LM1084RS [HTC]

5A L.D.O. VOLTAGE REGULATOR (Adjustable & Fixed); 5A L.D.O.稳压器（可调和固定）


型号：	LM1084RS
厂家：	HTC KOREA TAEJIN TECHNOLOGY CO.
描述：	5A L.D.O. VOLTAGE REGULATOR (Adjustable & Fixed) 5A L.D.O.稳压器（可调和固定）稳压器
文件：	总7页 (文件大小：250K)
中文：	中文翻译
下载：	下载PDF数据表文档文件

5A L.D.O. VOLTAGE REGULATOR (Adjustable & Fixed)

LM1084

FEATURES

● Output Current of 5A

TO-263 PKG

● Fast Transient Response

● 0.04% Line Regulation

● 0.2% Load Regulation

● Internal Thermal and Current Limiting

● Adjustable or Fixed Output Voltage(1.5V, 1.8V, 2.5V, 3.3V, 5.0V)

● Surface Mount Package TO-263 3LD and TO-252 3L

● 100% Thermal Limit Burn-in

TO-252 PKG

● Low Dropout Voltage 1.5V at 5A Output Current

● Moisture Sensitivity Level 3

APPLICATIONS

1. ADJ / GND 2. OUTPUT 3. INPUT

* Heatsink surface connected to Pin 2.

● High Efficiency Linear Regulators / Power Supply

● High Efficiency "Green" Computer Systems

● Constant Current Regulators

ORDERING INFORMATION

● Portable Instrumentation

Device

Package

● SMPS Post-Regulator

LM1084R-X.X

LM1084RS-X.X

TO-263 3LD

TO-252 3LD

● Adjustable Power Supplies

● Powering VGA & Sound Card

(X.X=VOUT=1.5V, 1.8V, 2.5V, 3.3V, 5.0V, ADJ)

DESCRIPTION

The LM1084 series of positive adjustable and fixed regulators are designed to provide 5A with high efficient.

All internal circuitry is designed to operate down to 1.3V input to output differential.

On-chip trimming adjusts the reference voltage to 1%.

It's low dropout voltage and fast transient response make it ideal for low voltage microprocessor applications.

Internal current and thermal limiting provides protection against any overload condition that would create

excessive junction temperature.

TEST & TYPICAL APPLICATION CIRCUIT

LM1084-3.3V

LM1084-ADJ

Note

V_REF=V_OUT-V_ADJ=1.25V(Typ.)

(1) C1 needed if device is far away from filter capacitors.

(2) C2 minimum value required for stability.

I_ADJ=55㎂(Typ.)

V_OUT= V_REFx (1+RF2/RF1) + I_ADJx RF2

Nov. 2010 - Rev. 1.3.

HTC

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5A L.D.O. VOLTAGE REGULATOR (Adjustable & Fixed)

LM1084

ABSOLUTE MAXIMUM RATINGS

CHARACTERISTIC

SYMBOL

V_IN

VALUE

UNIT

Supply Voltage

Topr

Tstg

Tjc

0 ~ 125

Operating Junction Temperature Range

Storage Temperature Range

℃

-65 ~ 150

300

C/W

Thermal Resistance Junction to Case TO-263

Thermal Resistance Junction to Ambient TO-263

Lead Temperature (Soldering) 10 sec.

Maximum Output Current

Tja

Tsol

Imax

℃

ELECTRICAL CHARACTERISTICS I_OUT=100mA, T_A=25°C, unless otherwise specified.

PARAMETER

1.5V Version

TEST CONDITIONS

MIN

1.470

1.764

2.450

3.234

4.900

TYP

1.5

1.8

2.5

3.3

MAX

1.530

1.836

2.550

3.366

5.100

UNIT

0 < I_OUT< 5A, 3.3V < V_IN

Output Voltage

1.8V Version

0 < I_OUT< 5A, 3.75V < V_IN

0 < I_OUT< 5A, 4.0V < V_IN

0 < I_OUT< 5A, 4.8V < V_IN

0 < I_OUT< 5A, 6.5V < V_IN

Output Voltage

2.5V Version

Output Voltage

3.3V Version

Output Voltage

5.0V Version

Output Voltage

All Voltage Options

V_IN=5V, I_LOAD= 10mA

1.238

1.225

1.25

1.262

1.275

Note 1

Reference Voltage (V_REF

)

1.5V ≤ (V_IN-V_OUT) ≤ 10V, 10mA ≤ I_OUT≤ 5A

V_IN=5V, V_ADJ= 0V

Min. Load Current

Line Regulation ^{Note 1}

Load Regulation ^{Note 1}

Dropout Voltage ^Note1,3

1.5V ≤ V_IN-V_OUT≤ 10V, I_OUT=10mA T_J=25℃

10mA ≤ I_OUT≤ 5A, V_IN-V_OUT=1.5V, T_J=25℃

ΔV_REF= 1% , I_OUT= 5A

0.04

0.2

0.4

1.3

1.5

V_IN-V_OUT= 1.5V

Current Limit I_OUT(MAX)

6.5

1.4V≤(V_IN-V_OUT) Adjustable Only

10mA ≤ I_OUT≤ 5A, V_IN-V_OUT=1.5V, T_J=25℃

1.5V ≤ V_IN-V_OUT≤ 10V, I_OUT=10mA, T_J=25℃

V_IN-V_OUT= 3V, I_OUT= 5A

Ground Pin Current

Audust Pin Current

0.003

Ripple Rejection^{Note 2}

V_IN-V_OUT= 1.5V, I_OUT= 10mA

Temperature Coefficient

0.005

%/℃

Notes :

1 : Low duty pulse testing with Kelvin connections required.

2 : 120Hz input ripple (CADJ for ADJ = 25uF, Cout = 25uF)

3 : ΔV_OUT, ΔV_REF= 1%

HTC

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5A L.D.O. VOLTAGE REGULATOR (Adjustable & Fixed)

LM1084

TYPICAL PERFORMANCE CHARACTERISTICS

Figure 1. Dropout Voltage vs Output Current

Figure 2. Reference Voltage vs Temperature

Figure 3. Load Regulation vs. Output Current

Figure 4. Minimum Load Current

Figure 5. Adjust Pin Current vs Temperature

Figure 6. Ripple Rejection vs. Frequency

(Fixed Versions)

HTC

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5A L.D.O. VOLTAGE REGULATOR (Adjustable & Fixed)

LM1084

Figure 7. Ripple Rejection vs. Frequency (Adjustable Versions)

APPLICATIONS INFORMATION

LM1084-ADJ

Figure 8. Resistor Divider Scheme for the Adjustable Version

LM1084-XX

Figure 9. Protection Diode Scheme for Fixed Output Regulators

HTC

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5A L.D.O. VOLTAGE REGULATOR (Adjustable & Fixed)

LM1084

APPLICATION INFORMATION

The LM1084 series of adjustable and fixed regulators are easy to use and have all the protection features

expected in high performance voltage regulators : short circuit protection and thermal shut-down.

Pin compatible with older three terminal adjustable regulators, these devices offer the advantage of a lower

dropout voltage, more precies reference tolerance and improved reference stability with temperature.

STABILITY

The circuit design used in the LM1084 series requires the use of an output capacitor as part of the device

frequency compensation.

The addition of 150uF aluminum electrolytic or a 22uF solid tantalum on the output will ensure stability for

all operating conditions. When the adjustment terminal is bypassed with a capacitor to improve the ripple

rejection, the requirement for an output capacitor increases. The value of 22uF tantalum or 150uF aluminum

covers all cases of bypassing the adjustment terminal. Without bypassing the adjustment terminal smaller

capacitors can be used with equally good results.

To ensure good transient response with heavy load current changes capacitor values on the order of 100uF

are used in the output of many regulators. To further improve stability and transient response of these devices

larger values of output capacitor can be used.

PROTECTION DIODES

Unlike older regulators, the LM1084 family does not need any

protection diodies between the adjustment pin and the output and

from the output tu the input to prevent over-stressing the die.

Internal resistors are limiting the internal current paths on the

LM1084 adjustment pin, therfore even with capacitors on the

adjustment pin no protection diode is needed to ensure device

safety under short-circuit conditions.

LM1084

Diodes between the input and output are not usually needed.

Microsecond surge currents of 50A to 100A can be handled by

Figure 10.

the internal diode between the input and output pins of the device. In norminal operations it is difficult to get

those values of surge currents even with the use of large output capacitances. If high value output capacitors

are used, such as 1000uF to 5000uF and the input pin is instantaneously shorted to ground, damage can occur.

A diode from output to input is recommended, when a crowbar circuit at the input of the LM1084 is used.

Normal power supply cycling or even plugging and unplugging in the system will not generate current large

enough to do any damage.

The adjustment pin can be driven on a transient basis ±25V, with respect to the output without any device

degradation. As with any IC regulator, none the protection circuitry will be functional and the internal

transistors will break diwn if the maximum inout to output voltage differential is exceeded.

HTC

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5A L.D.O. VOLTAGE REGULATOR (Adjustable & Fixed)

LM1084

RIPPLE REJECTION

The ripple rejection values are measured with the adjustment pin bypassed. The impedance of the adjust pin

capacitor at the ripple frequency should be less than the value of R1 (normally 100Ω to 120Ω) for a proper

bypassing and ripple rejection approaching the values shown. The size of the required adjust pin capacitor is

a function of the input ripple frequency. If R1=100Ω at 120Hz the adjust pin capacitor should be 25uF.

At 100kHz only 0.22uF is needed.

The ripple rejection will be a function of output voltage, in circuits without an adjust pin bypass capacitor.

The output ripple will increase directly as a ratio of the output voltage to the reference voltage (V_OUT/V_REF

)

OUTPUT VOLTAGE

The LM1084 series develops a 1.25V reference voltage between

the output and the adjust terminal. Placing a resistor between these

two terminals causes a constant current to flow through R1 and down

throuth R2 to set the overall output voltage.

LM1084

This current is normally the specified minium load current of 10mA.

Because IADJ is very small and constant it represents a small error

and it can usually be ignored.

Figure 11.

LOAD REGULATION

True remote sheet specification it is not possible to provide,

because the LM1084 is a three terminal device.

LM1084

The resistance of the wire connecting the regulator to the load

will limit the load regulation.

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.

The best load regulation is obtained when the top of the resistor

divider R1 is connected directly to the case not to the load. If R1

were connected to the load, the effective resistance between the

regulator and the load would be:

Figure 12.

[R_PX(R2+R1)]/R1 , R_P= Parasitic Line Resistance

Connected as shown Figure.12 R is not multiplied by the divider ratio. Using 16-gauge wire the parasitic line

resistance is about 0.004Ω per foot, transllating to 4mV/ft at 1A load current.

HTC

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5A L.D.O. VOLTAGE REGULATOR (Adjustable & Fixed)

LM1084

THERMAL CONSIDERATIONS

The LM1084 series have internal power and thermal limiting circuitry designed to protect the device under

overload cinditions. However maximum junction temperature ratings should not be exceeded under continous

normal load conditions.

Careful consideration must be given to all sourses of thermal resistance from junction to ambient, including

junction-to- ase, case-to-heat sink interface and heat sink resistance itself. To ensure safe operating

temperatures and reflect more accurately the device temperature, new thermal resistance specifications have

been developed. Unlike order reguators with a single junction-to-case thermal resistance speccification, the

data section for these new regulators provides a separate thermal resistance and maximum juntion temperature

for both the Control Section and the Power Transistor. Calculations for both temperatures under certain

conditions of ambient temperature and heat sink resistance and to ensure that both thermal limits are met.

Junction-to-case thermal resistance is specified from the IC junction to the bottom of the case directly below

the die. This is the lowest resistance path for the heat flow. In order to ensure the best possible thermal flow

from this area of the package to the heat sink proper mounting is required. Thermal compound at the case-

to-heat sink interface is recommended. A thermarlly conductive spacer can be used, if the case of the device

must be electrically isolated, but its added contribution to thermal resistance has to be considered.

HTC

- 7 -

LM1084RS [HTC]

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