LM3940IT-3.3全新原装原理图各脚功能电路原理芯片引脚定义-中国IC网-芯三七

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产品型号LM3940IT-3.3的概述

LM3940IT-3.3芯片详解一、概述 LM3940IT-3.3是一款高精度低压差线性稳压器，专为微处理器供电及其他敏感电子设备的电源需求而设计。该稳压器支持3.3V输出，提供稳定的电源供应，能够在输入电压变化和负载电流波动的情况下保持稳定，为数字电路、模拟电路和混合信号电路提供了优异的性能。二、详细参数 2.1 电气参数 - 输入电压范围：2.9V 至 30V - 输出电压：3.3V - 输出电流：最大可达1A - 静态电流：约为5 mA - 低压差：Typ. 0.1V（在1A负载下） - 负载调节：0.1% - 线性调节：0.01% - 工作温度范围：-40°C 到 +125°C - 封装：TO-220 2.2 功能特性 - 过热保护：内置过温保护机制，可以在芯片温度过高时自动关闭输出。 - 短路保护：能够在短路情况发生时保持稳定运行，避免损坏设备。 - 较低的噪声：具...

产品型号LM3940IT-3.3的Datasheet PDF文件预览

May 1999

LM3940

1A Low Dropout Regulator for 5V to 3.3V Conversion

General Description

The LM3940 is a 1A low dropout regulator designed to pro-

vide 3.3V from a 5V supply.

Features

n Output voltage specified over temperature

n Excellent load regulation

n Guaranteed 1A output current

n Requires only one external component

n Built-in protection against excess temperature

n Short circuit protected

The LM3940 is ideally suited for systems which contain both

5V and 3.3V logic, with prime power provided from a 5V bus.

Because the LM3940 is a true low dropout regulator, it can

hold its 3.3V output in regulation with input voltages as low

as 4.5V.

The T0-220 package of the LM3940 means that in most ap-

plications the full 1A of load current can be delivered without

using an additional heatsink.

Applications

n Laptop/Desktop Computers

n Logic Systems

The surface mount TO-263 package uses minimum board

space, and gives excellent power dissipation capability when

soldered to a copper plane on the PC board.

Typical Application

DS012080-1

Required if regulator is located more than 1" from the power supply filter capacitor or if battery power is used.

See Application Hints.

DS012080

www.national.com

Connection Diagram/Ordering Information

DS012080-2

DS012080-3

3-Lead TO-220 Package

(Front View)

Order Part Number LM3940IT-3.3

NSC Drawing Number TO3B

3-Lead TO-263 Package

(Front View)

Order Part Number LM3940IS-3.3

NSC Drawing Number TS3B

DS012080-10

3-Lead SOT-223

(Front View)

Order Part Number LM3940IMP-3.3

Package Marked L52B

NSC Drawing Number MA04A

DS012080-27

DS012080-28

16-Lead Ceramic Dual-in-Line Package

(Top View)

Order Part Number LM3940J-3.3-QML

5962-9688401QEA

16-Lead Ceramic Surface-Mount Package

(Top View)

Order Part Number LM3940WG-3.3-QML

5962-9688401QXA

NSC Drawing Number J16A

NSC Drawing Number WG16A

www.national.com

Absolute Maximum Ratings (Note 1)

If Military/Aerospace specified devices are required,

please contact the National Semiconductor Sales Office/

Distributors for availability and specifications.

Operating Junction Temperature Range

Lead Temperature (Soldering, 5 seconds)

Power Dissipation (Note 2)

−40˚C to +125˚C

260˚C

Internally Limited

7.5V

Input Supply Voltage

ESD Rating (Note 3)

2 kV

Storage Temperature Range

−65˚C to +150˚C

Electrical Characteristics

Limits in standard typeface are for T_J25˚C, and limits in boldface type apply over the full operating temperature range. Un-

less otherwise specified: V_IN5V, I_L1A, C_OUT33 µF.

Symbol Parameter Conditions

Typical

3.3

LM3940 (Note 4)

Units

min

3.20

3.13

max

3.40

3.47

V_O

Output Voltage

5 mA ≤ I_L≤ 1A

Line Regulation

Load Regulation

Output Impedance

I_L5 mA

4.5V ≤ V_O≤ 5.5V

50 mA ≤ I_L≤ 1A

I_L(DC) 100 mA

Z_O

I_L(AC) 20 mA (rms)

mΩ

120 Hz

I_Q

Quiescent Current

4.5V ≤ V_IN≤ 5.5V

I_L5 mA

V_IN5V

110

150

0.5

110

1.7

200

250

I_L1A

e_n

Output Noise Voltage

BW 10 Hz–100 kHz

µV (rms)

I_L5 mA

V_O− V_IN

Dropout Voltage

(Note 5)

I_L1A

0.8

1.0

I_L100 mA

150

200

I_L(SC)

Short Circuit Current

R_L

1.2

Note 1: Absolute maximum ratings indicate limits beyond which damage to the component may occur. Electrical specifications do not apply when operating the de-

vice outside of its rated operating conditions.

Note 2: The maximum allowable power dissipation is a function of the maximum junction temperature, T , the junction-to-ambient thermal resistance, θ , and the

J−A

ambient temperature, T . Exceeding the maximum allowable power dissipation will cause excessive die temperature, and the regulator will go into thermal shutdown.

The value of θ

(for devices in still air with no heatsink) is 60˚C/W for the TO-220 package, 80˚C/W for the TO-263 package, and 174˚C/W for the SOT-223 package.

J−A

The effective value of θ

can be reduced by using a heatsink (see Application Hints for specific information on heatsinking).

J−A

Note 3: ESD rating is based on the human body model: 100 pF discharged through 1.5 kΩ.

Note 4: All limits guaranteed for T

25˚C are 100% tested and are used to calculate Outgoing Quality Levels. All limits at temperature extremes are guaranteed

via correlation using standard Statistical Quality Control (SQC) methods.

Note 5: Dropout voltage is defined as the input-output differential voltage where the regulator output drops to a value that is 100 mV below the value that is measured

at V

5V.

www.national.com

Typical Performance Characteristics

Dropout Voltage

vs Temperature

Output Voltage

vs Temperature

DS012080-13

DS012080-15

DS012080-14

Quiescent Current

vs Temperature

Quiescent Current vs Load

Quiescent Current vs V_IN

DS012080-18

DS012080-17

DS012080-16

Line Transient Response

Load Transient Response

Ripple Rejection

DS012080-20

DS012080-19

DS012080-21

Low Voltage Behavior

Output Impedance

Peak Output Current

DS012080-22

DS012080-24

DS012080-23

www.national.com

Application Hints

EXTERNAL CAPACITORS

The figure below shows the voltages and currents which are

present in the circuit, as well as the formula for calculating

the power dissipated in the regulator:

The output capacitor is critical to maintaining regulator stabil-

ity, and must meet the required conditions for both ESR

(Equivalent Series Resistance) and minimum amount of ca-

pacitance.

MINIMUM CAPACITANCE:

The minimum output capacitance required to maintain stabil-

ity is 33 µF (this value may be increased without limit).

Larger values of output capacitance will give improved tran-

sient response.

ESR LIMITS:

The ESR of the output capacitor will cause loop instability if

it is too high or too low. The acceptable range of ESR plotted

versus load current is shown in the graph below. It is essen-

tial that the output capacitor meet these requirements,

or oscillations can result.

DS012080-6

I + I

L G

(V − V

IN OUT

) I + (V ) I

IN G

FIGURE 2. Power Dissipation Diagram

The next parameter which must be calculated is the maxi-

mum allowable temperature rise, T_R(max). This is calcu-

lated by using the formula:

T_R(max) T_J(max) − T_A(max)

Where: T_J(max) is the maximum allowable junction tem-

perature, which is 125˚C for commercial

grade parts.

T_A(max) is the maximum ambient temperature

which will be encountered in the applica-

tion.

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

mum allowable value for the junction-to-ambient thermal re-

sistance, θ_(J−A), can now be found:

θ_(J−A)T_R(max)/P_D

DS012080-5

IMPORTANT: If the maximum allowable value for θ_(J−A)is

found to be ≥ 60˚C/W for the TO-220 package, ≥ 80˚C/W for

the TO-263 package, or ≥174˚C/W for the SOT-223 pack-

age, no heatsink is needed since the package alone will dis-

sipate enough heat to satisfy these requirements.

FIGURE 1. ESR Limits

It is important to note that for most capacitors, ESR is speci-

fied only at room temperature. However, the designer must

ensure that the ESR will stay inside the limits shown over the

entire operating temperature range for the design.

If the calculated value for θ_(J−A)falls below these limits, a

heatsink is required.

For aluminum electrolytic capacitors, ESR will increase by

about 30X as the temperature is reduced from 25˚C to

−40˚C. This type of capacitor is not well-suited for low tem-

perature operation.

HEATSINKING TO-220 PACKAGE PARTS

The TO-220 can be attached to a typical heatsink, or se-

cured to a copper plane on a PC board. If a copper plane is

to be used, the values of θ_(J−A)will be the same as shown in

the next section for the TO-263.

Solid tantalum capacitors have a more stable ESR over tem-

perature, but are more expensive than aluminum electrolyt-

ics. A cost-effective approach sometimes used is to parallel

an aluminum electrolytic with a solid Tantalum, with the total

capacitance split about 75/25% with the Aluminum being the

larger value.

If two capacitors are paralleled, the effective ESR is the par-

allel of the two individual values. The “flatter” ESR of the Tan-

talum will keep the effective ESR from rising as quickly at low

temperatures.

HEATSINKING

A heatsink may be required depending on the maximum

power dissipation and maximum ambient temperature of the

application. Under all possible operating conditions, the junc-

tion temperature must be within the range specified under

Absolute Maximum Ratings.

To determine if a heatsink is required, the power dissipated

by the regulator, P_D, must be calculated.

www.national.com

As a design aid, Figure 4 shows the maximum allowable

power dissipation compared to ambient temperature for the

TO-263 device (assuming θ_(J−A)is 35˚C/W and the maxi-

mum junction temperature is 125˚C).

Application Hints (Continued)

If a manufactured heatsink is to be selected, the value of

heatsink-to-ambient thermal resistance, θ_(H−A), must first be

calculated:

θ_(H−A)θ_(J−A)− θ_(C−H)− θ_(J−C)

Where: θ_(J−C)is defined as the thermal resistance from

the junction to the surface of the case. A

value of 4˚C/W can be assumed for θ_(J−C)

for this calculation.

θ_(C−H)

is defined as the thermal resistance be-

tween the case and the surface of the heat-

sink. The value of θ_(C−H)will vary from

about 1.5˚C/W to about 2.5˚C/W (depend-

ing on method of attachment, insulator,

etc.). If the exact value is unknown, 2˚C/W

should be assumed for θ_(C−H)

DS012080-8

When a value for θ_(H−A)is found using the equation shown,

a heatsink must be selected that has a value that is less than

or equal to this number.

FIGURE 4. Maximum Power Dissipation vs T_AMBfor

the TO-263 Package

Figure 5 and Figure 6 show the information for the SOT-223

package. Figure 6 assumes a θ_(J−A)of 74˚C/W for 1 ounce

copper and 51˚C/W for 2 ounce copper and a maximum

junction temperature of 125˚C.

θ_(H−A)is specified numerically by the heatsink manufacturer

in the catalog, or shown in a curve that plots temperature rise

vs power dissipation for the heatsink.

HEATSINKING TO-263 AND SOT-223 PACKAGE PARTS

Both the TO-263 (“S”) and SOT-223 (“MP”) packages use a

copper plane on the PCB and the PCB itself as a heatsink.

To optimize the heat sinking ability of the plane and PCB,

solder the tab of the package to the plane.

Figure 3 shows for the TO-263 the measured values of θ_(J−A)

for different copper area sizes using a typical PCB with 1

ounce copper and no solder mask over the copper area used

for heatsinking.

DS012080-11

FIGURE 5. θ_(J−A)vs Copper (2 ounce) Area for the

SOT-223 Package

DS012080-7

FIGURE 3. θ_(J−A)vs Copper (1 ounce) Area for the

TO-263 Package

As shown in the figure, increasing the copper area beyond 1

square inch produces very little improvement. It should also

be observed that the minimum value of θ_(J−A)for the TO-263

package mounted to a PCB is 32˚C/W.

DS012080-12

FIGURE 6. Maximum Power Dissipation vs T_AMBfor

the SOT-223 Package

Please see AN1028 for power enhancement techniques to

be used with the SOT-223 package.

www.national.com

Physical Dimensions inches (millimeters) unless otherwise noted

3-Lead SOT-223 Package

Order Part Number LM3940IMP-3.3

NSC Package Number MA04A

www.national.com

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

3-Lead TO-220 Package

Order Part Number LM3940IT-3.3

NSC Package Number TO3B

www.national.com

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

3-Lead TO-263 Package

Order Part Number LM3940IS-3.3

NSC Package Number TS3B

www.national.com

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

16-Lead Ceramic Dual-in-Line Package

Order Part Number LM3940J-3.3-QML

5962-9688401QEA

NSC Drawing Number J16A

www.national.com

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

16-Lead Ceramic Surface-Mount Package

Order Part Number LM3940WG-3.3-QML

5962-9688401QXA

NSC Package Number WG16A

LIFE SUPPORT POLICY

NATIONAL’S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT

DEVICES OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT AND GENERAL

COUNSEL OF NATIONAL SEMICONDUCTOR CORPORATION. As used herein:

1. Life support devices or systems are devices or

systems which, (a) are intended for surgical implant

into the body, or (b) support or sustain life, and

whose failure to perform when properly used in

accordance with instructions for use provided in the

labeling, can be reasonably expected to result in a

significant injury to the user.

2. A critical component is any component of a life

support device or system whose failure to perform

can be reasonably expected to cause the failure of

the life support device or system, or to affect its

safety or effectiveness.

National Semiconductor

Corporation

Americas

Tel: 1-800-272-9959

Fax: 1-800-737-7018

Email: support@nsc.com

National Semiconductor

Europe

National Semiconductor

Asia Pacific Customer

Response Group

Tel: 65-2544466

Fax: 65-2504466

National Semiconductor

Japan Ltd.

Tel: 81-3-5639-7560

Fax: 81-3-5639-7507

Fax: +49 (0) 1 80-530 85 86

Email: europe.support@nsc.com

Deutsch Tel: +49 (0) 1 80-530 85 85

English Tel: +49 (0) 1 80-532 78 32

Français Tel: +49 (0) 1 80-532 93 58

Italiano Tel: +49 (0) 1 80-534 16 80

Email: sea.support@nsc.com

www.national.com

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.

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LM3940IT-3.3产品参数

型号:	LM3940IT-3.3
Brand Name：	Texas Instruments
生命周期：	Not Recommended
零件包装代码：	SFM
包装说明：	TO-220, SIP3,.1TB
针数：	3
Reach Compliance Code：	not_compliant
ECCN代码：	EAR99
HTS代码：	8542.39.00.01
Factory Lead Time：	1 week
风险等级：	7.49
可调性：	FIXED
最大回动电压 1：	1 V
标称回动电压 1：	0.31 V
最大绝对输入电压：	7.5 V
最大输入电压：	5.5 V
最小输入电压：	4.5 V
JESD-30 代码：	R-PSFM-T3
JESD-609代码：	e0
长度：	14.986 mm
最大电网调整率：	0.04%
最大负载调整率：	0.08%
湿度敏感等级：	1
功能数量：	1
输出次数：	1
端子数量：	3
工作温度TJ-Max：	125 °C
工作温度TJ-Min：	-40 °C
最高工作温度：	125 °C
最低工作温度：	-40 °C
最大输出电流 1：	1 A
最大输出电压 1：	3.47 V
最小输出电压 1：	3.13 V
标称输出电压 1：	3.3 V
封装主体材料：	PLASTIC/EPOXY
封装代码：	TO-220
封装等效代码：	SIP3,.1TB
封装形状：	RECTANGULAR
封装形式：	FLANGE MOUNT
包装方法：	TUBE
峰值回流温度（摄氏度）：	NOT APPLICABLE
认证状态：	Not Qualified
调节器类型：	FIXED POSITIVE SINGLE OUTPUT LDO REGULATOR
座面最大高度：	4.7 mm
子类别：	Other Regulators
表面贴装：	NO
技术：	BIPOLAR
端子面层：	Tin/Lead (Sn/Pb)
端子形式：	THROUGH-HOLE
端子节距：	2.54 mm
端子位置：	SINGLE
处于峰值回流温度下的最长时间：	NOT APPLICABLE
最大电压容差：	5.2%
宽度：	10.16 mm
Base Number Matches：	1

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产品型号LM3940IT-3.3的概述

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