LX8383B-00CP [MICROSEMI]

7.5 A LOW DROPOUT POSITIVE REGULATORS; 7.5低压差稳压器正


型号：	LX8383B-00CP
厂家：	Microsemi
描述：	7.5 A LOW DROPOUT POSITIVE REGULATORS 7.5低压差稳压器正稳压器
文件：	总7页 (文件大小：202K)
中文：	中文翻译
下载：	下载PDF数据表文档文件

LIN DOC #: 8383

LX8383-xx/8383A-xx/8383B-xx

7. 5A 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 LX8383/8383A/8383B series ICs are

positive regulators designed to provide

7.5A output current. All internal circuitry

is designed to operate down to a 1V in-

put-to-output differential, so the LX8383/

83A/83B can operate with greater effi-

ciency than previously available devices.

The dropout voltage for each product is

fully specified as a function of load cur-

rent. Dropout is guaranteed at a maxi-

mum of 1.3V for the LX8383A/83B and

1.5V for the LX8383, at maximum output

current, decreasing at lower load currents.

Fixed versions are also available and speci-

fied in the Available Options table below.

The LX8383B offers a tighter voltage ref-

erence tolerance: 0.8% initial accuracy and

1% over line, load and temperature. The

LX8383/83A have 1% initial accuracy and

2% over line, load and temperature.

The LX8383/83A/83B series devices are

OUTPUT VOLTAGE

■ GUARANTEED < 1.3V HEADROOM AT

7.5A (LX8383A/8383B)

■ GUARANTEED < 1.5V HEADROOM AT

7.5A (LX8383)

■ OUTPUT CURRENT OF 7.5A MINIMUM

p 0.015% LINE REGULATION

p 0.15% LOAD REGULATION

■ EVALUATION BOARD AVAILABLE:

REQUEST LXE9001 EVALUATION KIT

pin-compatible with earlier 3-terminal

regulators, such as the 117 series prod-

ucts. While a 10µF output capacitor is

required on both input and output of these

new devices, this capacitor is generally

included in most regulator designs.

The LX8383/83A/83B series quiescent

current flows into the load, thereby

increasing efficiency. This feature

contrasts with PNP regulators, where up

to 10% of the output current is wasted as

quiescent current. The LX8383I/8383AI is

specified over the industrial temperature

range of -25°C to +125°C and the

LX8383C/8383AC/8383BC is specified

over the commercial range of 0°C to

+125°C.

APPLICATIONS

■ PENTIUM^®PROCESSOR APPLICATIONS

■ HIGH EFFICIENCY LINEAR REGULATORS

■ POST REGULATORS FOR SWITCHING

POWER SUPPLIES

■ BATTERY CHARGERS

■ CONSTANT CURRENT REGULATORS

■ CYRIX^®6x86^TM

■ AMD-K5^TM

PRODUCT HIGHLIGHT

AVAILABLE OPTIONS PER PAR T #

3.3V, 7.5A REGULATOR

Output

Part #

Voltage

OUT

LX8383/83A/83B-00

LX8383/83A/83B-33

Other voltage options may be available —

Please contact factory for details.

Adjustable

3.3V

3.38V at 7.5A

_IN≥ 4.75V

LX8383A

121Ω

1500µF

2x 330µF, 6.3V

Oscon SA type

from Sanyo

-or-

ADJ

6.3V

6MV1500GX

from Sanyo

3x 1500µF, 6.3V

6MV1500GX

from Sanyo

205

Ω

Application of the LX8383A for the standard voltage (non VRE) Pentium Processor motherboard

with less than 130mV dynamic response to a 7.5A load transient.

PACKAGE ORDER INFORMATION

Plastic TO-220

3-pin

Plastic TO-247

Dropout

Voltage

T_A(°C)

0 to 125

-25 to 125

3-terminal

1.5V

1.3V

1.5V

1.3V

LX8383-xxCP

LX8383A-xxCP

LX8383B-xxCP

LX8383-xxIP

LX8383-xxCV

LX8383A-xxCV

LX8383B-xxCV

LX8383-xxIV

LX8383A-xxIP

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

LX8383A-xxIV

F O R F U R T H E R I N F O R M AT I O N C A L L ( 7 1 4 ) 8 9 8 - 8 1 2 1

Rev. 1.0 12/96

11861 WESTERN AVENUE, GARDEN GROVE, CA. 92841

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

LX8383-xx/8383A-xx/8383B-xx

7. 5A L O W

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O S I T I V E

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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

Operating Junction Temperature

TAB IS V_OUT

V_IN

V_OUT

ADJ / GND*

Plastic (P & V Packages)....................................................................................... 150°C

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

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

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 ON REVERSE SIDE IS V_OUT

THERMAL DATA

V_IN

V_OUT

P PACKAGE:

ADJ / GND*

THERMAL RESISTANCE-JUNCTION TO TAB, θ_JT

THERMAL RESISTANCE-JUNCTION TO AMBIENT, θ_JA

V PACKAGE:

2.7°C/W

60°C/W

V PACKAGE

(Top View)

* Pin 1 is GND for fixed voltage versions.

THERMAL RESISTANCE-JUNCTION TO TAB, θ_JT

THERMAL RESISTANCE-JUNCTION TO AMBIENT, θ_JA

1.6°C/W

35°C/W

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

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

All of the above assume no ambient airflow.

BLOCK DIAGRAM

V_IN

Bias

Circuit

Bandgap

Circuit

Control

Circuit

Output

Circuit

Thermal

Limit Circuit

V_OUT

SOA Protection

Circuit

ADJ or

GND*

Current

Limit Circuit

* This pin GND for fixed voltage versions.

Rev. 1.0 12/96

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

LX8383-xx/8383A-xx/8383B-xx

7. 5A 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 LX8383-xxC/8383A-xxC/8383B-xxC with 0°C ≤

T_A≤ 125°C, the LX8383-xxI/8383A-xxI with -25°C ≤ T_A≤ 125°C; V_IN- V_OUT= 3V; I_OUT= 7.5A. Low duty cycle pulse testing techniques are used which

maintains junction and case temperatures equal to the ambient temperature.)

LX8383-00/83A-00/83B-00 (Adjustable)

LX8383/83A/83B-00

Parameter

Symbol

Test Conditions

Units

Min. Typ.

Max.

Reference Voltage

(Note 4)

LX8383/83A-00

LX8383B-00

V_REF

I_OUT= 10mA, T_A= 25°C

10mA ≤ I_OUT≤ I_{OUT (MAX)}, 1.5V ≤ (V - V_OUT), V ≤ 10V, P ≤ P_MAX

1.238 1.250 1.262

1.225 1.250 1.270

1.240 1.250 1.260

1.238 1.250 1.262

I_OUT= 10mA, T_A= 25°C

10mA ≤ I_OUT≤ I_{OUT (MAX)}, 1.5V ≤ (V - V_OUT), V ≤ 10V, P ≤ P_MAX

Line Regulation (Note 2)

Load Regulation (Note 2)

∆V_REF1.5V ≤ (V_IN- V_OUT), V_IN≤ 7V

0.015

0.035

0.15

0.3

0.2

0.3

%/W

(V_IN)

1.5V ≤ (V_IN- V_OUT), V_IN≤ 10V

∆V_REFV_OUT≥ V_REF, V_IN- V_OUT= 3V, 10mA ≤ I_OUT≤ 7.5A, T_A= 25°C

(I_OUT

0.4

0.5

)

V_IN- V_OUT= 3V, 10mA ≤ I_OUT≤ 7.5A

Thermal Regulation

∆V_OUT(Pwr) T_A= 25°C, 20ms pulse

V_OUT= 5V, f =120Hz, C_OUT= 100µf Tantalum, V_IN= 6.5V

C_ADJ= 10µF, I_OUT= 7.5A

0.01

0.02

Ripple Rejection (Note 3)

0.2

1.2

100

1.5

1.3

µA

Adjust Pin Current

Adjust Pin Current Change (Note 4)

I_ADJ

∆ I_ADJ10mA ≤ I_OUT≤ I_{OUT (MAX)}, 1.5V ≤ (V - V_OUT), V ≤ 10V

Dropout Voltage

LX8383-00

∆V

∆V_REF= 1%, I_OUT= 7.5A

LX8383A/83B-00

Minimum Load Current

I_{OUT (MIN)}

≤ 10V

7.5

9.5

0.25

0.3

0.003

Maximum Output Current

Temperature Stability (Note 3)

Long Term Stability (Note 3)

I_{OUT (MAX)}(V_IN- V_OUT) ≤ 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

LX8383-33/83A-33/83B-33 (3.3V Fixed)

LX8383/83A/83B-33

Parameter

Symbol

Test Conditions

Units

Min. Typ.

Max.

Output Voltage

(Note 4)

LX8383/83A-33

LX8383B-33

V_OUT

V_IN= 5V, I_OUT= 0mA, T_A= 25°C

3.267

3.235

3.274

3.267

3.3

3.333

3.365

3.326

3.333

4.75V ≤ V_IN≤ 10V, 0mA ≤ I_OUT≤ 7.5A, P ≤ P_MAX

V_IN= 5V, I_OUT= 0mA, T_A= 25°C

4.75V ≤ V_IN≤ 10V, 0mA ≤ I_OUT≤ 7.5A, P ≤ P_MAX

Line Regulation (Note 2)

∆V_OUT4.75V ≤ V_IN≤ 7V

(V_IN)

% / W

4.75V ≤ V_IN≤ 10V

Load Regulation (Note 2)

Thermal Regulation

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= 7.5A

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)}, V_IN≤ 7V

1.5

1.3

Dropout Voltage

LX8383-33

LX8383A/83B-33

7.5

9.5

0.25

0.3

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

0.003

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.

Note 4. See Maximum Output Current Section above.

Rev. 1.0 12/96

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

LX8383-xx/8383A-xx/8383B-xx

7. 5A 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)

TheLX8383/83A/83BseriesICsareeasytouseLow-Dropout(LDO)

Power Supply

LX8383/83A

/83B

ADJ

OUT

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 LX8383/83A/

83B series. Please see the table below for recommended minimum

capacitor values.

Full Load

(Smaller resistor)

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 LX8383/83A/83B 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 LX8383/83A/83B 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. 1.0 12/96

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

LX8383-xx/8383A-xx/8383B-xx

7. 5A 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

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.

LX8383/83A/83B

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 LX8383/83A/83B regulators are three-terminal devices,

it is not possible to provide true remote load sensing. Load

regulation will be limited by the resistance of the wire connecting

the regulator 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 connected to the load, the effective resistance between the

regulator 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

LX8383/83A/83B

Line Resistance

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

M = 2.5V/1.25V= 2

OUT

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 LX8383/83A/83B 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. 1.0 12/96

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

LX8383-xx/8383A-xx/8383B-xx

7. 5A 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 (2.54 mm) 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

roomtemperature. Ifa3-terminalregulatorusedtosupply2.50volts

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_θJT

R_θCS

R_θSA

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

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

for the installed regulator.

P_D= (V_IN(MAX)- V_OUT) I_OUT= (5.0V-2.8V) 5.0A

= 11.0W

THERMAL CONSIDERATIONS

125°C - 50°C

R_θSA

- (2.7°C/W + 1.0°C/W)

The LX8383/83A/83B 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

(5.0V-2.8V) 5.0A

= 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. 1.0 12/96

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

LX8383-xx/8383A-xx/8383B-xx

7. 5A 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

TYPICAL APPLICATIONS

LX8383/83A/83B

OUT

LX8383/83A/83B

OUT

V_IN

(Note A)

V_IN

V_OUT**

V_OUT

ADJ

121Ω

ADJ

10µF

100µF

C1*

10µF

150µF

10µF*

* C1 improves ripple rejection.

X_Cshould be ≈ R1 at ripple

frequency.

365Ω

* 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

LX8383/83A/83B

V_IN

(Note A)

OUT

ADJ

121Ω

100µF

10µF

TTL

Output

2N3904

365Ω

FIGURE 6 — 5V REGULATOR WITH SHUTDOWN

LX8383/83A/83B-33

V_IN

OUT

3.3V

GND

10µF Tantalum

or 100µF Aluminum

Min. 15µF Tantalum or

100µF Aluminum capacitor.

May be increased without

limit. ESR must be less

than 50mΩ.

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.

Cyrix is a registered trademark and 6x86 is a trademark of Cyrix Corporation. K5 is a trademark of AMD.

Rev. 1.0 12/96

LX8383B-00CP [MICROSEMI]

相关型号：

LX8383B-00CV

LX8383B-33

LX8383B-33CP

LX8383B-33CV

LX8384

LX8384-00

LX8384-00CDD

LX8384-00CDD-TR

LX8384-00CDDT

LX8384-00CDT

LX8384-00CDT-TR

LX8384-00CDTT