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Date: 1/21/05
SPX1581 5A Ultra Low Dropout Voltage Regulator
Copyright 2005 Sipex Corporation
SPX1581
DESCRIPTION
FEATURES
■ Low Dropout Voltage 500mV at 5A Full Load Current
■ Adjustable Ouput Down to 1.2V from ATX Power Supply
■ Fixed Output Voltages of 3.3V, 2.8V and 2.5V
■ Extremely Tight Load and Line Regulation
■ Standard 5-Terminal Low Cost TO-220 and TO-263
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 400mV(Typ.) and offers fast transient
response. This device is suitable for Pentium applications requiring 2.8V, 2.5V from 3.3V ATX power supplies, where
a low current input voltage 1V greater 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 of 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 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.
5A Ultra Low Dropout Voltage Regulator
Fast Response, Adjustable & Fixed
APPLICATIONS
■ 3.3V to 2.8V ATX Power Supplies
■ 3.3V to 2.9V for Portable PENTIUMTM Processor
■ 5V to 3.5V VRE Supply
■ High efficiency "Green" Computer Systems
13
25
4
SPX1581
5 Pin TO-263
SENSE
ADJ
OR
FIXED
V
OUT
V
CNTRL
V
IN
3
2
1
SPX1581
5 Pin TO-220
SENSE
ADJ
OR
FIXED
V
OUT
V
CNTRL
V
IN
4 5
C4
2x330F
2.5V
VOUT
R1
124
R2
124
VOUT
SENSE
C2
10F
VCTRL
C1
330F
3.3V
VIN
5V
VCTRL
SPX1581
5
4
2
3
1
(1) VCTRL needed when VIN < 5V.
(2) VOUT = VREF (1+R2/R1)+IADJ R2.
(3) VREF is measured across adjust to sense.
ADJ
VIN
C3
.033F
C4
2x330F
2.5V
VOUT
SENSE
C2
10F
VCTRL
C1
330F
3.3V
VIN
5V
VCTRL
SPX1581
5
4
2
3
1
(1) VCTRL needed when VIN < 5V.
GND
VIN
Typical Fixed Regulator
Adjustable Regulator
TYPICAL APPLICATIONS CIRCUIT
Now Available in Lead Free Packaging