LX8584x-xx
TM
®
7A Low Dropout Positive Regualtors
P
RODUCTION
D
ATA
S
HEET
DESCRIPTION
KEY FEATURES
Three Terminal Adjustable or
Fixed Output
Guaranteed 1% Voltage
Accuracy over Temperature
(LX8584B)
Guaranteed < 1.2V Headroom
at 7A (LX8584A)
Guaranteed < 1.4V Headroom
at 7A (LX8584/84B)
Output Current of 7A
Fast Transient Response
1% Voltage Reference Initial
Accuracy
Output Short Circuit Protection
Built-in Thermal Shutdown
Evaluation Board Available:
Request LXE9001 Evaluation
Kit
APPLICATIONS
IMPORTANT:
For the most current data, consult
MICROSEMI’s
website:
http://www.microsemi.com
PRODUCT HIGHLIGHT
T
HE
A
PPLICATION OF THE
LX8584A & LX1431
IN A
75 & 166 MH
Z
P54C P
ROCESSORS
U
SING
3.3V C
ACHE
5V
3
V
IN
V
OUT
2
V
O
7A
(See Table Below)
LX8584A
1kΩ
ADJ
1
1kΩ
bs
0.01µF
250pF
2
1
220µF
10V
Low ESR
from
Sanyo
3
COL
V
+
REF
8
1k
0.1%
100µF x 6
10V
AVX TYPE
TPS
ol
et
PLACE IN µP SOCKET CAVITY
The LX8584/84A/84B series ICs
are low dropout three-terminal
positive regulators with a nominal 7A
output current. This product family is
ideally suited for Pentium® Processor
and Power PCTM applications
requiring fast transient response. The
LX8584A is
guaranteed to have <
1.2V at 7A
and the LX8584/84B
<
1.4V at 7A dropout voltage,
making
them ideal to provide well regulated
outputs of 2.5V to 3.6V using a 5V
input supply. In addition,
the
LX8584B also offers ±1% maximum
voltage reference accuracy over
temperature.
Fixed versions are also
available and are specified in the
Available Options table below.
Current limit is trimmed above 7.1A
to ensure adequate output current and
controlled short-circuit current. On-chip
thermal limiting provides protection
against any combination of overload
that would create excessive junction
temperatures. The LX8584/84A series
products are available in both the
through-hole versions of the industry
standard 3-pin TO-220 and TO-247
power packages.
The LX1431
Programmable Reference utilzed in
conjunction with the LX8584 7A LDO
products offer precision output voltage
(see application below) and are ideal for
use in VRE applications.
WWW .
Microsemi
.C
OM
3x
330µF, 6.3V
Low ESR
Oscon Type
from Sanyo
LX1431
2.84kΩ
0.1%
21k
1%
Input Output Differential V
µP
Load
0.1µF
50V
1µF x 10
SMD
SGND FGND
5
6
JP1
O
V
OUT
3.50
3.38
JP1
Short
Open
TYPICAL APPLICATION
120/166MHz, VRE, 3.3V Cache
75/90/100/133MHz, STND, 3.3V Cache
e
D
ROPOUT
V
OLT AGE VS
.
O
UTPUT
C
URRENT
1.5
Pentium™ Processor Supplies
Power PC™ Supplies
Microprocessor Supplies
Low Voltage Logic Supplies
Post Regulator for Switching
Supply
LX8584/84A
T
J
= 125 °C
LX8584
1.0
LX8584A
0.5
0
1.75
3.5
5.25
7
Thick traces represent high current traces which must be low resistance /
low inductance in order to achieve good transient response.
Output Current - (A)
LX8584
X
LX8584
X
PACKAGE ORDER INFO
AVAILABLE OPTIONS
T
J
(°C) Dropout Voltage
1.4V
1.2V
Copyright
©
1997
Rev. 1.3, 2005-11-11
P
Plastic TO-220
3 pin
RoHS Compliant
Transition DC: 0543
Part #
LX8584/A/B-00
LX8584/A/B/-33
Output
Voltage
Adjustable
3.3V
0 to 125
LX8584-xxCP
LX8584B-xxCP
LX8584A-xxCP
Other voltage options may be available –
please contact factory for details.
Note: xx refers to output voltage, please see table to right. Available in Tape & Reel. Append the letters “TR” to the part number. (i.e. LX8584-xxCP-TR)
Microsemi
Integrated Products Division
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 1
LX8584x-xx
TM
®
7A Low Dropout Positive Regualtors
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................................................................................................8A
Maximum Operating Junction Temperature .................................................................150°
Storage Temperature Range.........................................................................-65°C to 150°C
Package Peak Temp. for Solder Reflow (40 seconds maximum 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 GND
3
2
1
WWW .
Microsemi
.C
OM
V
IN
V
OUT
ADJ/GND*
P P
ACKAGE
(Top View)
RoHS 100% Matte Tin Lead Finish
P
Plastic TO-220 3-Pin
THERMAL RESISTANCE
-
JUNCTION TO
T
AB
,
θ
JT
THERMAL RESISTANCE
-
JUNCTION TO
A
MBIENT
,
θ
JA
Junction Temperature Calculation: T
J
= T
A
+ (P
D
x
θ
JA
).
The
θ
JA
numbers are guidelines for the thermal performance of the device/pc-board system. All of the
above assume no ambient airflow.
O
bs
P
ACKAGE
D
ATA
P
ACKAGE
D
ATA
Copyright
©
1997
Rev. 1.3, 2005-11-11
ol
et
2.7°C/W
60°C/W
THERMAL DATA
Microsemi
Integrated Products Division
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
e
Page 2
LX8584x-xx
TM
®
7A Low Dropout Positive Regualtors
P
RODUCTION
D
ATA
S
HEET
ELECTRICAL CHARACTERISTICS
Unless otherwise specified, the following specifications apply over the operating ambient temperature for the LX8585-xxC / 84A-xxC /
84B-xxC with 0°C
≤
T
A
≤
125°C; VIN – VOUT = 3V; IOUT = 7A. Low duty cycle pulse testing techniques are used which maintains
junction and case temperatures equal to the ambient temperature.
Parameter
Symbol
Test Conditions
LX8584x-xx
Min
Typ
Max
1.238
1.225
1.240
1.25
1.250
1.250
1.263
1.275
1.260
V
WWW .
Microsemi
.C
OM
Units
LX8584-00 / 84A-00 / 84B-00 (ADJUSTABLE)
I
OUT
= 10mA, T
A
= 25°C
10mA < I
OUT
< 7A, 1.5V < (V
IN
- V
OUT
),
Reference
V
IN
< 7V, P < P
MAX
V
REF
Voltage
I
OUT
= 10mA, T
A
=25°C
LX8584B-00
10mA < I
OUT
< 7A, 1.5V < (V
IN
– V
OUT
),
V
IN
< 7V, P < P
MAX
Line Regulations (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
< 7A
Thermal Regulation
∆V
OUT
(Pwr) T
A
= 25°C, 20ms pulse
V
OUT
= 3.3V, f = 120Hz, C
OUT
= 100µF Tantalum,
Ripple Rejection (Note 3)
V
IN
= 5V, C
ADJ
= 10µF, I
OUT
= 7A
Adjust Pin Current
I
ADJ
10mA < I
OUT
< 7A, 1.5V < (V
IN
– V
OUT
),
Adjust Pin Current Change
∆I
ADJ
V
IN
< 7V
LX8584A
∆V
∆V
REF
= 1%, I
OUT
= 7A
Dropout Voltage LX8584/84B
∆V
REF
= 1%, I
OUT
= 7A
LX8584/84B
∆V
REF
= 1%, I
OUT
= 6A
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
= 125°C, 1000hs
RMS Output Noise (% of V
OUT
)
V
OUT(RMS)
T
A
= 25°C, 10Hz < f < 10kHz
LX8584-33 / 84A-33 / 84B-33 (3.3V Fixed
V
IN
= 5V, I
OUT
= 0mA, T
A
= 25°C
LX8584B-33
4.75V < V
IN
< 10V, 0mA < I
OUT
< 7A,
Output
P < P
MAX
V
OUT
Voltage
V
IN
= 5V, I
OUT
= 0mA, T
A
= 25°C
LX8584/84A-33
4.75 < V
IN
< 10V, 0mA < I
OUT
< 7A, P < P
MAX
∆V
OUT
4.75V < V
IN
< 7V
Line Regulation (Note 2)
(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
∆V
OUT
(Pwr) T
A
= 25°C, 20ms pulse
Ripple Rejection (Note 3)
C
OUT
= 100µF (Tantalum), I
OUT
= 7.5V
Quiescent Current
I
Q
0mA < I
OUT
< I
OUT(MAX)
, 4.75V < V
IN
< 10V
LX8584-xx
∆V
OUT
= 1%, I
OUT
= I
OUT(MAX)
Dropout Voltage LX8584A-xx
∆V
∆V
OUT
= 1%, I
OUT
= I
OUT(MAX
)
LX8584B-xx
∆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
= 125°C, 1000hs
RMS Output Noise (% of V
OUT
)
T
A
= 25°C, 10Hz < f < 10kHz
V
OUT(RMS)
(Note 3)
LX8584/84A-00
ol
et
65
83
55
0.2
7
1.1
1.2
1.1
2
8
0.25
0.3
0.003
3.30
3.30
3.30
3.30
1
2
5
0.01
83
4
3.267
3.234
3.274
3.267
60
7
8
0.25
0.3
0.003
e
1.238
1.250
1.263
0.20
0.5
0.02
0.035
0.1
0.01
100
5
1.2
1.4
1.3
10
1
3.333
3.366
3.326
3.333
6
10
15
0.02
10
1.4
1.2
1.4
1
%
%
%/W
dB
µA
µA
V
V
V
mA
A
%
%
%
bs
V
O
mV
mV
mV
%/W
dB
mA
V
A
%
%
%
E
LECTRICALS
E
LECTRICALS
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.
Copyright
©
1997
Rev. 1.3, 2005-11-11
Microsemi
Integrated Products Division
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 3
LX8584x-xx
TM
®
7A Low Dropout Positive Regualtors
P
RODUCTION
D
ATA
S
HEET
THEORY OF OPERATION
The LX8584/84A/84B 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 LX8584 /
84A / 84B 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 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 stable operation.
Recommended Capacitor Values
Input
Output
Adj
10µF
15µF Tantalum, 100µF Aluminum
None
10µF
47µF Tantalum, 200µF Aluminum
15µF
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 undershoot, can be quickly compared in order to
develop an optimum solution.
Power Supply
IN
LX8584/84A
/84B
ADJ
OUT
Minumum Load
(Larger resistor)
Full Load
(Smaller resistor)
R
DSON
<< R
L
1 sec
WWW .
Microsemi
.C
OM
Star Ground
10ms
Figure 1 –
Dynamic Input and Output Test
Overload Recovery
Like almost all IC power regulators, the LX8584/84A/84B
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 LX8584/84A/84B 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.
O
bs
ol
et
Microsemi
e
A
PPLICATIONS
A
PPLICATIONS
Copyright
©
1997
Rev. 1.3, 2005-11-11
Integrated Products Division
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 4
LX8584x-xx
TM
®
7A Low Dropout Positive Regualtors
P
RODUCTION
D
ATA
S
HEET
APPLICATION NOTE
Overload Recovery
(continued)
If this limited current is not sufficient to develop the designed
voltage across the output resistor, the voltage will stabilize at some
lower value, and will never reach the designed value. Under these
circumstances, it may be necessary to cycle the input voltage
down to zero in order to make the regulator output voltage return
to regulation.
RIPPLE REJECTION
Ripple rejection can be improved by connecting a capacitor
between the ADJ pin and ground. The value of the capacitor
should be chosen so that the impedance of the capacitor is equal in
magnitude to the resistance of R
1
at the ripple frequency. The
capacitor value can be determined by using this equation:
C
=
1/(6.28 * F
R
* R
1
)
Where:
C
≡
the value of the capacitor in Farads; select an
equal or larger standard value.
F
R
≡
the ripple frequency in Hz
R
1
≡
the value of resistor R1 in ohms
At a ripple frequency of 120Hz, with R1 = 100Ω
C
=
1/(6.28 * 120Hz * 100
Ω
)
=
13.3µF
The closest equal or larger standard value should be used, in this
case; 15μF.
When an ADJ pin bypass capacitor is used, output ripple
amplitude will be essentially independent of the output voltage. If
an ADJ pin bypass capacitor is not used, output ripple will be
proportional to the ratio of the output voltage to the reference
voltage:
WWW .
Microsemi
.C
OM
V
IN
LX8584/84A/84B
OUT
IN
ADJ
I
ADJ
50µA
V
OUT
V
REF
R1
a multiplier for the ripple seen when the ADJ
pin is optimally bypassed.
V
REF
= 1.25V.
For example, if V
OUT
= 2.5V the output ripple will be:
M = 2.5V / 1.25V = 2
Output ripple will be twice as bad as it would be if the ADJ pin
were to be bypassed to ground with a properly selected capacitor.
OUTPUT VOLTAGE
The LX8584/84A/84B ICs develop a 1.25V reference voltage
between the output and the adjust terminal (See Figure 2). By
placing a resistor, R1, between these two terminals, a constant
current is caused to flow through R1 and down through R2 to set
the overall output voltage. Normally this current is the specified
minimum load current of 10mA. Because I
ADJ
is very small and
constant when compared with the current through R
1
, it represents
a small error and can usually be ignored.
Where
bs
M
≡
M
=
V
OUT
/V
REF
O
ol
et
R
Peff
=
R
P
*
⎜
LOAD REGULATION
Because the LX8584/84A/84B regulators are three-terminal
devices, it is not possible to provide true remote load sensing.
Load regulation will be limited by the resistance of the wire
connecting the regulator to the load. The data sheet specification
for load regulation is measured at the bottom of the package.
Negative side sensing is a true Kelvin connection, with the
bottom of the output divider returned to the negative side of the
load. Although it may not be immediately obvious, best load
regulation is obtained when the top of the resistor divider, (R1), is
connected directly to the case of the regulator, not to the load.
This is illustrated in Figure 3. If R
1
were connected to the load,
the effective resistance between the regulator and the load would
be:
Where RP
≡
actual parasitic line resistance
When the circuit is connected as shown in Figure 3, the parasitic
resistance appears as its actual value, rather than the higher R
Peff
.
LX8584/84A/84B
OUT
IN
ADJ
R1
R2
R
P
Parasitic
Line Resistance
Connect
R1 to Case
of Regulator
V
IN
e
Figure 2 –
Basic Adjustable Regulator
V
OUT
= V
REF
1 + R2 + I
ADJ
R2
R1
R2
⎛
R2
+
R1
⎞
⎟
⎝
R1
⎠
R
L
Connect
R2
to Load
A
PPLICATIONS
A
PPLICATIONS
Figure 3 –
Connections for Best Load Regulation
Copyright
©
1997
Rev. 1.3, 2005-11-11
Microsemi
Integrated Products Division
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 5
DSP and ARM Processors
京公网安备 11010802033920号
EEWORLD
