®
SPX1580
7A Ultra Dropout Voltage Regulator
Fast Response, Adjustable & Fixed
FEATURES
■
Low Dropout Voltage 540mV at 7A Full Load Current
■
Adjustable Ouput Down to 1.25V from ATX Power Supply
■
Fixed Output Voltages of 3.3V and 2.5V
■
Extremely Tight Load and Line Regulation
■
Standard 5-Terminal Low Cost TO-220 and TO-263
ADJ OR FIXED
SENSE
V
CNTRL
V
OUT
V
IN
SPX1580
SPX1580
5 Pin TO-220
5 Pin TO-263
1
2
3
1 2 3 4 5
■
Replacement to Industry Standard LT1580
APPLICATIONS
ADJ OR FIXED
SENSE
■
3.3V ATX Power Supplies
■
3.3V to 2.9V for Portable PENTIUM
TM
Processor
■
5V to 3.5V VRE Supply
■
High efficiency "Green" Computer Systems
Now Available in Lead Free Packaging
DESCRIPTION
The
SPX1580 is a 7A 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
or 2.5V and does not require any external resistors. The SPX1580 features a low dropout of 540mV(Typ.)
and offers fast transient response. This device is suitable for Pentium applications requiring 2.5V from 3.3V
ATX power supplies, where a low current input voltage 1V greater than the output voltage is available. 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 SPX1580 is also an excellent choice as a post regulator for switching
supplies applications.
The SPX1580 offers protection against over-current faults, reversed input polarity, over temperature
operation and positive and negative transient voltage.
The SPX1580 is offered in a 5 pin TO-220 and TO-263 compatible with industry standard 5-terminal
regualtors. For 5A, 3A and 1.5A ultra low dropout versions refer to SPX1581, SPX1582 and SPX1583 data
sheets respectively.
TYPICAL APPLICATIONS CIRCUITS
3.3V
V
IN
5V
V
CTRL
V
IN
C1
33µF
V
CTRL
5
SPX1580
4
2
ADJ
C2
10µF
R2
124Ω
1
SENSE
R1
124Ω
C4
68µF
C2
10µF
3
V
OUT
2.5V
V
OUT
3.3V
V
IN
5V
V
CTRL
V
IN
C1
33µF
V
CTRL
V
CNTRL
V
OUT
V
IN
5
SPX1580
4
2
3
1
V
OUT
2.5V
V
OUT
SENSE
GND
C4
68µF
(1) V
CTRL
needed when V
IN
< 5V.
(2) V
OUT
= V
REF
(1+R
2
/R
1
)+I
ADJ
R
2
.
(3) V
REF
is measured across adjust to sense.
(1) V
CTRL
needed when V
IN
< 5V.
Date: 5/14/04
SPX1580 7A Ultra Dropout Voltage Regulator
©Copyright 2004 Sipex Corporation
1
ABSOLUTE MAXIMUM RATINGS
Power Dissipation ..................................... Internally Limited
Lead Temp. (Soldering, 10 Seconds) ......................... 300°C
Storage Temperature Range ..................... -65°C to +150°C
Operating Junction Temperature Range
SPX1580 Control Section ............................. 0°C to +125°C
SPX1580 Power Transistor .......................... 0°C to +150°C
Input Supply Voltage ..................................................... 7V
V
CTRL
Input Voltage .................................................... 13.2V
ELECTRICAL CHARACTERISTICS
Electrical characteristics at V
OUT
= V
SENSE
, V
ADJ
= 0V, T
A
= 25ºC, C
CTL
= C
PWR
= C
OUT
= 33µF tantalum cap unless otherwise specified.
The
♦
denotes the specifications which apply over the -40°C to 85°C temperature range, unless otherwise specified.
PARAMETER
2.5V Version
Output Voltage
MIN.
TYP.
MAX.
UNITS
CONDITIONS
2.45
2.40
2.5
2.5
2.55
V
2.60
♦
V
CTRL
= 4.5V to 12V, V
IN
= V
OUT
+0.8V, I
O
= 10mA to 7A
3.3V Version
Output Voltage
3.234
3.168
All Voltage Options
Reference Voltage (Note 3)
1.237
1.231
Line Regulation
-
-
Load Regulation (Note 1)
-
-
Dropout Voltage Minimum
VIN (Note 2) (VIN - VOUT)
Current Limit
Minimum Load Current
7.1
-
-
Thermal Regulation
Ripple Rejection
Control Pin Current
-
60
-
-
Adjustable Pin Current
-
1.25
-
1.0
-
1.1
-
0.54
-
5
-
0.002
80
60
-
50
1.263
V
1.269
-
mV
3.0
-
mV
5.0
0.80
-
-
mA
10
0.02
-
-
mA
130
-
µA
120
Thermal Resistance
TO-220 & TO-263
-
-
2
60
-
ºC/W
-
♦
♦
%/W
dB
♦
30mS Pulse
V
CTRL
= 5V, V
IN
= 5V, I
O
= 7A
V
CTRL
= 4.5V, V
IN
=V
OUT
+ 0.8V, I
O
= 7A
V
CTRL
= 4.5V, V
IN
= 2.05V, I
O
=
10mA
Junction to Case (Ø
C
)
J
Junction to Ambient (Ø
C
)
J
©Copyright 2004 Sipex Corporation
3.3
3.3
3.366
V
3.432
♦
♦
V
CTRL
= 4.5V to 12V, V
IN
= V
OUT
+0.8V, I
O
= 10mA to 7A
V
CTRL
= 4.5V, V
IN
= 2.05V, I
O
=
10mA
♦
V
CTRL
= 4.5V, V
IN
= 2.05V, I
O
=
10mA to 7A
V
CTRL
= 4.5V to 12V, V
IN
= V
OUT
+
0.8V to 5.5V, I
O
= 10mA
V
CTRL
= 4.5V to 12V, V
IN
= V
OUT
+
0.8V, I
O
= 10mA
V
CTRL
= 4.75V, I
O
= 7A
V
CTRL
= 4.5V, V
IN
= 2.05V,
V
OUT
= 100mV
V
CTRL
= 5V, V
IN
=V
OUT
+ 0.8V
♦
♦
V
A
Date: 5/14/04
SPX1580 7A Ultra Dropout Voltage Regulator
2
PIN DESCRIPTION
Pin Number
1
Pin Name
SENSE
DESCRIPTION
Allows Kelvin sense of V
OUT
at load. (Positive side of the reference
voltage of the device)
Negative side of the reference voltage for the device. Adding a
small bypass capacitor from ADJ pin to ground will improve the
transient response.
Power output of the device.
Supply pin for the control circuitry of the device. The current flow
into this pin will be about 1% of the output current. V
CTRL
must be
between 0.1V and 1.3V greater than the ouput voltage for the
device to regulate.
Output load current is supplied through this pin. V
IN
must be
between 0.1V and 0.8V greater than the output voltage for this
device to regulate.
2
3
ADJ
V
OUT
4
V
CTRL
5
V
IN
BLOCK DIAGRAM
(4) V
CTRL
V
IN
(5)
S.O.A
CURRENT
LIMIT
AMPLIFIER
LIMIT
SENSE
V
OUT
(3)
THERMAL OVERLOAD
SENSE (1)
VOLTAGE
REGULATION
AMPLIFIER
V
REF
ADJ (2)
APPLICATION INFORMATION
The SPX1580 is designed as a high performance
and low cost solution for application requiring a
lower dropout than traditional NPN regulators.
The SPX1580 uses a separate input voltage V
CTRL
( V
CTRL
≥
V
OUT
+ 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 dissi-
pation*, and lower heatsink and cooling fan cost.
A typical application would use 3.3V for V
IN
and 5.0V for V
CTRL
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.
The SPX1580 can power the 2.5V core voltage
for microprocessors such as a PentiumPC
TM
,
P55C
TM
, AMD5k86
TM
and K6
TM
and the IBM
PowerPC
TM
603EV and 604EV processors.
Date: 5/14/04
SPX1580 7A Ultra Dropout Voltage Regulator
©Copyright 2004 Sipex Corporation
3
APPLICATION INFORMATION
Output Capacitor
An output capacitor for SPX1580 is for circuit
compensation for the device to prevent
oscilliation. The minimum size of the output
capacitor is either a 330µF aluminum electro-
lytic capacitor or 33uF tantalum. Larger capaci-
tor values improve the regulator transient re-
sponse performance and increase surge load
capability. The output capacitor should have an
ESR not more than 0.3Ω.
Adjustable Regulator Design
1.25V reference voltage is being developed be-
tween the SENSE pin and the ADJ pin of the
SPX1580. Adding two external resistors (see fig
1.) will allow setting the output voltage from
1.25V to 6V. R
1
is chosen so that this current is
specified minimum load current of 10mA. R
2
is
given by the formula: V
OUT
= V
REF
(1+ R
2
/R
1
)
+ I
ADJ
(R
2
). The current flowing from the ADJ
pin is typicaly 50uA. This ADJ pin contributes
to the final V
OUT
but is usually neglected.
Connecting the sense pin to the top of the resis-
tor divider will improve load regualtion.
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 bypass capacitor from ADJ pin to
ground improves transient response. A 330pF
ceramic capacitor is recommended.
3.3V
V
IN
5V
V
CTRL
V
IN
C1
33µF
V
CTRL
5
SPX1580
4
2
ADJ
C2
10µF
3
1
V
OUT
2.5V
V
OUT
SENSE
R1
124Ω
C3
68µF
C4
0.033µF
R2
124Ω
(1) V
CTRL
needed when V
IN
< 5V.
(2) V
OUT
= V
REF
(1+R
2
/R
1
)+I
ADJ
R
2
.
(3) V
REF
is measured across adjust to sense.
Figure 1. Adjustable Regulator.
Date: 5/14/04
SPX1580 7A Ultra Dropout Voltage Regulator
©Copyright 2004 Sipex Corporation
4
3.3V
V
IN
5V
V
CTRL
C1
33µF
V
IN
5
SPX1580
4
3
1
2
GND
V
OUT
2.5V
V
OUT
V
CTRL
SENSE
C2
10µF
C3
68µF
(1) V
CTRL
needed when V
IN
< 5V.
Figure 2. Typical Fixed Regulator.
Date: 5/14/04
SPX1580 7A Ultra Dropout Voltage Regulator
©Copyright 2004 Sipex Corporation
5
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