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Features
(Preliminary)
EP1084
5A Low Dropout Linear Regulator
Description
EP1084 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.
EP1084 is also well suited for other applications
such as VGA cards. EP1084 is guaranteed to
have lower than 1.4V 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.
• Output current limiting
• Adjustable output voltage or fixed 1.5V, 1.8V,
2.5V, 3.3V, 5.0V
• Good noise rejection
• 1.4V maximum dropout at full load current
• Built-in thermal shutdown
• Fast transient response
• Packages: TO252, TO263
Applications
• PC peripheral
• Low Voltage Logic Supplies
• Post Regulator for Switching Power Supply
Typical Application
Fixed Mode Regulator
5.0V to 2.5V Adjustable Regulator
V
OUT
= V
REF
×
⎜
1
+
⎛
⎝
R2
⎞
R1
⎠
⎟
V
REF
=1.25V
R1
≒
100Ω~200Ω
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Pin Assignment
EP1084
Ordering Information
Pin Description
Pin
1
2
Name
FB
(GND)
V
OUT
Function
Adjustable (Ground only for fixed mode) A resistor divider from this pin to the
V
OUT
pin and ground sets the output voltage. (Ground only for Fixed-Mode)
The output of the regulator. A minimum of 10uF (0.15Ω
≤
ESR
≤
20Ω) capacitor
must be connected from this pin to ground to insure stability.
The input pin of regulator. Typically a large storage capacitor (0.15Ω≤ ESR
≤
20Ω) 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 1.4V (1.3V) higher than V
OUT
in order for the device to
regulate properly.
3
V
IN
Absolute Maximum Rating
Symbol
V
I
P
D
T
STG
T
OP
DC Supply Voltage
Power Dissipation
Storage Temperature Range
Operating Junction Temperature Range
Item
Rating
(Note 2)
Units
V
°C
°C
15
Internally Limited
-65 ~ +150
0 ~ +150
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Electrical Characteristics
(Under operating conditions)
Symbol
V
REF
Parameter
Reference Voltage
EP1084-adj
EP1084-15
EP1084-18
EP1084-25
EP1084-33
EP1084-50
EP1084-adj
EP1084-15
EP1084-18
EP1084-25
EP1084-33
EP1084-50
V
D
I
LIMIT
I
O
T
S
Dropout Voltage
Current Limit
Minimum Load Current
Temperature Stability
Thermal
Resistance
Thermal
Resistance
TO-252
TO-263
TO-252
TO-263
I
OUT
=10mA
Junction-to-Ambient (No
heat sink ;No air flow)
Junction-to-Case
(Control circuitry/Power
transistor)
Conditions
T
J
=25°C, I
OUT
=10mA,
(V
IN
-V
OUT
) =1.5V
T
J
=25°C, I
OUT
=10mA,
V
OUT
+1.5V<V
IN
<12V
T
J
=25°C, I
OUT
=10mA,
3V≤V
IN
≤12V
T
J
=25°C, I
OUT
=10mA,
3.3V≤V
IN
≤12V
T
J
=25°C, I
OUT
=10mA,
4V≤V
IN
≤12V
T
J
=25°C, I
OUT
=10mA,
4.8V≤V
IN
≤12V
T
J
=25°C, I
OUT
=10mA,
6.5V≤V
IN
≤12V
T
J
=25°C, V
IN
=3.3V,
(Note1, 2)
0mA<I
OUT
<5A
T
J
=25°C, V
IN
=3V,
(Note1, 2)
0mA<I
OUT
<5A
T
J
=25°C, V
IN
=3.3V,
(Note1, 2)
0mA<I
OUT
<5A
T
J
=25°C, V
IN
=4V,
(Note1, 2)
0mA<I
OUT
<5A
T
J
=25°C, V
IN
=5V,
(Note1, 2)
0mA<I
OUT
<5A
T
J
=25°C, V
IN
=8V,
(Note1, 2)
0mA<I
OUT
<5A
I
OUT
=5A(∆V
OUT
=1%V
OUT
)
(V
IN
-V
OUT
)=5V
5.1
5
0.5
98
83
10
0.65/2.7
12
15
20
26
45
1.3
1.470
1.764
2.450
3.235
4.900
1.500
1.800
2.500
3.300
5.000
Min.
1.225
Typ.
1.250
EP1084
Max.
1.275
0.2
1.530
1.836
2.550
3.365
5.100
1
15
18
25
33
50
1.4
10
Units
V
%
REG
LINE
Line
Regulation
V
%
REG
LOAD
Load
Regulation
mV
V
A
mA
%
°C/W
θ
JA
θ
JC
°C/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.
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Typical Performance Characteristics
EP1084
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Functional Block Diagram
V
IN
EP1084
V
OUT
+
+
Current
Limit
Thermal
Shutdown
1.25V
+
-
FB
Introduction
The EP1084 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 V
IN
-1.4V. The EP1084 only needs 1.4V differential between V
IN
and V
OUT
to maintain output regulation. In
addition, the output voltage tolerances are also extremely tight and they include the transient response
as part 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 EP1084 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 EP1084 can be programmed to any voltages in the range of 1.25V to V
IN
-1.4V with the addition of
R1 and R2 external resistors according to the following formula:
The EP1084 keeps a constant 1.25V between the output pin and the FB pin. By placing a resistor R1
across these two pins a constant current flows through R1, adding to the I
FB
current and into the R2
resistor producing a voltage equal to the (1.25/R1)*R2+I
FB
*R2 which will be added to the 1.25V to set the
output voltage. This is summarized in the above equation. Since the minimum load current requirement
of the EP1084 is 10mA, R1 is typically selected to be 121Ω resistor so that it automatically satisfies the
minimum current requirement. Notice that since I
FB
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=121Ω and R2=200Ω the error due to I
FB
is
only 0.3% of the nominal set point.
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