LX8586.PDF

LX8586 / LX8586A

6A Low Dropout Positive Regulators

P RODUCTION D ATA S HEET

DESCRIPTION

KEY FEATURES

ThreeeTerminal Adjustable or

Fixed Output

Guaranteed < 1.1V Headroom at

6A (LX8586A)

Guaranteed < 1.3V Headroom at

6A (LX8586)

Output Current of 6A Minimum

Fast Transient Response

1% Voltage Reference Initial

Accuracy

Output Short Circuit Protection

Built in Thermal Shutdown

Evaluation Board Available:

Request LXE9001 Evaluation Kit

Current limit is trimmed above 6.1A

to ensure adequate output current and

controlled short-circuit current. On-chip

thermal limiting provides protection

against any combination of overload

that would create excessive junction

temperatures. The LX8586/86A series

devices are available in both through-

hole versions of the industry-standard,

3-pin TO-220 power packages. Along

with the standard μP supply

applications, the LX8586 series of

products are ideal for Pentium ® Pro

Processor applications such as GTL+

Bus terminators (see application

below).

IMPORTANT: For the most current data, consult MICROSEMI ’s website: http://www.microsemi.com

APPLICATIONS

GTL+ Bus Terminators

Pentium ® Processor Supplies

PowerPC ® Supplies

Microprocessor Supplies

Low Voltage Logic Supplies

Post Regulator for Switching

Supply

LXE9001 Evaluation Board for

Pentium ® Applications Available

Consult Factory

CYRIX ® 6x86™

AMD-K5™ and AMD-K6™

PRODUCT HIGHLIGHT

1.5V, 6 A R EGULA TO R

H.S. (Note A)

From Silverbox

Power Supply

3.3V

LX8586

1.5V/6A

To GTL+

Terminator

OUT

1500 µF

Sanyo

6MV1500GX

ADJ

121 Ω

±1%

4x 1500 µF

Sanyo

6MV1500GX

24.3 Ω

±1%

A PPLICA TION OF LX8586 AS 1.5V GTL + B US T ERMINA TO R

Note A: See application note, page 3.

PACKAGE ORDER INFO

Available Options Per Part #

Part # Output Voltage

LX8586/86A-00 Adjustable

LX8586/86A-33 3.3V

Other voltage options may be available;

please contact factory for details.

T A ( ° C)

Dropout

Voltage

Plastic TO-220

3 pin

RoHS Compliant

Transition DC: 0543

1.3V

LX8586-xxCP

0 to 125

“xx” refers to output voltage, see table to right.

Note: Available in Tape & Reel. Append the letters “TR” to the part number.

(i.e. LX8586A-00CP-TR)

1.1V

LX8586A-xxCP

Pentium is a registered Trademark of Intel Corporation

Cyrix is a registered Trademark of Cyrix Corporation.

K5 & K6 are trademarks of Advanced Micro Devices

PowerPC is a trademark of International Business Machine

Rev. 1.0a, 2005-11-10

Microsemi

Integrated Products Division

11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570

Page 1

The LX8586/86A series ICs are

low dropout three-terminal regulators

with a minimum of 6A output current.

Pentium ® Processor, Power PCTM,

Cyrix ® 6x86TM and AMD-K5™

applications requiring fast transient

response are ideally suited for this

product family. The LX8586A is

guaranteed to have < 1.1V at 6A and

the LX8586 < 1.3V at 6A dropout

voltage, making them ideal to provide

well-regulated outputs of 2.5V to 3.6V

using a 5V input supply. Fixed

versions are also available and

specified in the Available Options

table below.

LX8586 / LX8586A

6A Low Dropout Positive Regulators

P RODUCTION D ATA S HEET

ABSOLUTE MAXIMUM RATINGS

PACKAGE PIN OUT

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

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

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

Operating Temperature Range ................................................................................... 150°C

Maximum Operating Junction Temperature .............................................................. 150°C

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

Peak Package Solder Reflow Temp.(40 seconds max. exposure) .................. 260°C (+0 -5)

Tab is V OUT

V IN

V OUT

ADJ/GND*

P P ACKAGE

(Top View)

*Pin 1 is GND for fixed Voltage Versions

RoHS Package is100% Matte Tin Lead Finish

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

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

THERMAL DATA

P Plastic TO-2203-Pin

THERMAL RESISTANCE - JUNCTION TO T AB , θ JT

2.7 ° C/W

THERMAL RESISTANCE - JUNCTION TO A MBIENT , θ JA

60 ° C/W

Junction Temperature Calculation: T J = T A + (P D x θ JA ).

The θ JA numbers are guidelines for the thermal performance of the device/pc-board system. All of the

above assume no ambient airflow.

Rev. 1.0a, 2005-11-10

Microsemi

Integrated Products Division

11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570

Page 2

LX8586 / LX8586A

6A Low Dropout Positive Regulators

P RODUCTION D ATA S HEET

ELECTRICAL CHARACTERISTICS

Unless otherwise specified, the following specifications apply over the operating ambient temperature 0°C ≤ T A ≤ 70°C; V IN – V OUT =

3V, I OUT = 6A. Low duty cycle pulse testing techniques are used which maintains junction and case temperatures equal to the ambient

temperature.

Parameter

Symbol

Test Conditions

LX8586/86A-00

Units

Min

Typ Max

` LX8586-00 / LX8586A-00 (ADJUSTABLE)

I OUT = 10mA, T A = 25°C

1.238 1.250 1.262

Reference Voltage

V REF

10mA < I OUT < 6A, 1.5V < (V IN – V OUT ),

V IN < 7V, P < P MAX

1.225 1.250 1.275

Line Regulation (Note 2)

∆V REF (V IN ) I OUT = 10mA, 1.5V < (V IN – V OUT ), V IN < 7V

0.035 0.20

Load Regulation (Note 2) ∆V REF (I OUT ) V IN – V OUT = 3V, 10mA < I OUT < 6A

0.1

0.5

Thermal Regulation

∆V OUT (Pwr) T A = 25°C, 20ms pulse

0.01

0.02 % /W

V OUT = 3.3V, f = 120Hz, C OUT = 100µF Tantalum,

V IN = 5V, C ADJ = 10µF, T A = 25°C, I OUT = 6A

Ripple Rejection (Note 3)

Adjust Pin Current

I ADJ

100

µA

Adjust Pin Current Change

∆I ADJ

10mA < I OUT < 6A, 1.5V < (V IN – V OUT ), V IN < 7V

0.2

µA

Dropout Voltage

LX8586-00

∆V

∆V REF = 1%, I OUT = 6A

1.1

1.3

LX8586A-00

∆V REF = 1%, I OUT = 6A

0.9

1.1

Minimum Load Current

I OUT(MIN) IN < 7V

Maximum Output Current

I OUT(MAX) 1.4V < (V IN – V OUT ), V IN < 7V

6.1

Temperature Stability

∆V OUT (T)

0.25

Long Term Stability

∆V OUT (t) T A = 125°C, 1000hrs

0.3

RMS Output Noise (% of V OUT )

V OUT(RMS) A = 25°C, 10Hz < f < 10kHz

0.003

` LX8586-33 / LX8586A-33 (3.3V FIXED)

Output Voltage

V OUT

V IN = 5V, I OUT = 0mA, T A = 25°C

3.267

3.3

3.333

4.75V < V IN < 10V, 0mA < I OUT < 6A, P < P MAX

3.235

3.3

3.365

Line Regulation (Note 2)

∆V OUT (V IN )

4.75V < V IN < 7V

4.75V < V IN < 10V

Load Regulation (Note 2) ∆V OUT (I OUT ) V IN = 5V, 10mA < I OUT < I OUT(MAX)

Thermal Regulation (Note 3) ∆V OUT (Pwr) T A = 25°C, 20ms pulse

0.01

0.02 % /W

Ripple Rejection (Note 3)

C OUT = 100µF Tantalum, I OUT = 6A, T A = 25°C

Quiescent Current

I Q

0mA < I OUT < I OUT(MAX) , 4.75 < V IN < 10V

Dropout Voltage

LX8586-33

∆V

∆V OUT = 1%, I OUT < I OUT(MAX)

1.1

1.3

LX8586A-33

∆V OUT = 1%, I OUT < I OUT(MAX)

0.9

1.1

Maximum Output Current

I OUT(MAX) IN < 7A

6.1

Temperature Stability (Note 3) ∆V OUT (T)

0.25

Long Term Stability (Note 3) ∆V OUT (t) T A = 25°C, 1000 hrs

0.3

V OUT(RMS) A = 25°C, 10Hz < f < 10kHz 0.003 %

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. 1.0a, 2005-11-10

Microsemi

Integrated Products Division

11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570

Page 3

RMS Output Noise (% of V OUT )

(Note 3)

LX8586 / LX8586A

6A Low Dropout Positive Regulators

P RODUCTION D ATA S HEET

APPLICATION NOTE

The LX8586/86A series ICs are easy to use Low-Dropout (LDO)

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 LX8586/86A

series. Please see the table below for recommended minimum

capacitor values.

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.

Power Supply

LX8586/86A

OUT

Minumum Load

(Larger resistor)

Full Load

(Smaller resistor)

ADJ

R DSON << R L

1 sec

10ms

Star Ground

Figure 1 - Dynamic Input and Output Test

O VERLOAD R ECOVERY

Like almost all IC power regulators, the LX8586/86A

regulators are equipped with Safe Operating Area (SOA)

protection. The SOA circuit limits the regulator's maximum

output current to progressively 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 LX8586/86A 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.

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 case where the regulator is supplying regulated voltage to a

resistive 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 through the regulator to develop the

designed output voltage across the load resistance. If the output

resistor is short-circuited to ground, the input-to-output voltage

difference across the regulator suddenly 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 permit the regulator to

supply to its output terminal. When the short 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 by the SOA

circuit, based on the large input-to-output voltage across the

regulator at the time the short circuit is removed from the output.

S TABILITY

The output capacitor is part of the regulator’s frequency

compensation 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 pin bypassing is used, the required output capacitor value

increases. 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. The table below shows recommended

minimum capacitance values for stable operation.

Input Output Adj

10µF 15µF Tant, 100µF Alum. None

10µF 47µF Tant, 220µF Alum 15µF

Chart – Recommended Capacitor Values

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.

The circuit shown in Figure 1 can be used to observe the

transient 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 undershoot, can be quickly compared in order to

develop an optimum solution.

Rev. 1.0a, 2005-11-10

Microsemi

Integrated Products Division

11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570

Page 4

LX8586 / LX8586A

6A Low Dropout Positive Regulators

P RODUCTION D ATA S HEET

APPLICATION NOTE

O VERLOAD R ECOVERY (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 will never 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.

R IPPLE R EJECTION

Ripple rejection can be improved by connecting a capacitor

between the ADJ pin and ground. The value of the capacitor

should 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:

C = 1 / (6.28 * F R * R1)

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:

M = V OUT /V REF

Where: M ≡ a multiplier for the ripple seen when the ADJ

pin is optimally bypassed.

V REF = 1.25V.

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

M = 2.5V/1.25V = 2

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.

O UTPUT V OLTAGE

The LX8586/86A 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. Because I ADJ is very small and

constant when compared with the current through R1, it represents

a small error and can usually be ignored.

V IN

LX8586/86A

OUT

V OUT

ADJ

V REF

I ADJ

50 µA

V OUT = V REF 1 + + I ADJ R2

Figure 2 - Basic Adjustment Regulator

L OAD R EGULATION

Because the LX8586/86A 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:

⎛ +

⎠

Peff

where: R P ≡ Actual parasitic line resistance.

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

resistance appears as its actual value, rather than the higher R PEFF

LX8586/86A

OUT

R P

Parasitic

Line Resistance

V IN

ADJ

Connect

R1 to Case

of Regulator

R L

Connect

to Load

Figure 3 - Connections for Best Load Regulation

Rev. 1.0a, 2005-11-10

Microsemi

Integrated Products Division

11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570

Page 5

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