LX8584-00CP [MICROSEMI]
7 A LOW DROPOUT POSITIVE REGULATORS; 7低压差稳压器正
| 型号： | LX8584-00CP |
| 厂家： | 
Microsemi |
| 描述： | 7 A LOW DROPOUT POSITIVE REGULATORS |
| 文件： | 总7页 (文件大小：208K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
LIN DOC #: 8584
LX8584-xx/8584A-xx/8584B-xx
7 A L O W
D
R O P O U T
P
O S I T I V E
R
E G U L A T O R S
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
P R O D U C T I O N D A T A S H E E T
DESCRIPTION
KEY FEATURES
■ THREE-TERMINAL ADJUSTABLE OR FIXED
The LX8584/84A/84B series ICs are low drop-
out three-terminal positive regulators with a
nominal 7A output current. This product
family is ideally suited for Pentium® Proces-
sor and Power PCTM applications requiring
fast transient response. The LX8584A isguar-
anteed 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 of-
fers ±1% maximum voltage reference ac-
curacy 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 con-
trolled short-circuit current. On-chip ther-
mal limiting provides protection against any
combination of overload that would create
excessive junction temperatures.
The LX8584/84A series products are avail-
able in both the through-hole versions of
the industry standard 3-pin TO-220 and
TO-247 power packages.
The LX1431 Programmable Reference in
conjunction with the LX8584 7A LDO prod-
ucts offer precision output voltage (see ap-
plication below) and are ideal for use in VRE
applications.
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
p FAST TRANSIENT RESPONSE
p 1% VOLTAGE REFERENCE INITIAL
ACCURACY
p OUTPUT SHORT CIRCUIT PROTECTION
p BUILT-IN THERMAL SHUTDOWN
■ EVALUATION BOARD AVAILABLE:
REQUEST LXE9001 EVALUATION KIT
PRODUCT HIGHLIGHT
APPLICATIONS
■ PENTIUM PROCESSOR SUPPLIES
■ POWER PC SUPPLIES
■ MICROPROCESSOR SUPPLIES
■ LOW VOLTAGE LOGIC SUPPLIES
■ POST REGULATOR FOR SWITCHING SUPPLY
THE APPLICATION OF THE LX8584A & LX1431 IN A
75 & 166MHZ P54C PROCESSORS USING 3.3V CACHE
VO 7A
(See Table Below)
PLACE IN µP SOCKET CAVITY
3
2
VIN
VOUT
LX8584A
5V
3x
330µF, 6.3V
1kW
Low ESR
Oscon Type
from Sanyo
ADJ
1
0.01µF
1kW
DROPOUT VOLTAGE V S.
OUTPUT CURRENT
100µF x 6
10V
AVX TYPE
TPS
250pF
2
1
COL
1.5
1.0
0.5
1k
0.1%
µP
Load
TJ = 125°C
LX8584/84A
3
8
V+
220µF
10V
Low ESR
from
Sanyo
REF
2.84kW
0.1%
21k
1%
LX1431
1µF x 10
SMD
0.1µF
50V
LX8584
JP1
SGND FGND
5
6
LX8584A
VOUT
JP1
TYPICAL APPLICATION
3.50
3.38
Short
Open
120/166MHz, VRE, 3.3V Cache
75/90/100/133MHz, STND, 3.3V Cache
Thick traces represent high current traces which must be low resistance /
low inductance in order to achieve good transient response.
0
1.75
3.5
5.25
7
Output Current - (A)
PACKAGE ORDER INFORMATION
AVAILABLE OPTIONS PER PART #
Plastic TO-220
3-pin
Plastic TO-247
3-terminal
Dropout
Voltage
TA (°C)
Part #
LX8584/A/B-00
Output Voltage
Adjustable
3.3V
P
V
LX8584-xxCP
LX8584B-xxCP
LX8584A-xxCP
LX8584-xxCV
LX8584B-xxCV
LX8584A-xxCV
1.4V
1.2V
LX8584/A/B-33
Other voltage options may be available —
Please contact factory for details.
0 to 125
"xx" refers to output voltage, please see table above.
F O R F U R T H E R I N F O R M AT I O N C A L L ( 7 1 4 ) 8 9 8 - 8 1 2 1
Copyright © 1997
Rev. 1.2 4/97
1
11861 WESTERN AVENUE, GARDEN GROVE, CA. 92841
P R O D U C T D A T A B O O K 1 9 9 6 / 1 9 9 7
LX8584-xx/8584A-xx/8584B-xx
7 A L O W
D
R O P O U T
P
O S I T I V E
R
E G U L AT O R S
P R O D U C T I O N D A T A S H E E T
ABSOLUTE MAXIMUM RATINGS (Note 1)
PACKAGE PIN OUTS
Power Dissipation .................................................................................. Internally Limited
Input Voltage................................................................................................................ 10V
Input to Output Voltage Differential........................................................................... 10V
Maximum Output Current ............................................................................................. 8A
Operating Junction Temperature
TAB IS VOUT
3
VIN
2
1
VOUT
ADJ / GND*
Plastic (P Package) ................................................................................................ 150°C
Storage Temperature Range ...................................................................... -65°C to 150°C
Lead Temperature (Soldering, 10 seconds) ............................................................. 300°C
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.
TAB ON REVERSE SIDE IS VOUT
3
2
1
VIN
THERMAL DATA
VOUT
ADJ / GND*
P PACKAGE:
THERMAL RESISTANCE-JUNCTION TO TAB, θJT
THERMAL RESISTANCE-JUNCTION TO AMBIENT, θJA
V PACKAGE:
2.7°C/W
60°C/W
V PACKAGE
(Top View)
* Pin 1 is GND for fixed voltage versions.
THERMAL RESISTANCE-JUNCTION TO TAB, θJT
THERMAL RESISTANCE-JUNCTION TO AMBIENT, θJA
1.6°C/W
35°C/W
Junction Temperature Calculation: TJ = TA + (PD x θJA).
The θJA numbers are guidelines for the thermal performance of the device/pc-board system.
All of the above assume no ambient airflow.
Copyright © 1997
Rev. 1.2 4/97
2
P R O D U C T D A T A B O O K 1 9 9 6 / 1 9 9 7
LX8584-xx/8584A-xx/8584B-xx
7 A L O W
D
R O P O U T
P
O S I T I V E
R
E G U L A T O R S
P R O D U C T I O N D A T A S H E E T
ELECTRICAL CHARACTERISTICS
(Unless otherwise specified, these specifications apply over the operating ambient temperatures for the LX8584-xxC/84A-xxC/84B-xxC with 0°C ≤ TA ≤ 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.)
LX8584-00/84A-00/84B-00 (Adjustable)
LX8584/84A/84B-00
Parameter
Symbol
Test Conditions
Units
Min. Typ.
Max.
1.238 1.250 1.263
1.225 1.250 1.275
1.240 1.250 1.260
1.238 1.250 1.263
V
V
Reference Voltage
LX8584/84A-00
LX8584B-00
VREF
IOUT = 10mA, TA = 25°C
10mA ≤ IOUT ≤ 7A, 1.5V ≤ (V - VOUT), VIN ≤ 7V, P ≤ PMAX
IOUT = 10mA, TA = 25°C
IN
V
V
10mA ≤ IOUT ≤ 7A, 1.5V ≤ (V - VOUT), VIN ≤ 7V, P ≤ PMAX
IN
Line Regulation (Note 2)
Load Regulation (Note 2)
Thermal Regulation
∆VREF (VIN) IOUT = 10mA, 1.5V ≤ (VIN - VOUT), VIN ≤ 7V
VIN - VOUT = 3V, 10mA ≤ IOUT ≤ 7A
∆VOUT(Pwr) TA = 25°C, 20ms pulse
VOUT = 3.3V, f =120Hz, COUT = 100µf Tantalum, VIN = 5V
0.035
0.1
0.2
0.5
%
%
%/W
dB
∆VREF (IOUT
)
0.01
83
0.02
Ripple Rejection (Note 3)
65
CADJ = 10µF, IOUT = 7A
Adjust Pin Current
Adjust Pin Current Change
IADJ
∆IADJ
∆V
55
0.2
1.1
1.2
1.1
2
100
5
µA
µA
V
10mA ≤ IOUT ≤ 7A, 1.5V ≤ (V - VOUT), VIN ≤ 7V
IN
Dropout Voltage
LX8584A
∆VREF = 1%, IOUT = 7A
∆VREF = 1%, IOUT = 7A
∆VREF = 1%, IOUT = 6A
1.2
1.4
1.3
10
LX8584/84B
LX8584/84B
V
V
Minimum Load Current
Maximum Output Current
Temperature Stability
IOUT(MIN) VIN ≤ 7V
IOUT (MAX) 1.4V ≤ (VIN - VOUT), VIN ≤ 7V
∆VOUT (T)
mA
A
7
8
0.25
0.3
0.003
%
%
%
Long Term Stability
∆VOUT (t) TA = 125°C, 1000 hrs
VOUT (RMS) TA = 25°C, 10Hz ≤ f ≤ 10kHz
1
RMS Output Noise (% of VOUT
)
LX8584-33/84A-33/84B-33 (3.3V Fixed)
LX8584/84A/84B-33
Parameter
Symbol
Test Conditions
Units
Min. Typ.
Max.
3.267
3.234
3.274
3.267
3.30
3.30
3.30
3.30
1
3.333
3.366
3.326
3.333
6
V
V
V
Output Voltage
LX8584/84A-33
LX8584B-33
VOUT
VIN = 5V, IOUT = 0mA, TA = 25°C
4.75V ≤ VIN ≤ 10V, 0mA ≤ IOUT ≤ 7A, P ≤ PMAX
VIN = 5V, IOUT = 0mA, TA = 25°C
4.75V ≤ VIN ≤ 10V, 0mA ≤ IOUT ≤ 7A, P ≤ PMAX
V
Line Regulation (Note 2)
∆VOUT
4.75V ≤ VIN ≤ 10V
VIN = 5V, 0mA ≤ IOUT ≤ IOUT (MAX)
∆VOUT(Pwr) TA = 25°C, 20ms pulse
COUT = 100µF (Tantalum), IOUT = 7.5V
4.75V ≤ VIN ≤ 7V
mV
mV
mV
% / W
dB
mA
V
(VIN)
2
10
Load Regulation (Note 2)
Thermal Regulation
∆VOUT (IOUT
)
5
0.01
83
15
0.02
Ripple Rejection (Note 3)
Quiescent Current
60
7
IQ
0mA ≤ IOUT ≤ IOUT (MAX) , 4.75V ≤ VIN ≤ 10V
∆VOUT = 1%, IOUT = IOUT (MAX)
∆VOUT = 1%, IOUT = IOUT (MAX)
4
10
1.4
1.2
1.4
Dropout Voltage
LX8584-xx
LX8584A-xx
LX8584B-xx
∆V
V
V
∆VOUT = 1%, IOUT = IOUT (MAX)
`
8
A
Maximum Output Current
IOUT (MAX)
VIN ≤ 7V
0.25
0.3
%
%
Temperature Stability (Note 3)
Long Term Stability (Note 3)
∆VOUT (T)
1
∆VOUT (t) TA = 125°C, 1000 hours
0.003
%
RMS Output Noise (% of VOUT) (Note 3) VOUT (RMS) TA = 25°C, 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.
Copyright © 1997
Rev. 1.2 4/97
3
P R O D U C T D A T A B O O K 1 9 9 6 / 1 9 9 7
LX8584-xx/8584A-xx/8584B-xx
7 A L O W
D
R O P O U T
P
O S I T I V E
R
E G U L AT O R S
P R O D U C T I O N D A T A S H E E T
APPLICATION NOTES
Minumum Load
(Larger resistor)
TheLX8584/84A/84BseriesICsareeasytouseLow-Dropout(LDO)
Power Supply
LX8584/84A
/84B
ADJ
IN
OUT
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.
Full Load
(Smaller resistor)
RDSON << RL
1 sec
10ms
Star Ground
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.
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 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 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.
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 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
pinbypassingisused,therequiredoutputcapacitorvalueincreases.
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.
Thetablebelowshowsrecommendedminimumcapacitancevalues
for stable operation.
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
casewheretheregulatorissupplyingregulatedvoltagetoaresistive
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
throughtheregulatortodevelopthedesignedoutputvoltageacross
theloadresistance. Iftheoutputresistorisshort-circuitedtoground,
theinput-to-outputvoltagedifferenceacrosstheregulatorsuddenly
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
permittheregulatortosupplytoitsoutputterminal. Whentheshort
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
bytheSOAcircuit,basedonthelargeinput-to-outputvoltageacross
theregulatoratthetimetheshortcircuitisremovedfromtheoutput.
RECOMMENDED CAPACITOR VALUES
INPUT
OUTPUT
ADJ
None
15µF
10µF
10µF
15µF Tantalum, 100µF Aluminum
47µF Tantalum, 220µF Aluminum
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.
ThecircuitshowninFigure1canbeusedtoobservethetransient
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.
Copyright © 1997
Rev. 1.2 4/97
4
P R O D U C T D A T A B O O K 1 9 9 6 / 1 9 9 7
LX8584-xx/8584A-xx/8584B-xx
7 A L O W
D
R O P O U T
P
O S I T I V E
R
E G U L A T O R S
P R O D U C T I O N D A T A S H E E T
APPLICATION NOTES
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 willnever 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.
LX8584/84A/84B
IN
OUT
VIN
VOUT
ADJ
VREF
R1
R2
IADJ
50µA
RIPPLE REJECTION
R2
R1
VOUT = VREF 1 +
+ IADJ R2
Ripple rejection can be improved by connecting a capacitor
betweentheADJpinandground. Thevalueofthecapacitorshould
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:
FIGURE 2 — BASIC ADJUSTABLE REGULATOR
LOAD REGULATION
C = 1 / (6.28 F R1)
*
*
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 R1
were connected to the load, the effective resistance between the
regulator and the load would be:
R
where: C ≡ the value of the capacitor in Farads;
select an equal or larger standard value.
FR ≡ the ripple frequency in Hz
R1 ≡ the value of resistor R1 in ohms
At a ripple frequency of 120Hz, with R1 = 100Ω:
C = 1 / (6.28 120Hz 100Ω) = 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:
R2+R1
R1
RPeff = RP
*
where: RP ≡ Actual parasitic line resistance.
M = VOUT/VREF
When the circuit is connected as shown in Figure 3, the parasitic
resistance appears as its actual value, rather than the higher RPeff.
where: M ≡ a multiplier for the ripple seen when the
ADJ pin is optimally bypassed.
VREF = 1.25V.
R
ParaPsitic
LX8584/84A/84B
IN
Line Resistance
For example, if VOUT = 2.5V the output ripple will be:
M = 2.5V/1.25V= 2
OUT
VIN
ADJ
Connect
R1 to Case
of Regulator
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.
R1
R2
RL
OUTPUT VOLTAGE
Connect
R2
The LX8584/84A/84BICs 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.
BecauseIADJisverysmallandconstantwhencomparedwiththecurrent
through R1, it represents a small error and can usually be ignored.
to Load
FIGURE 3 — CONNECTIONS FOR BEST LOAD REGULATION
Copyright © 1997
Rev. 1.2 4/97
5
P R O D U C T D A T A B O O K 1 9 9 6 / 1 9 9 7
LX8584-xx/8584A-xx/8584B-xx
7 A L O W
D
R O P O U T
P
O S I T I V E
R
E G U L AT O R S
P R O D U C T I O N D A T A S H E E T
APPLICATION NOTES
LOAD REGULATION (continued)
Even when the circuit is optimally configured, parasitic resistance
can be a significant source of error. A 100 mil (2.54 mm) wide PC
trace built from 1 oz. copper-clad circuit board material has a
parasitic resistance of about 5 milliohms per inch of its length at
roomtemperature. Ifa3-terminalregulatorusedtosupply2.50volts
is connected by 2 inches of this trace to a load which draws 5 amps
of current, a50 millivolt dropwill appearbetween theregulatorand
the load. Even when the regulator output voltage is precisely
2.50 volts, the load will only see 2.45 volts, which is a 2% error. It
is important to keep the connection between the regulator output
pin and the load as short as possible, and to use wide traces or
heavy-gauge wire.
can be used, as long as its added contribution to thermal resistance
is considered. Note that the case of all devices in this series is
electrically connected to the output.
Example
Given: VIN = 5V
VOUT = 2.8V, IOUT = 5.0A
Ambient Temp., TA = 50°C
RθJT = 2.7°C/W for TO-220
300 ft/min airflow available
Find: Proper Heat Sink to keep IC's junction
temperature below 125°C.**
The minimum specified output capacitance for the regulator
should be located near the reglator package. If several capacitors
are used in parallel to construct the power system output capaci-
tance, any capacitors beyond the minimum needed to meet the
specified requirements of the regulator should be located near the
sections of the load that require rapidly-changing amounts of
current. Placing capacitors near the sources of load transients will
help ensure that power system transient response is not impaired
by the effects of trace impedance.
To maintain good load regulation, wide traces should be used on
the input side of the regulator, especially between the input
capacitors and the regulator. Input capacitor ESR must be small
enoughthatthevoltageattheinputpindoesnotdropbelowVIN(MIN)
during transients.
Solution: The junction temperature is:
TJ = PD (RθJT + RθCS + RθSA) + TA
where: PD ≡ Dissipated power.
RθJT ≡ Thermal resistance from the junction to the
mounting tab of the package.
RθCS ≡ Thermal resistance through the interface
between the IC and the surface on which
it is mounted. (1.0°C/W at 6 in-lbs
mounting screw torque.)
RθSA
≡
Thermal resistance from the mounting surface
to ambient (thermal resistance of the heat sink).
TS ≡ Heat sink temperature.
TJ TC TS
TA
VIN (MIN) = VOUT + VDROPOUT (MAX)
Rq JT
RqCS
RqSA
where: VIN (MIN)
VOUT
≡ the lowest allowable instantaneous
voltage at the input pin.
≡ the designed output voltage for the
power supply system.
First, find the maximum allowable thermal resistance of the
heat sink:
TJ - TA
RθSA
=
- (RθJT + RθCS)
PD
VDROPOUT (MAX) ≡ the specified dropout voltage
for the installed regulator.
PD = (VIN(MAX) - VOUT) IOUT = (5.0V-2.8V) 5.0A
*
= 11.0W
THERMAL CONSIDERATIONS
125°C - 50°C
RθSA
=
- (2.7°C/W + 1.0°C/W)
The LX8584/84A/84B regulators have internal power and thermal
limiting circuitry designed to protect each device under overload
conditions. For continuous normal load conditions, however,
maximum junction temperature ratings must not be exceeded. It is
important to give careful consideration to all sources of thermal
resistance from junction to ambient. This includes junction to case,
case to heat sink interface, and heat sink thermal resistance itself.
Junction-to-case thermal resistance is specified from the IC
junction to the back surface of the case directly opposite the die.
This is the lowest resistance path for heat flow. Proper mounting
is required to ensure the best possible thermal flow from this area
of the package to the heat sink. Thermal compound at the case-to-
heat-sink interface is strongly recommended. If the case of the
device must be electrically isolated, a thermally conductive spacer
(5.0V-2.8V) 5.0A
*
= 3.1°C/W
Next,selectasuitableheatsink. Theselectedheatsinkmusthave
RθSA≤ 3.1°C/W. Thermalloyheatsink6296BhasRθSA =3.0°C/Wwith
300ft/min air flow.
Finally, verify that junction temperature remains within speci-
fication using the selected heat sink:
TJ = 11W (2.7°C/W + 1.0°C/W + 3.0°C/W) + 50°C = 124°C
** Although the device can operate up to 150°C junction, it is recom-
mended for long term reliability to keep the junction temperature
below 125°C whenever possible.
Copyright © 1997
Rev. 1.2 4/97
6
P R O D U C T D A T A B O O K 1 9 9 6 / 1 9 9 7
LX8584-xx/8584A-xx/8584B-xx
7 A L O W
D
R O P O U T
P
O S I T I V E
R
E G U L A T O R S
P R O D U C T I O N D A T A S H E E T
TYPICAL APPLICATIONS
LX8584/84A/84B
OUT
LX8584/84A/84B
OUT
VIN
(Note A)
(Note A)
VIN
IN
VOUT**
5V
VOUT
IN
ADJ
R1
121W
R1
121W
1%
ADJ
10µF
C2
100µF
C1*
10µF
150µF
R2
1k
R2
C1
10µF*
* C1 improves ripple rejection.
XC should be » R1 at ripple
frequency.
365W
1%
* Needed if device is far from filter capacitors.
R2
R1
**VOUT = 1.25V 1 +
FIGURE 4 — IMPROVING RIPPLE REJECTION
FIGURE 5 — 1.2V - 8V ADJUSTABLE REGULATOR
LX8584/84A/84B
VIN
(Note A)
OUT
IN
5V
ADJ
121W
1%
100µF
10µF
1k
TTL
Output
2N3904
365W
1%
1k
FIGURE 6 — 5V REGULATOR WITH SHUTDOWN
LX8584/84A/84B-33
VIN
OUT
IN
3.3V
GND
10µF Tantalum
or 100µF Aluminum
Min. 15µF Tantalum or
100µF Aluminum capacitor.
May be increased without
limit. ESR must be less
than 50mW.
FIGURE 7 — FIXED 3.3V OUTPUT REGULATOR
Note A: VIN (MIN) = (Intended VOUT) + (VDROPOUT (MAX)
)
Pentium is a registered trademark of Intel Corporation.
Power PC is a trademark of International Business Machines Corporation..
Copyright © 1997
Rev. 1.2 4/97
7
相关型号：
©2020 ICPDF网 联系我们和版权申明