D ts e t
aa h e
R c e t r lc r nc
o h se Ee to is
Ma u a t r dCo o e t
n fc u e
mp n n s
R c e tr b a d d c mp n ns ae
o h se rn e
o oet r
ma ua trd u ig ete dewaes
n fcue sn i r i/ fr
h
p rh s d f m te oiia s p l r
uc a e r
o h r n l u pi s
g
e
o R c e tr waes rce td f m
r o h se
fr e rae r
o
te oiia I. Al rce t n ae
h
r nl P
g
l e rai s r
o
d n wi tea p o a o teOC
o e t h p rv l f h
h
M.
P r aetse u igoiia fcoy
at r e td sn r n la tr
s
g
ts p o rmso R c e tr e eo e
e t rga
r o h se d v lp d
ts s lt n t g aa te p o u t
e t oui s o u rne
o
rd c
me t o e c e teOC d t s e t
es r x e d h
M aa h e.
Qu l yOv riw
ai
t
e ve
• IO- 0 1
S 90
•A 92 cr ct n
S 1 0 et ai
i
o
• Qu l e Ma ua trr Ls (
ai d
n fcues it QML MI- R -
) LP F
385
53
•C a sQ Mitr
ls
lay
i
•C a sVS a eL v l
ls
p c ee
• Qu l e S p l r Ls o D sr uos( L )
ai d u pi s it f it b tr QS D
e
i
•R c e trsacic l u pir oD A a d
o h se i
r ia s p l t L n
t
e
me t aln u t a dD A sa d r s
es lid sr n L tn ad .
y
R c e tr lcrnc , L i c mmi e t
o h se Ee t is L C s o
o
tdo
t
s p ligp o u t ta s t f c so r x e t-
u pyn rd cs h t ai y u tme e p ca
s
t n fr u lya daee u loto eoiial
i s o q ai n r q a t h s r n l
o
t
g
y
s p l db id sr ma ua trr.
u pi
e yn ut
y n fcues
T eoiia ma ua trr d ts e t c o a yn ti d c me t e e t tep r r n e
h r n l n fcue’ aa h e a c mp n ig hs o u n r cs h ef ma c
g
s
o
a ds e ic t n o teR c e tr n fcue v rino ti d vc . o h se Ee t n
n p c ai s f h o h se ma ua trd eso f hs e ie R c e tr lcr -
o
o
isg aa te tep r r n eo i s mio d co p o u t t teoiia OE s e ic -
c u rne s h ef ma c ft e c n u tr rd cs o h r n l M p c a
o
s
g
t n .T pc lv le aefr eee c p r o e o l. eti mii m o ma i m rt g
i s ‘y ia’ au s r o rfrn e up s s ny C r n nmu r xmu ai s
o
a
n
ma b b s do p o u t h rceiain d sg , i lt n o s mpetsig
y e a e n rd c c aa tr t , e in smuai , r a l e t .
z o
o
n
© 2 1 R cetr l t n s LC Al i t R sre 0 1 2 1
0 3 ohs E cr i , L . lRg s eevd 7 1 0 3
e e oc
h
T l r m r, l s v iw wrcl . m
o e n oe p ae it w . e c o
a
e
s
o ec
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
■
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
ADJ OR FIXED
SENSE
V
CNTRL
V
OUT
V
IN
SPX1581
5 Pin TO-263
SPX1581
5 Pin TO-220
1 2 3 4 5
1 2 3 4 5
APPLICATIONS
■
3.3V to 2.8V ATX Power Supplies
■
3.3V to 2.9V for Portable PENTIUM
TM
Processor
■
5V to 3.5V VRE Supply
■
High efficiency "Green" Computer Systems
ADJ OR FIXED
SENSE
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
V
IN
5V
V
CTRL
V
IN
C1
330µF
V
CTRL
5
SPX1581
4
2
ADJ
C2
10µF
C3
.033µF
R2
124Ω
1
SENSE
R1
124Ω
C4
2x330µF
3
V
OUT
2.5V
V
OUT
3.3V
V
IN
5V
V
CTRL
V
IN
C1
330µF
V
CTRL
5
SPX1581
4
2
GND
C2
10µF
1
SENSE
3
V
OUT
2.5V
V
OUT
V
CNTRL
V
OUT
V
IN
C4
2x330µF
(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.
Adjustable Regulator
Typical Fixed Regulator
Date: 2/11/05
SPX1581 5A Ultra Low Dropout Voltage Regulator
©Copyright 2005 Sipex Corporation
1
ABSOLUTE MAXIMUM RATINGS
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
Input Supply Voltage ..................................................... 6V
V
CTRL
Input Voltage ....................................................... 13V
ELECTRICAL CHARACTERISTICS
Electrical characteristics at V
OUT
= V
SENSE
, V
ADJ
= 0V, T
A
=25°C, C
CTL
= C
PWR
= C
OUT
= 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
2.8V Version
Output Voltage
3.3V Version
Output Voltage
All Voltage Options
Reference Voltage
Line Regulation
Load Regulation (Note 1)
Dropout Voltage Min. V
CTRL
(Note 2) (V
CTRL
- V
OUT
)
Dropout Voltage Min. V
IN
(Note 2) (V
IN
- V
OUT
)
Current Limit
Minimum Load Current
Thermal Regulation
Ripple Rejection
Control Pin Current
Adjustble Pin Current
Thermal Resistance
TO-220-5
Thermal Resistance
TO-263-5
5.1
5
0.002
80
60
50
120
3
50
3
60
10
0.02
1.0
1.0
1.10
0.40
3.0
5.0
1.25
0.50
MIN
2.450
2.400
2.744
2.688
3.234
3.168
1.238
TYP
2.5
MAX
2.550
2.600
2.856
2.912
3.366
3.432
1.263
UNITS
♦
CONDITIONS
V
V
CTRL
= 6.0V to 12V, V
IN
= 3.0V to 5.0V, I
O
=10mA
♦
I
O
= 10mA to 5A
V
CTRL
= 6.3V to 12V, V
IN
=3.3V to 12V, I
O
=10mA
♦
I
O
= 10mA to 5A
V
CTRL
= 6.3V to 12V, V
IN
= 3.3V + 0.8V, I
O
=10mA
♦
I
O
= 10mA to 5A
V
CTRL
= 2.75V, V
IN
= 2.00V, I
O
= 10mA
V
CTRL
=2.7V to 12V,V
IN
= 2.05V to 5.5V,I
O
=10mA to 5A
V
CTRL
= 2.5V to 12V, V
IN
= 1.75V to 5.5V, I
O
=10mA
♦
V
ADJ
=0V
♦
V
CTRL
= 2.75V, V
IN
= 2.1V, I
O
=10mA to 5A, V
ADJ
= 0V
V
ADJ
= 0V
V
IN
= 2.05V, I
O
= 1A
V
ADJ
= 0V
V
IN
= 2.75V, I
O
= 5A
V
CTRL
= 2.75V, V
IN
= 2.05V,
∆
V
OUT
= 100mV, V
ADJ
= 0V
♦
V
CTRL
= 5V, V
IN
=3.3V, V
ADJ
=0V
30ms Pulse
V
CTRL
= 3.75V, V
IN
= 3.75V, I
O
= 2.5A, V
ADJ
=0V
T
J
=25, V
RIPPLE
=1Vpp at 120Hz
♦
V
ADJ
= 0V
V
CTRL
= 2.75V, V
IN
= 2.05V, I
O
= 5A
V
CTRL
= 2.75V, V
IN
= 2.05V, V
ADJ
=0V, I
O
= 10mA
♦
°C/W
°C/W
°C/W
°C/W
Junction to Case
(θ
JC
)
Junction to Ambient (θ
JA
)
Junction to Case (θ
JC
)
Junction to Ambient (θ
JA
)
2.8
V
3.3
3.3
1.25
V
V
mV
mV
V
V
A
mA
%/W
dB
mA
µA
60
120
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 V
IN
and V
OUT
or V
CTRL
and V
OUT
required to
maintain regulation at V
OUT
95% Nominal V
OUT
.
Note 3:
V
REF
is measured across Adjust pin to Sense pin.
Date: 2/11/05
SPX1581 5A Ultra Low Dropout Voltage Regulator
©Copyright 2005 Sipex Corporation
2
PIN DESCRIPTION
PIN NUMBER
1
2
PIN NAME
SENSE
ADJ
DESCRIPTION
Allows Kelvin sense of V
OUT
at the 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 the 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 1.0V
and 1.3V greater than the output 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.
3
4
V
OUT
V
CTRL
5
V
IN
Note that TAB is internally connected to Pin 3.
FUNCTIONAL 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)
Date: 2/11/05
SPX1581 5A Ultra Low Dropout Voltage Regulator
©Copyright 2005 Sipex Corporation
3
APPLICATION 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
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 5V for V
IN
and
3.3V 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 SPX1581 can power the 2.5V core voltage
for microprocessors such as a Pentium
TM
,
P55C
TM
, AMD5k86
TM
and K6
TM
and the IBM
PowerPC
TM
603EV and 604EV processors.
Power sequencing of V
IN
and V
CTRL
is re-
quired. Apply V
IN
before V
CTRL
for proper
operation
Adjustable Regulator Design
1.25V reference voltage is being developed be-
tween 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. 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 50µA. 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 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.
Power Up Sequencing
* The reduction of heat dissipation is a result of the
increase of the regulator efficiency (efficiency = V
OUT
/V
IN
).
The SPX158x requires a power up sequence in
that V
IN
must applied before V
CTRL
to prevent a
latch up condition. If this is not possible then a
series 10Ω resistor should be added to the V
CTRL
input to prevent the device from entering a latch
up if V
CTRL
is applied before V
IN
.
Date: 2/11/05
SPX1581 5A Ultra Low Dropout Voltage Regulator
©Copyright 2005 Sipex Corporation
4
Altera SoC
