-1-52

PULSE ENGINEERING, INC. #PE-92102

HURRICANE #HL-AG210LL

11765 TA01

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0

LOAD CURRENT (A)

THESE ARE LOW COST POWDERED IRON CORES. OPTIMUM EFFICIENCY

AND SMALLEST SIZE IS OBTAINED BY USING A LOW LOSS CORE SUCH

AS MAGNETICS INC. KOOL Mµ. SEE EFFICIENCY GRAPH.

11765 TA02

11765fb

LT1176/LT1176-5

ABSOLUTE MAXIMUM RATINGS

(Note 1)

Input Voltage.............................................................38V

Switch Voltage with Respect to Input Voltage...........50V

Switch Voltage with Respect to Ground Pin

Pin Voltage (Forced) .........................................5.5V

LIM

Maximum Operating Ambient Temperature Range

LT1176C/LT1176C-5................................. 0°C to 70°C

Maximum Operating Junction Temperature Range

LT1176C/LT1176C-5............................... 0°C to 125°C

Storage Temperature Range .................. –65°C to 150°C

Lead Temperature (Soldering, 10 sec)...................300°C

(V Negative) (Note 7)............................................20V

Feedback Pin Voltage........................................–2V, 10V

Shutdown Pin Voltage (Not to Exceed V )...............35V

Status Pin Voltage

(Current Must Be Limited to 5mA When Status Pin

Switches ON)........................................................30V

*These thermal resistance numbers are for typical mounting technique. Lower thermal

resistance can be obtained with large copper lands, thermal glues or heat sinks.

PIN CONFIGURATION

TOP VIEW

19 NC

TOP VIEW

LIM

GND

17 GND

16 GND

LIM

GND

15 GND

GND

STATUS

GND

14 GND

FB/SENSE

SHUTDOWN

13 STATUS

12 SHUTDOWN

11 NC

N8 PACKAGE

8-LEAD PLASTIC DIP

FB/SENSE

= 125°C, θ = 90°C/W

NC 10

JMAX

SW PACKAGE

20-LEAD PLASTIC SOL

JMAX

= 125°C, θ = 50°C/W

ORDER INFORMATION

LEAD FREE FINISH

LT1176CN8#PBF

LT1176CN8-5#PBF

LT1176CSW#PBF

LT1176CSW-5#PBF

TAPE AND REEL

PART MARKING*

PACKAGE DESCRIPTION

8-Lead Plastic DIP

TEMPERATURE RANGE

0°C to 125°C

LT1176CN8

LT1176CN8-5

LT1176CSW

LT1176CSW-5

8-Lead Plastic DIP

0°C to 125°C

LT1176CSW#TRPBF

LT1176CSW-5#TRPBF

20-Lead Plastic SOL

0°C to 125°C

Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container.

For more information on lead free part marking, go to: http://www.linear.com/leadfree/

For more information on tape and reel specifications, go to: http://www.linear.com/tapeandreel/

11765fb

LT1176/LT1176-5

ELECTRICAL CHARACTERISTICS ^Thel denotes the specifications which apply over the full operating

temperature range, otherwise specifications are at T_A= 25°C. T_J= 25°C, V_IN25V, unless otherwise noted.

PARAMETER

CONDITIONS

MIN

TYP

MAX

UNITS

Switch ON Voltage (Note 2)

= 0.2A

= 1A

1.1

1.4

Switch OFF Leakage

= 25V, V = 0

150

250

µA

= V

, V = 0 (Note 8)

MAX SW

Supply Current (Note 3)

Minimum Supply Voltage

Switch Current Limit (Note 5)

= 2.5V, V ≤ 35V

SHDN

7.5

µA

= 0.1V (Device Shutdown) (Note 9)

140.0

300

Normal Mode

Startup Mode (Note 4)

7.3

3.5

8.0

4.8

Open

1.2

1.7

1.2

0.8

2.2

LIM

= 10k (Note 6)

= 7k (Note 6)

LIM

Maximum Duty Cycle

Switching Frequency

100

110

120

kHz

= 0V Through 2k (Note 5) (LT1176)

SENSE

= 0V (Note 5) (LT1176-5)

Switching Frequency Line Regulation

Error Amplifier Voltage Gain (Note 10)

Error Amplifier Transconductance (Note 10)

Error Amplifier Source and Sink Current

8V ≤ V ≤ V

(Note 8)

MAX

0.03

2000

5000

0.1

%/V

V/V

1V ≤ V ≤ 4V

3700

8000

µmho

Source (V = 2V or V

= 4V)

= 5.5V)

100.0

0.7

140

1.0

225.0

1.6

µA

SENSE

Sink (V = 2.5V or V

Feedback Pin Bias Current (LT1176)

Reference Voltage (LT1176)

= V

0.5

µA

REF

V = 2V

2.155

4.85

2.21

2.265

Reference Voltage Tolerance (LT1176)

REF

(Nominal) = 2.21V

0.5

1.0

All Conditions of Input Voltage, Output Voltage,

Temperature and Load Current

Sense Voltage (LT1176-5)

V = 2V

5.15

Sense Voltage Tolerance (LT1176-5)

OUT

(Nominal) = 5V

0.5

0.1

All Conditions of Input Voltage,

Temperature and Load Current

Sense Pin Divider Resistance (LT1176-5)

Output Voltage Line Regulation

kΩ

8V ≤ V ≤ V

(Note 8)

MAX

0.005

0.02

%/V

V Voltage at 0% Duty Cycle

1.5

–4.0

Overtemperature

mV/°C

Multiplier Reference Voltage

Shutdown Pin Current

SHDN

= 5V

µA

≤ V

(@ 2.5V)

THRESHOLD

Shutdown Thresholds

Switch Duty Cycle = 0

Fully Shutdown

2.2

0.1

2.45

0.30

2.7

0.5

Status Window

As a Percent of Output Voltage

Status High Level

= 10µA Sourcing

3.5

4.5

5.0

STATUS

11765fb

LT1176/LT1176-5

ELECTRICAL CHARACTERISTICS ^Thel denotes the specifications which apply over the full operating

temperature range, otherwise specifications are at T_A= 25°C. T_J= 25°C, V_IN25V, unless otherwise noted.

PARAMETER

CONDITIONS

= 1.6mA Sinking

MIN

TYP

0.25

MAX

UNITS

Status Low Level

Status Delay Time

Status Minimum Width

0.4

STATUS

µs

Note 1: Stresses beyond those listed under Absolute Maximum Ratings

may cause permanent damage to the device. Exposure to any Absolute

Maximum Rating condition for extended periods may affect device

reliability and lifetime.

Note 5: Switch frequency is internally scaled down when the feedback pin

voltage is less than 1.3V to avoid extremely short switch-on times. During

testing, V or V

is adjusted to give a minimum switch-on time of

SENSE

1µs.

Note 2: To calculate maximum switch ON voltage at current between low

Note 6: I = (R – 1k)/7.65k

LM LIM

and high conditions, a linear interpolation may be used.

Note 7: Switch to input voltage limitation must also be observed.

Note 8: V = 35V

Note 9: Does not include switch leakage.

Note 10: Error amplifier voltage gain and transconductance are

specified relative to the internal feedback node. To calculate gain and

Note 3: A feedback pin voltage (V ) of 2.5V forces the V pin to its low

MAX

clamp level and the switch duty cycle to zero. This approximates the

zero load condition where duty cycle approaches zero. The LT1176-5 has

= 5.5V.

SENSE

Note 4: Total voltage from V pin to ground pin must be ≥ 8V after

transconductance from the sense pin (Output) to the V pin on the

start-up for proper regulation.

LT1176-5, multiply by 0.44.

Application Hints

Although the LT1176 has a peak switch rating of 1.2A and a maximum duty

cycle of 85%, it must be used cautiously in applications which require high

switch current and high duty cycle simultaneously, to avoid excessive chip

temperature. Thermal resistance is 90°C/W for the 8-pin DIP package and

50°C/W for the 20-pin SO. This limits continuous chip power dissipation to

the 0.5W to 1W range. These numbers assume typical mounting techniques.

Extra or thick copper connected to the leads can reduce thermal resistance.

Bonding the package to the board or using a clip style heat sink can also help.

Thefollowingformulaswillgivechippowerdissipationandpeakswitchcurrent

for the standard buck converter. Note that surges less than 30 seconds do not

need to be considered from a thermal standpoint, but for proper regulation,

they must not result in peak switch currents exceeding the 1.2A limit.

Power = I

(V /V ) + V [7mA + 3mA (V /V ) + 0.012 (I

)]

LOAD OUT IN

OUT IN

LOAD

= I + [V (V – V )]/2E (V )(L)

LOAD(PEAK) OUT IN OUT IN

PEAK

Example: V = 15V, V

= 5V, I

= 0.5A Continuous, 0.8A Peak,

LOAD

OUT

L = 100µH

Power (I

= 0.5A) = 0.38W

= 0.8A) = 0.97A

LOAD

PEAK LOAD

Where component size or height is critical, we suggest using solid tantalum

capacitors (singly or in parallel), but be sure to use units rated for switching

applications. Coiltronics is a good source for low profile surface mount

inductorsandAVXmakeshighqualitysurfacemounttantalumcapacitors.For

further help, use Application Notes 19 and 44,LTC’s SwitcherCAD^®computer

design program, and our knowledgeable application department.

11765fb

LT1176/LT1176-5

BLOCK DIAGRAM

INPUT SUPPLY

0.3V

10µA

320µA

µPOWER

6V TO ALL

CIRCUITRY

REGULATOR

AND BIAS

SHUTDOWN

500Ω

–

2.35V

CURRENT LIMIT

SHUTDOWN

CURRENT LIMIT

COMP

0.16Ω

–

LIM

4.5V

10k

SHUTDOWN

FREQ SHIFT

R/S

LATCH

100kHz

OSCILLATOR

SYNC

OUTPUT

VOLTAGE

MONITOR

P-P

400Ω

–

ANALOG

X MULTIPLIER

XYZ

STATUS

ERROR

AMP

PULSE WIDTH

COMPARATOR

SWITCH

OUTPUT

2.21V

–

)

11765 BD

2.8k

2.2k*

24V (EQUIVALENT)

FB/SENSE

*CONNECTED ON 5V VERSION ONLY

11765fb

LT1176/LT1176-5

PACKAGE DESCRIPTION

N8 Package

8-Lead PDIP (Narrow .300 Inch)

(Reference LTC DWG # 05-08-1510)

.400ꢁ

(10.160)

MAX

ꢀ

.255 .015ꢁ

(6.4ꢀꢀ 0.381)

.130 .005

.300 – .325

.045 – .065

(3.302 0.12ꢀ)

(1.143 – 1.651)

(ꢀ.620 – 8.255)

.065

(1.651)

TYP

.008 – .015

(0.203 – 0.381)

.120

.020

(0.508)

MIN

(3.048)

MIN

+.035

.325

–.015

.018 .003

(0.45ꢀ 0.0ꢀ6)

.100

(2.54)

BSC

+0.889

8.255

(

)

N8 1002

–0.381

NOTE:

INCHES

1. DIMENSIONS ARE

MILLIMETERS

ꢁTHESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS.

MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED .010 INCH (0.254mm)

11765fb

LT1176/LT1176-5

REVISION HISTORY

REV

DATE

DESCRIPTION

PAGE NUMBER

01/11 Corrected Typical Application

Updated part markings in Order Information

Revised Electrical Characteristics

Updated Package Description

2/11

Revised Shutdown Pin Current in Electrical Characteristics

11765fb

Information furnished by Linear Technology Corporation is believed to be accurate and reliable.

However, no responsibility is assumed for its use. Linear Technology Corporation makes no representa-

tion that the interconnection of its circuits as described herein will not infringe on existing patent rights.

LT1176/LT1176-5

PACKAGE DESCRIPTION

SW Package

20-Lead Plastic Small Outline (Wide .300 Inch)

(Reference LTC DWG # 05-08-1620)

.050 BSC .045 .005

.030 .005

TYP

.496 – .512

(12.598 – 13.005)

NOTE 4

19 18

14 13 12 11

.325 .005

.420

MIN

.394 – .419

(10.007 – 10.643)

NOTE 3

N/2

RECOMMENDED SOLDER PAD LAYOUT

.291 – .299

(7.391 – 7.595)

NOTE 4

.037 – .045

.093 – .104

.010 – .029

(0.940 – 1.143)

¥ 45∞

(2.362 – 2.642)

(0.254 – 0.737)

.005

(0.127)

RAD MIN

0 – 8 TYP

.050

(1.270)

BSC

.004 – .012

.009 – .013

(0.102 – 0.305)

NOTE 3

(0.229 – 0.330)

.014 – .019

.016 – .050

(0.406 – 1.270)

INCHES

(MILLIMETERS)

S20 (WIDE) 0502

(0.356 – 0.482)

TYP

NOTE:

1. DIMENSIONS IN

2. DRAWING NOT TO SCALE

3. PIN 1 IDENT, NOTCH ON TOP AND CAVITIES ON THE BOTTOM OF PACKAGES ARE THE MANUFACTURING OPTIONS.

THE PART MAY BE SUPPLIED WITH OR WITHOUT ANY OF THE OPTIONS

4. THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS.

MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED .006" (0.15mm)

11765fb

LT 0211 REV B • PRINTED IN USA

LinearTechnology Corporation

1630 McCarthy Blvd., Milpitas, CA 95035-7417

●

 LINEAR TECHNOLOGY CORPORATION 1993

(408) 432-1900 FAX: (408) 434-0507 www.linear.com

LT1176-5_15 [Linear]

相关型号：

LT1176CN

LT1176CN8

LT1176CN8#PBF

LT1176CN8-5

LT1176CS

LT1176CS-5

LT1176CSW

LT1176CSW#PBF

LT1176CSW#TR

LT1176CSW#TRPBF

LT1176CSW-5

LT1176CSW-5#PBF