B4251CK5-3.5 datasheet, PDF - EEWORLD Datasheet

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B4251CK5-3.5: DescriptionRegulator; CategoryPower/power management The power supply circuit; File Size170KB，5 Pages; ManufacturerBay Linear Inc

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Regulator

B4251CK5-3.5 Parametric

Parameter Name	Attribute value
Maker	Bay Linear Inc
package instruction	,
Reach Compliance Code	unknown

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Bay Linear

Inspire the Linear Power

250mA Low Dropout Voltage Regulators

ON/OFF & BYPASS

B4251

Description

The B4251 series are a group of positive output voltage,

five-pin regulators, which provide a high current even

when the input/output voltage differential is small. Low

power consumption and high accuracy is achieved

though CMOS and programmable fuse technologies.

Output voltage: 2.0V to 6.0V in 0.1V increments.

The B4251 consists of a high-precision voltage

reference, an error correction circuit, and a current

limited output driver. Key features include a Shutdown

Pin that reduces supply current to 0.5µA max and a

470pF Bypass input to ground reduces noise present on

the internal reference, which in turn significantly reduce

output noise. If output noise is not concern, this input

maybe left unconnected. Larger capacitor values cap be

used, but results in longer time period to rated output

voltage when power initially applied.

The ON/OFF pin enables the output to be turned off,

resulting in reduced power consumption. Provided in

SOT-25 (150mW) packages minimizes the usage of

board real state.

Features

•

Maximum Output Current: 250 mA.

Highly Accurate Output Voltage +/- 1.4%

Only 19µA Power Consumption MAX

Shutdown Supply Current 1µA

Ground Current of Less than 5µA

Very Low Dropout

0.12V at 100mA

0.23V at 250mA

Shutdown Mode for Power Savings

With ON/OFF & BYPASS Features

Offered in SOT-89 & SOT-25 Packages

PIN-to-PIN S-818

Applications

•

Battery Powered Equipment

Notebook PC, Palmtops, PDA

Portable Cameras and Video Recorders

Reference Voltage Sources

Cellular / GSM / PCS Phones

Pin Connection

Ordering Information

Package

SOT-25

SOT-89

Part No.

B4251CK5-X.X

B4251CR-X.X

SOT-25 (K5)

SOT-89 (R)

X.X = Fixed Output Voltages from 2.0V to 6.0V

out

Bypass

out

Vss

ON/OFF (Enable) Function

Part No

B4251

ON/Off

High

Low

OUT

OFF

ON/OFF

GND

On/Off

Top View

Bay Linear, Inc

2478 Armstrong Street, Livermore, CA 94550 Tel: (925) 606-5950, Fax: (925) 940-9556

www.baylinear.com

B4251

Absolute Maximum Ratings

Parameter

Input Voltage

Output Current

Output Voltage

On/Off Voltage

Continual Total Power Dissipation

Operating Ambient Temperature

Storage Temperature

Symbol

OUT

On/Off

SOT-25

SOT-89

OPR

STG

Ratings

500

-0.3 to V

0.3

-0.3 to V

IN+

0.3

150

300

-30 to 80

-40 to 125

Units

°C

Electrical Characteristics (T

= 25°C, V

= V

OUT +

0.5V; unless otherwise noted)

Parameter

Output Voltage Accuracy

Line Regulation

∆V

OUT

/∆V

-V

OUT

Load Regulation

Maximum Output Current

Current Limit

Shutdown Supply Current

Shutdown Input Bias Current

Shutdown Exit Delay

Shutdown Input Threshold Low

Shutdown Input Threshold High

Ground Pin Current

Dropout Voltage

Thermal Shutdown Temperature

Conditions

= 1mA

= 0 to 150mA

= 100mA,

OUT

+ 0.1V)<V

<6V

VIN 6V, 0mA < I

< 120mA C

OUT

= 1µF

250

160

=25°C

VSHDN=V

IN,

=25°C

CBP=0µF C

OUT

=1µF, I

= 1mA

=2.5 to 5.5V

OUT

= 0mA……150mA

= 150mA

= 250 mA

MIN

-1.4%

-2%

TYP

0.2

0.01

500

0.01

0.4

160

200

155

MAX

+1.4%

+2%

0.3

0.04

UNIT

%/V

%/mV

100

150

µA

µsec

µA

°C

250

280

Marking Format

SOT-25

FXWW

F = B4251

Variables

X = Voltage Codes

B = 2.0

C = 2.5

D = 2.8

E = 3.0

3.3

3.5

5.0

WW = Work Week Code

SOT-25 = 01 to 99

Bay Linear, Inc

2478 Armstrong Street, Livermore, CA 94550 Tel: (925) 606-5950, Fax: (925) 940-9556

www.baylinear.com

B4251

PRODUCT DESCRIPTION

The B4251 is precision fixed output voltage regulator.

Unlike bipolar regulators, the B4251 supply current

does not increase with load current. In addition, V

out

remains stable and within regulator at very low load

currents (an important consideration in RTC and

CMOS RAM battery back-up application).

Figure 1 shows a typical application circuit. The

regulator is enabled any time the shutdown input is at

or above V

IH.

And shutdown (disabled) when SHDN is

at or below V

. SHDN maybe controlled by a CMOS

logic gate, or I/O port of a micro controller. If the

SHDN input is not. Required, it should be connected

directly to the supply. While in shutdown, supply

current decreases to 0.05µA (typical) and V

out

falls to

zero volts.

Power Dissipation

The amount of power the regulator dissipates is

primarily a function of input and output voltage, and

output current. The following equation is used to

calculate worst case power dissipation:

Where:

= worst case actual power dissipation

INMAX

= Maximum voltage on V

OUTMIN

=Minimum regulator output voltage

LOADMAX

= maximum output (LOAD) Current

The maximum allowable power dissipation is function

of the maximum ambient temperature (T

AMAX

). The

maximum allowable die temperature (125°C) and the

thermal resistance from junction-to-air (θ

). The 5-

pin SOT-23A package has a

of approximately

220°C/Watt when mounted on a single layer FR4

dielectric copper clad PC board.

DMAX

=(T

JMAX

-T

AMAX

Where all terms are previously defined

This can be caused in conjunction with other equation

to ensure regulator thermal operation is within limit.

For example:

Given:

INMAX

=3.0V+10%

OUTMIN

=2.7V-2.5%

LOADMAX

=40 mA

JMAX

=125°C

AMAX

=55°C

Find:

1. Actual power dissipation

2. Maximum allowable dissipation

Actual power dissipation:

=(V

INMAX

-V

OUTMIN

LOADMAX

=[(3.0 x 1.1)-(2.7 x 0.975)]40 x 10

-3

=26.7mW

Maximum allowable power dissipation:

DMAX

=(T

JMAX

-T

AMAX

)

=(125-55)/220

=318Mw

These equations can be used to calculate maximum

current and/or input voltage limits.

www.baylinear.com

=(V

INMAX

-V

OUTMIN

LOADMAX

Bypass Input

A 470pF capacitor connected from the bypass input to

ground reduces noise present on the internal reference,

which in turn significantly reduces output noise. If

output noise is not a concern, this input maybe left

unconnected. Larger capacitor values maybe used, but

it results in a longer time period to rated output

voltage power is initially applied.

Output Capacitor

A 1µF (min) capacitor from V

out

to ground is required.

Then output capacitor should have an effective series

resistance of 5Ω or less. A 1µA capacitor should be

connected from V

to GND if there is more than 10

inches of wire between the regulator and the AC filter

capacitor, or if a battery is used as the power source.

Aluminum electrolytic or tantalum capacitor types can

be used. (since many aluminum electrolytic capacitors

freeze at approximately- 30°C, solid tantalums are

recommended for applications operating below –25

°C.)

When operating from sources other than

batteries, supply-noise rejection and transient response

can be improved by increasing the value of the input

and output capacitors and employing passive filtering

techniques.

Thermal Considerations

Thermal Shutdown

Integrated thermal protection circuitry shuts the

regulator off when die temperature exceeds 160°C.

The regulator remaining off until the die temperature

drops to approximately 150

°C.

Bay Linear, Inc

2478 Armstrong Street, Livermore, CA 94550 Tel: (925) 606-5950, Fax: (925) 940-9556

B4251

SOT-25 Packaging Outline

B (5 PLACES)

SYMBOL

MILLIMETERS

INCHES

MIN.

0.90

0.30

0.10

2.70

1.40

1.70

2.50

MAX

1.30

0.10

MIN.

.035

.012

.004

.106

.055

.066

.098

MAX.

.051

.004

.019

.0137

.122

.071

.082

.118

NOTE:

1. REFER TO APPLICABLE

2. CONTROLLING DIMENTION : MILLIMETER

3. PACKAGE SURFACE FINISHING TO BE SMOOTH

FINISH.

0.80 REF

0.50

0.35

3.10

1.80

2.10

3.00

.0315 REF

0.95 BSC.

.037 BSC.

MIN 0.2

MIN .0078

Bay Linear, Inc

2478 Armstrong Street, Livermore, CA 94550 Tel: (925) 606-5950, Fax: (925) 940-9556

www.baylinear.com

Advance Information-

These data sheets contain descriptions of products that are in development. The specifications are based on the engineering calculations,

computer simulations and/ or initial prototype evaluation.

Preliminary Information-

These data sheets contain minimum and maximum specifications that are based on the initial device characterizations. These limits are

subject to change upon the completion of the full characterization over the specified temperature and supply voltage ranges.

The application circuit examples are only to explain the representative applications of the devices and are not intended to guarantee any circuit

design or permit any industrial property right to other rights to execute. Bay Linear takes no responsibility for any problems related to any

industrial property right resulting from the use of the contents shown in the data book. Typical parameters can and do vary in different

applications. Customer’s technical experts must validate all operating parameters including “ Typical” for each customer application.

LIFE SUPPORT AND NUCLEAR POLICY

Bay Linear products are not authorized for and should not be used within life support systems which are intended for surgical

implants into the body to support or sustain life, in aircraft, space equipment, submarine, or nuclear facility applications without

the specific written consent of Bay Linear President.

Bay Linear, Inc

2478 Armstrong Street, Livermore, CA 94550 Tel: (925) 606-5950, Fax: (925) 940-9556

www.baylinear.com

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