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Электронный компонент: LX8383

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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 VOLTAGE

s GUARANTEED < 1.3V HEADROOM AT
7.5A (LX8383A/8383B)

s GUARANTEED < 1.5V HEADROOM AT
7.5A (LX8383)

s OUTPUT CURRENT OF 7.5A MINIMUM
p 0.015% LINE REGULATION
p 0.15% LOAD REGULATION

s EVALUATION BOARD AVAILABLE:
REQUEST LXE9001 EVALUATION KIT
The LX8383/8383A/8383B series ICs are
positive regulators designed to provide
7.5A output current. All internal circuitry
is designed to operate down to a 1V in-
put-to-output differential, so the LX8383/
83A/83B can operate with greater effi-
ciency than previously available devices.
The dropout voltage for each product is
fully specified as a function of load cur-
rent. Dropout is guaranteed at a maxi-
mum of 1.3V
for the LX8383A/83B and
1.5V for the LX8383, at maximum output
current, decreasing at lower load currents.
Fixed versions are also available and speci-
fied in the Available Options table below.
The LX8383B offers a tighter voltage ref-
erence tolerance: 0.8% initial accuracy and
1% over line, load and temperature. The
LX8383/83A have 1% initial accuracy and
2% over line, load and temperature.
The LX8383/83A/83B series devices are
pin-compatible with earlier 3-terminal
regulators, such as the 117 series prod-
ucts. While a 10F output capacitor is
required on both input and output of these
new devices, this capacitor is generally
included in most regulator designs.
The LX8383/83A/83B series quiescent
current flows into the load, thereby
increasing efficiency. This feature
contrasts with PNP regulators, where up
to 10% of the output current is wasted as
quiescent current. The LX8383I/8383AI is
specified over the industrial temperature
range of -25C to +125C and the
LX8383C/8383AC/8383BC is specified
over the commercial range of 0C to
+125C.
7 . 5 A L
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R
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P
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A T A
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
Copyright 1996
Rev. 1.0 12/96
11861 W
ESTERN
A
VENUE
, G
ARDEN
G
ROVE
, CA. 92841
LX8383-xx/8383A-xx/8383B-xx
LIN D
O C
#: 8383
1
A P P L I C A T I O N S
s PENTIUM
PROCESSOR APPLICATIONS
s HIGH EFFICIENCY LINEAR REGULATORS
s POST REGULATORS FOR SWITCHING
POWER SUPPLIES
s BATTERY CHARGERS
s CONSTANT CURRENT REGULATORS
s CYRIX
6x86
TM
s AMD-K5
TM
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-247
3-terminal
V
1.5V
LX8383-xxCP
LX8383-xxCV
0 to 125
1.3V
LX8383A-xxCP
LX8383A-xxCV
1.3V
LX8383B-xxCP
LX8383B-xxCV
-25 to 125
1.5V
LX8383-xxIP
LX8383-xxIV
1.3V
LX8383A-xxIP
LX8383A-xxIV
Application of the LX8383A for the standard voltage (non VRE) Pentium Processor motherboard
with less than 130mV dynamic response to a 7.5A load transient.
P R O D U C T H I G H L I G H T
LX8383A
205
1%
1%
3.38V at 7.5A
V
IN
4.75V
OUT
IN
ADJ
1500F
6.3V
6MV1500GX
from Sanyo
2x 330F, 6.3V
Oscon SA type
from Sanyo
-or-
3x 1500F, 6.3V
6MV1500GX
from Sanyo
121
3.3V, 7.5A R
E G U L AT O R
Dropout
Voltage
F O R F U R T H E R I N F O R M A T I O N C A L L ( 7 1 4 ) 8 9 8 - 8 1 2 1
LX8383/83A/83B-00
Adjustable
LX8383/83A/83B-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.
"xx" refers to output voltage, please see table above.
7 . 5 A L
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LX8383-xx/8383A-xx/8383B-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 1996
Rev. 1.0 12/96
2
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H E E T
ABSOLUTE MAXIMUM RATINGS
(Note 1)
Power Dissipation .................................................................................. Internally Limited
Input Voltage ................................................................................................................ 10V
Input to Output Voltage Differential ........................................................................... 10V
Operating Junction Temperature
Plastic (P & V Packages) ....................................................................................... 150C
Storage Temperature Range ...................................................................... -65C to 150C
Lead Temperature (Soldering, 10 seconds) ............................................................. 300C
PACKAGE PIN OUTS
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
2.7C/W
THERMAL RESISTANCE-JUNCTION TO AMBIENT,




JA
60C/W
V PACKAGE:
THERMAL RESISTANCE-JUNCTION TO TAB,




JT
1.6C/W
THERMAL RESISTANCE-JUNCTION TO AMBIENT,




JA
35C/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.
THERMAL DATA
V
IN
V
OUT
ADJ / GND*
3
2
1
V PACKAGE
(Top View)
* Pin 1 is GND for fixed voltage versions.
BLOCK DIAGRAM
Thermal
Limit Circuit
Control
Circuit
Bandgap
Circuit
Output
Circuit
Bias
Circuit
V
OUT
V
IN
SOA Protection
Circuit
Current
Limit Circuit
ADJ or
GND*
TAB IS V
OUT
TAB ON REVERSE SIDE IS V
OUT
P PACKAGE
(Top View)
* Pin 1 is GND for fixed voltage versions.
* This pin GND for fixed voltage versions.
7 . 5 A L
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LX8383-xx/8383A-xx/8383B-xx
P R O D U C T D A T A B O O K 1 9 9 6 / 1 9 9 7
3
Copyright 1996
Rev. 1.0 12/96
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Reference Voltage
LX8383/83A-00
V
REF
I
OUT
= 10mA, T
A
= 25C
(Note 4)
10mA
I
OUT
I
OUT (MAX)
, 1.5V
(V
IN
- V
OUT
), V
IN
10V, P
P
MAX
LX8383B-00
I
OUT
= 10mA, T
A
= 25C
10mA
I
OUT
I
OUT (MAX)
, 1.5V
(V
IN
- V
OUT
), V
IN
10V, P
P
MAX
Line Regulation (Note 2)
V
REF
1.5V
(V
IN
- V
OUT
), V
IN
7V
(V
IN
)
1.5V
(V
IN
- V
OUT
), V
IN
10V
Load Regulation (Note 2)
V
REF
V
OUT
V
REF
, V
IN
- V
OUT
= 3V, 10mA
I
OUT
7.5A, T
A
= 25C
(I
OUT
)
V
IN
- V
OUT
= 3V, 10mA
I
OUT
7.5A
Thermal Regulation
V
OUT
(Pwr)
T
A
= 25C, 20ms pulse
Ripple Rejection (Note 3)
V
OUT
= 5V, f =120Hz, C
OUT
= 100f Tantalum, V
IN
= 6.5V
C
ADJ
= 10F, I
OUT
= 7.5A
Adjust Pin Current
I
ADJ
Adjust Pin Current Change (Note 4)
I
ADJ
10mA
I
OUT
I
OUT (MAX)
, 1.5V
(V
IN
- V
OUT
), V
IN
10V
Dropout Voltage
LX8383-00
V
V
REF
= 1%, I
OUT
= 7.5A
LX8383A/83B-00
V
REF
= 1%, I
OUT
= 7.5A
Minimum Load Current
I
OUT (MIN)
V
IN
10V
Maximum Output Current
I
OUT (MAX)
(V
IN
- V
OUT
)
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
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
(Unless otherwise specified, these specifications apply over the operating ambient temperatures for the LX8383-xxC/8383A-xxC/8383B-xxC with 0C
T
A
125C, the LX8383-xxI/8383A-xxI with -25C
T
A
125C; V
IN
- V
OUT
= 3V; I
OUT
= 7.5A. Low duty cycle pulse testing techniques are used which
maintains junction and case temperatures equal to the ambient temperature.)
Parameter
Symbol
Test Conditions
Units
LX8383/83A/83B-00
Min.
Typ.
Max.
1.238
1.250
1.262
V
1.225
1.250
1.270
V
1.240
1.250
1.260
V
1.238
1.250
1.262
V
0.015
0.2
%
0.035
0.3
%
0.15
0.4
%
0.3
0.5
%
0.01
0.02
%/W
65
83
dB
55
100
A
0.2
5
A
1.2
1.5
V
1
1.3
V
2
10
mA
7.5
9.5
A
0.25
%
0.3
1
%
0.003
%
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.
Note 4. See Maximum Output Current Section above.
Parameter
Symbol
Test Conditions
Units
LX8383/83A/83B-33
Min.
Typ.
Max.
Output Voltage
LX8383/83A-33
V
OUT
V
IN
= 5V, I
OUT
= 0mA, T
A
= 25C
(Note 4)
4.75V
V
IN
10V, 0mA
I
OUT
7.5A, P
P
MAX
LX8383B-33
V
IN
= 5V, I
OUT
= 0mA, T
A
= 25C
4.75V
V
IN
10V, 0mA
I
OUT
7.5A, 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
V
OUT
(Pwr)
T
A
= 25C, 20ms pulse
Ripple Rejection (Note 3)
C
OUT
= 100F (Tantalum), I
OUT
= 7.5A
Quiescent Current
I
Q
0mA
I
OUT
I
OUT (MAX)
, 4.75V
V
IN
10V
Dropout Voltage
LX8383-33
V
V
OUT
= 1%, I
OUT
I
OUT (MAX)
, V
IN
7V
LX8383A/83B-33
V
OUT
= 1%, I
OUT
I
OUT (MAX)
, V
IN
7V
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
3.274
3.3
3.326
V
3.267
3.3
3.333
V
1
6
mV
2
10
mV
5
15
mV
0.01
0.02
% / W
60
83
dB
4
10
mA
1.5
V
1.3
V
7.5
9.5
A
0.25
1
%
0.3
%
0.003
%
LX8383-00/83A-00/83B-00 (Adjustable)
LX8383-33/83A-33/83B-33 (3.3V Fixed)
7 . 5 A L
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LX8383-xx/8383A-xx/8383B-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 1996
Rev. 1.0 12/96
4
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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 LX8383/83A/83B 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 LX8383/83A/
83B 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
LX8383/83A
/83B
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 LX8383/83A/83B 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 LX8383/83A/83B 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.
7 . 5 A L
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LX8383-xx/8383A-xx/8383B-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 1996
Rev. 1.0 12/96
P
R O D U C T I O N
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H E E T
A P P L I C A T I O N N O T E S
FIGURE 2 -- BASIC ADJUSTABLE REGULATOR
R2+R1
R1
LX8383/83A/83B
OUT
IN
ADJ
V
OUT
V
IN
R1
R2
V
REF
I
ADJ
50A
V
OUT
= V
REF
1 + + I
ADJ
R2
R2
R1
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 R1 at the ripple frequency. The
capacitor value can be determined by using this equation:
C = 1 / (6.28 * F
R
* R1)
where: C
the value of the capacitor in Farads;
select an equal or larger standard value.
F
R
the ripple frequency in Hz
R1
the value of resistor R1 in ohms
At a ripple frequency of 120Hz, with R1 = 100
:
C = 1 / (6.28 * 120Hz * 100
) = 13.3F
The closest equal or larger standard value should be used, in this
case, 15F.
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:
M = V
OUT
/V
REF
where: M
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 LX8383/83A/83B 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 R1, it represents a small error and can usually be ignored.
LOAD REGULATION
Because the LX8383/83A/83B 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 R1
were connected to the load, the effective resistance between the
regulator and the load would be:
R
Peff
= R
P
*
where: R
P
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
.
LX8383/83A/83B
OUT
IN
ADJ
V
IN
R1
R2
R
L
R
P
Parasitic
Line Resistance
Connect
R1 to Case
of Regulator
Connect
R2
to Load
FIGURE 3 -- CONNECTIONS FOR BEST LOAD REGULATION