SU1084
5A
Low Dropout
Positive
Elektronische Bauelemente
RoHS Compliant Product
Adjustable or
Fixed-Mode Regulator
Description
The SU1084 is a low dropout at positive adjustable or fixed-mode
regulator with min. of
5A
output current capability. The product is
specifically designed to provide well-regulated supply for low voltage
IC applications such as high-speed bus termination and low current
3.3V logic supply. SU1084 is also well suited for other applications
such as VGA cards. SU1084 is guaranteed to have lower than 1.5V
dropout at full load current making it ideal to provide well regulated
outputs of 1.25V to
3.3V with 4.7 to 12V input supply.
Features
*
1.5V Max. Dropout
At
Full Load Current
* Adjustable
Output Voltage
or Fixed 1.5V,1.8V,2.5V,3.3V,5.0V
* Output Current Limiting
* Good Noise Rejection
* Fast Transient Response
* Built-in Thermal Shutdown
REF.
A
b
L4
c
L3
L1
E
Millimeter
REF.
Min.
Max.
4.40
4.80
c2
0.76
1.00
b2
0.00
0.30
B D
0.36
0.5
e
1.50 REF.
L
2.29
2.79
9.80
10.4
L2
Millimeter
Min.
Max.
1.25
1.45
1.17
1.47
8.6
9.0
2.54 REF.
14.6
15.8
0˚
8˚
1.27 REF.
Block Diagram
Typical Circuit
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01-Jun-2002 Rev. A
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4
SU1084
Elektronische Bauelemente
5A
Low Dropout
Positive
Adjustable or
Fixed-Mode Regulator
Pin Descriptions
Name
Adj (GND)
Vout
O
I/O
PIN#
1
2
Adjustable (Ground only for fixed mode)
The output of the regulator. A minimum of 10uF capacitor must be connected from this pin to
ground to insure stability.
The input pin of regulator .Typically a large storage capacitor is connected from this pin to ground
ge
not sag
minimum dropout voltage during
load
to insure that the input voltage does
not sag below
the minimum dropout voltage during the
theload
s
not sag
below theminimum dropout voltage during the load
transient response .This pin must always be 1.5V
higher than
Vout in
inorder for the device to
higher
Vout
order
the device to
VV
higher
thanVout in
order for
for the device to
regulate properly.
FUNCTION
Vin
I
3
Absolute Maximum Ratings
Parameter
DC Supply Voltage
Power Dissipation
Storage Temperature Range
Operating Juction Temperature Range
Symbol
V
IN
P
D
T
ST
T
OP
Ratings
-0.3 to 12
Internally Limited
-65~+150
0~+150
Unit
V
o
o
C
C
Electrical Characteristics
Symbol
V
REF
Parameter
SU1084ADJ
SU1084-1.5
SU1084-1.8
Output Voltage
SU1084-2.5
SU1084-3.3
SU1084-5.0
Line Regulation
SU1084XXX
SU1084ADJ
SU1084-1.5
Load Regulation
SU1084-1.8
SU1084-2.5
SU1084-3.3
SU1084-5.0
Vo
I
LIM
I
MIN
I
ADJ
IQ
Dropout Voltage
Current Limit
Minimum Load Current
Adjust Pin Current
Quiescent Current
Temperature Stability
JA
JC
Thermal Resistance
Junction-to-Ambient(No
heat sink ;No air flow)
Thermal Resistance
Junction-to-Case
Conditions(Notes)
Io=10mA, Tj=25 : , (Vin-Vout )=1.5V
Io=10mA, Tj=25 : , 3.0V Vin 12V
Io=10mA, Tj=25 : , 3.3V Vin 12V
Io=10mA, Tj=25 : , 4.0V Vin 12V
Io=10mA, Tj=25 : , 4.8V Vin 12V
Io=10mA, Tj=25 : , 6.5V Vin 12V
Io=10mA, Vout+1.5V<Vin<12V, Tj=25 :
Vin=3.3V, 0mA<Io<5A, TJ=25 : (Note 1,2)
Vin=3.0V, 0mA<Io<5A, TJ=25 : (Note 1,2)
Vin=3.3V, 0mA<Io<5A, TJ=25 : (Note 1,2)
Vin=4.0V, 0mA<Io<5A, TJ=25 : (Note 1,2)
Vin=5.0V, 0mA<Io<5A, TJ=25 : (Note 1,2)
Vin=8.0V, 0mA<Io<5A, TJ=25 : (Note 1,2)
Io=5.0A( Vout=1% Vout)
Vin-Vout=5V
Vin=5V (adjustable model)
Vin=12V, Io=10mA
Vin=12V, Io=0mA (fixed model)
Io=10mA
-
5.1
-
-
-
-
-
-
MIN
1.225
1.470
1.764
2.450
3.235
4.900
-
-
-
-
-
-
-
TYP
1.250
1.500
1.800
2.500
3.300
5.000
-
-
12
15
20
26
40
1.4
-
5
55
-
0.5
91
10
MAX
1.275
1.530
1.836
2.550
3.365
5.100
0.2
1
15
18
25
33
50
1.5
-
10
100
12
-
-
-
UNIT
V
V
V
V
V
V
%
%
mV
mV
mV
mV
mV
V
A
mA
uA
mA
%
: /w
: /w
Note 1: See thermal regulation specifications for changes in output voltage due to heating effects. Line and load regulation are measured
at a constant junction Temperature by low duty cycle pulse testing .Load regulation is measured at the output lead =1/18” from the
package.
Note 2: Line and load regulation are guaranteed up to the maximum power dissipation of 15W. Power dissipation is determined by the
difference between input and output and the output current .Guaranteed maximum power dissipation will not be available over the
full input/output range.
http://www.SeCoSGmbH.com/
Any changing of specification will not be informed individual
01-Jun-2002 Rev. A
Page
2
of
4
SU1084
Elektronische Bauelemente
5A
Low Dropout
Positive
Adjustable or
Fixed-Mode Regulator
Functional Description
Introduction
The
SU1084
adjustable Low Dropout (LDO) regulator is a 3 terminal device that can easily be programmed with the
addition of two external resistors to any voltages within the range of 1.25V to 2.5V. The
SU1084
only needs 1.5V
differential between Vin and Vout to maintain output regulation, the output voltage tolerances are also extremely tight and
they include the transient response as port of the specification. For example, Intel VRE specification calls for a total of
+/-100mV including initial tolerance, load regulation and 0 to 5.0A load step. The
SU1084
is specifically designed to meet
the fast current transient needs as well as providing an accurate initial voltage, reducing the overall system cost with the
need for fewer output capacitors.
Output Voltage Setting
The
SU1084
can be programmed to any voltages in the range of 1.25V to 5V with the addition of R1 and R2 external
resistors According to the following formula:
SU1084
The
SU1084
keeps a constant 1.25V between the output pin and the adjust pin. By placing a resistor R1 across these two
pins a constant current flows through R1, adding to the
Iadj
current requirement of the
SU1084
is 10mA, R1 is typically
selected to be 121 resistor so that It automatically satisfies the minimum current requirement .Notice that since Iadj is
typically in the range of 55uA it only adds a small error to the output voltage and should only be considered when a very
precise output voltage setting is required. For example, in a typical 3.3V application where R1=121 and R2=200 the
error due to Iadj is only 0.3% of the nominal set point.
Load Regulation
Since the
SU1084
is only a 3 terminal device, it is not possible to provide true remote sensing of the output voltage at the
load.
The best load Regulation is achieved when the bottom side of R2 is connected to the load and the top-side of R1 resistor is
connected directly to the case or the Vout pin of the regulator and not to the load. It is important to note that for high current
applications, this can re-present a significant percentage of the overall load regulation and one must keep the path from the
regulator to the load as short as possible to minimize this effect.
Stability
The
SU1084
requires the use of an output capacitor as part of the frequency compensation in order to make the regulator
stable. For most applications a minimum of 10uF aluminum electrolytic capacitor insures both stability and good transient
response.
Thermal Design
The
SU1084
incorporates an internal shutdown that protects the device when the junction temperature exceeds the
maximum allowable junction temperatures. Although this device can operate with junction temperatures in the range of
150 ,
it is recommended that the selected heat sink be chosen such that during maximum continuous load operation the
junction temperature is kept below the temperature.
Layout Consideration
The output capacitors must be located as close to the Vout terminal of the device as possible .It is recommended to use a
section of a layer of the PC board as a plane to connect the Vout pin to the output capacitors to prevent any high frequency
oscillation that may result due to excessive trace inductance.
h tp://www.SeCoSGmbH.com/
Any changing of specification will not be informed individual
01-Jun-2002 Rev. A
Page
3
of
4
SU1084
Elektronische Bauelemente
5A
Low Dropout
Positive
Adjustable or
Fixed-Mode Regulator
Performance Characteristics
h tp://www.SeCoSGmbH.com/
Any changing of specification will not be informed individual
01-Jun-2002 Rev. A
Page
4
of
4
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