®
SPX2815
1.5A Low Dropout Voltage Regulator
Adjustable & Fixed Output, Fast Response
FEATURES
■
Adjustable Output Down To 1.2V
■
Fixed Output Voltages 1.5V, 2.5V, 3.3V,
5.0V
■
Output Current of 1.5A
■
Low Dropout Voltage 1.1V Typ.
■
Extremely Tight Load And Line Regulation
■
Current & Thermal Limiting
■
Standard 3-Terminal Low Cost TO-220,
TO-263 & TO-252
■
Similar To Industry Standard LT1086/
LT1586
APPLICATIONS
■
Powering VGA & Sound Card
■
Power PC
TM
Supplies
■
SMPS Post-Regulator
■
High Efficiency “Green” Computer Sys-
tems
■
High Efficiency Linear Power Supplies
■
Portable Instrumentation
■
Constant Current Regulators
■
Adjustable Power Supplies
■
Battery charger
DESCRIPTION
The SPX2815 is a low power 1.5A adjustable and fixed voltage regulators that are very easy to
use. It requires only 2 external resistors to set the output voltage for adjustable version. The
SPX2815 are designed for low voltage applications that offers lower dropout voltage and faster
transient response. This device is an excellent choice for use in powering low voltage
microprocessor that require a lower dropout, faster transient response to regulate from +2.5V to
3.8V supplies and as a post regulator for switching supplies applications. The SPX2815 features
low dropout of a maximum 1.2V.
The SPX2815 offers over current limit and protection against over-current faults, reversed input
polarity, reversed load insertion, and positive and negative transient voltage. The IQ of this device
flows into the load, which increases efficiency.
The SPX2815 are offered in a 3-pin TO-220, TO-263 & TO-252 packages compatible with other
3 terminal regulators. For a 3A low dropout regulator refer to the SPX1587 data sheet.
TO-263-3 (T)
TO-220-3 (U)
TO-252 (R)
1
2
3
1
2
3
1
2
3
ADJ/GND
ADJ/GND
V
OUT
V
IN
ADJ/GND
V
OUT
V
IN
Top View
Front View
V
OUT
V
IN
Front View
Rev. 5/05/03
SPX2815 1.5A Low Dropout Voltage Regulato
© Copyright 2003 Sipex Corporation
1
ABSOLUTE MAXIMUM RATINGS
Lead Temp. (Soldering, 10 Seconds) .......................................... 300°C
Storage Temperature Range ......................................... -65° to +150°C
Operating Junction Temperature Range
SPX2815 Control Section .................................... -45°C +125°C
SPX2815 Power Transistor ................................. -45°C +150°C
Maximum Input Supply Voltage ...................................................... 10V
Input to Output Voltage Differential ................................................ 10V
ELECTRICAL CHARACTERISTICS
(NOTE 1) at I
OUT
= 10mA, Ta=25°C, unless otherwise specified.
PARAMETER
1.5V Version
Output Voltage (Note 2)
2.5V Version
Output Voltage (Note 2)
3.3V Version
Output Voltage (Note 2)
5.0V Version
Output Voltage (Note 2)
All Voltage Options
Reference Voltage (V
REF
)
Min. Load Current (Note 3)
Line Regulation (∆V
REF
(V
IN
))
Load Regulation(∆V
REF
(I
OUT
))
V
IN
≤
7V, P≤ P
MAX
1.5V≤ (V
IN
-V
OUT
)≤5.75V, 10mA≤I
OUT
≤1.5A
1.5V≤ (V
IN
-V
OUT
)≤5.75V
2.75V≤V
IN
≤7V,
I
OUT
=10mA, T
J
=25°C (Note 3)
V
IN
≤7V,
I
OUT
=0mA, T
J
=25°C (Note 2)
10mA≤I
OUT
≤1.5A,
(V
IN
-V
OUT
)=3V, T
J
=25°C
(Note 3)
0≤I
OUT
≤1.5A,
V
IN
=7V, T
J
=25°C (Note 2)
Dropout Voltage
Current Limit
I
OUT
(MAX)
Long Term Stability
Thermal Regulation
(∆V
OUT
(Pwr))
Temperature Stability
(∆V
OUT
(T))
Output Noise, RMS
Thermal Resistance
10Hz to 10khz T
A
=25°C
TO-220
DD Package
Junction to Tab
Junction to Ambient
Junction to Tab
Junction to Ambient
0.25
0.003
3.0
60
3.0
60
0.25
0.003
3.0
60
3.0
60
%
% V
O
°C/W
°C/W
∆V
REF
=1%
I
OUT
=1.5A (Note 3)
I
OUT
≤
1.5A (Note 2)
0.05
1.1
0.3
1.2
0.05
1.1
0.3
1.2
%
V
A
2.5
0.3
(Note 2)
0.01
1.7
1
0.02
2.5
0.3
(Note 2)
0.01
1.7
1
0.020
%
%/W
1.225 1.250 1.270 1.225 1.250 1.270
5
0.005
0.005
0.05
10
0.2
0.2
0.3
5
0.005
0.005
0.05
10
0.2
0.2
0.3
V
mA
%
%
%
SPX2815-5.0V, 0
≤I
OUT
≤1.5A,
5.5V≤V
IN
≤7V
5.0
4.95
4.900
5.0
5.0
4.90 5.05
4.850 5.100
5.0
5.0
5.10
5.150
V
V
SPX2815-3.3V, 0
≤I
OUT
≤1.5A,
4.75V≤V
IN
≤7V
3.267
3.240
3.3
3.3
3.333 3.234
3.360 3.201
3.3
3.3
3.366
3.399
V
V
SPX2815-2.5V,0
≤I
OUT
≤1.5A,
3.5V≤V
IN
≤7V
2.5
2.475
2.450
2.5
2.5
2.450 2.525
2.425 2.550
2.5
2.5
2.550
2.575
V
V
SPX2815-1.5V, 0
≤I
OUT
≤1.5A,
2.75V≤V
IN
≤7V
1.485
1.470
1.5
1.5
1.515 1.470
1.530 1.455
1.5
1.5
1.530
1.545
V
V
CONDITIONS
MIN
TYP
MAX
MIN
TYP
SPX2815
MAX UNITS
SPX2815A
V
IN
=7V
1.4V≤ (V
IN
- V
OUT
) (Note3)
T
A
=125°C, 1000 Hrs.
T
A
=25°C, 20 ms pulse
NOTES:
The Bold specifications apply to the full operating temperature range.
Note 1: Changes in output voltage due to heating effects are covered under the specification for thermal
regulation.
Note 2: Fixed Version Only
Note 3: Adjustable Version Only
Rev. 5/05/03
SPX2815 1.5A Low Dropout Voltage Regulator
© Copyright 2003 Sipex Corporation
2
APPLICATION INFORMATION
The SPX2815 incorporates protection against
over-current faults, reversed load insertion, over
temperature operation, and positive and nega-
tive transient voltage. However, the use of an
output capacitor is required in order to insure the
stability and the performances.
Stability
M = V
OUT
/ V
REF
Where M = multiplier for the ripple seen when
the ADJ pin is optimally bypassed.
V
REF
= Reference Voltage
Reducing parasitic resistance and inductance
One solution to minimize parasitic resistance
and inductance is to connect in parallel capaci-
tors. This arrangement will improve the tran-
sient response of the power supply if your sys-
tem requires rapidly changing current load con-
dition.
Thermal Consideration
The output capacitor is part of the regulator’s
frequency compensation system. Either a 22µF
aluminum electrolytic capacitor or a 10µF solid
tantalum capacitor between the output terminal
and ground guarantees stable operation for all
operating conditions.
However, in order to minimize overshoot and
undershoot, and therefore optimize the design,
please refer to the section ‘Ripple Rejection’.
Ripple Rejection
Although the SPX2815 offers some limiting
circuitry for overload conditions, it is necessary
not to exceed the maximum junction tempera-
ture, and therefore to be careful about thermal
resistance. The heat flow will follow the lowest
resistance path, which is the Junction-to-case
thermal resistance. In order to insure the best
thermal flow of the component, a proper mount-
ing is required. Note that the case of the device
is electrically connected to the output. In case
the case has to be electrically isolated, a ther-
mally conductive spacer can be used. However
do not forget to consider its contribution to
thermal resistance.
Assuming:
V
IN
=10V, V
OUT
=5V, I
OUT
=1.5A, T
A
=50°C/W,
θ
Heatsink Case
=6°C/W,θ
θ
JC
=3°C/W
Heatsink Case
=0.5°C/W,
Ripple rejection can be improved by adding a
capacitor between the ADJ pin and ground.
When ADJ pin bypassing is used, the value of
the output capacitor required increases to its
maximum (22µF for an aluminum electrolytic
capacitor, or 10µF for a solid tantalum capaci-
tor). If the ADJ pin is not bypass, the value of the
output capacitor can be lowered to 100µF for an
electrolytic aluminum capacitor or 4.7µF for a
solid tantalum capacitor.
However the value of the ADJ-bypass capacitor
should be chosen with respect to the following
equation:
C = 1 / ( 6.28 * F
R
* R
1
)
Where C = value of the capacitor in Farads
(select an equal or larger standard value),
F
R
= ripple frequency in Hz,
R
1
= value of resistor R1 in Ohms.
If an ADJ-bypass capacitor is use, the amplitude
of the output ripple will be independent of the
output voltage. If an ADJ bypass capacitor is not
used, the output ripple will be proportional to
the ratio of the output voltage to the reference
voltage:
Power dissipation under this condition
P
D
= (V
IN
- V
OUT
) * I
OUT
= 7.5W
Junction Temperature
T
J
= T
A
+ P
D
* (θ
Case - HS
+
θ
HS
+
θ
JC
)
For Control & Power Sections
T
J
= 50 + 7.5*(0.5+6=3) = 121.25°C
121.25°C<T
J (max)
for Control & Power Sections.
In both case reliable operation is insured by
adequate junction temperature.
Rev. 5/05/03
SPX2815 1.5A Low Dropout Voltage Regulato
© Copyright 2003 Sipex Corporation
3
APPLICATION INFORMATION: Continued
V
OUT
SPX2815
V
REF
I
ADJ
50µA
V
OUT
= V
REF
* (1+R
2
/R
1
) +I
ADJ
* R
2
R
2
R
1
V
OUT
V
IN
5V
C
1
10µF
SPX2815
V
OUT
3.3V
C
1
10µF
Figure 2. Basic Adjustable Regulator
Figure 3. Basic Fixed Regulator
Output Voltage
Consider Figure 2. The resistance R
1
generates
a constant current flow, normally the specified
load current of 10mA.
This current will go through the resistance R
2
to
set the overall output voltage. The current I
ADJ
is
very small and constant.
Therefore its contribution to the overall output
voltage is very small and can generally be ig-
nored.
Load Regulation
and not to the load. For the same reason, it is best
to connect the resistor R
2
to the Negative side of
the load.
Output Voltage
The fixed voltage LDO voltage regulators are
simple to use regulators since the V
OUT
is preset
to the specifications. It is important however, to
provide the proper output capacitance for stabil-
ity and improvement. For most operating condi-
tions a capacitance of 22uF tantalum or 100uF
electrolytic will ensure stability and prevent
oscillation.
Parasitic line resistance can degrade load regu-
lation. In order not to affect the behavior of the
regulator, it is best to connect directly the R
1
resistance from the resistor divider to the case,
R
P
Parasitic Line
Resistance
V
OUT
SPX2815
Connect R
1
to
Case of Regulator
R
1
R
L
R
2
Connect R
2
to Load
Figure 4. Basic Adjustable Regulator
Rev. 5/05/03
SPX2815 1.5A Low Dropout Voltage Regulator
© Copyright 2003 Sipex Corporation
4
APPLICATION INFORMATION: Continued
V
IN
C
1
IN
SPX2815
ADJ
OUT
V
IN
10µF +
SPX2815
ADJ
OUT
C
2
R
1
V
OUT
R
1
LOAD
V
OUT
= V
REF
(1+R
2
/R
1
) +I
ADJ
R
2
R
2
Figure 4. 1.5V Current Output Regulator
Figure 5. Typical Adjustable Regulator
(Note A)
V
IN
+
10µF
SPX2815
IN
OUT
5V
SPX2815
V
OUT
R
1
121kΩ
1%
10µF
V
IN
(Note A)
+
IN
ADJ
OUT
5V
121kΩ
1%
+
ADJ
10µF
1k
2N3904
1k
10µF
*C
1
improves ripple rejection.
X
C
should be ~ R1 at ripple frequency
R
2
365Ω
1%
+
C
1
10µF*
TTL
Input
365Ω
1%
Note A: V
IN(MIN)
= (Intended V
OUT
) + (V
DROPOUT (MAX)
)
Note A: V
IN(MIN)
= (Intended V
OUT
) + (V
)
DROPOUT (MAX)
Figure 5. Improving Ripple Rejection
Figure 7. 5V Regulator with Shutdown
Rev. 5/05/03
SPX2815 1.5A Low Dropout Voltage Regulato
© Copyright 2003 Sipex Corporation
5
京公网安备 11010802033920号
EEWORLD
