Datasheet B4251CK5-6.0, B4251CK5-5.9, B4251CK-4.8, B4251CK-4.7, B4251CK-4.6 Datasheet (BAYLI)

Bay Linear, Inc

2478 Armstrong Street, Livermore, CA 94550 Tel: [phone], Fax: [phone] www.baylinear.com

250mA Low Dropout Voltage Regulators

B4251

ON/OFF & BYPASS

Pin Connection

Ordering Information

Package Part No.

SOT-25 B4251CK5-X.X

SOT-89 B4251CR-X.X

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

ON/OFF (Enable) Function

Part No ON/Off V

OUT

High ON

B4251

Low OFF

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

b

oard 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

Bay Linear

Inspire the Linear Power

SOT-89 (R)

Top View

On/OffV

in

Vss

3

21

4

5

V

out

NC

SOT-25 (K5)

Top View

ON/OFF

V

in

GND

32

1

45

V

out

Bypass

Bay Linear, Inc

2478 Armstrong Street, Livermore, CA 94550 Tel: [phone], Fax: [phone] www.baylinear.com

B4251

Absolute Maximum Ratings

Parameter Symbol Ratings Units

Input Voltage VIN 12 V
Output Current I

OUT

500 mA

Output Voltage V

OUT

V

SS

-0.3 to VIN 0.3 V

On/Off Voltage On/Off VSS -0.3 to V

IN+

0.3 V

Continual Total Power Dissipation SOT-25

SOT-89

Pd

150
300

mW

Operating Ambient Temperature T

OPR

-30 to 80

°C

Storage Temperature T

STG

-40 to 125

°C

Electrical Characteristics (Ta = 25°C, V

IN

= V

OUT +

0.5V; unless otherwise noted)

Parameter Conditions MIN TYP MAX UNIT

IO = 1mA -1.4% - +1.4%

Output Voltage Accuracy

I

O

= 0 to 150mA -2% - +2%

V

Line Regulation
∆V

OUT

/∆VIN-V

OUT

I

O

= 100mA,

(V

OUT

+ 0.1V)<VIN<6V

0.2 0.3 %/V

Load Regulation

VIN 6V, 0mA < I

O

< 120mA C

OUT

= 1µF

0.01

0.04 %/mV

Maximum Output Current 250
Current Limit 160 500

mA

Shutdown Supply Current

T

A

=25°C

0.01 1

µA

Shutdown Input Bias Current

VSHDN=V

IN, TA

=25°C

0.01 100

nA

Shutdown Exit Delay

CBP=0µF C

OUT

=1µF, IO = 1mA

30 150

µsec
Shutdown Input Threshold Low Vin=2.5 to 5.5V 0.4 V
Shutdown Input Threshold High Vin=2.5 to 5.5V 2 V
Ground Pin Current I

OUT

= 0mA……150mA

2 5

µA

IO = 150mA 160 250

Dropout Voltage

I

O

= 250 mA

200 280

mV

Thermal Shutdown Temperature

155

°C

Marking Format

SOT-25

FXWW

F = B4251

Variables

X = Voltage Codes WW = Work Week Code

B = 2.0 F = 3.3

SOT-25 = 01 to 99

C = 2.5 G = 3.5

D = 2.8 H = 5.0

E = 3.0

Bay Linear, Inc

2478 Armstrong Street, Livermore, CA 94550 Tel: [phone], Fax: [phone] 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

IL

. 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.

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

in

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.

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:

P

D

=(V

INMAX-VOUTMIN)ILOADMAX

Where:
P

D

= worst case actual power dissipation

V

INMAX

= Maximum voltage on V

IN

V

OUTMIN

=Minimum regulator output voltage

I

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

JA

). The 5-

pin SOT-23A package has a θ

JA

of approximately
220°C/Watt when mounted on a single layer FR4
dielectric copper clad PC board.

P

DMAX

=(T

JMAX-TAMAX

)/ θ

JA

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:

V

INMAX

=3.0V+10%

V

OUTMIN

=2.7V-2.5%

I

LOADMAX

=40 mA

T

JMAX

=125°C

T

AMAX

=55°C

Find:

1. Actual power dissipation

2. Maximum allowable dissipation

Actual power dissipation:

P

D

=(V

INMAX-VOUTMIN)ILOADMAX

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

-3

=26.7mW

Maximum allowable power dissipation:

P

DMAX

=(T

JMAX-TAMAX

)

=(125-55)/220

=318Mw
These equations can be used to calculate maximum
current and/or input voltage limits.

Bay Linear, Inc

2478 Armstrong Street, Livermore, CA 94550 Tel: [phone], Fax: [phone] www.baylinear.com

B4251

SOT-25 Packaging Outline

L

A1

C

A2

A

D

B (5 PLACES)

H

E

e1

e

MILLIMETERS

SYMBOL

0

0.90

0.30

0.80 REF

2.70

0.10

1.40

1.70

0.95 BSC.

MIN 0.2

2.50

MIN. MAX MIN. MAX.

A

A1

A2

B

C

D

E

e

e1

H

L

0

.035

.012

.0315 REF

.106

.004

.055

.066

.037 BSC.

MIN .0078

.098

0.10

1.30

0.50

3.10

0.35

1.80

2.10

3.00

.004

.051

.019

.122

.0137

.071

.082

.118

INCHES

NOTE:

1. REFER TO APPLICABLE

2. CONTROLLING DIMENTION : MILLIMETER

3. PACKAGE SURFACE FINISHING TO BE SMOOT

H

FINISH.

Bay Linear, Inc

2478 Armstrong Street, Livermore, CA 94550 Tel: [phone], Fax: [phone] 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.

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