Datasheet

ManualsBrandsLINEAR TECHNOLOGY ManualsVoltage RegulatorsPrecision Adjustment Low Drop Voltage Regulator, Positive

LT1083/LT1084/LT1085

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Three-Terminal Adjustable

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Output Current of 3A, 5A or 7.5A

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Operates Down to 1V Dropout

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Guaranteed Dropout Voltage at Multiple Current Levels

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Line Regulation: 0.015%

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Load Regulation: 0.01%

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100% Thermal Limit Functional Test

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Fixed Versions Available

The LT1083 series of positive adjustable regulators are

designed to provide 7.5A, 5A and 3A with higher efficiency

than currently available devices. All internal circuitry is

designed to operate down to 1V input-to-output differen-

tial and the dropout voltage is fully specified as a function

of load current. Dropout is guaranteed at a maximum of

1.5V at maximum output current, decreasing at lower load

currents. On-chip trimming adjusts the reference voltage

to 1%. Current limit is also trimmed, minimizing the stress

on both the regulator and power source circuitry under

overload conditions.

The LT1083/LT1084/LT1085 devices are pin compatible

with older three-terminal regulators. A 10µF output ca-

pacitor is required on these new devices. However, this is

included in most regulator designs.

Unlike PNP regulators, where up to 10% of the output

current is wasted as quiescent current, the LT1083 quies-

cent current flows into the load, increasing efficiency.

7.5A, 5A, 3A Low Dropout

Positive Adjustable Regulators

FEATURES

DESCRIPTION

TYPICAL APPLICATION

121Ω

OUT

ADJ

365Ω

10µF

5V AT 7.5A

LT1083

≥ 6.5V

1083/4/5 ADJ TA01

10µF*

TANTALUM

*REQUIRED FOR STABILITY

5V, 7.5A Regulator

APPLICATIONS

DEVICE OUTPUT CURRENT*

LT1083 7.5A

LT1084 5.0A

LT1085 3.0A

*For a 1.5A low dropout regulator see the LT1086 data sheet.

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High Efficiency Linear Regulators

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Post Regulators for Switching Supplies

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Constant Current Regulators

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Battery Chargers

OUTPUT CURRENT

INPUT/OUTPUT VOLTAGE DIFFERENTIAL (V)

2

1

0



1083/4/5 ADJ TA02



FULL LOAD

Dropout Voltage vs Output Current

Summary of content (16 pages)

PAGE 1
LT1083/LT1084/LT1085 7.5A, 5A, 3A Low Dropout Positive Adjustable Regulators U DESCRIPTION FEATURES ■ ■ ■ ■ ■ ■ ■ ■ Three-Terminal Adjustable Output Current of 3A, 5A or 7.5A Operates Down to 1V Dropout Guaranteed Dropout Voltage at Multiple Current Levels Line Regulation: 0.015% Load Regulation: 0.
PAGE 2
LT1083/LT1084/LT1085 W W U W ABSOLUTE MAXIMUM RATINGS “M” Grades: Control Section............. – 55°C to 150°C Power Transistor .......... – 55°C to 200°C Storage Temperature Range ................. – 65°C to 150°C Lead Temperature (Soldering, 10 sec).................. 300°C UU U Power Dissipation............................... Internally Limited Input-to-Output Voltage Differential “C” Grades........................................................... 30V “I” Grades ...................................
PAGE 3
LT1083/LT1084/LT1085 ELECTRICAL CHARACTERISTICS PARAMETER Load Regulation CONDITIONS (VIN – VOUT) = 3V 10mA ≤ IOUT ≤ IFULL LOAD TJ = 25°C (Notes 1, 2, 3, 5) MIN ● Dropout Voltage Current Limit LT1083 LT1084 LT1085 Minimum Load Current Thermal Regulation LT1083 LT1084 LT1085 Ripple Rejection Adjust Pin Current ∆VREF = 1%, IOUT = IFULLLOAD (Notes 4, 5, 7) ● (VIN – VOUT) = 5V (VIN – VOUT) = 25V (VIN – VOUT) = 5V (VIN – VOUT) = 25V (VIN – VOUT) = 5V (VIN – VOUT) = 25V (VIN – VOUT) = 25V TA = 25°C, 30ms
PAGE 4
LT1083/LT1084/LT1085 U W TYPICAL PERFORMANCE CHARACTERISTICS LT1083 Dropout Voltage LT1083 Short-Circut Current 12 MINIMUM INPUT/OUTPUT DIFFERENTIAL (V) 2 0.10 INDICATES GUARANTEED TEST POINT SHORT-CIRCUIT CURRENT (A) 0°C ≤ TJ ≤ 125°C 1 TJ = 150°C TJ = 25°C TJ = –55°C 25°C 10 150°C 8 6 –55°C 4 IFULL LOAD 2 0.05 0 –0.05 –0.10 –0.15 GUARANTEED –0.
PAGE 5
LT1083/LT1084/LT1085 U W TYPICAL PERFORMANCE CHARACTERISTICS Minimum Operating Current Temperature Stability 100 9 7 6 5 TJ = 150°C 4 TJ = 25°C 3 ADJUST PIN CURRENT (µA) 90 8 1.26 1.25 1.
PAGE 6
LT1083/LT1084/LT1085 U W TYPICAL PERFORMANCE CHARACTERISTICS LT1085 Ripple Rejection 90 80 70 60 (VIN – VOUT) ≥ VDROPOUT 50 40 30 CADJ = 200µF AT FREQUENCIES < 60Hz CADJ = 25µF AT FREQUENCIES > 60Hz IOUT = 3A 100 1k 10k FREQUENCY (Hz) 50 40 10 VOUT = 5V CADJ = 25µF COUT = 25µF LT1085CK 0 0 0 0.5 2.5 2.0 1.0 1.5 OUTPUT CURRENT (A) 1083/4/5 ADJ G19 OUTPUT VOLTAGE DEVIATION (V) 0.4 CADJ = 1µF 0 CIN = 1µF COUT = 10µF TANTALUM LOAD CURRENT (A) –0.
PAGE 7
LT1083/LT1084/LT1085 W BLOCK DIAGRAM VIN + – THERMAL LIMIT VOUT 1083/4/5 ADJ BD VADJ U W U U APPLICATIONS INFORMATION The LT1083 family of three-terminal adjustable regulators is easy to use and has all the protection features that are expected in high performance voltage regulators. They are short-circuit protected, and have safe area protection as well as thermal shutdown to turn off the regulator should the junction temperature exceed about 165°C.
PAGE 8
LT1083/LT1084/LT1085 U W U U APPLICATIONS INFORMATION Normally, capacitor values on the order of 100µF are used in the output of many regulators to ensure good transient response with heavy load current changes. Output capacitance can be increased without limit and larger values of output capacitor further improve stability and transient response of the LT1083 regulators. input pin instantaneously shorted to ground, can damage occur.
PAGE 9
LT1083/LT1084/LT1085 U W U U APPLICATIONS INFORMATION The problem occurs with a heavy output load when the input voltage is high and the output voltage is low, such as immediately after removal of a short. The load line for such a load may intersect the output current curve at two points. If this happens, there are two stable output operating points for the regulator. With this double intersection, the power supply may need to be cycled down to zero and brought up again to make the output recover.
PAGE 10
LT1083/LT1084/LT1085 U W U U APPLICATIONS INFORMATION Connected as shown, RP is not multiplied by the divider ratio. RP is about 0.004Ω per foot using 16-gauge wire. This translates to 4mV/ft at 1A load current, so it is important to keep the positive lead between regulator and load as short as possible and use large wire or PC board traces. compound at the case-to-heat sink interface is strongly recommended.
PAGE 11
LT1083/LT1084/LT1085 U TYPICAL APPLICATIONS 7.5A Variable Regulator T1 TRIAD F-269U L 1MH C30B IN 20Ω 3 110VAC 20Ω T2 1 + 750Ω* 100µF 50,000µF 2 1N914 2k OUTPUT ADJUST 1N4003 1µF 16k* 560Ω 15V 82k 15k –15V 8 2 + 3 10k LT1004-1.2 16k* 200k 11k* 7 –15V 0.1µF – 1 1N4148 NC 15V 4 100pF 2N3904 8 –15V 7 2.7k 4 LT1011 * 1% FILM RESISTOR L: DALE TO-5 TYPE T2: STANCOR 11Z-2003 1.5k 0V TO 35V OA TO 7.5A LT1004-1.
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LT1083/LT1084/LT1085 U TYPICAL APPLICATIONS Paralleling Regulators VIN IN LT1083 2 FEET #18 WIRE* OUT ( ) ADJ VOUT = 1.25V 1 + R2 R1 IOUT = 0A TO 15A 0.015Ω IN LT1083 OUT *THE #18 WIRE ACTS AS BALLAST RESISTANCE INSURING CURRENT SHARING BETWEEN BOTH DEVICES ADJ R1 120Ω LT1083/4/5 ADJ TA03 R2 Improving Ripple Rejection VIN IN LT1083 R1 121Ω 1% ADJ + VOUT 5V OUT 10µF + 150µF R2 365Ω 1% + C1 25µF* *C1 IMPROVES RIPPLE REJECTION.
PAGE 13
LT1083/LT1084/LT1085 U TYPICAL APPLICATIONS High Efficiency Regulator with Switching Preregulator 1mH VIN 28V IN + LT1083 VOUT OUT ADJ 10,000µF MR1122 240Ω 470Ω 10k 1N914 28V 1k 1M 2k 4N28 10k + 1083/4/5 ADJ TA06 LT1011 10k – 28V 1N914 1.2V to 15V Adjustable Regulator VIN IN LT1083 C1* 10µF VOUT† OUT R1 90.
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LT1083/LT1084/LT1085 U PACKAGE DESCRIPTION Dimension in inches (millimeters) unless otherwise noted. K Package 2-Lead TO-3 Metal Can 1.177 – 1.197 (29.90 – 30.40) 0.655 – 0.675 (16.64 – 17.15) 0.210 – 0.220 (5.33 – 5.59) 0.320 – 0.350 (8.13 – 8.89) 0.760 – 0.775 (19.30 – 19.69) 0.060 – 0.135 (1.524 – 3.429) 0.151 – 0.161 (3.84 – 4.09) DIA, 2 PLACES 0.167 – 0.177 (4.24 – 4.49) R 0.425 – 0.435 (10.80 – 11.05) 0.067 – 0.077 (1.70 – 1.96) 0.420 – 0.480 (10.67 – 12.19) 0.495 – 0.525 (12.57 – 13.
PAGE 15
LT1083/LT1084/LT1085 U PACKAGE DESCRIPTION Dimension in inches (millimeters) unless otherwise noted. M Package 3-Lead DD 0.060 (1.524) TYP 0.390 – 0.415 (9.906 – 10.541) 0.165 – 0.180 (4.191 – 4.572) 15° TYP 0.059 (1.499) TYP 0.330 – 0.370 (8.382 – 9.398) 0.045 – 0.055 (1.143 – 1.397) ( +0.008 0.004 –0.004 +0.203 0.102 –0.102 ) 0.095 – 0.115 (2.413 – 2.921) ( 0.090 – 0.110 (2.286 – 2.794) +0.012 0.143 – 0.020 +0.305 3.632 –0.508 ) 0.013 – 0.023 (0.330 – 0.584) 0.050 (1.270) TYP 0.
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LT1083/LT1084/LT1085 U.S. Area Sales Offices NORTHEAST REGION Linear Technology Corporation One Oxford Valley 2300 E. Lincoln Hwy.,Suite 306 Langhorne, PA 19047 Phone: (215) 757-8578 FAX: (215) 757-5631 SOUTHEAST REGION Linear Technology Corporation 17060 Dallas Parkway Suite 208 Dallas, TX 75248 Phone: (214) 733-3071 FAX: (214) 380-5138 SOUTHWEST REGION Linear Technology Corporation 22141 Ventura Blvd.