Datasheet

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LT1585A/LT1585A-3.3

1585afa

5A Low Dropout

Fast Response

Positive Regulators

Adjustable and Fixed

The LT

1585A/LT1585A-3.3 are low dropout 3-terminal

regulators with 5A output current capability. Design has

been optimized for low voltage applications where tran-

sient response and minimum input voltage are critical.

Similar to the LT1084 family, these regulators feature

lower dropout voltage and faster transient response.

These improvements make them ideal for low voltage

microprocessor applications requiring a regulated 2.5V to

3.6V output with an input supply below 7V.

Current limit is trimmed to ensure specified output current

and controlled short-circuit current. On-chip thermal lim-

iting provides protection against any combination of over-

load that would create excessive junction temperatures.

The LT1585A/LT1585A-3.3 are available in the industry

standard 3-pin TO-220 power package.

■

Fast Transient Response

■

Guaranteed Dropout Voltage at Multiple Currents

■

Load Regulation: 0.05% Typ

■

Trimmed Current Limit

■

On-Chip Thermal Limiting

■

Standard 3-Pin TO-220 Power Package

■

Pentium

Processor Supplies

■

PowerPC

Supplies

■

Other 2.5V to 3.6V Microprocessor Supplies

■

Low Voltage Logic Supplies

■

Battery-Powered Circuitry

■

Post Regulator for Switching Supply

LT1585ACT Adjustable

LT1585ACT-3.3 3.3V Fixed

, LTC and LT are registered trademarks of Linear Technology Corporation.

Pentium is a registered trademark of Intel Corporation. PowerPC is a trademark of IBM Corporation.

NOTE: MICROPROCESSOR APPLICATIONS WITH LOAD TRANSIENTS OF 3.8A REQUIRE

OUTPUT DECOUPLING CAPACITANCE >1300µF ON FIXED VOLTAGE PARTS TO ACHIEVE

< 50mV OF DEVIATION FROM NOMINAL OUTPUT. CONSULT FACTORY FOR DETAILS

Dropout Voltage vs Output Current

3.3V, 5A Regulator

LT1585A-3.3

≥ 4.75V

1585A TA01

10µF

* REQUIRED FOR STABILITY

3.3V

C2*

100µF

+ +

OUTPUT CURRENT (A)

INPUT/OUTPUT DIFFERENTIAL (V)

1.5

1.4

1.3

1.2

1.1

1.0

0.9

0.8

0.7

0.6

0.5

LT1585A TA02

FULL LOAD

DESCRIPTIO

FEATURES

APPLICATIO S

TYPICAL APPLICATIO

Summary of content (12 pages)

PAGE 1
LT1585A/LT1585A-3.3 5A Low Dropout Fast Response Positive Regulators Adjustable and Fixed U FEATURES DESCRIPTIO ■ The LT ®1585A/LT1585A-3.3 are low dropout 3-terminal regulators with 5A output current capability. Design has been optimized for low voltage applications where transient response and minimum input voltage are critical. Similar to the LT1084 family, these regulators feature lower dropout voltage and faster transient response.
PAGE 2
LT1585A/LT1585A-3.3 W W U W ABSOLUTE MAXIMUM RATINGS Storage Temperature Range ................. – 65°C to 150°C Lead Temperature (Soldering, 10 sec).................. 300°C UU U VIN ............................................................................. 7V Operating Junction Temperature Range Control Section ................................... 0°C to 125°C Power Transistor .................................
PAGE 3
LT1585A/LT1585A-3.3 ELECTRICAL CHARACTERISTICS The ● denotes specificatons which apply over the specified temperature range, otherwise specifications are at TA = 25°C. PARAMETER CONDITIONS Ripple Rejection LT1585A Thermal Regulation LT1585A-3.3 f = 120Hz, COUT = 100µF Tant., (VIN – VOUT) = 3V, IOUT = 5A f = 120Hz, COUT = 100µF Tant., VIN = 6.3V, IOUT = 5A LT1585A LT1585A-3.3 TA = 25°C, 30ms Pulse TA = 25°C, 30ms Pulse ● MIN TYP 60 72 0.004 ● Temperature Stability TA = 125°C, 1000 Hrs. 0.
PAGE 4
LT1585A/LT1585A-3.3 U W TYPICAL PERFORMANCE CHARACTERISTICS Output Voltage vs Temperature Using Adjustable LT1585A 3.70 3.65 1.265 3.60 1.260 1.255 1.250 1.245 1.240 LT1585A-3.3 Output Voltage vs Temperature 3.35 VOUT SET WITH 1% RESISTORS 3.34 VOUT = 3.6V 3.33 OUTPUT VOLTAGE (V) 1.275 1.270 OUTPUT VOLTAGE (V) REFERENCE VOLTAGE (V) LT1585A Reference Voltage vs Temperature 3.55 3.50 VOUT = 3.45V 3.45 VOUT = 3.38V 3.40 3.35 VOUT = 3.3V 3.32 3.31 VOUT = 3.3V 3.30 3.29 3.28 3.27 1.235 3.
PAGE 5
LT1585A/LT1585A-3.3 W W SI PLIFIED SCHE ATIC VIN + – THERMAL LIMIT VOUT ADJ GND LT1585A • BD FOR FIXED VOLTAGE DEVICE U W U U APPLICATIONS INFORMATION General The LT1585A/LT1585A-3.3 3-terminal regulators are easy to use and have all the protection features expected in high performance linear regulators. The devices are short-circuit protected, safe-area protected and provide thermal shutdown to turn off the regulators should the junction temperature exceed about 150°C.
PAGE 6
LT1585A/LT1585A-3.3 U W U U APPLICATIONS INFORMATION tor tolerance (sometimes ranging up to ±100%), equivalent series resistance, equivalent series inductance and capacitance temperature coefficient. The LT1585A/ LT1585A-3.3 frequency compensation optimizes frequency response with low ESR capacitors. In general, use capacitors with an ESR of less than 1Ω. On the adjustable LT1585A, bypassing the adjust terminal improves ripple rejection and transient response.
PAGE 7
LT1585A/LT1585A-3.3 U W U U APPLICATIONS INFORMATION A protection diode between the input and output pins is usually not needed. An internal diode between the input and output pins on the LT1585A/LT1585A-3.3 can handle microsecond surge currents of 50A to 100A. Even with large value output capacitors it is difficult to obtain those values of surge currents in normal operation.
PAGE 8
LT1585A/LT1585A-3.3 U W U U APPLICATIONS INFORMATION load regulation is obtained when the top of resistor divider R1 connects directly to the regulator output and not to the load. Figure 5 illustrates this point. If R1 connects to the load, the effective resistance between the regulator and the load is: Load Regulation It is not possible to provide true remote load sensing because the LT1585A/LT1585A-3.3 are 3-terminal devices.
PAGE 9
LT1585A/LT1585A-3.3 U W U U APPLICATIONS INFORMATION Thermal Considerations The LT1585A/LT1585A-3.3 family protects the device under overload conditions with internal power and thermal limiting circuitry. However, for normal continuous load conditions, do not exceed maximum junction temperature ratings. It is important to consider all sources of thermal resistance from junction-to-ambient.
PAGE 10
LT1585A/LT1585A-3.3 U TYPICAL APPLICATIONS N Minimum Parts Count LT1585A Adjustable Circuit for the Intel 120MHz Pentium Processor THERMALLOY 7020B-MT 4.75V TO 5.25V + 3.50V 5A OUT IN C1 TO C3 220µF 10V AVX TPS 3 EACH PLACE IN MICROPROCESSOR SOCKET CAVITY LT1585ACT ADJ C4 330nF 16V AVX X7R 0805 R1 110Ω 0.1% R2 197Ω 0.1% + C5 TO C10 100µF 10V AVX TPS 6 EACH C11 TO C20 1µF 16V AVX Y5V 0805 10 EACH LT1585A TA04 AVX CORP. (803) 448-9411 THERMALLOY INC. (214) 243-4321 DO NOT SUBSTITUTE COMPONENTS.
PAGE 11
LT1585A/LT1585A-3.3 U TYPICAL APPLICATIONS N Guaranteed LT1585A Circuit for the Intel 100MHz and Higher Frequency Pentium Processors (Meets Intel Specifications with Worst-Case Tolerances) THERMALLOY 7021B-MT 5V SEE NOTE 5 3 + C2 TO C4 220µF 10V AVX TPS 3 EACH IN PLACE IN MICROPROCESSOR SOCKET CAVITY OUT 2 SEE NOTE 6 LT1585A + R1 1k ADJ 1 C6 R2 0.01µF 1k C5 33pF NPO C1 0.
PAGE 12
LT1585A/LT1585A-3.3 U PACKAGE DESCRIPTION T Package 3-Lead Plastic TO-220 (Reference LTC DWG # 05-08-1420) .147 – .155 (3.734 – 3.937) DIA .390 – .415 (9.906 – 10.541) .165 – .180 (4.191 – 4.572) .045 – .055 (1.143 – 1.397) .230 – .270 (5.842 – 6.858) .460 – .500 (11.684 – 12.700) .570 – .620 (14.478 – 15.748) .330 – .370 (8.382 – 9.398) .980 – 1.070 (24.892 – 27.178) .520 – .570 (13.208 – 14.478) .100 (2.540) BSC .218 – .252 (5.537 – 6.401) .013 – .023 (0.330 – 0.584) .028 – .038 (0.711 – 0.