LX8587-15CDT [MICROSEMI]

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型号：	LX8587-15CDT
厂家：	Microsemi
描述：	暂无描述稳压器
文件：	总8页 (文件大小：213K)
中文：	中文翻译
下载：	下载PDF数据表文档文件

LIN DOC #: 8587

LX8587-xx/8587A-xx

3 A L O W

R O P O U T

O S I T I V E

E G U L AT O R S

T H E I N F I N I T E P O W E R O F I N N O V A T I O N

P R O D U C T I O N D A T A S H E E T

DESCRIPTION

KEY FEATURES

■ Three-Terminal Adjustable Or Fixed

The LX8587/8587A series ICs are low

dropout three-terminal positive regulators

with a nominal 3A output current. Pen-

tium^®Processor and Power PC^TMappli-

cations requiring fast transient response

are ideally suited for this product family.

The LX8587A is guaranteed to have

< 1.2V dropout at 3A and the LX8587

< 1.3V at the same current, making

them ideal to provide well-regulated out-

puts of 2.5V to 3.6V using a 5V input

supply. Fixed versions are also available

and specified in the Available Options

table below.

Current limit is trimmed above 3.1A to

ensure adequate output current and con-

Output

■ Guaranteed ≤ 1.2V Headroom At 3A

trolled short-circuit current. On-chip

thermal limiting provides protection

against any combination of overload con-

ditions that would create excessive junc-

tion temperatures.

The LX8587/87A family of products are

available in both TO-220 through-hole

as well as TO-263 surface-mount pack-

ages. For higher current applications,

see the LX8585 and LX8584 data sheets.

(LX8587A)

■ Guaranteed ≤ 1.3V Headroom At 3A

(LX8587)

■ Output Current Of 3A

p Fast Transient Response

p 1% Voltage Reference Initial Accuracy

p Output Short Circuit Protection

p Built-In Thermal Shutdown

APPLICATIONS

■ Pentium Processor Supplies

■ Power PC Supplies

IMPORTANT: For the most current data, consult LinFinity's web site: http://www.linfinity.com.

■ Microprocessor Supplies

■ Low Voltage Logic Supplies

■ Post Regulator For Switching Supply

■ ASIC & Low Voltage Chipset Supplies

■ Graphics & Sound Cards

PRODUCT HIGHLIGHT

TYPICAL APPLICATION OF THE LX8587/87A IN A 5V TO 3.3V MOTHERBOARD APPLICATION

■ Processor I/O Supply

V_IN

4.75

3.3V/3A

LX8587A

121

2x 1500µF

AVAILABLE OPTIONS PER PAR T #

1500µF

6MV1500GX

Sanyo

Output

6MV1500GX

Part #

Voltage

200

LX8587/87A-00

LX8587/87A-15

LX8587/87A-33

Adjustable

1.5V

3.3V

Other voltage options may be available —

The output capacitors must be low ESR and low ESL type for good transient response.

Please contact factory for details.

PACKAGE ORDER INFORMATION

Plastic TO-220

3-pin

Plastic TO-263

Dropout

Voltage

T_A(°C)

3-pin

1.3V

1.2V

LX8587-xxCP

LX8587-xxCDD

0 to 125

LX8587A-xxCP

LX8587A-xxCDD

Note: All surface-mount packages are available in Tape & Reel.

Append the letter "T" to part number. (i.e. LX8587A-00CDDT)

"xx" refers to output voltage, please see table above.

L I N F I N I T Y M I C R O E L E C T R O N I C S I N C .

11861 WESTERN AVENUE, GARDEN GROVE, CA. 92841, 714-898-8121, FAX: 714-893-2570

Rev. 1.2 3/98

P R O D U C T D A T A B O O K 1 9 9 6 / 1 9 9 7

LX8587-xx/8587A-xx

3 A LO W

R O P O U T

O S I T I V E

E G U L AT O R S

P R O D U C T I O N D A T A S H E E T

ABSOLUTE MAXIMUM RATINGS (Note 1)

PACKAGE PIN OUTS

Power Dissipation ................................................................................ Internally Limited

Input Voltage ............................................................................................................... 10V

Input to Output Voltage Differential.......................................................................... 10V

Maximum Output Current............................................................................................. 5A

Operating Junction Temperature

Plastic (P Package) ...............................................................................................150°C

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

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

TAB IS V_OUT

V_IN

V_OUT

ADJ /

GND*

P PACKAGE

(Top View)

* Pin 1 is GND for fixed voltage versions.

Note 1. Exceeding these ratings could cause damage to the device. All voltages are with

respect to Ground. Currents are positive into, negative out of the specified terminal.

TAB IS V_OUT

THERMAL DATA

V_IN

P PACKAGE:

V_OUT

THERMAL RESISTANCE-JUNCTION TO TAB, θ_JT

THERMAL RESISTANCE-JUNCTION TO AMBIENT, θ_JA

DD PACKAGE:

3.0°C/W

60°C/W

ADJ / GND*

DD PACKAGE

(Top View)

THERMAL RESISTANCE-JUNCTION TO TAB, θ_JT

THERMAL RESISTANCE-JUNCTION TO AMBIENT, θ_JA

3.0°C/W

60°C/W*

* Pin 1 is GND for fixed voltage versions.

Junction Temperature Calculation: T_J= T_A+ (P x θ_JA).

The θ_JAnumbers are guidelines for the thermal ^Dperformance of the device/pc-board system.

All of the above assume no ambient airflow.

* With package soldered to 0.5 in.²copper area over back-side ground plane or internal

power plane, θ_JAcan vary from 20°C/W to 40°C/W, depending on mounting technique.

Rev. 1.2 3/98

P R O D U C T D A T A B O O K 1 9 9 6 / 1 9 9 7

LX8587-xx/8587A-xx

3 A L O W

R O P O U T

O S I T I V E

E G U L AT O R S

P R O D U C T I O N D A T A S H E E T

ELECTRICAL CHARACTERISTICS

(Unless otherwise specified, these specifications apply over the operating ambient temperatures for the LX8587-xx/87A-xx with 0°C ≤ T_A≤ 125°C;

V_IN- V_OUT= 3V; I_OUT= 3A. Low duty cycle pulse testing techniques are used which maintains junction and case temperatures equal to the ambient temperature.)

LX8587-00/87A-00 (Adjustable)

LX8587/87A-00

Parameter

Symbol

Test Conditions

Units

Min. Typ.

Max.

Reference Voltage

V_REF

I_OUT= 10mA, T_A= 25°C

10mA ≤ I_OUT≤ 3A, 1.5V ≤ (V_IN- V_OUT), V_IN≤ 7V, P ≤ P_MAX

∆V_REF(V_IN) I_OUT= 10mA, 1.5V ≤ (V_IN- V_OUT), V_IN≤ 7V

V_IN- V_OUT= 3V, 10mA ≤ I_OUT≤ 3A

∆V_OUT(Pwr) T_A= 25°C, 20ms pulse

V_OUT= 3.3V, f =120Hz, C_OUT= 100µf Tantalum, V_IN= 5V

1.238 1.250 1.262

1.225 1.250 1.275

Line Regulation (Note 2)

Load Regulation (Note 2)

Thermal Regulation

0.035

0.1

0.2

0.5

%/W

∆V_REF(I_OUT

)

0.01

0.02

Ripple Rejection (Note 3)

C_ADJ= 10µF, I_OUT= 3A

Adjust Pin Current

I_ADJ

∆I_ADJ

∆V

0.2

1.1

100

1.3

1.2

µA

Adjust Pin Current Change

10mA ≤ I_OUT≤ 3A, 1.5V ≤ (V_IN- V_OUT), V_IN≤ 7V

∆V_REF= 1%, I_OUT= 3A

Dropout Voltage

LX8587-00

LX8587A-00

Minimum Load Current

Maximum Output Current

Temperature Stability

Long Term Stability

I_OUT(MIN)

V_IN≤ 7V

3.0

0.25

I_OUT(MAX)1.4V ≤ (V_IN- V_OUT), V_IN≤ 7V

∆V_OUT(T)

∆V_OUT(t) T_A= 125°C, 1000 hrs

V_{OUT (RMS)}T_A= 25°C, 10Hz £ f £ 10kHz

0.003

RMS Output Noise (% of V_OUT

)

LX8587-15/87A-15 (1.5V Fixed)

LX8587-15/87A-15

Min. Typ. Max.

Parameter

Symbol

Test Conditions

Units

1.485

1.470

1.5

1.515

1.530

Output Voltage

V_OUT

V_IN= 5V, I_OUT= 0mA, T_A= 25°C

3.0V ≤ V_IN≤ 7V, 0mA ≤ I_OUT≤ 3A, P ≤ P_MAX

Line Regulation (Note 2)

∆V_OUT4.75V ≤ V_IN≤ 7V

(V_IN)

% / W

4.75V ≤ V_IN≤ 10V

V_IN= 5V, 0mA ≤ I_OUT≤ I_{OUT (MAX)}

0.01

7.5

0.02

Load Regulation (Note 2)

Thermal Regulation (Note 3)

Ripple Rejection (Note 3)

Quiescent Current

∆V_OUT(I_OUT

)

∆V_OUT(Pwr) T_A= 25°C, 20ms pulse

C_OUT= 100µF (Tantalum), I_OUT= 3A

I_Q

0mA ≤ I_OUT≤ I_{OUT (MAX)}, 4.75V ≤ V_IN≤ 10V

∆V_OUT= 1%, I_OUT≤ I_{OUT (MAX)}

1.3

1.2

Dropout Voltage

LX8587-15

∆V

1.1

LX8587A-15

∆V_OUT= 1%, I_OUT≤ I_{OUT (MAX)}

3.0

5.0

0.25

0.3

0.003

Maximum Output Current

I_{OUT (MAX)}V_IN≤ 7V

Temperature Stability (Note 3)

Long Term Stability (Note 3)

∆V_OUT(T)

∆V_OUT(t) T_A= 125°C, 1000 hours

RMS Output Noise (% of V_OUT) (Note 3) V_{OUT (RMS)}T_A= 25°C, 10Hz ≤ f ≤ 10kHz

Note 2. Regulation is measured at constant junction temperature, using pulse testing with a low duty cycle. Changes in output voltage due to

heating effects are covered under the specification for thermal regulation.

Note 3. These parameters, although guaranteed, are not tested in production.

Rev. 1.2 3/98

P R O D U C T D A T A B O O K 1 9 9 6 / 1 9 9 7

LX8587-xx/8587A-xx

3 A LO W

R O P O U T

O S I T I V E

E G U L AT O R S

P R O D U C T I O N D A T A S H E E T

ELECTRICAL CHARACTERISTICS

LX8587-33/87A-33 (3.3V Fixed)

LX8587-33/87A-33

Min. Typ. Max.

Parameter

Symbol

V_OUT

Test Conditions

Units

Output Voltage

V_IN= 5V, I_OUT= 0mA, T_A= 25°C

4.75V ≤ V_IN≤ 10V, 0mA ≤ I_OUT≤ 3A, P ≤ P_MAX

∆V_OUT4.75V ≤ V_IN≤ 7V

3.267

3.235

3.3

3.333

3.365

Line Regulation (Note 2)

% / W

(V_IN)

4.75V ≤ V_IN≤ 10V

Load Regulation (Note 2)

Thermal Regulation (Note 3)

Ripple Rejection (Note 3)

Quiescent Current

∆V_OUT(I_OUT

)

V_IN= 5V, 0mA ≤ I_OUT≤ I_{OUT (MAX)}

∆V_OUT(Pwr) T_A= 25°C, 20ms pulse

C_OUT= 100µF (Tantalum), I_OUT= 3A

0.01

0.02

I_Q

∆V

0mA ≤ I_OUT≤ I_{OUT (MAX)}, 4.75V ≤ V_IN≤ 10V

∆V_OUT= 1%, I_OUT≤ I_{OUT (MAX)}

1.1

1.3

1.2

Dropout Voltage

LX8587-33

LX8587A-33

∆V_OUT= 1%, I_OUT≤ I_{OUT (MAX)}

3.0

5.0

0.25

0.3

0.003

Maximum Output Current

Temperature Stability (Note 3)

Long Term Stability (Note 3)

I_{OUT (MAX)}V_IN≤ 7V

∆V_OUT(T)

∆V_OUT(t) T_A= 125°C, 1000 hours

RMS Output Noise (% of V_OUT) (Note 3) V_{OUT (RMS)}T_A= 25°C, 10Hz ≤ f ≤ 10kHz

Note 2. Regulation is measured at constant junction temperature, using pulse testing with a low duty cycle. Changes in output voltage due to

heating effects are covered under the specification for thermal regulation.

Note 3. These parameters, although guaranteed, are not tested in production.

Rev. 1.2 3/98

P R O D U C T D A T A B O O K 1 9 9 6 / 1 9 9 7

LX8587-xx/8587A-xx

3 A L O W

R O P O U T

O S I T I V E

E G U L AT O R S

P R O D U C T I O N D A T A S H E E T

APPLICATION NOTES

Minumum Load

(Larger resistor)

The LX8587/87A series ICs are easy to use Low-Dropout (LDO)

Power Supply

OUT

LX8587/87A

voltage regulators. They have all of the standard self-protection

features expected of a voltage regulator: short circuit protection,

safe operating area protection and automatic thermal shutdown if

the device temperature rises above approximately 165°C.

Use of an output capacitor is REQUIRED with the LX8587/87A

series. Please see the table below for recommended minimum

capacitor values.

Full Load

(Smaller resistor)

ADJ

R_DSON<< R_L

1 sec

10ms

Star Ground

These regulators offer a more tightly controlled reference voltage

tolerance and superior reference stability when measured against

the older pin-compatible regulator types that they replace.

FIGURE 1 — Dynamic Input And Output Test

OVERLOAD RECOVERY

Like almost all IC power regulators, the LX8587/87A regulators are

equipped with Safe Operating Area (SOA) protection. The SOA

circuit limits the regulator's maximum output current to progres-

sively lower values as the input-to-output voltage difference

increases. By limiting the maximum output current, the SOA circuit

keeps the amount of power that is dissipated in the regulator itself

within safe limits for all values of input-to-output voltage within the

operating range of the regulator. The LX8587/87A SOA protection

system is designed to be able to supply some output current for all

values of input-to-output voltage, up to the device breakdown

voltage.

Under some conditions, a correctly operating SOA circuit may

prevent a power supply system from returning to regulated

operation after removal of an intermittent short circuit at the output

of the regulator. This is a normal mode of operation which can be

seen in most similar products, including older devices such as 7800

series regulators. It is most likely to occur when the power system

input voltage is relatively high and the load impedance is relatively

low.

STABILITY

The output capacitor is part of the regulator’s frequency compen-

sation system. Many types of capacitors are available, with different

capacitance value tolerances, capacitance temperature coefficients,

and equivalent series impedances. For all operating conditions,

connection of a 220µF aluminum electrolytic capacitor or a 47µF

solid tantalum capacitor between the output terminal and ground

will guarantee stable operation.

If a bypass capacitor is connected between the output voltage

adjust (ADJ) pin and ground, ripple rejection will be improved

(please see the section entitled “RIPPLE REJECTION”). When ADJ

pinbypassingisused,therequiredoutputcapacitorvalueincreases.

Output capacitor values of 220µF (aluminum) or 47µF (tantalum)

provide for all cases of bypassing the ADJ pin. If an ADJ pin bypass

capacitor is not used, smaller output capacitor values are adequate.

Thetablebelowshowsrecommendedminimumcapacitancevalues

for stable operation.

When the power system is started “cold”, both the input and

output voltages are very close to zero. The output voltage closely

follows the rising input voltage, and the input-to-output voltage

difference is small. The SOA circuit therefore permits the regulator

to supply large amounts of current as needed to develop the

designed voltage level at the regulator output. Now consider the

casewheretheregulatorissupplyingregulatedvoltagetoaresistive

load under steady state conditions. A moderate input-to-output

voltage appears across the regulator but the voltage difference is

small enough that the SOA circuitry allows sufficient current to flow

throughtheregulatortodevelopthedesignedoutputvoltageacross

theloadresistance. Iftheoutputresistorisshort-circuitedtoground,

theinput-to-outputvoltagedifferenceacrosstheregulatorsuddenly

becomes larger by the amount of voltage that had appeared across

the load resistor. The SOA circuit reads the increased input-to-

output voltage, and cuts back the amount of current that it will

permittheregulatortosupplytoitsoutputterminal. Whentheshort

circuit across the output resistor is removed, all the regulator output

current will again flow through the output resistor. The maximum

current that the regulator can supply to the resistor will be limited

bytheSOAcircuit,basedonthelargeinput-to-outputvoltageacross

theregulatoratthetimetheshortcircuitisremovedfromtheoutput.

RECOMMENDED CAPACITOR VALUES

INPUT

OUTPUT

ADJ

None

15µF

10µF

15µF Tantalum, 100µF Aluminum

47µF Tantalum, 220µF Aluminum

In order to ensure good transient response from the power supply

system under rapidly changing current load conditions, designers

generally use several output capacitors connected in parallel. Such

an arrangement serves to minimize the effects of the parasitic

resistance (ESR) and inductance (ESL) that are present in all

capacitors. Cost-effective solutions that sufficiently limit ESR and

ESL effects generally result in total capacitance values in the range

of hundreds to thousands of microfarads, which is more than

adequate to meet regulator output capacitor specifications. Output

capacitance values may be increased without limit.

ThecircuitshowninFigure1canbeusedtoobservethetransient

response characteristics of the regulator in a power system under

changing loads. The effects of different capacitor types and values

on transient response parameters, such as overshoot and under-

shoot, can be quickly compared in order to develop an optimum

solution.

Rev. 1.2 3/98

P R O D U C T D A T A B O O K 1 9 9 6 / 1 9 9 7

LX8587-xx/8587A-xx

3 A LO W

R O P O U T

O S I T I V E

E G U L AT O R S

P R O D U C T I O N D A T A S H E E T

APPLICATION NOTES

OVERLOAD RECOVERY (continued)

If this limited current is not sufficient to develop the designed

voltage across the output resistor, the voltage will stabilize at some

lower value, and willnever reach the designed value. Under these

circumstances, it may be necessary to cycle the input voltage down

to zero in order to make the regulator output voltage return to

regulation.

LX8587/87A

OUT

V_IN

V_OUT

ADJ

V_REF

I_ADJ

50µA

RIPPLE REJECTION

V_OUT= V_REF1 +

+ I_ADJR2

Ripple rejection can be improved by connecting a capacitor

betweentheADJpinandground. Thevalueofthecapacitorshould

be chosen so that the impedance of the capacitor is equal in

magnitude to the resistance of R1 at the ripple frequency. The

capacitor value can be determined by using this equation:

FIGURE 2 — Basic Adjustable Regulator

LOAD REGULATION

C = 1 / (6.28 F R1)

Because the LX8587/87A regulators are three-terminal devices, it is

not possible to provide true remote load sensing. Load regulation

willbelimitedbytheresistanceofthewireconnectingtheregulator

to the load. The data sheet specification for load regulation is

measured at the bottom of the package. Negative side sensing is a

true Kelvin connection, with the bottom of the output divider

returned to the negative side of the load. Although it may not be

immediately obvious, best load regulation is obtained when the top

of the resistor divider, (R1), is connected directly to the case of the

regulator, not to the load. This is illustrated in Figure 3. If R1 were

connectedtotheload,theeffectiveresistancebetweentheregulator

and the load would be:

where: C ≡ the value of the capacitor in Farads;

select an equal or larger standard value.

F_R≡ the ripple frequency in Hz

R1 ≡ the value of resistor R1 in ohms

At a ripple frequency of 120Hz, with R1 = 100Ω:

C = 1 / (6.28 120Hz 100Ω) = 13.3µF

The closest equal or larger standard value should be used, in this

case, 15µF.

When an ADJ pin bypass capacitor is used, output ripple

amplitude will be essentially independent of the output voltage. If

an ADJ pin bypass capacitor is not used, output ripple will be

proportional to the ratio of the output voltage to the reference

voltage:

R2+R1

R_Peff= R_P

where: R_P≡ Actual parasitic line resistance.

M = V_OUT/V_REF

When the circuit is connected as shown in Figure 3, the parasitic

resistance appears as its actual value, rather than the higher R_Peff.

where: M ≡ a multiplier for the ripple seen when the

ADJ pin is optimally bypassed.

V_REF= 1.25V.

Para^Psitic

LX8587/87A

OUT

Line Resistance

For example, if V_OUT= 2.5V the output ripple will be:

M = 2.5V/1.25V= 2

V_IN

ADJ

Connect

R1 to Case

of Regulator

Output ripple will be twice as bad as it would be if the ADJ pin

were to be bypassed to ground with a properly selected capacitor.

R_L

OUTPUT VOLTAGE

Connect

The LX8587/87A ICs develop a 1.25V reference voltage between the

output and the adjust terminal (See Figure 2). By placing a resistor, R1,

between these two terminals, a constant current is caused to flow

through R1 and down through R2 to set the overall output voltage.

Normally this current is the specified minimum load current of 10mA.

BecauseI_ADJisverysmallandconstantwhencomparedwiththecurrent

through R1, it represents a small error and can usually be ignored.

to Load

FIGURE 3 — Connections For Best Load Regulation

Rev. 1.2 3/98

P R O D U C T D A T A B O O K 1 9 9 6 / 1 9 9 7

LX8587-xx/8587A-xx

3 A L O W

R O P O U T

O S I T I V E

E G U L AT O R S

P R O D U C T I O N D A T A S H E E T

APPLICATION NOTES

LOAD REGULATION (continued)

Even when the circuit is optimally configured, parasitic resistance

can be a significant source of error. A 100 mil wide PC trace built

from 1 oz. copper-clad circuit board material has a parasitic

resistance of about 5 milliohms per inch of its length at room

temperature. If a 3-terminal regulator used to supply 2.50 volts is

connected by 2 inches of this trace to a load which draws 5 amps

of current, a50 millivolt dropwill appearbetween theregulatorand

the load. Even when the regulator output voltage is precisely

2.50 volts, the load will only see 2.45 volts, which is a 2% error. It

is important to keep the connection between the regulator output

pin and the load as short as possible, and to use wide traces or

heavy-gauge wire.

can be used, as long as its added contribution to thermal resistance

is considered. Note that the case of all devices in this series is

electrically connected to the output.

Example

Given: V_IN= 5V

V_OUT= 2.8V, I_OUT= 5.0A

Ambient Temp., T_A= 50°C

R_θJT= 2.7°C/W for TO-220

300 ft/min airflow available

Find: Proper Heat Sink to keep IC's junction

temperature below 125°C.**

The minimum specified output capacitance for the regulator

should be located near the reglator package. If several capacitors

are used in parallel to construct the power system output capaci-

tance, any capacitors beyond the minimum needed to meet the

specified requirements of the regulator should be located near the

sections of the load that require rapidly-changing amounts of

current. Placing capacitors near the sources of load transients will

help ensure that power system transient response is not impaired

by the effects of trace impedance.

To maintain good load regulation, wide traces should be used on

the input side of the regulator, especially between the input

capacitors and the regulator. Input capacitor ESR must be small

enoughthatthevoltageattheinputpindoesnotdropbelowV_IN(MIN)

during transients.

Solution: The junction temperature is:

T_J= P_D(R_θJT+ R_θCS+ R_θSA) + T_A

where: P_D≡ Dissipated power.

R_θJT≡ Thermal resistance from the junction to the

mounting tab of the package.

R_θCS≡ Thermal resistance through the interface

between the IC and the surface on which

it is mounted. (1.0°C/W at 6 in-lbs

mounting screw torque.)

R_θSA

≡

Thermal resistance from the mounting surface

to ambient (thermal resistance of the heat sink).

T_S≡ Heat sink temperature.

T_JT_CT_S

T_A

V_{IN (MIN)}= V_OUT+ V_{DROPOUT (MAX)}

R_{q JT}

R_qCS

R_qSA

where: V_{IN (MIN)}

V_OUT

≡ the lowest allowable instantaneous

voltage at the input pin.

≡ the designed output voltage for the

power supply system.

First, find the maximum allowable thermal resistance of the

heat sink:

T_J- T_A

R_θSA

- (R_θJT+ R_θCS)

P_D

P_D= (V_IN(MAX)- V_OUT) I_OUT

V_{DROPOUT (MAX)}≡ the specified dropout voltage

for the installed regulator.

(5.0V-2.8V)

5.0A

THERMAL CONSIDERATIONS

= 11.0W

125°C - 50°C

(5.0V-2.8V) 5.0A

The LX8587/87A regulators have internal power and thermal

limiting circuitry designed to protect each device under overload

conditions. For continuous normal load conditions, however,

maximum junction temperature ratings must not be exceeded. It is

important to give careful consideration to all sources of thermal

resistance from junction to ambient. This includes junction to case,

case to heat sink interface, and heat sink thermal resistance itself.

Junction-to-case thermal resistance is specified from the IC

junction to the back surface of the case directly opposite the die.

This is the lowest resistance path for heat flow. Proper mounting

is required to ensure the best possible thermal flow from this area

of the package to the heat sink. Thermal compound at the case-to-

heat-sink interface is strongly recommended. If the case of the

device must be electrically isolated, a thermally conductive spacer

R_θSA

- (2.7°C/W+ 1.0°C/W)

= 3.1°C/W

Next,selectasuitableheatsink. Theselectedheatsinkmusthave

R_θSA≤ 3.1°C/W. Thermalloyheatsink6296BhasR_θSA=3.0°C/Wwith

300ft/min air flow.

Finally, verify that junction temperature remains within speci-

fication using the selected heat sink:

T_J= 11W (2.7°C/W + 1.0°C/W + 3.0°C/W) + 50°C = 124°C

** Although the device can operate up to 150°C junction, it is recom-

mended for long term reliability to keep the junction temperature

below 125°C whenever possible.

Rev. 1.2 3/98

P R O D U C T D A T A B O O K 1 9 9 6 / 1 9 9 7

LX8587-xx/8587A-xx

3 A LO W

R O P O U T

O S I T I V E

E G U L AT O R S

P R O D U C T I O N D A T A S H E E T

TYPICAL APPLICATIONS

LX8587/87A

OUT

LX8587/87A

OUT

V_IN

(Note A)

V_IN

V_OUT**

V_OUT

ADJ

121W

ADJ

10µF

121W

100µF

C1*

10µF

150µF

365W

* C1 improves ripple rejection.

X_Cshould be » R1 at ripple

frequency.

10µF*

* Needed if device is far from filter capacitors.

**V_OUT= 1.25V 1 +

FIGURE 4 — Improving Ripple Rejection

FIGURE 5 — 1.2V - 8V Adjustable Regulator

LX8587/87A

OUT

V_IN

(Note A)

ADJ

121W

100µF

10µF

TTL

Output

2N3904

365W

FIGURE 6 — 5V Regulator With Shutdown

LX8587-33/87A-33

V_IN

OUT

3.3V

GND

10µF Tantalum

or 100µF Aluminum

Min. 15µF Tantalum or

100µF Aluminum capacitor.

May be increased as needed.

ESR must be less than 50mW.

FIGURE 7 — Fixed 3.3V Output Regulator

Note A: V_{IN (MIN)}= (Intended V_OUT) + (V_{DROPOUT (MAX)}

)

Pentium is a registered trademark of Intel Corporation.

Power PC is a trademark of International Business Machines Corporation.

PRODUCTIONDATA-InformationcontainedinthisdocumentisproprietarytoLinFinity, andiscurrentasofpublicationdate. Thisdocument

may not be modified in any way without the express written consent of LinFinity. Product processing does not necessarily include testing of

all parameters. Linfinity reserves the right to change the configuration and performance of the product and to discontinue product at any time.

Rev. 1.2 3/98

LX8587-15CDT [MICROSEMI]

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