ISSUED DATE :2003/06/14
REVISED DATE :2006/03/29E
GU1084
5A Low Dropout Positive Adjustable or Fixed-Mode Regulator
The GU1084 is a low dropout positive adjustable or fixed mode regulator with minimum of 5.0A 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. GU1084 is also well suited for other
applications such as VGA cards. GU1084 is guaranteed to have lower than 1.5V dropout at full load current
making it ideal to provide well regulated outputs of 1.25 to 3.3V with 4.7 to 12V input supply.
Description
Features
&
maximum dropout at full load current
1.5V
Package Dimensions
&Built-in thermal shutdown
&Output current limiting
&Adjustable output voltage or fixed 1.5V,1.8V,2.5V,3.3V,5.0V
&Fast transient response
&Good noise rejection
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.
Typical Circuit
Block Diagram
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
to insure that the input voltage does not sag below the minimum dropout voltage during the load
transient response .This pin must always be 1.5V higher than Vout in order for the device to
regulate properly.
FUNCTION
Vin
I
3
GU1084
Page: 1/4
ISSUED DATE :2003/06/14
REVISED DATE :2006/03/29E
Absolute Maximum Ratings
Symbol
V
in
P
D
T
ST
T
OP
DC Supply Voltage
Power Dissipation
Storage Temperature
Operating Junction Temperature Range
Parameter
Ratings
-0.3 to 12
Internally Limited
-65 ~ + 150
0 ~ + 150
:
:
Unit
V
Electrical Characteristics
Symbol
V
REF
Parameter
GU1084ADJ
GU1084-1.5
GU1084-1.8
Output Voltage
GU1084-2.5
GU1084-3.3
GU1084-5.0
Line Regulation
GU1084XXX
GU1084ADJ
GU1084-1.5
Load Regulation
GU1084-1.8
GU1084-2.5
GU1084-3.3
GU1084-5.0
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
MIN
1.225
1.470
1.764
2.450
3.235
4.900
-
-
-
-
-
-
-
-
5.1
-
-
-
-
-
-
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.
GU1084
Page: 2/4
ISSUED DATE :2003/06/14
REVISED DATE :2006/03/29E
Functional Description
Introduction
The GU1084 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 GU1084 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 GU1084 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 GU1084 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:
The GU1084 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 GU1084 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 GU1084 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 GU1084 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 GU1084 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.
GU1084
Page: 3/4
ISSUED DATE :2003/06/14
REVISED DATE :2006/03/29E
Performance Characteristics
Important Notice:
All rights are reserved. Reproduction in whole or in part is prohibited without the prior written approval of GTM.
GTM reserves the right to make changes to its products without notice.
GTM semiconductor products are not warranted to be suitable for use in life-support Applications, or systems.
GTM assumes no liability for any consequence of customer product design, infringement of patents, or application assistance.
Head Office And Factory:
Taiwan:
No. 17-1 Tatung Rd. Fu Kou Hsin-Chu Industrial Park, Hsin-Chu, Taiwan, R. O. C.
TEL : 886-3-597-7061 FAX : 886-3-597-9220, 597-0785
China:
(201203) No.255, Jang-Jiang Tsai-Lueng RD. , Pu-Dung-Hsin District, Shang-Hai City, China
TEL : 86-21-5895-7671 ~ 4 FAX : 86-21-38950165
GU1084
Page: 4/4
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