D E S C R I P T I O N
K E Y F E A T U R E S
s Three-Terminal Adjustable Or Fixed
Output
s Guaranteed
1.2V Headroom At 3A
(LX8587A)
s Guaranteed
1.3V Headroom At 3A
(LX8587)
s Output Current Of 3A
p Fast Transient Response
p 1% Voltage Reference Initial Accuracy
p Output Short Circuit Protection
p Built-In Thermal Shutdown
The LX8587/8587A series ICs are low
dropout three-terminal positive regulators
with a nominal 3A output current. Pen-
tium
Processor and Power PC
TM
appli-
cations requiring fast transient response
are ideally suited for this product family.
The LX8587A is guaranteed to have
< 1.2V dropout at 3A and the LX8587
< 1.3V at the same current, making
them ideal to provide well-regulated out-
puts of 2.5V to 3.6V using a 5V input
supply. Fixed versions are also available
and specified in the Available Options
table below.
Current limit is trimmed above 3.1A to
ensure adequate output current and con-
trolled short-circuit current. On-chip
thermal limiting provides protection
against any combination of overload con-
ditions that would create excessive junc-
tion temperatures.
The LX8587/87A family of products are
available in both TO-220 through-hole
as well as TO-263 surface-mount pack-
ages. For higher current applications,
see the LX8585 and LX8584 data sheets.
A P P L I C A T I O N S
s Pentium Processor Supplies
s Power PC Supplies
s Microprocessor Supplies
s Low Voltage Logic Supplies
s Post Regulator For Switching Supply
s ASIC & Low Voltage Chipset Supplies
s Graphics & Sound Cards
s Processor I/O Supply
P R O D U C T H I G H L I G H T
Note: All surface-mount packages are available in Tape & Reel.
Append the letter "T" to part number. (i.e. LX8587A-00CDDT)
"xx" refers to output voltage, please see table above.
T
YPICAL
A
PPLICATION
OF
THE
LX8587/87A
IN
A
5V
TO
3.3V M
OTHERBOARD
A
PPLICATION
LX8587A
200
W
1500F
6MV1500GX
2x 1500F
Sanyo
6MV1500GX
V
IN
4.75
3.3V/3A
121
W
The output capacitors must be low ESR and low ESL type for good transient response.
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D
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S
H E E T
T
H E
I
N F I N I T E
P
O W E R
O F
I
N N O V A T I O N
LX8587-xx/8587A-xx
LIN D
O C
#: 8587
P A C K A G E O R D E R I N F O R M A T I O N
T
A
(C)
Plastic TO-220
3-pin
P
Plastic TO-263
3-pin
DD
0 to 125
1.3V
LX8587-xxCP
LX8587-xxCDD
1.2V
LX8587A-xxCP
LX8587A-xxCDD
Dropout
Voltage
LX8587/87A-00
Adjustable
LX8587/87A-15
1.5V
LX8587/87A-33
3.3V
Part #
Output
Voltage
A
VA I L A B L E
O
P T I O N S
P E R
P
A R T
#
Other voltage options may be available --
Please contact factory for details.
Copyright 1998
Rev. 1.2 3/98
1
11861 W
ESTERN
A
VENUE
, G
ARDEN
G
ROVE
, CA. 92841, 714-898-8121, F
AX
: 714-893-2570
L
I N
F
I N I T Y
M
I C R O E L E C T R O N I C S
I
N C
.
IMPORTANT: For the most current data, consult LinFinity's web site: http://www.linfinity.com.
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LX8587-xx/8587A-xx
P R O D U C T D A T A B O O K 1 9 9 6 / 1 9 9 7
Copyright 1998
Rev. 1.2 3/98
2
P
R O D U C T I O N
D
A T A
S
H E E T
A B S O L U T E M A X I M U M R AT I N G S
(Note 1)
Power Dissipation ................................................................................ Internally Limited
Input Voltage ............................................................................................................... 10V
Input to Output Voltage Differential .......................................................................... 10V
Maximum Output Current ............................................................................................. 5A
Operating Junction Temperature
Plastic (P Package) ............................................................................................... 150C
Storage Temperature Range ...................................................................... -65C to 150C
Lead Temperature (Soldering, 10 seconds) ............................................................ 300C
PACKAGE PIN OUTS
P PACKAGE
(Top View)
* Pin 1 is GND for fixed voltage versions.
Note 1. Exceeding these ratings could cause damage to the device. All voltages are with
respect to Ground. Currents are positive into, negative out of the specified terminal.
V
IN
V
OUT
ADJ /
GND*
3
2
1
P PACKAGE:
THERMAL RESISTANCE-JUNCTION TO TAB,
JT
3.0C/W
THERMAL RESISTANCE-JUNCTION TO AMBIENT,
JA
60C/W
DD PACKAGE:
THERMAL RESISTANCE-JUNCTION TO TAB,
JT
3.0C/W
THERMAL RESISTANCE-JUNCTION TO AMBIENT,
JA
60C/W*
Junction Temperature Calculation: T
J
= T
A
+ (P
D
x
JA
).
The
JA
numbers are guidelines for the thermal performance of the device/pc-board system.
All of the above assume no ambient airflow.
* With package soldered to 0.5 in.
2
copper area over back-side ground plane or internal
power plane,
JA
can vary from 20C/W to 40C/W, depending on mounting technique.
T H E R M A L D ATA
3
2
1
V
IN
ADJ / GND*
V
OUT
DD PACKAGE
(Top View)
* Pin 1 is GND for fixed voltage versions.
TAB IS V
OUT
TAB IS V
OUT
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LX8587-xx/8587A-xx
P R O D U C T D A T A B O O K 1 9 9 6 / 1 9 9 7
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Copyright 1998
Rev. 1.2 3/98
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H E E T
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(Unless otherwise specified, these specifications apply over the operating ambient temperatures for the LX8587-xx/87A-xx with 0C
T
A
125C;
V
IN
- V
OUT
= 3V; I
OUT
= 3A. Low duty cycle pulse testing techniques are used which maintains junction and case temperatures equal to the ambient temperature.)
Parameter
Symbol
Test Conditions
Units
LX8587/87A-00
Min.
Typ.
Max.
1.238
1.250
1.262
V
1.225
1.250
1.275
V
0.035
0.2
%
0.1
0.5
%
0.01
0.02
%/W
65
83
dB
55
100
A
0.2
5
A
1.1
1.3
V
1
1.2
V
2
10
mA
3.0
5
A
0.25
%
1
%
0.003
%
Reference Voltage
V
REF
I
OUT
= 10mA, T
A
= 25C
10mA
I
OUT
3A, 1.5V
(V
IN
- V
OUT
), V
IN
7V, P
P
MAX
Line Regulation (Note 2)
V
REF
(V
IN
) I
OUT
= 10mA, 1.5V
(V
IN
- V
OUT
), V
IN
7V
Load Regulation (Note 2)
V
REF
(I
OUT
)
V
IN
- V
OUT
= 3V, 10mA
I
OUT
3A
Thermal Regulation
V
OUT
(Pwr)
T
A
= 25C, 20ms pulse
Ripple Rejection (Note 3)
V
OUT
= 3.3V, f =120Hz, C
OUT
= 100f Tantalum, V
IN
= 5V
C
ADJ
= 10F, I
OUT
= 3A
Adjust Pin Current
I
ADJ
Adjust Pin Current Change
I
ADJ
10mA
I
OUT
3A, 1.5V
(V
IN
- V
OUT
), V
IN
7V
Dropout Voltage
LX8587-00
V
V
REF
= 1%, I
OUT
= 3A
LX8587A-00
V
REF
= 1%, I
OUT
= 3A
Minimum Load Current
I
OUT(MIN)
V
IN
7V
Maximum Output Current
I
OUT(MAX)
1.4V
(V
IN
- V
OUT
), V
IN
7V
Temperature Stability
V
OUT
(T)
Long Term Stability
V
OUT
(t) T
A
= 125C, 1000 hrs
RMS Output Noise (% of V
OUT
)
V
OUT (RMS)
T
A
= 25C, 10Hz
f 10kHz
Note 2. Regulation is measured at constant junction temperature, using pulse testing with a low duty cycle. Changes in output voltage due to
heating effects are covered under the specification for thermal regulation.
Note 3. These parameters, although guaranteed, are not tested in production.
Parameter
Symbol
Test Conditions
Units
LX8587-15/87A-15
Min.
Typ.
Max.
Output Voltage
V
OUT
V
IN
= 5V, I
OUT
= 0mA, T
A
= 25C
3.0V
V
IN
7V, 0mA
I
OUT
3A, P
P
MAX
Line Regulation (Note 2)
V
OUT
4.75V
V
IN
7V
(V
IN
)
4.75V
V
IN
10V
Load Regulation (Note 2)
V
OUT
(I
OUT
)
V
IN
= 5V, 0mA
I
OUT
I
OUT (MAX)
Thermal Regulation (Note 3)
V
OUT
(Pwr)
T
A
= 25C, 20ms pulse
Ripple Rejection (Note 3)
C
OUT
= 100F (Tantalum), I
OUT
= 3A
Quiescent Current
I
Q
0mA
I
OUT
I
OUT (MAX)
, 4.75V
V
IN
10V
Dropout Voltage
LX8587-15
V
V
OUT
= 1%, I
OUT
I
OUT (MAX)
LX8587A-15
V
OUT
= 1%, I
OUT
I
OUT (MAX)
Maximum Output Current
I
OUT (MAX)
V
IN
7V
Temperature Stability (Note 3)
V
OUT
(T)
Long Term Stability (Note 3)
V
OUT
(t) T
A
= 125C, 1000 hours
RMS Output Noise (% of V
OUT
) (Note 3) V
OUT (RMS)
T
A
= 25C, 10Hz
f
10kHz
1.485
1.5
1.515
V
1.470
1.5
1.530
V
1
6
mV
2
10
mV
5
7.5
mV
0.01
0.02
% / W
60
75
dB
4
10
mA
1.1
1.3
V
1
1.2
V
3.0
5.0
A
0.25
%
0.3
1
%
0.003
%
LX8587-00/87A-00 (Adjustable)
LX8587-15/87A-15 (1.5V Fixed)
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LX8587-xx/8587A-xx
P R O D U C T D A T A B O O K 1 9 9 6 / 1 9 9 7
Copyright 1998
Rev. 1.2 3/98
4
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E L E C T R I C A L C H A R A C T E R I S T I C S
Note 2. Regulation is measured at constant junction temperature, using pulse testing with a low duty cycle. Changes in output voltage due to
heating effects are covered under the specification for thermal regulation.
Note 3. These parameters, although guaranteed, are not tested in production.
Parameter
Symbol
Test Conditions
Units
LX8587-33/87A-33
Min.
Typ.
Max.
Output Voltage
V
OUT
V
IN
= 5V, I
OUT
= 0mA, T
A
= 25C
4.75V
V
IN
10V, 0mA
I
OUT
3A, P
P
MAX
Line Regulation (Note 2)
V
OUT
4.75V
V
IN
7V
(V
IN
)
4.75V
V
IN
10V
Load Regulation (Note 2)
V
OUT
(I
OUT
)
V
IN
= 5V, 0mA
I
OUT
I
OUT (MAX)
Thermal Regulation (Note 3)
V
OUT
(Pwr)
T
A
= 25C, 20ms pulse
Ripple Rejection (Note 3)
C
OUT
= 100F (Tantalum), I
OUT
= 3A
Quiescent Current
I
Q
0mA
I
OUT
I
OUT (MAX)
, 4.75V
V
IN
10V
Dropout Voltage
LX8587-33
V
V
OUT
= 1%, I
OUT
I
OUT (MAX)
LX8587A-33
V
OUT
= 1%, I
OUT
I
OUT (MAX)
Maximum Output Current
I
OUT (MAX)
V
IN
7V
Temperature Stability (Note 3)
V
OUT
(T)
Long Term Stability (Note 3)
V
OUT
(t) T
A
= 125C, 1000 hours
RMS Output Noise (% of V
OUT
) (Note 3) V
OUT (RMS)
T
A
= 25C, 10Hz
f
10kHz
3.267
3.3
3.333
V
3.235
3.3
3.365
V
1
6
mV
2
10
mV
5
15
mV
0.01
0.02
% / W
60
75
dB
4
10
mA
1.1
1.3
V
1
1.2
V
3.0
5.0
A
0.25
%
0.3
1
%
0.003
%
LX8587-33/87A-33 (3.3V Fixed)
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LX8587-xx/8587A-xx
P R O D U C T D A T A B O O K 1 9 9 6 / 1 9 9 7
5
Copyright 1998
Rev. 1.2 3/98
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A T A
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H E E T
A P P L I C A T I O N N O T E S
The LX8587/87A series ICs are easy to use Low-Dropout (LDO)
voltage regulators. They have all of the standard self-protection
features expected of a voltage regulator: short circuit protection,
safe operating area protection and automatic thermal shutdown if
the device temperature rises above approximately 165C.
Use of an output capacitor is REQUIRED with the LX8587/87A
series. Please see the table below for recommended minimum
capacitor values.
These regulators offer a more tightly controlled reference voltage
tolerance and superior reference stability when measured against
the older pin-compatible regulator types that they replace.
STABILITY
The output capacitor is part of the regulator's frequency compen-
sation system. Many types of capacitors are available, with different
capacitance value tolerances, capacitance temperature coefficients,
and equivalent series impedances. For all operating conditions,
connection of a 220F aluminum electrolytic capacitor or a 47F
solid tantalum capacitor between the output terminal and ground
will guarantee stable operation.
If a bypass capacitor is connected between the output voltage
adjust (ADJ) pin and ground, ripple rejection will be improved
(please see the section entitled "RIPPLE REJECTION"). When ADJ
pin bypassing is used, the required output capacitor value increases.
Output capacitor values of 220F (aluminum) or 47F (tantalum)
provide for all cases of bypassing the ADJ pin. If an ADJ pin bypass
capacitor is not used, smaller output capacitor values are adequate.
The table below shows recommended minimum capacitance values
for stable operation.
INPUT
OUTPUT
ADJ
10F
15F Tantalum, 100F Aluminum
None
10F
47F Tantalum, 220F Aluminum
15F
In order to ensure good transient response from the power supply
system under rapidly changing current load conditions, designers
generally use several output capacitors connected in parallel. Such
an arrangement serves to minimize the effects of the parasitic
resistance (ESR) and inductance (ESL) that are present in all
capacitors. Cost-effective solutions that sufficiently limit ESR and
ESL effects generally result in total capacitance values in the range
of hundreds to thousands of microfarads, which is more than
adequate to meet regulator output capacitor specifications. Output
capacitance values may be increased without limit.
The circuit shown in Figure 1 can be used to observe the transient
response characteristics of the regulator in a power system under
changing loads. The effects of different capacitor types and values
on transient response parameters, such as overshoot and under-
shoot, can be quickly compared in order to develop an optimum
solution.
RECOMMENDED CAPACITOR VALUES
FIGURE 1 -- Dynamic Input And Output Test
LX8587/87A
Power Supply
OUT
IN
ADJ
Star Ground
1 sec
10ms
R
DSON
<< R
L
Full Load
(Smaller resistor)
Minumum Load
(Larger resistor)
OVERLOAD RECOVERY
Like almost all IC power regulators, the LX8587/87A regulators are
equipped with Safe Operating Area (SOA) protection. The SOA
circuit limits the regulator's maximum output current to progres-
sively lower values as the input-to-output voltage difference
increases. By limiting the maximum output current, the SOA circuit
keeps the amount of power that is dissipated in the regulator itself
within safe limits for all values of input-to-output voltage within the
operating range of the regulator. The LX8587/87A SOA protection
system is designed to be able to supply some output current for all
values of input-to-output voltage, up to the device breakdown
voltage.
Under some conditions, a correctly operating SOA circuit may
prevent a power supply system from returning to regulated
operation after removal of an intermittent short circuit at the output
of the regulator. This is a normal mode of operation which can be
seen in most similar products, including older devices such as 7800
series regulators. It is most likely to occur when the power system
input voltage is relatively high and the load impedance is relatively
low.
When the power system is started "cold", both the input and
output voltages are very close to zero. The output voltage closely
follows the rising input voltage, and the input-to-output voltage
difference is small. The SOA circuit therefore permits the regulator
to supply large amounts of current as needed to develop the
designed voltage level at the regulator output. Now consider the
case where the regulator is supplying regulated voltage to a resistive
load under steady state conditions. A moderate input-to-output
voltage appears across the regulator but the voltage difference is
small enough that the SOA circuitry allows sufficient current to flow
through the regulator to develop the designed output voltage across
the load resistance. If the output resistor is short-circuited to ground,
the input-to-output voltage difference across the regulator suddenly
becomes larger by the amount of voltage that had appeared across
the load resistor. The SOA circuit reads the increased input-to-
output voltage, and cuts back the amount of current that it will
permit the regulator to supply to its output terminal. When the short
circuit across the output resistor is removed, all the regulator output
current will again flow through the output resistor. The maximum
current that the regulator can supply to the resistor will be limited
by the SOA circuit, based on the large input-to-output voltage across
the regulator at the time the short circuit is removed from the output.
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