LX8385x-xx
TM
®
3A Low Dropout Positive Regulators
P
RODUCTION
D
ATA
S
HEET
DESCRIPTION
The LX8385/85A/85B Series ICs are
positive regulators designed to provide 3A
output current. These regulators yield
higher efficiency than currently available
devices with all internal circuitry designed
to operate down to a 1V input-to-output
differential. In each of these products, the
dropout voltage is fully specified as a
function of load current. Dropout is
guaranteed at a maximum of 1.3V
(8385A/B) and 1.5V (8385) at maximum
output current, decreasing at lower load
currents.
In addition, on-chip trimming adjusts the
reference voltage tolerance to 1% maximum
at room temperature and 2% maximum over
the 0 to 125°C range for the LX8385A. The
LX8385B offers 0.8% tolerance at room
temperature and 1.0% maximum over line,
load and temperature. Fixed versions are
also available and specified in the Available
Options table below.
The LX8385/85A/85B Series devices are
pin-compatible with earlier 3-terminal
regulators, such as the 117 series products,
but they do require input and output
capacitors. A minimum 10µF capacitor is
required on the input and a 15µF or greater
on the output of these new devices for
stability. Although, these capacitors are
generally included in most regulator designs.
The LX8385/85A/85B 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 LX8385-xxI is specified over the
industrial temperature range of -25°C to
125°C, while the LX8385-xxC / 85A-xxC /
85B-xxC is specified over the commercial
range of 0°C to 125°C.
KEY FEATURES
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IMPORTANT:
For the most current data, consult
MICROSEMI’s
website:
http://www.microsemi.com
PRODUCT HIGHLIGHT
IN
5V
+
bs
121
Ω
1%
LX8385A
ADJ
*1500µF
6MV1500GX
Sanyo
ol
et
OUT
3.3V
at 3A
+
1500µF
2x 6MV1500GX
Sanyo
200
Ω
1%
O
T
A
(°C)
PACKAGE ORDER INFO
Plastic TO-220
Plastic TO-252
Max Ref Max Dropout
DT
(D-Pak) 3-Pin
P
3-Pin
Accuracy
Voltage
RoHS Compliant
RoHS Compliant
Transition DC: 0532
Transition DC: 0543
e
PART #
LX8385/85A/85B-00
LX8385/85A/85B-33
LX8385/85A/85B-05
Three-Terminal Adjustable Or
Fixed Output
Guaranteed 1% Voltage
Reference Accuracy Over Line,
Load, And Temperature
(LX8385B)
Guaranteed < 1.5V Headroom At
3A (LX8385)
Guaranteed < 1.3V Headroom At
3A (LX8385A/8385B)
0.015% Line Regulation
0.15% Load Regulation
APPLICATIONS
High Efficiency Linear
Regulators
Post Regulators For Switching
Power Supplies
Battery Chargers
Constant Current Regulators
Graphics & Standard Supplies
Processor I/O Supply
Low Voltage Memory & Chipset
Supplies
OUTPUT
VOLTAGE
Adjustable
3.3V
5.0V
Table 1
- Available Options
LX8385
X
LX8385
X
DD
Plastic TO-263
3-Pin
RoHS Compliant
Transition DC: 0535
0 to 125
-25 to 125
2.0%
2.0%
1.0%
2.0%
1.5V
1.3V
1.3V
1.5V
LX8385-xxCDT
LX8385A-xxCDT
LX8385B-xxCDT
LX8385-xxIDT
LX8385-xxCP
LX8385A-xxCP
LX8385B-xxCP
LX8385-xxIP
LX8385-xxCDD
LX8385A-xxCDD
LX8385B-xxCDD
LX8385-xxIDD
Note: Available in Tape & Reel. Append the letters “TR” to the part number. (i.e. LX8385-xxCP-TR)
Copyright
©
2000
Rev. 2.0b, 2005-10-25
Microsemi Inc.
Integrated Products Division
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 1
LX8385x-xx
TM
®
3A Low Dropout Positive Regulators
P
RODUCTION
D
ATA
S
HEET
ABSOLUTE MAXIMUM RATINGS
(NOTE 1)
Power Dissipation ................................................................................... Internally Limited
Input Voltage ................................................................................................................ 10V
Input to Output Voltage Differential............................................................................. 10V
Operating Junction Temperature................................................................................ 150°C
Storage Temperature Range....................................................................... -65°C to 150 °C
Peak Package Solder Reflow Temp (40 seconds max. exposure) .................260°C (+0, -5)
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 specified terminal.
PACKAGE PIN OUT
TAB is V
OUT
3
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Microsemi
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OM
V
IN
V
OUT
ADJ /
GND*
2
1
DD P
ACKAGE
(3-
PIN
)
(Top View)
ol
et
1
THERMAL DATA
DD
Plastic TO-263 3-Pin
THERMAL RESISTANCE
-
JUNCTION TO
A
MBIENT
,
θ
JA
THERMAL RESISTANCE
-
JUNCTION TO
T
AB
,
θ
JT
Plastic TO-220 3-Pin
THERMAL RESISTANCE
-
JUNCTION TO
A
MBIENT
,
θ
JA
THERMAL RESISTANCE
-
JUNCTION TO
T
AB
,
θ
JT
60°C/W
2.7°C/W
60°C/W
2.7°C/W
60°C/W
2.7°C/W
P
e
TAB is V
OUT
3
2
V
IN
V
OUT
ADJ/
GND*
DT P
ACKAGE
(3-
PIN
)
(Top View)
TAB is V
OUT
3
V
IN
V
OUT
ADJ /
GND*
2
1
DT
Plastic TO-252 3-Pin
THERMAL RESISTANCE
-
JUNCTION TO
A
MBIENT
,
θ
JA
THERMAL RESISTANCE
-
JUNCTION TO
T
AB
,
θ
JT
P P
ACKAGE
(3-
PIN
)
(Top View)
*Pin
1 is GND for fixed voltage versions
RoHS 100% Matte Tin Lead Finish
V
IN
O
Bias Circuit
bs
Therm al
Lim it Circuit
Bandgap
Circuit
Junction Temperature Calculation: T
J
= T
A
+ (P
D
x
θ
JT
).
The
θ
JA
&
θ
JT
numbers are guidelines for the thermal performance of the device/pc-board
system. All of the above assume no ambient airflow.
BLOCK DIAGRAM
Control
Circuit
Output
Circuit
SOA
Protection
Circuit
V
OUT
P
ACKAGE
D
ATA
P
ACKAGE
D
ATA
ADJ or
GND*
*Pin
1 is GND for fixed voltage versions
Current
Lim it Circuit
Copyright
©
2000
Rev. 2.0b, 2005-10-25
Microsemi Inc.
Integrated Products Division
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 2
LX8385x-xx
TM
®
3A Low Dropout Positive Regulators
P
RODUCTION
D
ATA
S
HEET
ELECTRICAL CHARACTERISTICS
WWW .
Microsemi
.C
OM
Unless otherwise specified, the following specifications apply over the operating ambient temperature for the LX8385x-xxC with
0°C
≤
T
A
≤
125°C and the LX8385-xxI with -25°C
≤
T
A
≤
125°C except where otherwise noted. Test conditions: V
IN
-V
OUT
= 3V;
I
OUT
= 3A. Low duty cycle pulse testing techniques are used which maintains junction and case temperatures equal to the ambient
temperature.
Parameter
Symbol
Test Conditions
LX8385x-xx
Typ
Max
1.250
1.262
Min
Units
LX8385-00 / 8385A-00 / 8385B-00 (ADJUSTABLE)
Reference Voltage
(Note 4)
LX8385/85A-00
V
REF
LX8385B-00
Line Regulation (Note 2)
Load Regulation (Note 2)
Thermal Regulation
Ripple Rejection (Note 3)
Adjust Pin Current
Adjust Pin Current Change (Note 4)
Dropout Voltage
LX8385-00
LX8385A/85B-00
Minimum Load Current
Maximum Output Current
Long Term Stability (Note 3)
Δ
V
REF
(V
IN
)
Δ
V
REF
(I
OUT
)
ΔV
OUT
(Pwr)
I
OUT
= 10mA, T
A
= 25°C
10mA < I
OUT
< 3A, 1.5V < (V
IN
-V
OUT
),
V
IN
< 10V, P < P
MAX
I
OUT
= 10mA, T
A
= 25°C
10mA < I
OUT
< 3A, 1.5V < (V
IN
-V
OUT
),
V
IN
< 10V, P < P
MAX
e
1.238
1.225
1.250
1.270
1.240
1.250
1.260
1.238
1.250
1.262
0.2
0.5
0.04
0.015
0.15
0.01
83
65
55
100
5
1.5
1.3
10
1
0.2
1.2
1.1
2
3
3.5
0.3
0.25
0.003
3.267
3.235
3.274
3.267
3.3
3.3
3.3
3.3
1
2
5
0.01
60
83
4
1.2
1.1
10
1.5
1.3
3.333
3.365
3.326
3.333
6
10
15
0.02
V
V
V
V
%
%
%/W
dB
µA
µA
V
V
mA
A
%
%
%
Temperature Stability (Note 3)
ΔV
OUT
(T)
RMS Output Noise (% of V
OUT
)
ΔV
OUT(RMS)
T
A
= 25°C, 10Hz < f < 10kHz
(Note 3)
LX8385-33/ 8385A-33/ 8385B-33 (3.3V FIXED)
Output Voltage
(Note 4)
LX8385/85A-33
LX8385B-33
V
IN
= 5V, I
OUT
= 0mA, T
A
= 25°C
4.75V < V
IN
< 10V, 0mA < I
OUT
< 3A, P < P
MAX
V
IN
= 5V, I
OUT
= 0mA, T
A
= 25°C
4.75V < V
IN
< 10V, 0A < I
OUT
< 3A, P < P
MAX
ΔV
OUT
(V
IN
)
ΔV
OUT
(I
OUT
)
ΔV
OUT
(Pwr)
I
Q
LX8385-33
LX8385A/85B-33
ΔV
4.75V < V
IN
< 7V
4.75V < V
IN
< 10V
V
IN
= 5V, 0mA < I
OUT
< I
OUT(MAX)
T
A
= 25°C, 20ms pulse
C
OUT
= 100µF (Tantalum), I
OUT
= 3A
0mA < I
OUT
< I
OUT(MAX)
, 4.75V < V < 10V
ΔV
OUT
= 1%, I
OUT
< I
OUT(MAX)
ΔV
OUT
= 1%, I
OUT
< I
OUT(MAX)
bs
I
OUT(MAX)
ΔV
OUT
(t)
V
OUT
ol
et
1.5V < (V
IN
-V
OUT
), V
IN
< 7V, I
OUT
= 10mA
V
OUT
> V
REF
, V
IN
- V
OUT
= 3V,
10mA < I
OUT
< 3A
T
A
= 25°C, 20ms pulse
V
OUT
= 5V, f= 120Hz, C
OUT
= 100µF Tantalum,
V
IN
= 6.5V, C
ADJ
= 10µF, I
OUT
= 3A
I
ADJ
ΔI
ADJ
ΔV
10mA < I
OUT
< I
OUT(MAX)
, 1.5V < (V
IN
-V
OUT
), V
IN
<10V
ΔV
REF
= 1%, I
OUT
= 3A
ΔV
REF
= 1%, I
OUT
= 3A
V
IN
< 10V
I
OUT(MIN)
(V
IN
- V
OUT
) < 7V, V
IN
< 10V
T
A
= 125°C, 1000 hours
V
V
V
V
mV
mV
mV
%/W
dB
mA
V
V
O
Line Regulation (note 2)
E
LECTRICALS
E
LECTRICALS
Load Regulation (note 2)
Thermal Regulation
Ripple Rejection (note 3)
Quiescent Current
Dropout Voltage
Copyright
©
2000
Rev. 2.0b, 2005-10-25
Microsemi Inc.
Integrated Products Division
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 3
LX8385x-xx
TM
®
3A Low Dropout Positive Regulators
P
RODUCTION
D
ATA
S
HEET
ELECTRICAL CHARACTERISTICS (CONTINUED)
WWW .
Microsemi
.C
OM
Unless otherwise specified, the following specifications apply over the operating ambient temperature for the LX8385x-xxC with
0°C
≤
T
A
≤
125°C and the LX8385-xxI with -25°C
≤
T
A
≤
125°C except where otherwise noted. Test conditions: V
IN
-V
OUT
= 3V;
I
OUT
= 3A. Low duty cycle pulse testing techniques are used which maintains junction and case temperatures equal to the ambient
temperature.
Parameter
Symbol
Test Conditions
LX8385x-xx
Min
Typ
Max
3
3.5
Units
LX8385-33 / 8385A-33 / 8385B- (3.3V FIXED)(CONTINUED)
Maximum Output Current
Temperature Stability (Note 3)
Long Term Stability (Note 3)
RMS Output Noise (% of V
OUT
)
(Note 3)
I
OUT(MAX)
ΔV
OUT
(T)
ΔV
OUT
(t)
V
OUT (RMS)
T
A
=125°C, 1000 hours
T
A
=25°C, 10Hz < f < 10kHz
V
IN
< 7V
e
0.25
0.3
1
0.003
4.950
5.00
5.050
5.100
5.040
5.050
10
25
0.02
4.900
5.00
4.960
5.00
4.950
5.00
2
5
0.01
83
4
1.2
1.1
3
3.5
0.25
0.3
0.003
1
60
10
1.5
1.3
A
%
%
%
LX8385-05 / 8385A-05 / 8385B-05 (5.0V FIXED)
Output Voltage
(Note 4)
LX8385/85A-05
LX8385B-05
Line Regulation (Note 2)
Load Regulation (Note 2)
Thermal Regulation
Ripple Rejection (Note 3)
Quiescent Current
Dropout Voltage
ol
et
V
IN
=7V, I
OUT
=0mA, T
A
=25°C
V
OUT
7V < V
IN
< 10V, 0mA < I
OUT
< 3A, P < P
MAX
V
IN
=7V, I
OUT
=0mA, T
A
=25°C
7V < V
IN
< 10V, 0mA < I
OUT
< 3A, P < P
MAX
ΔV
OUT
(V
IN
) 7V < V
IN
< 10V
ΔV
OUT
(I
OUT
)
ΔV
OUT
(Pwr)
I
Q
V
IN
=7V, 0mA < I
OUT
< I
OUT(MAX)
T
A
=25°C, 20ms pulse
C
OUT
=100µF (Tantalum), I
OUT
=3A
0mA < I
OUT
< I
OUT(MAX)
, 4.75V < V
IN
< 10V
ΔV
ΔV
OUT
=1%, I
OUT
< I
OUT(MAX)
ΔV
OUT
=1%, I
OUT
< I
OUT(MAX)
V
IN
< 10V
I
OUT(MAX)
ΔV
OUT
(T)
ΔV
OUT
(t)
T
A
=125°C, 1000 hours
V
OUT (RMS)
T
A
=25°C, 10Hz < f < 10kHz
V
V
V
V
mV
mV
%/W
dB
mA
V
V
A
%
%
%
Maximum Output Current
Temperature Stability (Note 3)
Long Term Stability (Note 3)
O
Note 2
Note 3
Note 4
RMS Output Noise (% of V
OUT
)
(Note 3)
bs
LX8385-33
LX8385A/85B-33
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.
These parameters, although guaranteed are not tested in production.
See Maximum Output Current Section
E
LECTRICALS
E
LECTRICALS
Copyright
©
2000
Rev. 2.0b, 2005-10-25
Microsemi Inc.
Integrated Products Division
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 4
LX8385x-xx
TM
®
3A Low Dropout Positive Regulators
P
RODUCTION
D
ATA
S
HEET
APPLICATION NOTES
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Microsemi
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OM
INPUT
10µF
10µF
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.
O
bs
Minimum Capacitor Values
OUTPUT
15µF Tantalum, 100µF Aluminum
47µF Tantalum, 220µF Aluminum
ADJ
None
15µF
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.
OVERLOAD RECOVERY
Like almost all IC power regulators, the LX8385/85A/85B
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 LX8385/85A/85B 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
Page 5
ol
et
Microsemi Inc.
e
FIGURE 1
- DYNAMIC INPUT AND OUTPUT TEST
The LX8385/85A/85B 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
LX8385/85A/85B 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.
Power
Supply
IN
LX8385x
ADJ
OUT
Minim um Load
(Larger resistor)
Full Load
(Sm aller
resistor)
R
DSON
<< R
L
Star Ground
10m s
1 sec
A
PPLICATIONS
A
PPLICATIONS
Copyright
©
2000
Rev. 2.0b, 2005-10-25
Integrated Products Division
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
PCB Design
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