SPX1581
5A Ultra Low Dropout Voltage Regulator
Fast Response, Adjustable & Fixed
FEATURES
■ Low Dropout Voltage 500mV at 5A Full Load Current
■ Adjustable Ouput Down to 1.2V from ATX Power Supply
SPX1581
■ Fixed Output Voltages of 3.3V, 2.8V and 2.5V
5 Pin TO-263
SPX1581
1 2 3 4 5
5 Pin TO-220
■ Extremely Tight Load and Line Regulation
1 2 3 4 5
■ 5V to 3.5V VRE Supply
■ High efficiency "Green" Computer Systems
VIN
VOUT
VCNTRL
VIN
VOUT
SENSE
■ 3.3V to 2.9V for Portable PENTIUMTM Processor
ADJ OR FIXED
■ 3.3V to 2.8V ATX Power Supplies
VCNTRL
SENSE
APPLICATIONS
ADJ OR FIXED
■ Standard 5-Terminal Low Cost TO-220 and TO-263
Now Available in Lead Free Packaging
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 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.
TYPICAL APPLICATIONS CIRCUIT
3.3V
VIN
5V
VCTRL
VIN
5
3
VOUT
2.5V
VOUT
SPX1581
C1
330µF
4
VCTRL
3.3V
VIN
1
2
SENSE
ADJ
5V
VCTRL
R1
124Ω
C4
2x330µF
C2
10µF
C3
.033µF
5
3
VOUT
SPX1581
4
VCTRL
2.5V
VOUT
1
2
SENSE
GND
C2
10µF
C4
2x330µF
R2
124Ω
(1) VCTRL needed when VIN < 5V.
(1) VCTRL needed when VIN < 5V.
(2) VOUT = VREF (1+R2/R1)+IADJ R2.
(3) VREF is measured across adjust to sense.
Adjustable Regulator
Date: 2/11/05
VIN
C1
330µF
Typical Fixed Regulator
SPX1581 5A Ultra Low Dropout Voltage Regulator
1
©Copyright 2005 Sipex Corporation
ABSOLUTE MAXIMUM RATINGS
Input Supply Voltage ..................................................... 6V
VCTRL Input Voltage ....................................................... 13V
Power Dissipation ..................................... Internally Limited
Storage Temperature Range ..................... -65°C to +150°C
Operating Junction Temperature Range
SPX1581 Control Section ............................. 0°C to +125°C
SPX1581 Power Transistor .......................... 0°C to +150°C
ELECTRICAL CHARACTERISTICS
Electrical characteristics at VOUT = VSENSE, VADJ = 0V, TA=25°C, CCTL = CPWR = COUT = 33µF tantalum cap otherwise specified.
The ♦ denotes the specifications which apply over full temperature range -40°C to +85°C, unless otherwise specified.
PARAMETER
2.5V Version
Output Voltage
MIN
TYP
MAX
2.450
2.400
2.5
2.550
2.600
V
VCTRL = 6.0V to 12V, VIN = 3.0V to 5.0V, IO =10mA
♦ IO = 10mA to 5A
2.744
2.688
2.8
2.856
2.912
V
VCTRL = 6.3V to 12V, VIN =3.3V to 12V, IO=10mA
♦ IO = 10mA to 5A
3.234
3.168
3.3
3.3
3.366
3.432
V
VCTRL = 6.3V to 12V, VIN = 3.3V + 0.8V, IO=10mA
♦ IO = 10mA to 5A
1.238
1.25
1.263
V
1.0
1.0
3.0
5.0
mV
VCTRL = 2.75V, VIN = 2.00V, IO = 10mA
VCTRL=2.7V to 12V,VIN = 2.05V to 5.5V,IO=10mA to 5A
VCTRL = 2.5V to 12V, VIN = 1.75V to 5.5V, IO=10mA
♦ VADJ=0V
♦ VCTRL = 2.75V, VIN = 2.1V, IO=10mA to 5A, VADJ = 0V
1.10
1.25
V
0.40
0.50
V
5
10
A
mA
0.002
80
0.02
%/W
dB
Control Pin Current
60
120
mA
Adjustble Pin Current
50
2.8V Version
Output Voltage
3.3V Version
Output Voltage
All Voltage Options
Reference Voltage
Line Regulation
mV
Load Regulation (Note 1)
Dropout Voltage Min. VCTRL
(Note 2) (VCTRL - VOUT)
Dropout Voltage Min. VIN
(Note 2) (VIN - VOUT)
Current Limit
Minimum Load Current
Thermal Regulation
Ripple Rejection
Thermal Resistance
TO-220-5
Thermal Resistance
TO-263-5
UNITS ♦ CONDITIONS
5.1
60
VADJ = 0V
VIN = 2.05V, IO = 1A
VADJ = 0V
VIN = 2.75V, IO = 5A
VCTRL = 2.75V, VIN = 2.05V, ∆ VOUT = 100mV, VADJ = 0V
♦ VCTRL = 5V, VIN=3.3V, VADJ=0V
µA
120
3
50
3
60
°C/W
°C/W
°C/W
°C/W
30ms Pulse
VCTRL = 3.75V, VIN = 3.75V, IO = 2.5A, VADJ=0V
TJ=25, VRIPPLE=1Vpp at 120Hz
♦ VADJ = 0V
VCTRL = 2.75V, VIN = 2.05V, IO = 5A
VCTRL = 2.75V, VIN = 2.05V, VADJ=0V, IO = 10mA
♦
Junction to Case (θJC)
Junction to Ambient (θJA)
Junction to Case (θJC)
Junction to Ambient (θJA)
Note 1: Low duty cycle pulse testing with Kelvin connections is required to order to maintain accurate data.
Note 2: Dropout voltage is defined as the minimum differential between VIN and VOUT or VCTRL and VOUT required to
maintain regulation at VOUT 95% Nominal VOUT.
Note 3: VREF is measured across Adjust pin to Sense pin.
Date: 2/11/05
SPX1581 5A Ultra Low Dropout Voltage Regulator
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©Copyright 2005 Sipex Corporation
PIN DESCRIPTION
PIN NUMBER
PIN NAME
DESCRIPTION
1
SENSE
Allows Kelvin sense of VOUT at the load. (Positive side of the reference
voltage of the 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
VOUT
Power output of the device.
4
VCTRL
Supply pin for the control circuitry of the device. The current flow into this
pin will be about 1% of the output current. VCTRL must be between 1.0V
and 1.3V greater than the output voltage for the
device to regulate.
5
VIN
Output load current is supplied through this pin. VIN must be between 0.1V
and 0.8V greater than the output voltage for this device to regulate.
Note that TAB is internally connected to Pin 3.
FUNCTIONAL DIAGRAM
(4) VCTRL
VIN (5)
S.O.A
LIMIT
CURRENT
LIMIT
AMPLIFIER
VOUT (3)
SENSE
THERMAL OVERLOAD
SENSE (1)
VOLTAGE
REGULATION
AMPLIFIER
Date: 2/11/05
VREF
SPX1581 5A Ultra Low Dropout Voltage Regulator
3
ADJ (2)
©Copyright 2005 Sipex Corporation
APPLICATION NOTES
The SPX1581 is designed as a high performance
and low cost solution for application requiring a
lower dropout than traditional NPN regulators.
Adjustable Regulator Design
1.25V reference voltage is being developed between the SENSE pin and the ADJ pin of the
SPX1581. Adding two external resistors (see fig
1.) will allow setting the output voltage from
1.25V to 6V. R1 is chosen so that this current is
specified minimum load current of 10mA. R2 is
given by the formula: VOUT = VREF (1+ R2/R1)
+ IADJ (R2). The current flowing from the ADJ
pin is typicaly 50µA. This ADJ pin contributes
to the final VOUT but is usually neglected.
Connecting the sense pin to the top of the resistor divider will improve load regualtion.
The SPX1581 uses a separate input voltage VCTRL
( VCTRL ≥ VOUT + 1.3V) to minimize the dropout
voltage. This allows the 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 VCTRL from a motherboard power
supply to provide a nominal 2.5V output. Using
the sense pin allows Kelvin measure the output,
reducing resistance-associated errors.
Lowering Noise
Using the SENSE pin to Kelvin the load will
increase accuracy of the output voltage during
load regulation. For the fixed voltage device,
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.
The SPX1581 can power the 2.5V core voltage
for microprocessors such as a PentiumTM,
P55CTM, AMD5k86TM and K6TM and the IBM
PowerPCTM 603EV and 604EV processors.
Power sequencing of VIN and VCTRL is required. Apply VIN before VCTRL for proper
operation
Power Up Sequencing
The SPX158x requires a power up sequence in
that VIN must applied before VCTRL to prevent a
latch up condition. If this is not possible then a
series 10Ω resistor should be added to the VCTRL
input to prevent the device from entering a latch
up if VCTRL is applied before VIN.
* The reduction of heat dissipation is a result of the
increase of the regulator efficiency (efficiency = VOUT/VIN).
Date: 2/11/05
SPX1581 5A Ultra Low Dropout Voltage Regulator
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©Copyright 2005 Sipex Corporation
PACKAGE: 5 Pin TO-220
E
U
øP
Q
H1
Package Outline Drawing
D
V
L
e3
b
e
e1
Based upon CARSEM TO-220 RevC
SEATING
PLANE
A
F
α {5x}
J1
C1
Date: 2/11/05
SPX1581 5A Ultra Low Dropout Voltage Regulator
5
©Copyright 2005 Sipex Corporation
PACKAGE: 5 Pin TO-263
E
Seating
Plane
A
E/2
C2
L1
Chamfer
Optional
D
1
3
2
4
H
5
c
SIDE VIEW
See Detail C
e
b
FRONT VIEW
Gauge Plane
Seating
Plane
θ
L
Thermal
Pad
BACK VIEW
L3
DETAIL C
5 Pin TO-263 JEDEC TO-263
(L1)
Inches
Controlling Dimension
D1
E1
Date: 2/11/05
A1
SYMBOL
A
A1
b
c
c2
D
D1
E
E1
e
H
L
L1
L3
O
MIN
0.160
0.000
0.020
0.015
0.045
0.330
0.270
0.380
0.245
NOM
.067 BSC
0.575
0.070
.010 BSC
0˚
-
SIPEX Pkg Signoff Date/Rev:
SPX1581 5A Ultra Low Dropout Voltage Regulator
6
MAX
0.190
0.010
0.039
0.029
0.065
0.380
0.420
0.625
0.110
0.066
8˚
Variation BA
Millimeters
Conversion Factor:
1 Inch = 25.40 mm
MIN
NOM
MAX
4.06
4.83
0.00
0.25
0.51
0.99
0.38
0.74
11.43
5.84
8.38
9.65
6.86
9.65
10.67
6.22
17.02 BSC
14.61
15.88
1.78
2.79
1.68
2.54 BSC
0˚
8˚
JL Jan18-06/Rev A
©Copyright 2005 Sipex Corporation
ORDERING INFORMATION
Part Number
Accuracy
SPX1581U5 ...............................
SPX1581U5-2-5 .........................
SPX1581U5-2-8 .........................
SPX1581U5-3-3 .........................
SPX1581T5 ................................
SPX1581T5/TR ..........................
SPX1581T5-2-5 .........................
SPX1581T5-2-5/TR ....................
SPX1581T5-3-3 .........................
SPX1581T5-3-3/TR ....................
Output Voltage
Packages
2.0% ............................. Adj .......................... 5-Pin TO-220
2.0% ............................ 2.5V ........................ 5-Pin TO-220
2.0% ............................ 2.8V ........................ 5-Pin TO-220
2.0% ............................ 3.3V ........................ 5-Pin TO-220
2.0% ............................. Adj .......................... 5-Pin TO-263
2.0% ............................. Adj .......................... 5-Pin TO-263
2.0% ............................ 2.5V ........................ 5-Pin TO-263
2.0% ............................ 2.5V ........................ 5-Pin TO-263
2.0% ............................ 3.3V ........................ 5-Pin TO-263
2.0% ............................ 3.3V ........................ 5-Pin TO-263
Available in lead free packaging. To order add "-L" suffix to part number.
Example: SPX1581T5-3-3/TR = standard; SPX1581T5-L-3-3/TR = lead free
/TR = Tape and Reel
Pack quantity is 500 for TO-263.
Solved by Sipex
TM
Sipex Corporation
Headquarters and
Sales Office
233 South Hillview Drive
Milpitas, CA 95035
TEL: (408) 934-7500
FAX: (408) 935-7600
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 herein; neither does it convey any license under its patent rights nor the rights of others.
Date: 2/11/05
SPX1581 5A Ultra Low Dropout Voltage Regulator
7
©Copyright 2005 Sipex Corporation