LT1268BCQ [Linear]

7.5A, 150kHz Switching Regulators; 7.5A ， 150kHz的开关稳压器


型号：	LT1268BCQ
厂家：	Linear
描述：	7.5A, 150kHz Switching Regulators 7.5A ， 150kHz的开关稳压器稳压器开关式稳压器或控制器电源电路开关式控制器
文件：	总4页 (文件大小：67K)
中文：	中文翻译
下载：	下载PDF数据表文档文件

LT1268B/ LT1268

7.5A, 150kHz

Switc hing Re g ula to rs

DESCRIPTIO

EATURE

■

Wide Input Voltage Range: 3.5V to 30V

Low Quiescent Current: 7mA

Internal 7.5A Switch

Very Few External Parts Required

Self-Protected Against Overloads

Available in Standard and Surface Mount

5-Pin Packages

The LT1268B and LT1268 are monolithic high power

switching regulators. Identical to the popular LT1070,

except for switching frequency (150kHz) and higher

switch current, they can be operated in all standard

switching configurations including buck, boost, flyback,

and inverting. A high current, high efficiency switch is

included on the die along with all oscillator, control, and

protection circuitry. Integration of all functions allows

the LT1268 to be built in standard 5-pin power packages.

This makes it extremely easy to use and provides “bust

proof” operations similar to that obtained with 3-pin

linear regulators.

■

Can Be Externally Synchronized

(See LT1072 Data Sheet)

O U

PPLICATI

■

High Efficiency Boost Converter

PC Power Supply with Multiple Outputs

Battery Upconverter

■

The LT1268 operate with supply voltages from 3.5V to

30V and draw only 7mA quiescent current. By utilizing

current mode switching techniques, it provides excellent

AC and DC load and line regulation.

Negative-to-Positive Converter

USER NOTE:

This data sheet is only intended to provide specifications, graphs, and a general functional

description of the LT1268B/LT1268. Application circuits are included to show the capability of the

LT1268B/LT1268.Acompletedesignmanual(AN19)shouldbeobtainedtoassistindevelopingnew

designs. This manual contains a comprehensive discussion of both the LT1070 and the external

components used with it, as well as complete formulas for calculating the values of these

components. The manual can also be used for the LT1268B/LT1268 factoring in the higher switch

current rating and higher operating frequency.

TheLT1268useanadaptiveanti-satswitchdrivetoallow

verywiderangingloadcurrents withnoloss inefficiency.

An externally activated shutdown mode reduces total

supply current to 100µA typical for standby operation.

TYPICAL APPLICATI

Boost Regulator with 5.3V ±1% Output

Efficiency of 5.3V Boost Converter

MBR1035

100

8µH, 5A*

2µH, 5A**

OUT

4.7V TO

5.3V

5.3V ±1%

3.75A

= 5.3V

D2, D3^†

1N4001

390µF

16V

= 4.7V

0.02

4.043k

0.1%

= 5V

LT1268B FB

CASE GND

220µF

16V

390µF

16V

1.24k

0.1%

0.068

220Ω

LOAD CURRENT (A)

LT1268 • TA01

*COILTRONICS CTX8-5-52

**COILTRONICS CTX2-5-52

^†OPTIONAL. D2 AND D3 ARE USED TO INCREASE

LT1268 • TA02

UNDERVOLTAGE LOCKOUT FROM 2.7V TO ≈4V.

LT1268B/ LT1268

W W W

ABSOLUTE AXI U RATI GS

PACKAGE RDER I FOR ATIO

Supply Voltage ....................................................... 30V

Switch Output Voltage ............................................ 60V

Feedback Pin Voltage (Transient, 1ms) ................ ±15V

Operating Junction Temperature Range

Operating............................................... 0°C to 125°C

Short-Circuit......................................... 0°C to 140°C

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

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

FRONT VIEW

ORDER PART

NUMBER

GND

LT1268CQ

LT1268BCQ

Q PACKAGE

5-LEAD DD

_JMAX= 125°C, θ_JC= 2°C/W, θ_JA= See Notes 5 and 6

FRONT VIEW

ORDER PART

NUMBER

GND

LT1268CT

LT1268BCT

T PACKAGE

5-LEAD TO-220

T_JMAX= 125°C, θ_JC= 2°C/W, θ_JA= 50°C/W

Consult factory for Industrial and Military parts

ELECTRICAL CHARACTERISTICS ^V= 15V, V = 0.5V, V_FB= V_REF, switch pin open, unless otherwise noted.

SYMBOL

PARAMETER

CONDITIONS

MIN

TYP

MAX

UNITS

Reference Voltage Measured at

Feedback Pin (Note 4)

LT1268B

1.235

1.224

1.244

1.253

1.264

REF

●

Reference Voltage

LT1268

1.224

1.214

1.244

1.264

1.274

Feedback Input Current

= V

REF

350

4400

200

750

1100

Error Amplifier Transconductance

Error Amplifier Source or Sink Current

Error Amplifier Clamp Voltage

∆I = ±25µA

3000

2400

6000

7000

µmho

V = 1.5V

150

120

350

400

µA

Hi Clamp, V = 1V

Lo Clamp, V = 1.5V

1.80

0.25

2.30

0.52

0.38

Reference Voltage Line Regulation

Error Amplifier Voltage Gain

Minimum Input Voltage

Supply Current

3V ≤ V ≤ V , V = 0.8V

●

0.03

%/V

V/V

MAX

0.9V ≤ V ≤ 1.4V

500

800

2.8

3.0

3V ≤ V ≤ V , V = 0.6V

MAX

Control Pin Threshold

Duty Cycle = 0

0.7

0.5

0.9

1.08

1.25

●

Output Switch Breakdown Voltage

3V ≤ V ≤ V , I = 1.5mA

MAX SW

SAT

Output Switch-ON Resistance

(Note 1, 3)

T ≤ 100°C

T ≤ 125°C

0.12

0.18

0.22

Ω

Control Voltage to Switch

Current Transconductance

A/V

Switch Current Limit (Note 3, 6)

Duty Cycle = 50%, T ≤ 100°C

●

7.50

6.50

LIM

Duty Cycle = 65%, T ≤ 100°C

LT1268B/ LT1268

SYMBOL

LECTRICAL CHARACTERISTICS ^V= 15V, V = 0.5V, V_FB= V_REF, switch pin open, unless otherwise noted.

PARAMETER

CONDITIONS

MIN

TYP

MAX

UNITS

∆I

Supply Current Increase

During Switch-ON Time

mA/A

∆I

Switching Frequency

120

150

180

kHz

●

MAX

Maximum Switch Duty Cycle

Shutdown Mode Supply Current

Shutdown Mode Threshold Voltage

3V ≤ V ≤ V , V = 0.05V

100

150

500

µA

MAX

3V ≤ V ≤ V

100

250

300

MAX

●

The

●

denotes specifications which apply over the full operating

has a thermal resistance of 20°C/W to 50°C/W (see graph). The following

formula will allow an estimate of maximum continuous switch current as a

function of power loss and duty cycle. See AN19 for more details.

temperature range.

Note 1: Measured with V in hi clamp, V = 0.8V.

Note 2: For duty cycles (DC) between 50% and 65%, minimum guaranteed

I_MAX

switch current is given by I = 6.25 (1.7 – DC).

LIM

_SW× DC

P = Power dissipation due to switch current

= Switch-ON resistance ≈0.15Ω

Note 3: Minimum current limit is reduced by 0.5A at 125°C. 100°C test

limits are guaranteed by correlation to 125°C tests.

Note 4: LT1268B reference voltage is specified at ±9mV to guarantee ±1%

output voltage accuracy when 0.1% external resistors are used to set

output voltage. To maintain output accuracy under load, load current

should be taken from the case and the ground pin should be connected

separately to output ground. See AN19 for details.

DC = Switch duty cycle

In a typical application where thermal resistance is 30°C/W, maximum

power might be limited to 2W and power allocated to switch loss is 1.5W.

For a duty cycle of 40%, this yields

Note 5: The Q package is intended for surface mount without a separate

heat sink. See graph for thermal resistance as a function of the mounting

area. This curve assumes no other heat dissipators adjacent to package.

1.5

0.15 × 0.4

I_MAX

= 5A

Obviously, a combination of high thermal resistance and high duty cycle

may restrict switch current to a value well below the 7.5A electrical limit.

Note 6: Maximum switch current may be limited by package power

dissipation, especially for the surface mount (Q) package. This package

W U

TYPICAL PERFOR A CE CHARACTERISTICS

Switch Current Limit vs Duty Cycle

Switch Saturation Voltage

Q Package Thermal Resistance

1.6

1.4

1.2

1.0

0.8

0.6

0.4

0.2

T = 25°C

SINGLE-SIDED BOARD, 1oz COPPER

–55°C

25°C

125°C

DOUBLE-SIDED BOARD, 1oz COPPER

BOTTOM COPPER AREA >100cm²

10 20 30 40 50 60 70 80 90 100

DUTY CYCLE (%)

TOP SURFACE COPPER AREA (cm²)

SWITCH CURRENT (A)

LT1268 • 603

LT1268 • TPC01

LT1268 • TPC02

InformationfurnishedbyLinearTechnologyCorporationis believedtobeaccurateandreliable.However,

no responsibility is assumed for its use. Linear Technology Corporation makes no representation that

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

LT1268B/ LT1268

TYPICAL APPLICATI

Boost Converter (5V TO 12V)

20µH

MBR1020

12V, 1.5A

LT1268CT

10.7k

1000µF

25V

GND

1.24k

1µF

LT1268 • TA03

PACKAGE DESCRIPTIO

Dimensions in inches (millimeters) unless otherwise noted.

0.401 ± 0.015

(10.185 ± 0.381)

0.060

(1.524)

0.175 ± 0.008

0.050 ± 0.008

(4.445 ± 0.203)

(1.270 ± 0.203)

15° TYP

+0.008

0.004

+0.012

0.331

8.407

–0.004

0.059

(1.499)

TYP

–0.020

Q Package

5-Lead DD

+0.203

0.102

+0.305

–0.508

(

)

–0.102

(

)

0.105 ± 0.008

(2.667 ± 0.203)

0.067 ± 0.010

(1.702 ± 0.254)

0.050 ± 0.012

(1.270 ± 0.305)

+0.012

–0.020

0.022 ± 0.005

(0.559 ± 0.127)

0.143

0.032 ± 0.008

(0.813 ± 0.203)

+0.305

–0.508

3.632

(

)

0.380 – 0.420

(9.652 – 10.668)

0.169 – 0.185

(4.293 – 4.699)

0.079 – 0.135

(2.007 – 3.429)

0.035 – 0.055

(0.889 – 1.397)

0.139 – 0.153

(3.531 – 3.886)

DIA

0.560 – 0.650

T Package

5-Lead TO-220

0.460 – 0.500

(11.68 – 12.70)

(14.224 – 16.510)

0.620 ± 0.020

(15.75 ± 0.508)

0.866 – 0.913

(21.996 – 23.190)

0.700 – 0.728

(17.780 – 18.491)

0.970 – 1.050

(24.64 – 26.67)

0.055 – 0.090

(1.397 – 2.286)

0.079 – 0.115

(2.007 – 2.921)

0.015 – 0.025

(0.381 – 0.635)

0.210 – 0.240

(5.334 – 6.096)

0.057 – 0.077

(1.448 – 1.956)

0.149 – 0.230

(3.785 – 5.842)

0.028 – 0.035

(0.711 – 0.889)

0.304 – 0.380

(7.722 – 9.652)

1268fs, sn1268 LT/GP 0194 10K REV 0 • PRINTED IN THE USA

LINEAR TECHNOLOGY CORPORATION 1994

Linear Technology Corporation

1630 McCarthy Blvd., Milpitas, CA 95035-7487

●

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

LT1268BCQ [Linear]

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LT1268BCQ#TR

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LT1268CQ#TR

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LT1268CT

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LT1268_15