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PDF LX8384X-XX Data sheet ( Hoja de datos )
| Número de pieza | LX8384X-XX | |
| Descripción | 5A Low Dropout Positive Regulators | |
| Fabricantes | Microsemi Corporation | |
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A MICROSEMI COMPANY
LX8384x-xx
5A Low Dropout Positive Regulators
PRODUCTION
The LX8384/84A/84B Series ICs are available and specified in the Available
positive regulators designed to provide 5A Options table below.
output current. These regulators yield The LX8384/84A/84B Series devices are
higher efficiency than currently available pin-compatible with earlier 3-terminal
devices with all internal circuitry designed regulators, such as the 117 series products,
to operate down to a 1V input-to-output but they do require input and output
differential. In each of these products, the capacitors. A minimum 10µF capacitor is
dropout voltage is fully specified as a required on the input and a 15µF or greater
function of load current. Dropout is on the output of these new devices for
guaranteed at a maximum of 1.3V (8384A) stability. Although, these capacitors are
and 1.5V (8384) at maximum output generally included in most regulator
current, decreasing at lower load currents. designs.
In addition, on-chip trimming adjusts the The LX8384/84A/84B Series quiescent
reference voltage tolerance to 1% maximum current flows into the load, thereby
at room temperature and 2% maximum over increasing efficiency. This feature contrasts
the 0 to 125°C range for the LX8384A, with PNP regulators where up to 10% of the
making this ideal for the Pentium P54C- output current is wasted as quiescent
VRE specification. The LX8384B offers current. The LX8384-xxI is specified over
0.8% tolerance at room temperature and the industrial temperature range of -25°C to
1.0% maximum over line, load and 125°C, while the LX8384-xxC/84A-
temperature. Fixed versions are also xxC/84B-xxC is specified over the
commercial range of 0°C to 125°C.
IMPORTANT: For the most current data, consult MICROSEMI’s website: http://www.microsemi.com
IN
5V
+
*1500µF
6MV1500GX
Sanyo
LX8384A
ADJ
OUT
121Ω
0.1%
218Ω
0.1%
3.5V
at 5A
+ 1500µF
5x 6MV1500GX
Sanyo
Three-Terminal Adjustable Or
Fixed Output
Guaranteed < 1.3V Headroom a
5A (LX8384A)
Guaranteed 2.0% Max.
Reference Tolerance (LX8384A)
Guaranteed 1.0% Max.
Reference Tolerance (LX8384B)
0.015% Line Regulation
0.15% Load Regulation
Pentium® Processor VRE
Application
High Efficiency Linear
Regulators
Power Regulators For Switching
Power Supplies
Battery Chargers
Constant Current Regulators
Cyrix® 6x86™
AMD-K5™
LX8384/84A/84B-00 Adjustable
LX8384/84A/84B-15
1.5V
LX8384/84A/84B-33
3.3V
Table 1 - Available Options
* Capacitors must have < 20mΩ
Total ESR for the VRE Specification
An Application of the LX8384A for the Pentium P54C Processors Meeting VRE Specification.
TA (°C)
Max Ref Max Dropout
Plastic TO-252
Accuracy Voltage DT (D-Pak) 3-Pin
P
Plastic TO-220
Plastic TO-263
3-Pin
DD 3-Pin
0 to 125
-25 to 125
2.0%
2.0%
1.0%
2.0%
1.5V
1.3V
1.3V
1.5V
LX8384-xxCDT
LX8384A-xxCDT
LX8384B-xxCDT
LX8384-xxIDT
LX8384-xxCP
LX8384A-xxCP
LX8384B-xxCP
LX8384-xxIP
LX8384-xxCDD
LX8384A-xxCDD
LX8384B-xxCDD
LX8384-xxIDD
Copyright © 2000
Rev. 2.1d, 2001-03-15
Note: Available in Tape & Reel.
Append the letter “T” to the part number. (i.e. LX8384-xxCPT)
Microsemi
Linfinity Microelectronics Division
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 1
1 page  
A MICROSEMI COMPANY
LX8384x-xx
5A Low Dropout Positive Regulators
PRODUCTION
The LX8384/84A/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
LX8384/84A/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 (<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.
!"#$ % &'
(
10µ 15µF Tantalum, 100µF Aluminum None
10µ 47µF Tantalum, 220µF Aluminum 15µF
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.
Power
S u p p ly
Minim um Load
IN LX 8384 x O U T (Larger resistor)
Full Load
ADJ
(Sm aller
resistor)
Star Ground
RDSON << RL
10m s
1 sec
FIG U R E 1 - DYNAM IC INPUT AND OUTPUT TEST
OVERLOAD RECOVERY
Like almost all IC power regulators, the LX8384/84A/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 LX8384/84A/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 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
Copyright © 2000
Rev. 2.1d, 2001-03-15
Microsemi
Linfinity Microelectronics Division
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 5
5 Page 
A MICROSEMI COMPANY
LX8384x-xx
5A Low Dropout Positive Regulators
PRODUCTION
Copyright © 2000
Rev. 2.1d, 2001-03-15
Pentium is a registered trademark of Intel Corporation. Cyrix is a registered trademark
and 6x86 is a trademark of the Cyrix Corporation. K5 is a registered trademark of AMD.
PRODUCTION DATA – Information contained in this document is proprietary to
LinFinity and is current as of publication date. This document may not be modified in any
way without the express written consent of LinFinity. Product processing does not
necessarily include testing of all parameters. LinFinity reserves the right to change the
configuration and performance of the product and to discontinue product at any time.
Microsemi
Linfinity Microelectronics Division
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 11
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