LT1176CSW#TRPBF [Linear]

LT1176/LT1176-5 - Step-Down Switching Regulator; Package: SO; Pins: 20; Temperature Range: 0°C to 70°C;


型号：	LT1176CSW#TRPBF
厂家：	Linear
描述：	LT1176/LT1176-5 - Step-Down Switching Regulator; Package: SO; Pins: 20; Temperature Range: 0°C to 70°C 稳压器开关
文件：	总4页 (文件大小：181K)
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

tion. The power switch, all oscillator and control circuitry,

and all current limit components are included on the chip.

The topology is a classic positive “buck” configuration but

several design innovations allows this device to be used as

a positive-to-negative converter, a negative boost con-

verter, and as a flyback converter. The switch output is

specified to swing below ground.

EATURE

1.2A On-Board Switch

■

100kHz Switching Frequency

Excellent Dynamic Behavior

DIP and Surface Mount Packages

Only 8mA Quiescent Current

Preset 5V Output Available

Operates Up to 35V Input

Micropower Shutdown Mode

The LT1176 uses a true analog multiplier in the feedback

loop.Thismakesthedevicerespondnearlyinstantaneously

to input voltage fluctuations and makes loop gain indepen-

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

regulator is significantly improved over previous designs.

O U

PPLICATI

■

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

■

Mulitple Output Buck Converter

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

withfrequencypresetat100kHzandcurrentlimitat1.7AAn

adjustable output is offered as well as a preset 5V version.

For further design details and application help, see the

LT1074/LT1076 data sheet and Application Note 44.

DESCRIPTIO

The LT1176 is a 1A monolithic bipolar switching regulator

which requires only a few external parts for normal opera-

TYPICAL APPLICATI

5V Buck Converter Efficiency

Basic 5V Positive Buck Converter

L1*

100µH

L = 100µH ON MAGNETICS INC.

SIZE T-50 KOOL Mµ CORE

5V, 0.8A

10V T0 35V

= 10V

LT1176-5

SENSE

1N5819

= 20V

GND

470µF

2.7k

25V

100µF

0.01µF

*COILTRONICS #100-1-52

PULSE ENGINEERING, INC. #PE-92102

HURRICANE #HL-AG210LL

LT1176/76-5 • 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.

LT1176/76-5 • TA02

LT1176/LT1176-5

W W W

ABSOLUTE AXI U RATI GS

PACKAGE RDER I FOR ATIO

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

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

Switch Voltage With Respect to Ground Pin

(V_SWNegative) (Note 6) ......................................... 20V

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

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

Status Pin Voltage

(Current Must Be Limited to 5mA When Status Pin

Switches “ON”) ................................................... 30V

I_LIMPin Voltage (Forced)...................................... 5.5V

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

TOP VIEW

ORDER PART

NUMBER

LIM

GND

STATUS

LT1176CN8

LT1176CN8-5

FB/SENSE

SHUTDOWN

N8 PACKAGE

8-LEAD PLASTIC DIP

T_{J MAX}= 125°C, θ_JA= 90°C/ W*

TOP VIEW

ORDER PART

NUMBER

19 NC

LIM

LT1176CS

LT1176CS-5

GND

17 GND

16 GND

GND

15 GND

GND

14 GND

13 STATUS

12 SHUTDOWN

11 NC

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

can be obtained with large copper lands, thermal glues or heatsinks.

FB/SENSE

NC 10

S PACKAGE

20-LEAD PLASTIC SOL

T_JMAX= 125 °C, θ_JA= 50°C/ W*

ELECTRICAL CHARACTERISTICS ^T_J^{= 25°C, V}_IN= 25V, unless otherwise noted

PARAMETER

CONDITIONS

MIN

TYP

MAX

UNITS

Switch “ON” Voltage (Note 1)

= 0.2A

= 1A

●

1.1

1.4

Switch “OFF” Leakage

= 25V, V = 0

150

250

µA

= V

, V = 0 (Note 7)

MAX SW

Supply Current (Note 2)

Minimum Supply Voltage

Switch Current Limit (Note 4)

= 2.5V, V ≤ 35V

SHDN

●

7.5

= 0.1V (Device Shutdown) (Note 8)

140.0

300

µA

Normal Mode

Startup Mode (Note 3)

●

7.3

3.5

8.0

4.8

Open

●

1.2

1.7

1.2

0.8

2.2

LIM

= 10k (Note 5)

= 7k (Note 5)

LIM

Maximum Duty Cycle

Switching Frequency

●

100

110

120

kHz

= 0V Through 2k (Note 4) (LT1176)

= 0V (Note 4) (LT1176-5)

SENSE

Switching Frequency Line Regulation

Error Amplifier Voltage Gain (Note 9)

Error Amplifier Transconductance (Note 9)

Error Amplifier Source and Sink Current

8V ≤ V ≤ V

(Note 7)

●

0.03

2000

5000

0.1

%/V

V/V

MAX

1V ≤ V ≤ 4V

3700

8000

µmho

Source (V = 2V or V

= 4V)

= 5.5V)

100.0

0.7

140.0

1.0

225.0

1.6

µA

SENSE

Sink (V = 2.5V or V

LT1176/LT1176-5

ELECTRICAL CHARACTERISTICS

T_J= 25°C, V_IN= 25V, unless otherwise noted

PARAMETER

CONDITIONS

MIN

TYP

0.5

MAX

UNITS

µA

Feedback Pin Bias Current (LT1176)

Reference Voltage (LT1176)

Reference Voltage Tolerance (LT1176)

= V

●

REF

V = 2V

2.155

4.85

2.21

2.265

(Nominal) = 2.21V

±0.5

±1.0

±1.5

±2.5

REF

All Conditions of Input Voltage, Output

Voltage, Temperature and Load Current

●

Sense Voltage (LT1176-5)

V = 2V

5.15

Sense Voltage Tolerance (LT1176-5)

(Nominal) = 5V

±0.5

±1.0

±2

±3

OUT

All Conditions of Input Voltage,

Temperature and Load Current

Sense Pin Divider Resistance (LT1176-5)

Output Voltage Line Regulation

kΩ

8V ≤ V ≤ V

(Note 7)

MAX

●

0.005

0.02

%/V

V Voltage at 0% Duty Cycle

1.5

–4.0

Over Temperature

mV/°C

Multiplier Reference Voltage

Shutdown Pin Current

= 5V

●

µA

SHDN

≤ V

( 2.5V)

THRESHOLD

●

SHDN

Shutdown Thresholds

Switch Duty Cycle = 0

Fully Shut Down

●

2.2

0.1

2.45

0.30

2.7

0.5

Status Window

As a Percent of Output Voltage

±4

±5

4.5

0.25

±6

5.0

0.4

Status High Level

Status Low Level

Status Delay Time

Status Minimum Width

= 10µA Sourcing

●

3.5

STATUS

= 1.6mA Sinking

µs

The

ture range.

●

denotes specifications which apply over the full operating tempera-

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 1µs.

SENSE

Note 1: To calculate maximum switch “ON” voltage at current between low

Note 5: I = (R – 1k)/7.65k

LM LIM

and high conditions, a linear interpolation may be used.

Note 6: Switch to input voltage limitation must also be observed.

Note 7: V = 35V

Note 8: Does not include switch leakage.

Note 9: Error amplifier voltage gain and transconductance are specified

relative to the internal feedback node. To calculate gain and transconduc-

Note 2: 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 3: Total voltage from V pin to ground pin must be ≥8V after start-

tance from the sense pin (Output) to the V pin on the LT1176-5, multiply

up for proper regulation.

Note 4: Switch frequency is internally scaled down when the feedback pin

by 0.44.

Power = I

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

)]

LOAD

Application Hints

LOAD OUT IN

OUT IN

= I

+ [V

(V – V )]/2E (V )(L)

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 heatsink can also help.

The following formulas will give chip power dissipation and peak switch

current 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.

PEAK

LOAD(PEAK)

OUT IN OUT IN

Example: V = 15V, V

= 5V, I

= 0.5A Continuous, 0.8A Peak,

OUT

LOAD

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 inductors and AVX makes high quality surface mount

tantalum capacitors. For further help, use Application Notes 19 and 44,

LTC’s SwitcherCAD computer design program, and our knowledgeable

application department.

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 represen-

tationthattheinterconnectionofitscircuitsasdescribedhereinwillnotinfringeonexistingpatentrights.

LT1176/LT1176-5

BLOCK DIAGRA

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

–

)

LT1176/76-5 • BD

2.8k

2.2k*

24V (EQUIVALENT)

FB/SENSE

*CONNECTED ON 5V VERSION ONLY

PACKAGE DESCRIPTIO

Dimensions in inches (milimeters) unless otherwise noted.

N Package 8-Lead Plastic DIP

0.400

(10.160)

MAX

0.130 ± 0.005

0.300 – 0.320

0.045 – 0.065

(3.302 ± 0.127)

(1.143 – 1.651)

(7.620 – 8.128)

0.065

(1.651)

TYP

0.250 ± 0.010

(6.350 ± 0.254)

0.009 – 0.015

(0.229 – 0.381)

0.125

0.020

(0.508)

MIN

(3.175)

MIN

+0.025

–0.015

0.045 ± 0.015

(1.143 ± 0.381)

0.325

+0.635

8.255

(

)

–0.381

0.100 ± 0.010

(2.540 ± 0.254)

0.018 ± 0.003

(0.457 ± 0.076)

S Package 20-Lead Plastic SOL

0.496 – 0.512

(12.598 – 13.005)

0.291 – 0.299

(7.391 – 7.595)

0.037 – 0.045

(0.940 – 1.143)

0.093 – 0.104

(2.362 – 2.642)

19 18

14 13 12 11

0.005

(0.127)

RAD MIN

0.010 – 0.029

(0.254 – 0.737)

× 45°

0° – 8° TYP

0.050

(1.270)

TYP

0.394 – 0.419

(10.007 – 10.643)

SEE

NOTE

0.004 – 0.012

(0.102 – 0.305)

0.009 – 0.013

(0.229 – 0.330)

SEE NOTE

0.014 – 0.019

0.016 – 0.050

(0.406 – 1.270)

(0.356 – 0.482)

TYP

NOTE:

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.

LT/GP 0393 10K REV 0

Linear Technology Corporation

1630 McCarthy Blvd., Milpitas, CA 95035-7487

●

LINEAR TECHNOLOGY CORPORATION 1993

(408) 432-1900 FAX: (408) 434-0507 TELEX: 499-3977

LT1176CSW#TRPBF [Linear]

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