Datasheet SPX1581T, SPX1581T-2.5, SPX1581T-2.8, SPX1581T-3.3, SPX1581U Datasheet (Sipex Corporation)

SPX1581

5A Ultra Low Dropout Voltage Regulator

Fast Response, Adjustable & Fixed

FEATURES APPLICATIONS

•

Low Dropout Voltage 500mV at 5A Full Load Current

•

Adjustable Output Down to 1.2V from ATX Power Supply

•

Fixed Output Voltages of 3.3V, 2.8V & 2.5V

• Extremely Tight Voltage and Line Regulation • High Efficiency “Green” Computer Systems

• Standard 5-Terminal Low Cost TO-220 & TO-263

PRODUCT DESCRIPTION

The SPX1581 is a 5A Low Dropout Regulator with extremely low dropout voltage. The adjustable version requires only two external
resistors to set the output voltage. The fixed version has a preset output of 3.3V, 2.8V or 2.5V and does not require any external
resistors. The SPX1581 features a low dropout of less than 400mV(typ.) and offers fast transient response.

for Pentium applications requiring 2.8V or 2.5V from 3.3V ATX power supplies,

than the output voltage is needed. With an external sense pin the load regulation is less than 1mV. This device is an excellent choice
for the use in powering low voltage microprocessors that require a lower dropout, fast transient response to regulate from 3.3V and 5V
supplies. The SPX1581 is also an excellent choice as a post regulator for switching supplies applications.

The SPX1581 offers full protection against over-current faults, reversed input polarity, over temperature operation and positive and
negative transient voltage.

The SPX1581 is offered in a 5 pin TO-220 and TO-263 compatible with industry standard 5-terminal regulators. For 7A, 3A and 1.5A
ultra low dropout versions refer to SPX1580, SPX1582 and SPX1583 data sheets respectively.

PIN CONNECTIONS

•

3.3V to 2.8V ATX Power Supplies

•

3.3V to 2.9V for Portable PENTIUM

•

5V to 3.5V VRE Supply

where a low current input voltage 1V greater



Processor

This device is suitable

TO-263-5 (T)

SPX1581

12

45

3

Top View

1. SENSE

2. ADJ or FIXED

3. V

OUT

4. V

CTRL

5. V

IN

TO-220-5 (U)

1. SENSE

SPX1581

21

2. ADJ or FIXED

3. V

OUT

543

4. V

CTRL

5. V

IN

Front View

Rev.10/30/00

SPX1581

ABSOLUTE MAXIMUM RATINGS

Power Dissipation.................................................... Internally Limited Input Supply Voltage.......................................................... 6V

Input Voltage ..........................................................13V

Lead Temp (soldering, 10 seconds)........................................... 300°C

Storage Temperature Range...................................... -65ºC to +150ºC

Operating Junction Temperature Range

SPX1581 Control Section .............................................0ºC to +125ºC

SPX1581 Power Transistor .......................................... 0ºC to +150ºC

ELECTRICAL CHARACTERISTICS

at VS =14V, Ta=25°C, Io=10mA, C2=100µF, unless otherwise specified. (Note 1)

(Boldface applies over full temperature range).

Parameters Conditions SPX1581

2.5V Version

V

CTRL

Units

Min Typ Max

Output Voltage V

=6.0V to 12V, VIN=3.0V to 5.0V, IO=10mA

CTRL

I

=10mA to

O

2.450

2.400

2.500 2.550

2.600

V

5A

2.8V Version

Output Voltage V

=6.3V to 12V, VIN=3.3V to 12V, IO=10mA

CTRL

I

=10mA to 5A

O

2.744

2.688

2.800 2.856

2.912

V

3.3V Version

Output Voltage V

All Voltage Options

Reference Voltage V

=6.3V to 12V, VIN=3.3V to 12V, IO=10mA

CTRL

I

=2.75V, VIN=2.00V, IO=10mA

CTRL

V

=2.7V to 12V, VIN=2.05V to 5.5V, IO=10mA to

CTRL

=10mA to 5A

O

3.234

3.168

1.238

3.300 3.366

V

3.462

1.250

1.263

V

5A

Line Regulation V

Load Regulation (Note1) V

Dropout Voltage Minimum V
(V

– V

OUT

)

CTRL

CTRL

(Note2)

Dropout Voltage Minimum VIN(Note2)
(V

- V

)

IN

OUT

Current Limit V

Minimum Load Current V

=2.5V to 12V, VIN=1.75V to 5.5V, IO=10mA

CTRL

V

=0V

ADJ

=2.75V, VIN=2.1V, IO=10mA to 5A,V

CTRL

=0V

V

ADJ

V

=2.05V, IO=1A

IN

=0V

V

ADJ

V

=2.75V, IO=5A

IN

=2.75V, VIN=2.05V,dVO=100mV,V

CTRL

=5V, VIN=3.3V,V

CTRL

=0V

ADJ

=0V

ADJ

0.40

ADJ

=0V

5.1

1.0

3.0

1.0 5.0

1.10 1.25

0.50

A

5 10

mV

mV

V

V

mA

Thermal Regulation 30ms Pulse 0.002 0.02 %W

Ripple Rejection V

Control Pin Current V

Adjustable Pin Current V

Thermal Resistance

Bold

The

specifications applying to the over full operating temperature range.

=3.75V VIN=3.75V, IO=2.5A,V

CTRL

T

V

J

ADJ

CTRL

CTRL

=25, V

=0V

=1Vpp at 120Hz

RIPPLE

=2.75V, VIN=2.05V, IO=5A
=2.75V, VIN=2.05V,V

TO-220-5

TO-263-5

ADJ

=0V

60 80 dB

=0V IO=10mA 50

ADJ

Junction to Case (

θ

JC

Junction to Ambient (

Junction to Case (

θ

JC

Junction to Ambient (

3

)

50

)

θ

JA

3

)

60

)

θ

JA

Note 1: Low duty cycle pulse testing with Kelvin connections are required to order to maintain accurate data.
Note 2: Dropout voltage is defined as the minimum differential between V
99% Nominal V
Note 3: V

REF

OUT.

is measured across the Adjust pin to Sense pin.

and V

IN

OUT

or V

CTRL

and V

required to maintain regulation at V

OUT

60 120

120

Rev.10/30/00

mA

µ

C/W

°

C/W

°

C/W

°

C/W

°

OUT

A

SPX1581

PIN DESCRIPTION

1. Sense = Allows Kelvin sense of V
device).

2. ADJ = Negative side of the reference voltage for the device. Adding a small bypass capacitor
from the ADJ pin to ground will improve the transient response.

3. V

4. V

5. V

= Power output of the device.

OUT

= Supply pin for the control circuitry of the device. The current flow into this pin will be

CTRL

about 1% of the output current. V
voltage for the device to regulate.

= Output load current is supplied through this pin. V

IN

greater than the output voltage for the device to regulate.

BLOCK DIAGRAM

APPLICATIONS NOTES

The SPX1581 is designed as a high performance and low cost
solution for application requiring a lower dropout than
traditional NPN regulators.
The SPX1581 uses a separate input voltage V
V

+ 1.3V) to minimize the dropout voltage. This allows the

OUT

2.5V power for the load to come from a 3.3V system supply.
As added benefit this will reduce the heat dissipation, and
lower heatsink and cooling fan cost. A typical application
would use 5V for Vin and 3.3V for V
power supply to provide a nominal 2.5V output. Using the
sense pin allows to Kelvin measure the output, reducing
resistive-associated errors.
The SPX1581 can power the 2.5V core voltage for
microprocessors such as Pentium, P55C, AMD5k86
and K6 and the IBM PowerPC 603EV and 604EV
processors.

*The reduction of heat dissipation is a result of the increase of the regulator
efficiency (efficiency = V

OUT

/ VIN).

at the load. (Positive side of the reference voltage of the

OUT

must be between 1.0V and 1.3V greater than the output

CTRL

must be between 0.1V and 0.8V

IN

(4) V

CTRL

CURRENT

LIMIT

AMPLIFIER

THERMAL OVERLOAD

VOLTAGE

REGULATION

AMPLIFIER

LIMIT

SENSE

S.O.A

V

REF

V

V

SENSE (1)

ADJ (2)

Adjustable Regulator Design

1.25V reference voltage is being developed between the
SENSE pin and the ADJ pin of the SPX1581. Adding two

CTRL

(V

CTRL

≥

external resistors (see fig 1.) will allow setting the output
voltage from 1.25V to 6V. R
specified minimum load current of 10mA. R
formula: V

OUT

= V

flowing from the ADJ pin is typically 50µA. This ADJ pin

from a motherboard

CTRL

contributes to the final VOUT but is usually neglected.
Connecting the sense pin to the top of the resistor divider will
improve load regulation.

Lowering Noise

Using the SENSE pin to Kelvin the load will increase accuracy
of the output voltage during load regulation. For the fixed
voltage devices, adding a capacitor at the GND pin will
improve transient response. This capacitor is chosen in the
range of 1µF to 0.1µF and will depend on the amount of
output capacitance in the system.

(5)

IN

(3)

OUT

(1+ R2/R1) + I

REF

is chosen so that this current is

1

is given by the

2

(R2). The current

ADJ

Rev.10/30/00

SPX1581

TYPICAL APPLICATION

3.3V
V

IN

5V
V

CTRL

C1
330uF

V

IN

V

CTRL

C2
10uF

3.3V
V

I

5V
V

CTRL

N

C1

330uF

V

IN

V

CTRL

C2
10uF

Fig. 1 Adjustable Regulator

SPX1581

ADJ

C3
.033uF

(1) V
(2) V
(3) V

needed when VIN < 5V.

CTRL

= V

OUT

REF

(1 + R2/ R1) + I

REF

is measured across adjust to sense.

Fig.2 Typical Fixed Regulator

SPX1581

GND

(1) V

is needed when VIN <5V.

CTRL

V

OUT

SENSE

R2.

ADJ

V

OUT

SENSE

2.5V
V

OUT

R1
124

Ω

C4
2 X 330uF

R2
124

Ω

2.5V
V

OUT

C4
2 X 330uF

Rev.10/30/00

SPX1581

ORDERING INFORMATION

Ordering No. Precision Output Voltages Packages

SPX1581U
SPX1581U-2.5
SPX1581U-2.8
SPX1581U-3.3
SPX1581T
SPX1581T-2.5
SPX1581T-2.8
SPX1581T-3.3

0.6% Adj 3 Lead TO-220

0.6% 2.5V 3 Lead TO-220

0.6% 2.8V 3 Lead TO-220

0.6% 3.3V 3 Lead TO-220

0.6% Adj 3 Lead TO-263

0.6% 2.5V 3 Lead TO-263

0.6% 2.8V 3 Lead TO-263

0.6% 3.3V 3 Lead TO-263

SIGNAL PROCESSING EXCELLENCE

Corporation

Sipex Corporation

Headquarters and Main Offices:

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

233 South Hillview Drive
Milpitas, CA 95035
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 circuit described
hereing; neither does it convey any license under its patent rights nor the rights of others.

Rev.10/30/00