Datasheet SPX1521U-3.3, SPX1521U-5.0, SPX1521S-2.5, SPX1521S-3.3, SPX1521S-5.0 Datasheet (Sipex Corporation)

Rev. 10/24/00

SPX1521

300mA Low Dropout Voltage Regulator

(PRELIMINARY INFORMATION)

FEATURES

APPLICATIONS

•

1%

Output Accuracy @ 2.5V, 3.3V, 5V, @ 300mA Output

•

Battery Powered Systems

•

Very Low Quiescent Current

•

Cordless Telephones

•

0.42V (Typ.) Dropout Voltage @ 300mA

•

Radio Control Systems

•

Extremely Tight Load And Line Regulation

•

Portable/Palm Top/Notebook Computers

•

Current & Thermal Limiting

•

Portable Consumer Equipment

•

Logic-Controlled Electronic Shutdown

•

Portable Instrumentation

•

Reverse Battery Protection

•

Bar Code Scanners

•

Output Programmable From 1.24 To 20V

•

SMPS Post-Regulator

•

Equivalent Replacement For LT1521

•

Voltage Reference

•

Automotive Electronics

PRODUCT DESCRIPTION

The SPX1521 is a low power voltage regulator. This device is an excellent choice for use in battery-powered applications such as
cordless telephones, radio control systems, and portable computers. The SPX1521 features very low quiescent current and very low
dropout voltage. This includes a tight initial tolerance of ± 1% max, and very low output temperature coefficient, making the SPX1521
useful as a low-power voltage reference.

The error flag output feature is used as power-on reset for warning of a low output voltage, due to falling voltage input of batteries.
The SPX1521 is offered in a SO-8, SOT-252, TO-223, TO-220 & TO-263 packages.

PIN CONNECTIONS

Top View

2

1

3

4

8

7

6

5

SPX1521

8-Pin Surface Mount (S)

Top View

SPX1521

132

SOT-223 (M3)

Top View

TO-263-3 (T)

1

SPX1521

2

3

Front View

TO-220-3 (U)

SPX1521

123

Front View

TO-252 (R)

3

2

1

SPX1521

V

OUT

SENSE/ ADJ

GND

ERROR

V

IN

GND

GND

SHDN

VINGND V

OUT

V

OUT

GND V

IN

V

OUT

GND

V

IN

V

OUT

GND

V

IN

SHDN

V

OUT

<0.25V

>2.8V

NC

OFF

ON

ON

Rev. 10/24/00

SPX1521

ABSOLUTE MAXIMUM RATINGS

Power Dissipation……………………...… Internally Limited Maximum Input Supply Voltage...................................... +20

V

Lead Temp. (Soldering, 5 Seconds)…………….……. 260°C

Shutdown Input Voltage ..................................... -0.6V to 6.5

V
Storage Temperature Range……………… -65°C to + 150°C
Operating Junction Temperature Range
SPX1521……………………………..… -40°C to + 125°C

ELECTRICAL CHARACTERISTICS

at Vs = ±15V, Ta = 25°C, unless otherwise specified.

Boldface

apply over the full

operating temperature range.

PARAMETER

CONDITIONS

(Note 2)

Typ.

SPX1521

Min Max

UNITS

2.5V Version

Output Voltage

1mA ≤I

L

≤

300mA

2.5

2.5

2.475

2.450

2.525

2.550

V

Reverse Output Current V

OUT

= 2.5V, VIN = 0V 16 25

µ

A

3.3V Version

Output Voltage

1mA ≤I

L

≤

300mA

3.3

3.3

3.267

3.217

3.333

3.382

V

Reverse Output Current V

OUT

= 3.3V, VIN = 0V 16 25

µ

A

5V Version

Output Voltage

1mA ≤I

L

≤

300mA

5.0

5.0

4.950

4.880

5.050

5.120

V

Reverse Output Current V

OUT

= 5.0V, VIN = 0V 16 25

µ

A

All Voltage Options

Output Voltage
Temperature Coefficient

(Note 1)

20

100

ppm/°C

Line Regulation ( Note 3)

6V ≤ V

IN

≤20V (Note 4)

1.5

10

%max

Load Regulation ( Note 3 ) IL = 1 to 300mA

I

L

= 0.1 to 1mA

0.04 0.20

0.30

%max

Dropout Voltage
( Note 5 )

I

L

= 1mA

I

L

= 300mA

0.13

0.42

0.16

0.25

0.55

0.70

MV

Ground Current I

L

= 1mA

I

L

= 10mA

I

L

= 50mA

I

L

= 100mA

I

L

= 300mA

100
350

1.5

4.0
7

150

500

2.5

7.0
14

µ

A

mA

Current Limit V

OUT

= 0 200

500

mA

Ripple Rejection VIN – V

OUT

1V (Avg), V

RIPPLE

= 0.5Vp-p

F

RIPPLE

= 120Hz, I

LOAD

= 0.3A, TJ = 25°C

58 50 dB

Input Reverse Leakage Current VIN = -20V, V

OUT

= 0V 1.0 mA

Rev. 10/24/00

SPX1521

Fig.2 Adjustable Voltage Regulator

V

IN

V

OUT

GND 2

81

3, 6, 7

ADJ

ERROR4SHUTDOWN

5

SPX1521

Note 1:

Output or reference voltage temperature coefficients defined as the worst case voltage change divided by the total temperature range.

Note 2:

Unless otherwise specified all limits are guaranteed for T

j

= 25°C, VIN = 6V, IL = 100µA and CL = 1µF. Additional conditions for the 8-pin versions are

feedback tied to 5V tap and output tied to output sense (V

OUT

= 5V) and V

SHUTDOWN

≤ 0.8V.

Note 3:

Regulation is measured at constant junction temperature, using pulse testing with a low duty cycle. Changes in output voltage due to heating effects are

covered under the specification for thermal regulation.

Note 4

: Line regulation for the SPX1521 is tested at 150°C for I

L

= 1 mA. For IL = 100µA and TJ = 125°C, line regulation is guaranteed by design to 0.2%. See

typical performance characteristics for line regulation versus temperature and load current.

Note 5:

Dropout voltage is defined as the input to output differential at which the output voltage drops 100 mV below its nominal value measured at 1V differential at

very low values of programmed output voltage, the minimum input supply voltage of 2V ( 2.3V over temperature) must be taken into account.

Note 6:

Comparator thresholds are expressed in terms of a voltage differential at the feedback terminal below the nominal reference voltage measured at 6V input. To

express these thresholds in terms of output voltage change, multiply by the error amplifier gain = V

OUT/VREF

= (R1 + R2)/R2. For example, at a programmed output

voltage of 5V, the Error output is guaranteed to go low when the output drops by 95 mV x 5V/1.235 = 384 mV. Thresholds remain constant as a percent of V

OUT

as

V

OUT

is varied, with the dropout warning occurring at typically 5% below nominal, 7.5% guaranteed.

APPLICATION HINTS

EXTERNAL CAPACITORS

The stability of the SPX1521 requires a 2.2µF or greater
capacitor between output and ground. Oscillation could occur
without this capacitor. Most types of tantalum or aluminum
electrolytic works fine here. For operations of below -25°C solid
tantalum is recommended since the many aluminum types have
electrolytes the freeze at about -30°C. The ESR of about 5Ω or
less and resonant frequency above 500kHz are the most
important parameters in the value of the capacitor. The capacitor
value can be increased without limit.
At lower values of output current, less output capacitance is
required for stability. For the currents below 10mA the value of
the capacitor can be reduced to 0.5µF and 0.15µF for 1mA. More
output capacitance needed for the 8-pin version at voltages below
5V since it runs the error amplifier at lower gain. At worst case
5µF or greater must be used for the condition of 250mA load at

1.23V output.
The SPX1521, unlike other low dropout regulators will remain
stable and in regulation with no load in addition to the internal
voltage divider. This feature is especially important in
application like CMOS RAM keep-alive. When setting the output
voltage of the SPX1521, a minimum load of 10mA is
recommended.
If there is more than 10 inches of wire between the input and the
AC filter capacitor or if a battery is used as the input then a 0.1µF
tantalum or aluminum electrolytic capacitor should be placed
from the input to the ground.
Instability can occur if there is stray capacitance to the SPX1521
feedback terminal (pin 7). This could cause more problems when
using a higher value of external resistors to set the output voltage.

This problem can be fixed by adding a 100pF capacitor between
output and feedback and increasing the output capacitor to at least

3.3µF.

ERROR DETECTION COMPARATOR OUTPUT

The Comparator produces a logic low output whenever the SPX1521
output falls out of regulation by more than around 5%. This is around
60mV offset divided by the 1.235 reference voltage. This trip level
remains 5% below normal regardless of the programmed output
voltage of the regulator. Figure 1 shows the timing diagram depicting
the ERROR signal and the regulator output voltage as the SPX1521
input is ramped up and down. The ERROR signal becomes low at
around 1.3V input, and goes high around 5V input (input voltage at
which Vout = 4.75). Since the SPX1521’s dropout voltage is load
dependent, the input voltage trip point (around 5V) will vary with the
load current. The output voltage trip point (approx. 4.75V) does not
vary with load.
The error comparator has an open-collector output, which requires an
external pull-up resistor. Depending on the system requirements the
resistor may be returned to 5V output or other supply voltage. In
determining the value of this resistor, note that the output is rated to
sink 400µA, this value adds to battery drain in a low battery
condition. Suggested values range from 100K to 1MΩ. If the output
is unused this resistor is not required.

PROGRAMMING THE OUTPUT VOLTAGE OF
SPX1521

The SPX1521 may be pin-strapped for 5V using its internal voltage
divider by tying Pin 1 (output) to Pin 2 (sense) and Pin 7 (feedback)
to Pin 6 (5V Tap).

+

+

+

+

4.75V

OUTPUT

VOLTA GE

ERROR*

_______

IN PU T

VO LT AG E 1.3V

5.0V

Figure 1. ER R O R O utput Tim ing

_______

* See Application Info.

Rev. 10/24/00

SPX1521

Also, it may be programmed for any output voltage between its

1.235V reference and its 30V maximum rating. As seen in
Figure 2, an external pair of resistors is required.
Refer to the below equation for the programming of the output
voltage::

V

OUT

= V

REF

× ( 1 + R1/ R2 )+ IFBR

1

The V

REF

is 1.235 and IFB is the feedback bias current, nominally

-20nA. The minimum recommended load current of 1 µA forces
an upper limit of 1.2 MΩ on value of R2. If no load is presented
the I

FB

produces an error of typically 2% in V

OUT

, which may be

eliminated at room temperature by trimming R

1

. To improve the

accuracy choose the value of R2 = 100k this reduces the error by

0.17% and increases the resistor program current by 12µA. Since
the SPX1521 typically draws 60 µA at no load with Pin 2 open­circuited this is a small price to pay

REDUCING OUTPUT NOISE

It may be an advantage to reduce the AC noise present at the output.
One way is to reduce the regulator bandwidth by increasing the size of
the output capacitor. This is the only way that noise can be reduced
on the 3 lead SPX1521 but is relatively inefficient, as increasing the
capacitor from 1µF to 220µF only decreases the noise from 430µV to
160µV Vrms for a 100kHz bandwidth at 5V output.
Noise could also be reduced fourfold by a bypass capacitor across R

1

,

since it reduces the high frequency gain from 4 to unity. Pick

C

BYPASS

≅

1 / 2πR

1

× 200 Hz

or choose 0.01µF. When doing this, the output capacitor must be
increased to 3.3µF to maintain stability. These changes reduce the
output noise from 430µV to 100µV Vrms for a 100kHz bandwidth at
5V output. With the bypass capacitor added, noise no longer scales
with output voltage so that improvements are more dramatic at higher
output voltages.

HEAT SINK REQUIREMENTS

Depending on the maximum ambient temperature and maximum
power dissipation a heat sink may be required with the SPX1521.
The junction temperature range has to be within the range
specified under Absolute Maximum Ratings under all possible
operating conditions. To find out if a heat sink is required, the
maximum power dissipation of the device needs to be calculated.
This is the maximum specific AC voltage that must be taken into
consideration at input. Figure 3 shows the condition and power
dissipation which should be calculated with the following
formula:

P

TOTAL

= (VIN - 5) IL + (VIN)I

G

Next step is to calculate the temperature rise T

R

(max). TJ (max)

maximum allowable junction temperature, T

A

(max) maximum

ambient temperature :

T

R

(max) = TJ (max) - TA (max)

Junction to ambient thermal resistance

θ

(j-A)

can be calculated

after determining of P

TOTAL & TR

(max):

θ

(J-A)

= TR (max)/P

(max)

If the

θ

(J-A)

is 60°C/W or higher, the device could be operated
without a heat sink. If the value is below 60°C/W then the heat
sink is required and the thermal resistance of the heat sink can be
calculated by the following formula,

θ

(J-C)

junction to case,

θ

(C-H)

case to heat sink,

θ

(H-A)

heat sink to ambient:

θ

(J-A)

=

θ

(J-C)

+

θ

(C-H)

+

θ

(H-A)

Figure 3. 5V Regulator Circuit

+

2.2uF

+

SPX1521

I

IN

I

G

I

L

5V

IN

OUT

GND

LOAD

IIN = IL + I

G

V

OUT

Rev. 10/24/00

SPX1521

TYPICAL APPLICATIONS

V

OUT

GND

+V

IN

+V

IN

*V

OUT

= 5V

4

SPX1521

10uF

+

SPX1521 FIXED +5V REGULATOR

V

OUT

ADJ

V

IN

SPX1521

R1

SPX1521 ADJUSTABLE REGULATOR

R2

Rev. 10/24/00

SPX1521

ORDERING INFORMATION

Ordering No. Output Voltage Packages

SPX1521S

Adj 8 Lead SOIC

SPX1521S-2.5

2.5V 8 Lead SOIC

SPX1521S-3.3

3.3V 8 Lead SOIC

SPX1521S-5.0

5.0V 8 Lead SOIC

SPX1521R

Adj 3 Lead TO-252

SPX1521R-2.5

2.5V 3 Lead TO-252

SPX1521R-3.3

3.3V 3 Lead TO-252

SPX1521R-5.0

5.0V 3 Lead TO-252

SPX1521M3

Adj 3 Lead SOT-223

SPX1521M3-2.5

2.5V 3 Lead SOT-223

SPX1521M3-3.3

3.3V 3 Lead SOT-223

SPX1521M3-5.0

5.0V 3 Lead SOT-223

SPX1521U-

Adj 3 Lead TO-220

SPX1521U-2.5

2.5V 3 Lead TO-220

SPX1521U-3.3

3.3V 3 Lead TO-220

SPX1521U-5.0

5.0V 3 Lead TO-220

SPX1521T

Adj 3 Lead TO-263

SPX1521T-2.5

2.5V 3 Lead TO-263

SPX1521T-3.3

3.3V 3 Lead TO-263

SPX1521T-5.0

5.0V 3 Lead TO-263

SIGNAL PROCESSING EXCELLENCE

Sipex Corporation

Headquarters and Main Offices:

22 Linnell Circle
Billerica, MA 01821
TEL: [phone]
FAX: [phone]
e-mail: [e-mail]

233 South Hillview Drive
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TEL: [phone]
FAX: [phone]

Sipex Corporation reserves the right to make changes to any products described herein. Sipex does not assume any liability arising out of the application or use of any product or ci rcuit described
hereing; neither does it convey any license under its patent rights nor the rights of others.

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