A
M I C R O S E M I
C O M P A N Y
LX8385x-xx
3A Low Dropout Positive Regulators
P
RODUCTION
D
ATA
S
HEET
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.
Three-Terminal Adjustable Or
W W W .
Microsemi
.
COM
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
High Efficiency Linear
IMPORTANT:
For the most current data, consult
MICROSEMI’s
website:
http://www.microsemi.com
Regulators
Post Regulators For Switching
Power Supplies
Battery Chargers
Constant Current Regulators
Graphics & Standard Supplies
Processor I/O Supply
Low Voltage Memory & Chipset
Supplies
IN
5V
+
*150 0µ F
6M V 1 500G X
S anyo
121
Ω
1%
OUT
LX 8385A
AD J
200
Ω
1%
+
3.3V
at 3A
LX8385/85A/85B-00
LX8385/85A/85B-33
LX8385/85A/85B-05
Adjustable
3.3V
5.0V
150 0µ F
2x 6M V 1 500G X
S anyo
Table 1
- Available Options
LX8385
X
LX8385
X
Max Ref Max Dropout
Accuracy
Voltage
0 to 125
2.0%
1.5V
2.0%
1.3V
1.0%
1.3V
-25 to 125 2.0%
1.5V
T
A
(°C)
Plastic TO-252
DT
(D-Pak) 3-Pin
LX8385-xxCDT
LX8385A-xxCDT
LX8385B-xxCDT
LX8385-xxIDT
Plastic TO-220
P
3-Pin
LX8385-xxCP
LX8385A-xxCP
LX8385B-xxCP
LX8385-xxIP
Plastic TO-263
DD
3-Pin
LX8385-xxCDD
LX8385A-xxCDD
LX8385B-xxCDD
LX8385-xxIDD
Note: Available in Tape & Reel.
Append the letter “T” to the part number. (i.e. LX8385-xxCPT)
Copyright
©
2000
Rev. 2.0a, 2001-03-15
Microsemi
Linfinity Microelectronics Division
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 1
A
M I C R O S E M I
C O M P A N Y
LX8385x-xx
3A Low Dropout Positive Regulators
P
RODUCTION
D
ATA
S
HEET
TA B is V
O U T
3
W W W .
Microsemi
.
COM
Power Dissipation....................................................................................Internally Limited
Input Voltage .................................................................................................................10V
Input to Output Voltage Differential..............................................................................10V
Operating Junction Temperature
Plastic (DT, DD, P Packages)................................................................................ 150°C
Storage Temperature Range .......................................................................-65°C to 150 °C
Lead Temperature (Soldering, 10 Seconds)............................................................... 300°C
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.
V
IN
V
OUT
AD J /
GND*
2
1
DD P
ACKAGE
(3-
PIN
)
(Top View)
TA B is V
O UT
3
V
IN
V
O UT
AD J/
G ND *
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
2
1
DT P
ACKAGE
(3-
PIN
)
(Top View)
TA B is V
O U T
3
P
V
IN
V
OUT
AD J /
G N D*
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
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.
V
IN
Bias C ircuit
T herm al
Lim it C ircuit
Bandgap
C ircuit
C ontrol
C ircuit
O utput
C ircuit
V
O UT
SO A
Protection
C ircuit
P
ACKAGE
D
ATA
P
ACKAGE
D
ATA
AD J or
GND*
*Pin
1 is GND for fixed voltage versions
C urrent
Lim it C ircuit
Copyright
©
2000
Rev. 2.0a, 2001-03-15
Microsemi
Linfinity Microelectronics Division
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 2
A
M I C R O S E M I
C O M P A N Y
LX8385x-xx
3A Low Dropout Positive Regulators
P
RODUCTION
D
ATA
S
HEET
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
1.238
1.225
1.240
1.238
1.250
1.250
1.250
1.250
0.015
0.15
0.01
65
83
55
10mA < I
OUT
< I
OUT(MAX)
, 1.5V < (V
IN
-V
OUT
), V
IN
<10V
0.2
1.2
1.1
2
3
3.5
0.3
0.25
0.003
1
100
5
1.5
1.3
10
1.262
1.270
1.260
1.262
0.2
0.5
0.04
W W W .
Microsemi
.
COM
Units
LX8385-00 / 8385A-00 / 8385B-00 (ADJUSTABLE)
Reference Voltage
(Note 4)
LX8385/85A-00
V
REF
LX8385B-00
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
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
V
V
V
V
%
%
%/W
dB
µA
µA
V
V
mA
A
%
%
%
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)
REF
REF
OUT
(Pwr)
(I
OUT
)
(V
IN
)
ADJ
I
OUT(MIN)
I
OUT(MAX)
REF
= 1%, I
OUT
= 3A
REF
= 1%, I
OUT
= 3A
V
IN
< 10V
(V
IN
- V
OUT
) < 7V, V
IN
< 10V
T
A
= 125°C, 1000 hours
Temperature Stability (Note 3)
RMS Output Noise (% of V
OUT
)
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
V
OUT
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
Line Regulation (note 2)
Load Regulation (note 2)
Thermal Regulation
Ripple Rejection (note 3)
Quiescent Current
Dropout Voltage
LX8385-33
LX8385A/85B-33
I
Q
3.267
3.235
3.274
3.267
OUT
(t)
OUT
(T)
3.3
3.3
3.3
3.3
1
2
5
0.01
3.333
3.365
3.326
3.333
6
10
15
0.02
V
V
V
V
mV
OUT
(V
IN
)
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
60
E
LECTRICALS
E
LECTRICALS
mV
mV
%/W
dB
OUT
OUT
(Pwr)
(I
OUT
)
83
4
1.2
1.1
10
1.5
1.3
mA
V
V
OUT
= 1%, I
OUT
< I
OUT(MAX)
OUT
= 1%, I
OUT
< I
OUT(MAX)
Copyright
©
2000
Rev. 2.0a, 2001-03-15
Microsemi
Linfinity Microelectronics Division
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 3
A
M I C R O S E M I
C O M P A N Y
LX8385x-xx
3A Low Dropout Positive Regulators
P
RODUCTION
D
ATA
S
HEET
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
0.25
T
A
=125°C, 1000 hours
T
A
=25°C, 10Hz < f < 10kHz
0.3
0.003
1
W W W .
Microsemi
.
COM
Units
LX8385-33 / 8385A-33 / 8385B- (3.3V FIXED)(CONTINUED)
Maximum Output Current
Temperature Stability (Note 3)
Long Term Stability (Note 3)
I
OUT(MAX)
V
IN
< 7V
A
%
%
%
OUT
(T)
OUT
(t)
RMS Output Noise (% of V
OUT
)
V
OUT (RMS)
(Note 3)
LX8385-05 / 8385A-05 / 8385B-05 (5.0V FIXED)
Output Voltage
(Note 4)
LX8385/85A-05
V
OUT
LX8385B-05
Line Regulation (Note 2)
Load Regulation (Note 2)
Thermal Regulation
Ripple Rejection (Note 3)
Quiescent Current
Dropout Voltage
LX8385-33
LX8385A/85B-33
Maximum Output Current
Temperature Stability (Note 3)
Long Term Stability (Note 3)
RMS Output Noise (% of V
OUT
)
(Note 3)
I
Q
V
IN
=7V, I
OUT
=0mA, T
A
=25°C
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
4.950
4.900
4.960
4.950
5.00
5.00
5.00
5.00
2
5
0.01
5.050
5.100
5.040
5.050
10
25
0.02
V
V
V
V
mV
mV
%/W
dB
OUT
(V
IN
)
OUT
OUT
(Pwr)
(I
OUT
)
7V < V
IN
< 10V
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
60
83
4
1.2
1.1
10
1.5
1.3
mA
V
V
A
%
I
OUT(MAX)
OUT
=1%, I
OUT
< I
OUT(MAX)
OUT
=1%, I
OUT
< I
OUT(MAX)
V
IN
< 10V
3
3.5
0.25
OUT
(T)
OUT
(t)
V
OUT (RMS)
T
A
=125°C, 1000 hours
T
A
=25°C, 10Hz < f < 10kHz
0.3
0.003
1
%
%
Note 2
Note 3
Note 4
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. 2.0a, 2001-03-15
Microsemi
Linfinity Microelectronics Division
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 4
A
M I C R O S E M I
C O M P A N Y
LX8385x-xx
3A Low Dropout Positive Regulators
P
RODUCTION
D
ATA
S
HEET
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.
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.
P o wer
S u pp ly
W W W .
Microsemi
.
COM
IN
LX 8385 x
AD J
OUT
Min im u m Lo ad
(L arg er re sistor)
Fu ll L oa d
(S m alle r
re sisto r)
R
D S O N
<< R
L
S ta r G rou nd
10m s
1 sec
F IG U R E 1
- D Y N A M IC IN P U T A N D O U T P U T T E S T
!"#$ % &'
10µF
10µF
(
None
15µF
15µF Tantalum, 100µF Aluminum
47µF Tantalum, 220µF Aluminum
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.
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
A
PPLICATIONS
A
PPLICATIONS
Copyright
©
2000
Rev. 2.0a, 2001-03-15
Microsemi
Linfinity Microelectronics Division
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
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