AS2810R [ETC]

Analog IC ; 模拟IC\n


型号：	AS2810R
厂家：	ETC
描述：	Analog IC 模拟IC\n 模拟IC
文件：	总7页 (文件大小：154K)
中文：	中文翻译
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AS2810

1A Low Dropout Voltage Regulator

Adjustable & Fixed Output,

Fast Response

FEATURES

APPLICATIONS

• Adjustable Output Down To 1.2V

• Fixed Output Voltages 1.5V, 2.5V, 3.0V, 3.3V, 5.0V

• Output Current Of 1A

• SCSI-II Active Terminator

• Portable Palmtap/Notebook Computer

• SMPS Post-Regulator

• Disk Drives

• Low Dropout Voltage 1.2V Typ.

• Extremely Tight Load And Line Regulation

• Current & Thermal Limiting

• Portable Consumer Equipment

• Portable Instrumentation

• Battery charger

• Standard 3-Terminal Low Cost TO-220, TO-263, TO-252 & SOT-223

PRODUCT DESCRIPTION

The AS2810 is a low power positive voltage regulator designed to meet 1A output current and comply with SCSI-II specifications with

fix output voltage of 2.85V. This device is an excellent choice for use in battery-powered applications and portable computers. The

AS2810 features very low quiescent current and very low dropout voltage of 1.2V at a full load and lower as output current decreases.

This product is available as adjustable or fixed 1.5V, 2.5V, 3.0V, 3.3V, and 5V output voltages.

The AS2810 is offered in a 3-pin surface mount packages SOT-223, TO-220, TO-252 & DD package. The output capacitor of 10µF

or larger is needed for the output stability of AS2810 as required by most other regulator circuits

ORDERING INFORMATION

TO-220

3-PIN

DD PLASTIC

3-PIN

SOT-223

3-PIN

TO-252

3-PIN

OPEPERATING JUNCTION

TEMP. RANGE

AS2810YU-X

AS2810YT-X

AS2810YM3-X

AS2810YR-X

-45 to +125°C

X= Output Voltage (1.5V, 2.5V, 3.0V, 3.3V, 5.0V and Blank for Adj.)

Y= Output Tolerance, A for 1%

Blank for 2%

Consult with factory for other fixed voltages.

PIN CONNECTIONS

TO-263-3 (T)

TO-220-3 (U)

SOT-223 (M3)

AS2810

TO-252 (R)

AS2810

ADJ/ GND

V_OUTV_IN

Top View

ADJ/GND V_OUTV_IN

Front View

V_IN

ADJ/GND

V_OUT

Top View

V_IN

ADJ/GND

OUT

Front View

Rev. 10/2/00

AS2810

ABSOLUTE MAXIMUM RATINGS

Lead Temp. (Soldering, 10 Seconds) .............................. 300°C

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

Operating Junction Temperature Range ......................

AS2810 Control Section............................ -45°C +125°C

AS2810 Power Transistor...........................-45°C +150°C

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

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

ELECTRICAL CHARACTERISTICS ^{(NOTE 1) at I}_OUT= 10mA, T_A=25°C, unless otherwise specified.

PARAMETER

CONDITIONS

Typ

AS2810A

AS2810

UNITS

Min

Max

Min

Max

1.5V Version

Output Voltage (Note 2)

AS2810-1.5V, 0 < I_OUT< 1A, 3.3V<V_IN<10V

AS2810-2.5V, 0 < I_OUT< 1A, 4.0V<V_IN<10V

1.5

1.485

1.47

1.515

1.53

1.470

1.455

1.530

1.545

2.5V Version

Output Voltage (Note 2)

2.5

2.475

2.525

2.450

2.550

2.45

2.55

2.425

2.575

2.85V Version

Output Voltage (Note 2)

2.85

2.822

2.879

2.793

2.907

AS2810-2.85V, 0 ≤ I_OUT≤ 1A, 4.5V≤V_IN≤10V

AS2810-3.0V, 0 ≤ I_OUT≤ 1A, 4.5V≤V_IN≤10V

2.793

2.907

2.650

2.936

3.0V Version

Output Voltage (Note 2)

2.970

3.030

2.94

3.06

2.940

3.060

2.79

3.09

3.3V Version

Output Voltage (Note 2)

3.3

3.267

3.234

3.333

3.366

3.234

3.069

3.366

3.399

AS2810-3.3V, 0 ≤ I_OUT≤ 1A, 4.8V≤V_IN≤10V

AS2810-5.0V, 0 ≤ I_OUT≤ 1A, 6.5V≤V_IN≤12V

5.0V Version

Output Voltage (Note 2)

4.950

5.050

4.9

5.1

4.900

5.100

4.65

5.15

All Voltage Options

Reference Voltage (V_REF

)

1.250

1.225

1.270

1.225

1.270

V_IN≤ 7V, P≤ Pmax

1.263

1.225

1.212

1.288

1.5V≤ (V_IN-V_OUT)≤5.75V, 10mA≤I_OUT≤1A

1.5V≤ (V_IN–V_OUT)≤5.75V

Min. Load Current (Note 3)

0.005

0.05

0.2

0.3

0.2

0.3

Line Regulation (∆V_REF(V_in))

2.75V≤V_IN≤7V, I_OUT=10mA, T_J=25ºC (Note 3)

V_IN≤7V, I_OUT=0mA, T_J=25ºC (Note 2)

Load Regulation(∆V_REF(I_OUT))

10mA≤I_OUT≤1A, (V_IN-V_OUT)=3V, T_J=25ºC

(Note 3)

0.05

1.1

0.3

1.2

0.3

1.2

0≤I_OUT≤1A, V_IN=7V, T_J=25ºC (Note 2)

Dropout Voltage

Current Limit

∆V_REF=1%

I_OUT= 1A (Note 3)

_OUT≤ 1A (Note 2)

V_IN=7V

1.2

_OUT(MAX)

1.4V ≤ (V_IN- V_OUT) (Note3)

Rev. 10/2/00

AS2810

ELECTRICAL CHARACTERISTICS (Cont.)

Long Term Stability

T_A=125ºC, 1000 Hrs.

0.3

(Note 2)

0.01

0.25

0.003

T_A=25ºC, 20 ms pulse

0.020

%/W

% Vo

Thermal Regulation (∆V_OUT(Pwr))

Temperature Stability (∆V_OUT(T))

Output Noise, RMS

10Hz to 10kHz T_A=25ºC

TO-220

Thermal Resistance

Junction to Tab

3.0

Junction to Ambient

DD Package

Junction to Tab

3.0

ºC/W

Junction to Ambient

SOT-223 Package

Junction to Tab

156

Junction to Ambient

The Bold specifications apply to the full operating temperature range.

Note 1: Changes in output voltage due to heating effects are covered under the specification for thermal regulation.

Note 2: Fixed Version Only

Note 3: Adjustable Version Only

Rev. 10/2/00

AS2810

APPLICATION HINTS

Reducing parasitic resistance and inductance

One solution to minimize parasitic resistance and inductance is

to connect in parallel capacitors. This arrangement will

improve the transient response of the power supply if your

system requires rapidly changing current load condition.

The AS2810 incorporates protection against over-current

faults, reversed load insertion, over temperature operation, and

positive and negative transient voltage. However, the use of

an output capacitor is required in order to improve the stability

and the performances.

Thermal Consideration

Stability

Although the AS2810 offers some limiting circuitry for

overload conditions, it is necessary not to exceed the

maximum junction temperature, and therefore to be careful

about thermal resistance. The heat flow will follow the lowest

resistance path, which is the Junction-to-case thermal

resistance. In order to insure the best thermal flow of the

component, a proper mounting is required. Note that the case

of the device is electrically connected to the output. In case

the case has to be electrically isolated, a thermally conductive

spacer can be used. However do not forget to consider its

contribution to thermal resistance.

The output capacitor is part of the regulator’s frequency

compensation system. Either a 22µF aluminum electrolytic

capacitor or a 10µF solid tantalum capacitor between the

output terminal and ground guarantees stable operation for all

operating conditions.

However, in order to minimize overshoot and undershoot, and

therefore optimize the design, please refer to the section

‘Ripple Rejection’.

Ripple Rejection

Assuming:

Ripple rejection can be improved by adding a capacitor

between the ADJ pin and ground as shown in figure 6. When

ADJ pin bypassing is used, the value of the output capacitor

required increases to its maximum (22µF for an aluminum

electrolytic capacitor, or 10µF for a solid tantalum capacitor).

If the ADJ pin is not bypass, the value of the output capacitor

can be lowered to 10µF for an electrolytic aluminum capacitor

or 4.7µF for a solid tantalum capacitor.

_IN= 10V, V_OUT= 5V, I_OUT= 1.5A, T_A= 50°C/W,

θ _{Heatsink Case}= 6°C/W, θ _{Heatsink Case}= 0.5°C/W, θ _JC= 3°C/W

Power dissipation under this condition

P_D= (V_IN– V_OUT) * I_OUT= 7.5W

Junction Temperature

T_J= T_A+ P_D* (θ _{Case - HS}+ θ _HS+ θ _JC

)

However the value of the ADJ-bypass capacitor should be

chosen with respect to the following equation:

For the Control Sections

C = 1 / ( 6.28 * F_R* R₁)

T_J= 50 + 7.5*(0.5+6=3) = 121.25°C

121.25°C < T_{J (max)}for the Control & Power Sections.

Where C

= value of the capacitor in Farads (select an

equal or larger standard value),

F_R= ripple frequency in Hz,

R₁= value of resistor R₁in Ohms.

In both case reliable operation is insured by adequate junction

temperature.

If an ADJ-bypass capacitor is use, the amplitude of the output

ripple will be independent of the output voltage. If an ADJ-

bypass capacitor is not used, the output ripple will be

proportional to the ratio of the output voltage to the reference

voltage:

M = V_OUT/ V_REF

Where M = multiplier for the ripple seen when the ADJ pin

is optimally bypassed.

_REF= Reference Voltage

Rev. 10/2/00

AS2810

Basic Adjustable Regulator

V_IN

V_OUT

AS2810

V_IN

V_REF

V_OUT

3.3V

R₁

R₂

AS2810

I_ADJ

50µA

10uF

V_OUT= V_REF* ( 1 + R/R₁) + I_ADJ* R₂

Basic Fixed Regulator

Fig.2 Basic Adjustable Regulator

Output Voltage

Consider Figure 2. The resistance R₁generates a constant

current flow, normally the specified load current of 10mA.

This current will go through the resistance R₂to set the overall

output voltage. The current I_ADJis very small and constant.

Therefore its contribution to the overall output voltage is very

small and can generally be ignored.

Output Voltage

The fixed voltage LDO voltage regulator are simple to use

regulators since the V_OUTis preset to the specifications. It is

important however, to provide the proper output capacitance

for stability and improvement. For most operating conditions

a capacitance of 22uF tantalum or 100uF electrolytic will

ensure stability and prevent oscillation.

Load Regulation

Parasitic line resistance can degrade load regulation. In order

not to affect the behavior of the regulator, it is best to connect

directly the R₁resistance from the resistor divider to the case,

and not to the load. For the same reason, it is best to connect

the resistor R₂to the Negative side of the load.

R_PParasitic Line

Resistance

V_IN

AS2810

Connect R ₁to

Case of Regulator

R₁

R_L

R₂

Connect R ₂to Load

Fig.3 Basic Adjustable Regulator

Rev. 10/2/00

AS2810

TYPICAL APPLICATIONS

V_IN

V_OUT

V_IN

OUT

AS2810

OUT

C₂

C₁

R₁

R₂

ADJ

R₁

ADJ

V_OUT= V_REF(1 + R ) + I_ADJR₂

R²₁

LOAD

Fig. 5 Typical Adjustable Regulator

Fig. 4 1A Current output Regulator

(Note A)

V_IN

(Note A)

OUT

V_OUT

AS2810

ADJ

AS2810

10µF

121Ω

ADJ

R₁

121Ω

10µF

100µF

TTL

Input

150µF

2N3904

*C₁improves ripple rejection. Xc

should be ~ R ₁at ripple frequency.

365Ω

R₂

365Ω

C₁

10µF*

Note A: V_IN(MIN)= (Intended V_OUT) + (V_{DROPOUT (MAX)}

)

Note A: V_IN(MIN)= (Intended V_OUT) + (V_{DROPOUT (MAX)}

)

Fig. 6 Improving Ripple Rejection

Fig.7 5V Regulator with Shutdown

Rev. 10/2/00

AS2810

TYPICAL CHARACTERISTICS

Rev. 10/2/00

AS2810R [ETC]

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