LX8587x-xx
TM
®
3A Low Dropout Positive Regulators
P
RODUCTION
D
ATA
S
HEET
DESCRIPTION
The LX8587/87A Series ICs are positive
regulators designed to provide 3A output
current. Pentium® Processor and Power
PC™ applications requiring fast transient
response are ideally suited for this product
family.
The LX8587A is guaranteed to have
<1.2 dropout at 3A and the LX8587 < 1.3V
at the same current, making them ideal to
provide well-regulated outputs 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 about 3.1A to
ensure adequate output current and
controlled short-circuit current. On-chip
thermal limiting provides protection against
any combination of overload conditions that
would create excessive junction
temperatures.
The LX8587/87A family of products are
available in the TO-220 through hole, the
TO-263 surface-mount, and the TO-252
surface-mount packages. For higher current
applications see the LX8585 and the
LX8584 data sheets.
KEY FEATURES
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Three-Terminal Adjustable Or
Fixed Output
Guaranteed < 1.2V Headroom At
3A (LX8587A)
Guaranteed < 1.3V Headroom At
3A (LX8587)
Output Current of 3A
Fast Transient Response
1% Voltage Reference Initial
Accuracy
Output Short Circuit Protection
Built-In Thermal Shutdown
APPLICATIONS
Pentium Processor Supplies
Power PC Supplies
Microprocessor Supplies
Low Voltage Logic Supplies
Post Regulator for Switching
Supply
ASIC & Low Voltage Chipset
Supplies
Graphics & Sound Cards
Processor I/O Supply
OUTPUT
VOLTAGE
Adjustable
1.5V
3.3V
IMPORTANT:
For the most current data, consult
MICROSEMI’s
website:
http://www.microsemi.com
PRODUCT HIGHLIGHT
T
YPICAL
A
PPLICATION OF THE
LX8587/87A
IN A
5V
TO
3.3V M
OTHERBOARD
IN
V
IN
> 4.75V
+
*1500µF
6MV1500GX
Sanyo
LX8587A
ADJ
200Ω
1%
OUT
121Ω
1%
+
3.3V
at 3A
1500µF
2x 6MV1500GX
Sanyo
PART #
LX8587/87A-00
The output capacitors must be low ESR and low ESL type for good transient response
.
LX8587/87A-15
LX8587/87A-33
Table 1
- Available Options
LX8587
X
LX8587
X
T
A
(°C)
0 to 125
Max Dropout
Voltage
1.3V
1.2V
DT
PACKAGE ORDER INFO
Plastic TO-220
Plastic TO-252
P
3-Pin
(D-Pak) 3-Pin
RoHS Compliant
Transition DC: 0543
DD
Plastic TO-263
3-Pin
RoHS Compliant
Transition DC: 0532
RoHS Compliant
Transition DC: 0535
LX8587-xxCDT
LX8587A-xxCDT
LX8587-xxCP
LX8587A-xxCP
LX8587-xxCDD
LX8587A-xxCDD
Note: Available in Tape & Reel. Append the letters “TR” to the part number. (i.e. LX8587-00CP-TR)
Copyright
©
2000
Rev. 2.0a, 2005-10-25
Microsemi
Integrated Products
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 1
LX8587x-xx
TM
®
3A Low Dropout Positive Regulators
P
RODUCTION
D
ATA
S
HEET
ABSOLUTE MAXIMUM RATINGS
Power Dissipation ................................................................................... Internally Limited
Input Voltage ................................................................................................................ 10V
Input to Output Voltage Differential............................................................................. 10V
Maximum Output Current............................................................................................... 5A
Maximum Operating Junction Temperature .............................................................. 150°C
Storage Temperature Range........................................................................ -65°C to 150°C
Peak Package Solder Reflow Temp. (40 seconds max. exposure) .................260°C (+0,-5)
Note:
Exceeding these ratings could cause damage to the device. All voltages are with respect to
Ground. Currents are positive into, negative out of specified terminal.
PACKAGE PIN OUT
TAB is V
OUT
3
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OM
V
IN
V
OUT
ADJ /
GND*
2
1
DD P
ACKAGE
(3-
PIN
)
(Top View)
TAB is V
OUT
3
V
IN
V
OUT
ADJ/
GND
*
THERMAL DATA
2
DD
Plastic TO-263 3-Pin
THERMAL RESISTANCE
-
JUNCTION TO
A
MBIENT
,
θ
JA
THERMAL RESISTANCE
-
JUNCTION TO
T
AB
,
θ
JT
Plastic TO-220 3-Pin
THERMAL RESISTANCE
-
JUNCTION TO
A
MBIENT
,
θ
JA
THERMAL RESISTANCE
-
JUNCTION TO
T
AB
,
θ
JT
1
60°C/W
2.7°C/W
60°C/W
2.7°C/W
60°C/W
2.7°C/W
DT P
ACKAGE
(3-
PIN
)
(Top View)
P
TAB is V
OUT
3
V
IN
V
OUT
ADJ /
GND*
2
1
DT
Plastic TO-252 3-Pin
THERMAL RESISTANCE
-
JUNCTION TO
A
MBIENT
,
θ
JA
THERMAL RESISTANCE
-
JUNCTION TO
T
AB
,
θ
JT
P P
ACKAGE
(3-
PIN
)
(Top View)
*Pin
1 is GND for fixed voltage versions
RoHS 100% Matte Tin Lead Finish
Junction Temperature Calculation: T
J
= T
A
+ (P
D
x
θ
JT
).
The
θ
JA
&
θ
JT
numbers are guidelines for the thermal performance of the device/pc-board
system. All of the above assume no ambient airflow.
P
ACKAGE
D
ATA
P
ACKAGE
D
ATA
Copyright
©
2000
Rev. 2.0a, 2005-10-25
Microsemi
Integrated Products
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 2
LX8587x-xx
TM
®
3A Low Dropout Positive Regulators
P
RODUCTION
D
ATA
S
HEET
WWW .
Microsemi
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OM
ELECTRICAL CHARACTERISTICS (CONTINUED)
Unless otherwise specified, the following specifications apply over the operating ambient temperature for the LX8585x-xxC with
0°C
≤
T
A
≤
125°C and the LX8585-xxI with -25°C
≤
T
A
≤
125°C except where otherwise noted. Test conditions: 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
LX8587x-xx
Min
Typ
Max
3.0
5.0
0.25
T
A
=125°C, 1000 hours
T
A
=25°C, 10Hz < f < 10kHz
0.3
0.003
1
Units
LX8587-15 / 8587A-15 (1.5V FIXED)(CONTINUED)
Maximum Output Current
Temperature Stability (Note 3)
Long Term Stability (Note 3)
RMS Output Noise (% of V
OUT
)
(Note 3)
LX8587-33/87A-33 (3.3V FIXED)
Output Voltage
V
OUT
V
IN
=5V, I
OUT
=0mA, T
A
=25°C
4.75V < V
IN
< 10V, 0mA < I
OUT
< 3A, P < P
MAX
4.75V < V
IN
< 7V
4.75V < V
IN
< 10V
V
IN
=5V, 0mA < I
OUT
< I
OUT(MAX)
T
A
=25°C, 20ms pulse
C
OUT
=100µF (Tantalum), I
OUT
=3A
I
Q
LX8587-33
LX8587A-33
Maximum Output Current
Temperature Stability (Note 3)
Long Term Stability (Note 3)
RMS Output Noise (% of V
OUT
)
(Note 3)
ΔV
I
OUT(MAX)
ΔV
OUT
(T)
ΔV
OUT
(t)
V
OUT (RMS)
T
A
=125°C, 1000 hours
T
A
=25°C, 10Hz < f < 10kHz
0mA < I
OUT
< I
OUT(MAX)
, 4.75V < V
IN
< 10V
ΔV
OUT
=1%, I
OUT
< I
OUT(MAX)
ΔV
OUT
=1%, I
OUT
< I
OUT(MAX)
V
IN
< 7V
3
60
3.267
3.235
3.3
3.3
1
2
5
0.01
75
4
1.1
1
5.0
0.25
0.3
0.003
1
10
1.3
1.2
3.333
3.365
6
10
15
0.02
V
V
mV
mV
mV
%/W
dB
mA
V
V
A
%
%
%
I
OUT(MAX)
ΔV
OUT
(T)
ΔV
OUT
(t)
V
OUT (RMS)
V
IN
< 7V
A
%
%
%
Line Regulation (Note 2)
Load Regulation (Note 2)
Thermal Regulation
Ripple Rejection (Note 3)
Quiescent Current
Dropout Voltage
ΔV
OUT
(V
IN
)
ΔV
OUT
(I
OUT
)
ΔV
OUT
(Pwr)
Note 2
Note 3
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.
These parameters, although guaranteed, are not tested in production.
E
LECTRICALS
E
LECTRICALS
Copyright
©
2000
Rev. 2.0a, 2005-10-25
Microsemi
Integrated Products
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 4
LX8587x-xx
TM
®
3A Low Dropout Positive Regulators
P
RODUCTION
D
ATA
S
HEET
APPLICATION NOTES
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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
165°C.
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
compensation 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 220µF aluminum
electrolytic capacitor or a 47µF (<400mΩ ESR) 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 220µF (aluminum) or 47µF
(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 operation.
Minimum Capacitor Values
INPUT
10µF
10µF
OUTPUT
15µF Tantalum, 100µF Aluminum
47µF Tantalum, 220µF Aluminum
ADJ
None
15µF
Power
Supply
IN
OUT
Minimum Load
(Larger resistor)
Full Load
(Smaller
resistor)
ADJ
R
DSON
<< R
L
Star Ground
10ms
1 sec
FIGURE 1
- DYNAMIC INPUT AND OUTPUT TEST
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 compared quickly in order to
develop an optimum solution.
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 progressively 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 opera-
tion 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
Page 5
A
PPLICATIONS
A
PPLICATIONS
Copyright
©
2000
Rev. 2.0a, 2005-10-25
Microsemi
Integrated Products
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
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