LMS8117AMPX-3.3 [NSC]

1A Low-Dropout Linear Regulator; 1A低压降线性稳压器


型号：	LMS8117AMPX-3.3
厂家：	National Semiconductor
描述：	1A Low-Dropout Linear Regulator 1A低压降线性稳压器稳压器
文件：	总16页 (文件大小：774K)
中文：	中文翻译
下载：	下载PDF数据表文档文件

April 2005

LMS8117A

1A Low-Dropout Linear Regulator

General Description

Features

n Available in 1.8V, 3.3V, and Adjustable Versions

The LMS8117A is a series of low dropout voltage regulators

with a dropout of 1.2V at 1A of load current. It has the same

pin-out as National Semiconductor’s industry standard

LM317.

n Space Saving SOT-223 and TO-252 Packages

n Current Limiting and Thermal Protection

n Output Current

The LMS8117A is available in an adjustable version, which

can set the output voltage from 1.25V to 13.8V with only two

external resistors. In addition, it is also available in two fixed

voltages, 1.8V and 3.3V.

n Temperature Range

n Line Regulation

n Load Regulation

0˚C to 125˚C

0.2% (Max)

0.4% (Max)

The LMS8117A offers current limiting and thermal shutdown.

Its circuit includes a zener trimmed bandgap reference to

assure output voltage accuracy to within 1%.

Applications

n Post Regulator for Switching DC/DC Converter

n High Efficiency Linear Regulators

n Battery Charger

The LMS8117A series is available in SOT-223 and TO-252

D-PAK packages. A minimum of 10µF tantalum capacitor is

required at the output to improve the transient response and

stability.

n Battery Powered Instrumentation

Typical Application

Fixed Output Regulator

10119628

DS101196

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Ordering Information

Temperature Range (T_J)

NSC

Drawing

Package

Packaging Marking

Transport Media

0˚C to +125˚C

LMS8117AMP-ADJ

LMS8117AMPX-ADJ

LMS8117AMP-1.8

LMS8117AMPX-1.8

LMS8117AMP-3.3

LMS8117AMPX-3.3

LMS8117ADT-ADJ

LMS8117ADTX-ADJ

LMS8117ADT-1.8

LMS8117ADTX-1.8

LMS8117ADT-3.3

LMS8117ADTX-3.3

3-lead SOT-223

LS0A

1k Tape and Reel

2k Tape and Reel

1k Tape and Reel

2k Tape and Reel

1k Tape and Reel

2k Tape and Reel

Rails

MP04A

LS00

LS01

3-lead TO-252

LMS8117ADT-ADJ

LMS8117ADT-1.8

LMS8117ADT-3.3

TD03B

2.5k Tape and Reel

Rails

2.5k Tape and Reel

Rails

2.5k Tape and Reel

Connection Diagrams

SOT-223

TO-252

10119699

Top View

10119638

Top View

Block Diagram

10119601

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Absolute Maximum Ratings (Note 1)

If Military/Aerospace specified devices are required,

please contact the National Semiconductor Sales Office/

Distributors for availability and specifications.

Soldering Information

Infrared (20 sec)

235˚C

2000V

ESD Tolerance (Note 3)

Maximum Input Voltage (V_INto GND)

LMS8117A-ADJ, LMS8117A-1.8,

Operating Ratings (Note 1)

Input Voltage (V_INto GND)

LMS8117A-ADJ, LMS8117A-1.8,

LMS8117A-3.3

20V

Power Dissipation (Note 2)

Junction Temperature (T_J)

(Note 2)

Internally Limited

15V

150˚C

Junction Temperature Range

(T_J)(Note 2)

0˚C to 125˚C

Storage Temperature Range

-65˚C to 150˚C

Electrical Characteristics

Typicals and limits appearing in normal type apply for T_J= 25˚C. Limits appearing in Boldface type apply over the entire junc-

tion temperature range for operation, 0˚C to 125˚C.

Min

(Note 5)

Typ

(Note 4)

Max

(Note 5)

Symbol

V_REF

Parameter

Conditions

Units

Reference Voltage

LMS8117A-ADJ

I_OUT= 10mA, V_IN-V_OUT= 2V, T_J= 25˚C

10mA ≤ I_OUT≤ 1A, 1.4V ≤ V_IN-V_OUT≤ 10V

LMS8117A-1.8

1.238

1.250

1.262

1.225

1.270

V_OUT

Output Voltage

I_OUT= 10mA, V_IN= 3.8V, T_J= 25˚C

0 ≤ I_OUT≤ 1A, 3.2V ≤ V_IN≤ 10V

LMS8117A-3.3

1.782

1.800

1.818

1.746

1.854

I_OUT= 10mA, V_IN= 5V T_J= 25˚C

0 ≤ I_OUT≤ 1A, 4.75V ≤ V_IN≤ 10V

3.267

3.300

3.333

3.235

3.365

∆V_OUT

Line Regulation (Note LMS8117A-ADJ

6) I_OUT= 10mA, 1.5V ≤ V_IN-V_OUT≤ 13.75V

0.035

0.2

LMS8117A-1.8

I_OUT= 0mA, 3.2V ≤ V_IN≤ 10V

LMS8117A-3.3

I_OUT= 0mA, 4.75V ≤ V_IN≤ 15V

0.2

∆V_OUT

Load Regulation (Note LMS8117A-ADJ

6) V_IN-V_OUT= 3V, 10mA ≤ I_OUT≤ 1A

0.4

LMS8117A-1.8

V_IN= 3.2V, 0 ≤ I_OUT≤ 1A

LMS8117A-3.3

V_IN= 4.75V, 0 ≤ I_OUT≤ 1A

I_OUT= 100mA

1.15

1.2

_IN-V _OUTDropout Voltage

1.1

1.15

1.2

1.4

(Note 7)

I_OUT= 500mA

I_OUT= 1A

1.25

1.9

I_LIMIT

Current Limit

V_IN-V_OUT= 5V, T_J= 25˚C

LMS8117A-ADJ

V_IN= 15V

1.0

Minimum Load

Current (Note 8)

Quiescent Current

1.7

LMS8117A-1.8

V_IN≤ 15V

LMS8117A-3.3

V_IN≤ 15V

%/W

Thermal Regulation

Ripple Regulation

T_A= 25˚C, 30ms Pulse

f_RIPPLE= 120Hz, V_IN-V_OUT= 3V

V_RIPPLE= 1V_PP

0.01

0.1

Adjust Pin Current

Change

120

µA

10mA ≤ I_OUT≤ 1A,

1.4V ≤ V_IN-V_OUT≤ 10V

0.2

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Electrical Characteristics (Continued)

Typicals and limits appearing in normal type apply for T_J= 25˚C. Limits appearing in Boldface type apply over the entire junc-

tion temperature range for operation, 0˚C to 125˚C.

Min

(Note 5)

Typ

(Note 4)

0.5

Max

(Note 5)

Symbol

Parameter

Conditions

Units

Temperature Stability

Long Term Stability

RMS Output Noise

Thermal Resistance

Junction-to-Case

Thermal Resistance

Junction-to-Ambient

(No heat sink;

T_A= 125˚C, 1000Hrs

0.3

(% of V_OUT), 10Hz ≤ f ≤ 10kHz

3-Lead SOT-223

0.003

15.0

˚C/W

3-Lead TO-252

3-Lead SOT-223

136

3-Lead TO-252 (Note 9)

No air flow)

Note 1: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for which the device is

intended to be functional, but specific performance is not guaranteed. For guaranteed specifications and the test conditions, see the Electrical Characteristics.

Note 2: The maximum power dissipation is a function of T

, θ , and T . The maximum allowable power dissipation at any ambient temperature is

JA A

J(MAX)

= (T –T )/θ . All numbers apply for packages soldered directly into a PC board.

J(MAX) A JA

Note 3: For testing purposes, ESD was applied using human body model, 1.5kΩ in series with 100pF.

Note 4: Typical Values represent the most likely parametric norm.

Note 5: All limits are guaranteed by testing or statistical analysis.

Note 6: Load and line regulation are measured at constant junction room temperature.

Note 7: The dropout voltage is the input/output differential at which the circuit ceases to regulate against further reduction in input voltage. It is measured when the

output voltage has dropped 100mV from the nominal value obtained at V = V

+1.5V.

OUT

Note 8: The minimum output current required to maintain regulation.

Note 9: Minimum pad size of 0.038in

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Typical Performance Characteristics

Dropout Voltage (V_IN-V

)

Short-Circuit Current

OUT

10119623

10119622

Load Regulation

LMS8117A-ADJ Ripple Rejection vs. Current

10119606

10119624

LMS8117A-ADJ Ripple Rejection

Temperature Stability

10119607

10119625

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Typical Performance Characteristics (Continued)

Adjust Pin Current

LMS8117A-1.8 Load Transient Response

10119626

10119608

LMS8117A-3.3 Load Transient Response

LMS8117A-1.8 Line Transient Response

10119610

10119609

LMS8117A-3.3 Line Transient Response

10119611

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Application Note

1.0 EXTERNAL CAPACITORS/STABILITY

1.1 Input Bypass Capacitor

An input capacitor is recommended. A 10µF tantalum on the

input is a suitable input bypassing for almost all applications.

1.2 Adjust Terminal Bypass Capacitor

The adjust terminal can be bypassed to ground with a by-

pass capacitor (C_ADJ) to improve ripple rejection. This by-

pass capacitor prevents ripple from being amplified as the

output voltage is increased. At any ripple frequency, the

impedance of the C_ADJshould be less than R1 to prevent the

ripple from being amplified:

1/(2π*f_RIPPLE*C_ADJ

)

The R1 is the resistor between the output and the adjust pin.

Its value is normally in the range of 100-200Ω. For example,

with R1 = 124Ω and f_RIPPLE= 120Hz, the C_ADJshould be

11µF.

10119617

FIGURE 1. Basic Adjustable Regulator

3.0 LOAD REGULATION

1.3 Output Capacitor

The output capacitor is critical in maintaining regulator sta-

bility, and must meet the required conditions for both mini-

mum amount of capacitance and ESR (Equivalent Series

Resistance). The minimum output capacitance required by

the LMS8117A is 10µF, if a tantalum capacitor is used. Any

increase of the output capacitance will merely improve the

loop stability and transient response. The ESR of the output

capacitor should be greater than 0.5Ω and less than 5Ω. In

the case of the adjustable regulator, when the C_ADJis used,

a larger output capacitance (22µf tantalum) is required.

The LMS8117A regulates the voltage that appears between

its output and ground pins, or between its output and adjust

pins. In some cases, line resistances can introduce errors to

the voltage across the load. To obtain the best load regula-

tion, a few precautions are needed.

Figure 2, shows a typical application using a fixed output

regulator. The Rt1 and Rt2 are the line resistances. It is

obvious that the V_LOADis less than the V_OUTby the sum of

the voltage drops along the line resistances. In this case, the

load regulation seen at the R_LOADwould be degraded from

the data sheet specification. To improve this, the load should

be tied directly to the output terminal on the positive side and

directly tied to the ground terminal on the negative side.

2.0 OUTPUT VOLTAGE

The LMS8117A adjustable version develops a 1.25V refer-

ence voltage, V_REF, between the output and the adjust ter-

minal. As shown in Figure 1 , this voltage is applied across

resistor R1 to generate a constant current I1. The current

I_ADJfrom the adjust terminal could introduce error to the

output. But since it is very small (60µA) compared with the I1

and very constant with line and load changes, the error can

be ignored. The constant current I1 then flows through the

output set resistor R2 and sets the output voltage to the

desired level.

For fixed voltage devices, R1 and R2 are integrated inside

the devices.

For fixed voltage devices, R1 and R2 are integrated inside

the devices.

10119618

FIGURE 2. Typical Application using Fixed Output

Regulator

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Application Note (Continued)

When the adjustable regulator is used (Figure 3), the best

performance is obtained with the positive side of the resistor

R1 tied directly to the output terminal of the regulator rather

than near the load. This eliminates line drops from appearing

effectively in series with the reference and degrading regu-

lation. For example, a 5V regulator with 0.05Ω resistance

between the regulator and load will have a load regulation

due to line resistance of 0.05Ω x I_L. If R1 (=125Ω) is con-

nected near the load, the effective line resistance will be

0.05Ω (1+R2/R1) or in this case, it is 4 times worse. In

addition, the ground side of the resistor R2 can be returned

near the ground of the load to provide remote ground sens-

ing and improve load regulation.

10119615

FIGURE 4. Regulator with Protection Diode

5.0 HEATSINK REQUIREMENTS

When an integrated circuit operates with an appreciable

current, its junction temperature is elevated. It is important to

quantify its thermal limits in order to achieve acceptable

performance and reliability. This limit is determined by sum-

ming the individual parts consisting of a series of tempera-

ture rises from the semiconductor junction to the operating

environment. A one-dimensional steady-state model of con-

duction heat transfer is demonstrated in Figure 5. The heat

generated at the device junction flows through the die to the

die attach pad, through the lead frame to the surrounding

case material, to the printed circuit board, and eventually to

the ambient environment. Below is a list of variables that

may affect the thermal resistance and in turn the need for a

heatsink.

10119619

FIGURE 3. Best Load Regulation using Adjustable

Output Regulator

4.0 PROTECTION DIODES

R^θJC(Component

Variables)

R^θCA(Application

Variables)

Under normal operation, the LMS8117A regulators do not

need any protection diode. With the adjustable device, the

internal resistance between the adjust and output terminals

limits the current. No diode is needed to divert the current

around the regulator even with capacitor on the adjust ter-

minal. The adjust pin can take a transient signal of 25V with

respect to the output voltage without damaging the device.

Leadframe Size & Material Mounting Pad Size,

Material, & Location

No. of Conduction Pins

Placement of Mounting

Pad

Die Size

PCB Size & Material

Traces Length & Width

Adjacent Heat Sources

When a output capacitor is connected to a regulator and the

input is shorted to ground, the output capacitor will discharge

into the output of the regulator. The discharge current de-

pends on the value of the capacitor, the output voltage of the

regulator, and rate of decrease of V_IN. In the LMS8117A

regulators, the internal diode between the output and input

pins can withstand microsecond surge currents of 10A to

20A. With an extremely large output capacitor (≥1000 µF),

and with input instantaneously shorted to ground, the regu-

lator could be damaged.

Die Attach Material

Molding Compound Size

and Material

Volume of Air

Ambient Temperatue

Shape of Mounting Pad

In this case, an external diode is recommended between the

output and input pins to protect the regulator, as shown in

Figure 4.

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Application Note (Continued)

10119637

FIGURE 5. Cross-sectional view of Integrated Circuit Mounted on a printed circuit board. Note that the case

temperature is measured at the point where the leads contact with the mounting pad surface

The LMS8117A regulators have internal thermal shutdown to

protect the device from over-heating. Under all possible

operating conditions, the junction temperature of the

LMS8117A must be within the range of 0˚C to 125˚C. A

heatsink may be required depending on the maximum power

dissipation and maximum ambient temperature of the appli-

cation. To determine if a heatsink is needed, the power

dissipated by the regulator, P_D, must be calculated:

T_R(max)=T_J(max)-T_A(max)

where T_J(max) is the maximum allowable junction tempera-

ture (125˚C), and T_A(max) is the maximum ambient tem-

perature which will be encountered in the application.

Using the calculated values for T_R(max) and P_D, the maxi-

mum allowable value for the junction-to-ambient thermal

resistance (θ_JA) can be calculated:

θ_JA= T_R(max)/P_D

I_IN= I_L+ I_G

If the maximum allowable value for θ_JAis found to be

≥136˚C/W for SOT-223 package or ≥92˚C/W for TO-252

package, no heatsink is needed since the package alone will

dissipate enough heat to satisfy these requirements. If the

calculated value for θ_JAfalls below these limits, a heatsink is

required.

P_D= (V_IN-V_OUT)I + V_{IN G}

Figure 6 shows the voltages and currents which are present

in the circuit.

As a design aid, Table 1 shows the value of the θ_JAof

SOT-223 and TO-252 for different heatsink area. The copper

patterns that we used to measure these θ_JAs are shown at

the end of the Application Notes Section. Figure 7 and Figure

8 reflects the same test results as what are in the Table 1.

Figure 9 and Figure 10 shows the maximum allowable power

dissipation vs. ambient temperature for the SOT-223 and

TO-252 device. Figure 11 and Figure 12 shows the maxi-

mum allowable power dissipation vs. copper area (in²) for

the SOT-223 and TO-252 devices. Please see AN–1028 for

power enhancement techniques to be used with SOT-223

and TO-252 packages.

10119616

FIGURE 6. Power Dissipation Diagram

The next parameter which must be calculated is the maxi-

mum allowable temperature rise, T_R(max):

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Application Note (Continued)

TABLE 1. θ_JADifferent Heatsink Area

Layout

Copper Area

Thermal Resistance

Top Side (in²)*

Bottom Side (in²)

(θ_JA,˚C/W) SOT-223

(θ_JA,˚C/W) TO-252

0.0123

0.066

0.3

136

123

103

0.53

0.76

0.2

0.4

0.6

0.8

115

0.066

0.175

0.284

0.392

0.5

0.066

0.175

0.284

0.392

0.5

125

*Tab of device attached to topside copper

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Application Note (Continued)

10119636

FIGURE 10. Maximum Allowable Power Dissipation vs.

Ambient Temperature for TO-252

10119613

FIGURE 7. θ_JAvs. 1oz Copper Area for SOT-223

10119614

10119634

FIGURE 11. Maximum Allowable Power Dissipation vs.

1oz Copper Area for SOT-223

FIGURE 8. θ_JAvs. 2oz Copper Area for TO-252

10119635

10119612

FIGURE 12. Maximum Allowable Power Dissipation vs.

2oz Copper Area for TO-252

FIGURE 9. Maximum Allowable Power Dissipation vs.

Ambient Temperature for SOT-223

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Application Note (Continued)

10119620

FIGURE 13. Top View of the Thermal Test Pattern in Actual Scale

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Application Note (Continued)

10119621

FIGURE 14. Bottom View of the Thermal Test Pattern in Actual Scale

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Typical Application Circuits

10119629

1.25V to 10V Adjustable Regulator with Improved Ripple Rejection

10119627

5V Logic Regulator with Electronic Shutdown*

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Physical Dimensions inches (millimeters) unless otherwise noted

3-Lead SOT-223

NS Package Number MP04A

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Physical Dimensions inches (millimeters) unless otherwise noted (Continued)

3-Lead TO-252

NS Package Number TD03B

National does not assume any responsibility for use of any circuitry described, no circuit patent licenses are implied and National reserves

the right at any time without notice to change said circuitry and specifications.

For the most current product information visit us at www.national.com.

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