LX8385-33CP Microsemi Analog Mixed Signal Group, LX8385-33CP Datasheet - Page 7
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LX8385-33CP
Manufacturer Part Number
LX8385-33CP
Description
IC REG LDO POS 3A 3.3V TO220
Manufacturer
Microsemi Analog Mixed Signal Group
Datasheet
1.LX8385-00CP.pdf
(11 pages)
Specifications of LX8385-33CP
Regulator Topology
Positive Fixed
Voltage - Output
3.3V
Voltage - Input
Up to 10V
Voltage - Dropout (typical)
1.2V @ 3A
Number Of Regulators
1
Current - Output
3A (Min)
Operating Temperature
0°C ~ 125°C
Mounting Type
Through Hole
Package / Case
TO-220-3
Lead Free Status / RoHS Status
Lead free / RoHS Compliant
Current - Limit (min)
-
Available stocks
Company
Part Number
Manufacturer
Quantity
Price
Company:
Part Number:
LX8385-33CP
Manufacturer:
LINFINITY
Quantity:
2 550
Copyright © 2000
Rev. 2.0b, 2005-10-25
LOAD REGULATION (continued)
resistance can be a significant source of error. A 20 mil. wide PC
trace built from 1 oz. copper-clad circuit board material has a
parasitic resistance of about 25 milliohms per inch of its length at
room temperature. If a 3-terminal regulator used to supply 2.50
volts is connected by 2 inches of this trace to a load which draws
1.5 amps of current, a 75 millivolt drop will appear between the
regulator and the load. Even when the regulator output voltage is
precisely 2.50 volts, the load will only see 2.43 volts, which is a
3% 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.
should be located near the regulator package. If several capacitors
are used in parallel to construct the power system output
capacitance, 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.
on the input side of the regulator, especially between the input
capacitors and the regulator. Input capacitor ESR must be small
enough that the voltage at the input pin does not drop below
V
THERMAL CONSIDERATIONS
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 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 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.
IN(MIN)
where: V
The LX8385/85A/85B regulators have internal power and
Even when the circuit is configured optimally, parasitic
The minimum specified output capacitance for the regulator
To maintain good load regulation, wide traces should be used
Junction-to-case thermal resistance is specified from the IC
TM
during transients.
V
V
OUT
DROPOUT(MAX)
IN(MIN)
V
ΙΝ(ΜΙΝ)
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
=
≡ the lowest allowable instantaneous
≡ the designed output voltage for the
≡ the specified dropout voltage for the
V
voltage at the input pin.
power supply system.
installed regulator.
OUT
+
V
DROPOUT(MA
A P P L I C A T I O N N O T E S
X)
Integrated Products Division
Microsemi Inc.
®
have R
12°C/W.
fication using the selected heat sink:
term reliability to keep the junction temperature below 125°C whenever possible.
Example
heat sink:
** Although the device can operate up to 150°C junction, it is recommended for long
T
3A Low Dropout Positive Regulators
R
Next, select a suitable heat sink. The selected heat sink must
Finally, verify that junction temperature remains within speci-
J
Given:
Find:
Solution: The junction temperature is:
where: P
First, find the maximum allowable thermal resistance of the
P
θSA
=
D
( C O N T I N U E D )
θSA
3.75W(2.7
=
=
(V
(5.0V
< 3.1°C/W. Thermalloy heatsink 6230B has R
R
R
R
T
IN(MAX)
V
V
I
T
R
Proper Heat Sink to keep IC’s junction temperature
below 125°C.**
D
S
θJT
θCS
θSA
OUT
P
A
T
θJT
125
IN
OUT
RODUCTION
R
J
=
θ
T
−
SA
°
−
J
=
=
=
=
=
P
≡
≡
≡
≡
≡
2.5V)
C
°
R
D
V
C/W
=
−
R
(R
θ
OUT
JT
T
50
θSA
P
J
5V
2.5V
1.5A
50°C
2.7°C/W for TO-220
Dissipated power.
Thermal resistance from the junction to
the mounting tab of the package.
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).
Thermal resistance from the mounting
surface to ambient (thermal resistance
of the heat sink).
Heat Sink Temperature.
θJT
T
P
D
T
I )
−
*
°
+
C
D
J
1.5A
=
C
+
=
T
R
OUT
1.0
=
D
16
A
R
3.75W
θ
109
ATA
CS
−
θCS
3 .
°
=
T
C/W
(
−
°
R
(
S
+
C/W
5.0V
°
(2.7
S
θJT
C
R
R
HEET
θ
θSA
+
SA
+
°
T
C/W
12.0
R
−
)
A
θ
2.5V
+
CS
T
)
°
LX8385x-xx
+
A
C/W)
1.0
)
×
1.5A
°
C/W)
+
θSA
50
°
=
Page 7
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