Datasheet

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LT1587-1.5

Fixed 1.5V, 3A

Low Dropout

Fast Response

GTL

Regulator



The LT

1587-1.5 is a low dropout 3-terminal regulator

with a fixed 1.5V output voltage and 3A output current

capability. The design is optimized for low voltage applica-

tions where transient response and minimum input voltage

are critical. Similar to the LT1085, it has lower dropout and

faster transient response. These improvements make it

ideal for low voltage microprocessor applications, espe-

cially as the regulator in an Intel Pentium Pro processor

GTL

supply.

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 creates excessive junction temperatures.

The LT1587-1.5 is available in both the through-hole and

surface mount versions of the industry standard 3-pin

TO-220 power package.

DESCRIPTION

■

Fast Transient Response

■

Guaranteed Dropout Voltage at Multiple Currents

■

Load Regulation: 0.05% Typ

■

Trimmed Current Limit

■

On-Chip Thermal Limiting

FEATURES

APPLICATIONS

■

Intel Pentium

Pro Processor GTL

Supply

■

Low Voltage Logic Supplies

■

Battery-Powered Circuitry

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

Pentium is a registered trademark of Intel Corporation

TYPICAL APPLICATION

Intel Pentium Pro Processor GTL

Supply

C2, C3

100µF

10V

AVX TPS

C1

100µF

10V

AVX TPS

C4 TO 

C6

1µF

C8, C9

100µF

10V

AVX TPS

C10 TO C12

1µF

C7

100µF

10V

AVX TPS

R1

75Ω

R5

100Ω

R2

150Ω

REF

R4

150Ω

REF

R7

100Ω

R8

100Ω

R6

100Ω

R3

75Ω

OUT

GND

LT1587-1.5

3.3V 3.3V

= 1.5V

OUT

GND

LT1587-1.5

142 TOTAL SIGNAL LINES

•

•

C13

0.1µF

C14

0.1µF

LT1587 • TA01

NOTE: LTC RECOMMENDS SEPARATE 

GENERATORS AT EACH BUS END

TO ENSURE CURRENT SHARING

BETWEEN THE REGULATORS AND TO

MINIMIZE V

DISTRIBUTION DROPS

Summary of content (8 pages)

PAGE 1
LT1587-1.5 U DESCRIPTION FEATURES ■ ■ ■ ■ ■ The LT ®1587-1.5 is a low dropout 3-terminal regulator with a fixed 1.5V output voltage and 3A output current capability. The design is optimized for low voltage applications where transient response and minimum input voltage are critical. Similar to the LT1085, it has lower dropout and faster transient response.
PAGE 2
LT1587-1.5 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
LT1587-1.5 U W TYPICAL PERFORMANCE CHARACTERISTICS Short-Circuit Current vs Temperature Dropout Voltage vs Output Current 0.10 1.3 1.2 T = –5°C 1.1 1.0 T = 25°C 0.9 T = 125°C 0.8 0.7 OUTPUT VOLTAGE DEVIATION (%) SHORT-CIRCUIT CURRENT (A) GUARANTEED TEST POINTS 1.4 4.5 4.0 3.5 ∆I = 3A 0.05 0 –0.05 –0.10 –0.15 0.6 0.5 1.5 2.0 1.0 OUTPUT CURRENT (A) 2.5 3.0 3.0 –75 –50 –25 0 25 50 75 100 125 150 175 TEMPERATURE (°C) –0.
PAGE 4
LT1587-1.5 W W SI PLIFIED SCHE ATIC VIN + – THERMAL LIMIT VOUT GND LT1587 • BD U W U U APPLICATIONS INFORMATION General The LT1587-1.5 3-terminal regulator is easy to use and has all the protection features expected in a high performance linear regulator. The device is short-circuit protected, safe-area protected and provides thermal shutdown to turn off the regulator if the junction temperature exceeds about 150°C.
PAGE 5
LT1587-1.5 U W U U APPLICATIONS INFORMATION Large load current changes are exactly the situation presented by modern microprocessors and their peripheral circuitry. The load current step contains higher order frequency components that the output decoupling network must handle until the regulator throttles to the load current level. Capacitors are not ideal elements and contain parasitic resistance and inductance.
PAGE 6
LT1587-1.5 U W U U APPLICATIONS INFORMATION regulation is limited by the resistance of the wire connecting the regulators to the load. Load regulation per the data sheet specification is measured at the bottom of the package. For fixed voltage devices, negative side sensing is a true Kelvin connection with the Ground pin of the device returned to the negative side of the load. This is illustrated in Figure 3. VIN LT1587-1.5 IN OUT RP PARASITIC LINE RESISTANCE GND RL LT1587 • F03 Figure 3.
PAGE 7
LT1587-1.5 U PACKAGE DESCRIPTION Dimensions in inches (millimeters) unless otherwise noted. M Package 3-Lead Plastic DD Pak (LTC DWG # 05-08-1460) 0.256 (6.502) 0.060 (1.524) TYP 0.060 (1.524) 0.390 – 0.415 (9.906 – 10.541) 0.165 – 0.180 (4.191 – 4.572) 0.045 – 0.055 (1.143 – 1.397) 15° TYP 0.060 (1.524) 0.183 (4.648) 0.059 (1.499) TYP 0.330 – 0.370 (8.382 – 9.398) ( +0.008 0.004 –0.004 +0.203 0.102 –0.102 ) 0.095 – 0.115 (2.413 – 2.921) 0.075 (1.905) 0.300 (7.620) ( +0.305 3.632 –0.
PAGE 8
LT1587-1.5 RELATED PARTS PART NUMBER DESCRIPTION COMMENTS LTC ® 1392 Micropower Temperature, Power Supply and Differential Voltage Monitor Micropower Data Acquisition to Monitor System LTC1430 High Power Step-Down Switching Regulator Controller 5V to 3.3V at 10A or More LTC1472 Protected PCMCIA VCC and VPP Switching Matrix Single-Slot Power Switch LT1580 Very Low Dropout 7A Linear Regulator 0.54V Dropout at 7A, Fixed 2.