Silicon Core
Microelectronics
Corp.
GENERAL DESCRIPTION
CX1084
5A Low dropout voltage regulator
The CX1084 series of adjustable and fixed voltage regulators are designed to provide 5A output
current and to operate down to 1V input-to-output differential. The dropout voltage of the device is
guaranteed maximum 1.5V at maximum output current, decreasing at lower load currents.
On-chip trimming adjusts the reference voltage to 1%. Current limit is also trimmed, minimizing the
stress under overload conditions on both the regulator and power source circuitry.
The CX1084 devices are pin compatible with older three-terminal regulators and are offered in 3 lead
TO-220,2 lead TO-252 package and 3 and 2 lead TO-263 (Plastic DD).
FEATURES
Three Terminal Adjustable or Fixed Voltages*
5V, 1.8V, 2.5V, 2.85V, 3.3V and 5.0V
Output Current of 5A
Operates Down to 1V Dropout
Line Regulation: 0.2% Max.
Load Regulation: 0.4% Max.
TO-220 ,TO252and TO-263 package available
APPLICATIONS
High Efficiency Linear Regulators
Post Regulators for Switching Supplies
Microprocessor Supply
Constant Current Regulators
Battery Chargers
Notebook/Personal Computer Supplies
Portable Instrumentation
ORDERING INFORMATION
PACKAGE TYPE
3 LEAD TO-220
CX1084
CX1084-1.5
CX1084-2.5
CX1084-2.85
CX1084-3.0
CX1084-3.3
CX1084-3.5
CX1084-5.0
TO-252
CX1084
CX1084-1.5
CX1084-2.5
CX1084-2.85
CX1084-3.0
CX1084-3.3
CX1084-3.5
CX1084-5.0
2&3 LEAD TO-263
CX1084
CX1084-1.5
CX1084-2.5
CX1084-2.85
CX1084-3.0
CX1084-3.3
CX1084-3.5
CX1084-5.0
OPERATING JUNCTION
TEMPERATURE RANGE
0 to 125
C
0 to 125
C
0 to 125
C
0 to 125
C
0 to 125
C
0 to 125
C
0 to 125
C
0 to 125
C
PIN DESCRIPTIONS
FIXED VERSION
1- Ground
2- V
OUT
3- V
IN
ADJUSTABLE VERSION
1- Adjust
2- V
OUT
3- V
IN
Page 1 of 1
SPECIFICATION
CX1084
ABSOLUT MAXIMUM RATINGS
(Note 1)
Power Dissipation
Input Voltage
Operating Junction Temperature
Control Section
Power Transistor
Storage temperature
0°C to 125°C
0°C to 150°C
- 65°C to +150°C
Internally limited
22V
Soldering information
Lead Temperature (10 sec)
Thermal Resistance
TO-220 package
TO-263 package
φ
JA= 50°C/W
φ
JA= 30°C/W*
300°C
* With package soldering to copper area over backside
ground plane or internal power plane
φJA
can vary from
20°C/W to >40°C/W depending on mounting technique and
the size of the copper area.
ELECTRICAL CHARACTERISTICS
Electrical Characteristics at I
OUT
= 0 mA, and T
J
= +25°C unless otherwise specified.
Parameter
Reference Voltage
(Note 2)
Device
CX1084
Conditions
I
OUT
= 10 mA
10mA
≤I
OUT
≤5A,
1.5V≤ (V
IN
- V
OUT
)
≤12V
Min
1.238
1.225
Typ
1.250
1.250
Max
1.262
1.270
Units
V
V
Output Voltage
(Note 2)
CX1084-1.5
1.485
1.500
1.500
2.500
2.500
2.850
2.850
3.000
3.000
3.300
3.300
3.500
3.500
5.000
5.000
1.515
1.530
2.525
2.550
2.88
2.91
3.300
3.360
3.333
3.365
3.535
3.570
5.050
5.100
V
V
V
V
V
V
V
V
V
V
V
V
V
V
0≤I
OUT
≤5A
,3.0V≤V
IN
≤12V
0≤I
OUT
≤5A
,4.0V≤V
IN
≤12V
0≤I
OUT
≤5A
,4.35V≤V
IN
≤12V
0≤I
OUT
≤5A
,4.5V≤V
IN
≤12V
0≤I
OUT
≤5A
,4.75V≤V
IN
≤12V
0≤I
OUT
≤5A
,5.0V≤V
IN
≤12V
0≤I
OUT
≤5A
,6.5V≤V
IN
≤12V
1.470
2.475
2.450
2.82
2.79
2.970
2.940
3.267
3.235
3.465
3.430
4.950
4.900
CX1084-2.5
CX1084-2.85
CX1084-3.0
CX1084-3.3
CX1084-3.5
CX1084-5.0
Page 2 of 2
SPECIFICATION
Parameter
Line Regulation
CX1084
Device
Conditions
I
LOAD
= 10 mA
,
Min
Typ
0.3
0.6
0.1
0.2
3
6
3
6
3
6
3
6
3
7
3
6
5
10
1.3
Max
6
10
0.3
0.4
12
20
12
20
12
20
12
20
15
25
15
25
20
35
1.5
Units
mV
mV
%
%
mV
mV
mV
mV
mV
mV
mV
mV
mV
mV
mV
mV
mV
mV`
V
CX1084/-1.5/-2.5/-2.85/
-3.0/-3.3/-3.5/-5.0
1.5V≤(V
IN
– V
out
)
≤12V
(V
IN
– V
out
)
=3V,
10mA≤I
OUT
≤5A
V
IN
= 5V,
0≤I
OUT
≤5A
V
IN
= 5V,
0≤I
OUT
≤5A
V
IN
= 5V,
0≤I
OUT
≤5A
V
IN
= 5V,
0≤I
OUT
≤5A
V
IN
= 5V,
0≤I
OUT
≤5A
V
IN
= 5.25V,
0≤I
OUT
≤5A
V
IN
= 8V,
0≤I
OUT
≤5A
∆V
OUT
,
∆V
REF
= 1%, I
OUT
= 5 A
(Note 4)
(V
IN
- V
OUT
) = 5V
(V
IN
- V
OUT
) = 12V (Note 5)
5.00
Load Regulation
(Notes 2, 3)
CX1084-ADJ
CX1084-1.5
CX1084-2.5
CX1084-2.85
CX1084-3.0
CX1084-3.3
CX1084-3.5
CX1084-5.0
Dropout Voltage
(V
IN
-
V
OUT
)
Current Limit
CX1084/-1.5/-2.5/-2.85/
-3.0/-3.3/-3.5/-5.0
CX1084/-1.5/-2.5/-2.85/
-3.0/-3.3/-3.5/-5.0
6.00
7.00
A
Minimum Load
Current
Quiescent Current
CX1084
5
10
mA
CX1084/-1.5/-2.5/-2.85/
-3.0/-3.3/-3.5/-5.0
V
IN
≤
12V
f =120Hz , C
OUT
= 25
F Tantalum, I
OUT
=
5A,(V
IN
-V
OUT
) = 3V, C
ADJ
=25μF
60
5
10
mA
Ripple Rejection
CX1084
75
dB
CX1084-1.5
f =120Hz , C
OUT
= 25
F Tantalum, I
OUT
= 5A,
V
IN
= 4.5V
60
72
dB
CX1084-2.5
f =120Hz , C
OUT
= 25
F Tantalum, I
OUT
= 5A,
V
IN
= 5.5V
60
72
dB
CX1084-2.85
f =120Hz , C
OUT
= 25
F Tantalum, I
OUT
= 5A,
V
IN
= 6V
60
72
dB
CX1084-3.0
f =120Hz , C
OUT
= 25
F Tantalum, I
OUT
= 5A
V
IN
= 6V
60
72
dB
CX1084-3.3
f =120Hz , C
OUT
= 25
F Tantalum, I
OUT
= 5A
V
IN
= 6.3V
60
72
dB
CX1084-3.5
f =120Hz , C
OUT
= 25
F Tantalum, I
OUT
= 5A
V
IN
= 6.5V
60
72
dB
CX1084-5.0
f =120Hz , C
OUT
= 25
F Tantalum, I
OUT
= 5A,
V
IN
= 8V
60
68
dB
Page 3 of 3
SPECIFICATION
Parameter
Thermal Regulation
Adjust Pin Current
CX1084
Device
Conditions
T
A
= 25°C, 30ms pulse
10mA
≤
I
OUT
≤
5A , 1.5V
≤
(V
IN
- V
OUT
)
≤
12V
Min
Typ
0.008
55
Max
0.04
Units
%W
µA
CX1084
CX1084
120
0.2
5.0
µA
µA
Adjust Pin Current
Change
Temperature Stability
Long Term Stability
CX1084
10mA
≤
I
OUT
≤
5A , 1.5V
≤
(V
IN
- V
OUT
)
≤
12V
0.5
T
A
=125°C, 1000Hrs
0.3
1
%
%
RMS Output Noise
(% of V
OUT
)
Thermal Resistance
Junction-to-Case
T
A
= 25°C , 10Hz
≤
f
≤
10kHz
M Package: Control Circuitry/ Power Transistor
T Package: Control Circuitry/ Power Transistor
0.003
%
1.5/4.0
1.5/4.0
°C/W
°C/W
Parameters identified with
boldface type
apply over the full operating temperature range.
Note 1:
Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. For guaranteed specifications and test
conditions, see the
Electrical Characteristics
.
The guaranteed specifications apply only for the test conditions listed.
Note 2:
Line and Load regulation are guaranteed up to the maximum power dissipation of 15W. Power dissipation is determined by the
input/output differential and the output current. Guaranteed maximum power dissipation will not be available over the full input/output range.
Note 3:
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 ~1/8” from the package.
Note 4:
Dropout voltage is specified over the full output current range of the device.
Note 5:
Minimum load current is defined as the minimum output current required to maintain regulation. When (V
IN
- V
OUT
) = 12V the device
is guaranteed to regulate if the output current is greater than 10mA.
APPLICATION HINTS
The CX1084 series of adjustable and fixed regulators are easy to use and have all the protection features expected in
high performance voltage regulators: short circuit protection and thermal shut-down.
Pin compatible with older three terminal adjustable regulators, these devices offer the advantage of a lower dropout voltage,
more precise reference tolerance and improved reference stability with temperature.
Stability
The circuit design used in the CX1084 series
requires the use of an output capacitor as part of the
device frequency compensation. The addition of
150
uF
aluminum electrolytic or a 22uF solid tantalum on the
output will ensure stability for all operating conditions.
When the adjustment terminal is bypassed with a
capacitor to improve the ripple rejection, the requirement
for an output capacitor increases. The value of 22uF
tantalum or
150
uF aluminum covers all cases of
bypassing the adjustment terminal. Without bypassing
the adjustment terminal smaller capacitors can be used
with equally good results.
To ensure good transient response with heavy load
current changes capacitor values on the order of 100uF are
used in the output of many regulators. To further improve
stability and transient response of these devices larger
values of output capacitor can be used.
Protection Diodes
Unlike older regulators, the CX1084 family does not
need any protection diodes between the adjustment pin and
the output and from the output to the input to prevent
over-stressing the die. Internal resistors are limiting the
internal current paths on the CX1084 adjustment pin,
therefore even with capacitors on the adjustment pin no
protection diode is needed to ensure device safety under
short-circuit conditions.
Diodes between the input and output are not usually
Page 4 of 4
SPECIFICATION
needed. Microsecond surge currents of 50A to 100A can be
handled by the internal diode between the input and output
pins of the device. In normal operations it is difficult to get
those values of surge currents even with the use of large
output capacitances. If high value output capacitors are
used, such as 1000uF to 5000uF and the input pin is
instantaneously shorted to ground, damage can occur. A
diode from output to input is recommended, when a crowbar
circuit at the input of the CX1084 is used. Normal
power supply cycling or even plugging and unplugging in
the system will not generate current large enough to do any
damage. The adjustment pin can be driven on a transient
basis
25V, with respect to the output without any device
degradation. As with any IC regulator, none the protection
circuitry will be functional and the internal transistors will
break down if the maximum input to output voltage
differential is exceeded.
Ripple Rejection
CX1084
The ripple rejection values are measured with the
adjustment pin bypassed. The impedance of the adjust pin
capacitor at the ripple frequency should be less than the
value of R1 (normally 100Ωto120Ω) for a proper bypassing
and ripple rejection approaching the values shown. The size
of the required adjust pin capacitor is a function of the input
ripple frequency. If R1=100Ωat 120Hz the adjust pin
capacitor should be 25uF. At 10kHz only 0.22uF is needed.
The ripple rejection will be a function of output voltage,
in circuits without an adjust pin bypass capacitor. The
output ripple will increase directly as a ratio of the output
voltage to the reference voltage (V
OUT
/ V
REF
).
Output Voltage
The CX1084 series develops a 1.25V reference
voltage between the output and the adjust terminal. Placing
a resistor between these two terminals causes a constant
current to flow through R1 and down through R2 to set the
overall output voltage.
This current is normally the specified minimum load
current of 10mA. Because I
ADJ
is very small and constant it
represents a small error and it can usually be ignored.
D1
CX1084
IN
ADJ
OUT
V
IN
V
OUT
R1
C
OUT
150uF
V
IN
CX1084
IN
ADJ
OUT
V
OUT
V
REF
R1
C
ADJ
10uF
R2
I
ADJ
50uA
R2
Overload Recovery
When the power is first turned on, as the input voltage
rises, the output follows the input, permitting the regulator to
start up into heavy loads. During the start-up, as the input
voltage is rising, the input-to-output voltage differential
remains small, allowing the regulator to supply large output
currents. A problem can occur with a heavy output load
when the input voltage is high and the output voltage is low,
when the removal of an output short will not permit the
output voltage to recover. The load line for such a load may
intersect two points on the output current curve. In this
case, there are two stable output operating points for the
regulator. With this double intersection, the power supply
may need to be cycled down to zero and brought up again
to make the output recover.
V
OUT
= V
REF
1+ R2/R1)+I
ADJ
R2
Figure 1. Basic Adjustable Regulator
Load Regulation
True remote load sensing it is not possible to provide,
because the CX1084 is a three terminal device. The
resistance of the wire connecting the regulator to the load
will limit the load regulation. The data sheet specification for
load regulation is measured at the bottom of the package.
Negative side sensing is a true Kelvin connection, with the
bottom of the output divider returned to the negative side of
the load.
The best load regulation is obtained when the top of the
resistor divider R1 is connected directly to the case not to
the load. If R1 were connected to the load, the effective
Page 5 of 5
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