SPX1585
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
•
Output Current Of 5A
•
Low Dropout Voltage 1.1V Typ @ 5A.
•
Extremely Tight Load And Line Regulation
•
Current & Thermal Limiting
•
Standard 3-Terminal Low Cost TO-220 & TO-263
•
Similar To Industry Standard LT1085/LT1585
APPLICATIONS
•
Powering VGA & Sound Card
•
Power PC Supplies
•
SMPS Post-Regulator
•
High Efficiency “Green” Computer Systems
•
High Efficiency Linear Power Supplies
•
Portable Instrumentation
•
Constant Current Regulators
•
Adjustable Power Supplies
•
Battery charger
Now Available in Lead Free Packaging
PRODUCT DESCRIPTION
The SPX1585 is
a
low power 5A adjustable and fixed voltage regulator that is very easy to use. It requires only 2 external resistors to set
the output voltage for
the
adjustable version. The SPX1585
devices
are designed for low voltage applications that offer lower dropout
voltage and faster transient response. This device is an excellent choice for use in powering low voltage microprocessors 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 applica-
tions. The SPX1585 features low dropout of a maximum 1.2 volts.
The SPX1585 offers full protection against over-current faults, reversed input polarity, reversed load insertion, and positive and negative
transient voltage. On-Chip trimming adjusts the reference voltage to 1%. The I
Q
of this device flows into the load, which increases
efficiency.
The SPX1585
devices
are offered in a 3-pin TO-220 and TO-263 package compatible with other 3 terminal regulators. For a
n
8A low
dropout regulator, refer to the SPX1584 data sheet.
PIN CONNECTIONS
TO-263-3 (T)
3
V
IN
V
OUT
ADJ/GND
Front View
TO-220-3 (U)
3
V
IN
V
OUT
ADJ/GND
SPX1585
2
1
SPX1585
2
1
Top View
Note that TAB is connected to VOUT for both package types.
Date:
05/14/04
SPX1585
ABSOLUTE MAXIMUM RATINGS
Lead Temp. (Soldering, 10 Seconds) .............................. 300°C
Storage Temperature Range ............................ -65° to +150°C
Operating Junction Temperature Range
SPX1585 Control Section.......................... -45°C +125°C
SPX1585 Power Transistor.........................-45°C +150°C
Input Voltage........................................................ 10V
Input to Output Voltage Differential .................... 10V
ELECTRICAL CHARACTERISTICS
(NOTE 1)
at I
OUT
= 10mA, T
A
=25°C, unless otherwise specified.
PARAMETER
1.5V Version
Output Voltage (Note 2)
SPX1585-1.5V, 0 < I
OUT
< 5A, 3.3V<V
IN
<10V
1.5
1.485
1.47
1.515
1.53
2.525
2.55
3.333
3.366
1.47
1.455
2.45
2.425
3.234
3.069
1.53
1.545
2.55
2.575
3.366
3.399
V
V
V
CONDITIONS
Typ
SPX1585A
Min
Max
SPX1585
Min
Max
UNITS
2.5V Version
Output Voltage (Note 2)
SPX1585-2.5V, 0 < I
OUT
< 5A, 4.0V<V
IN
<10V
2.5
2.475
2.45
3.3V Version
Output Voltage (Note 2)
SPX1585-3.3V, 0 < I
OUT
< 5A, 4.8V<V
IN
<10V
3.3
3.267
3.234
All Voltage Options
Reference Voltage (Vref)
Min. Load Current (Note 3)
Line Regulation (∆Vref(Vin))
V
IN
≤
7V, P≤ P
MAX
1.5V≤ (V
IN
-V
OUT
)≤5.75V, 10mA≤I
OUT
≤5A
1.5V≤ (V
IN
–V
OUT
)≤5.75V
2.75V≤V
IN
≤7V,
Iout=10mA, T
J
=25ºC
(Note 3)
V
IN
≤7V,
I
OUT
=0mA, T
J
=25ºC (Note 2)
10mA≤I
OUT
≤5A,
(V
IN
-V
OUT
)=3V, T
J
=25ºC (Note 3)
0≤I
OUT
≤5A,
V
IN
=7V, T
J
=25ºC (Note 2)
Dropout Voltage
Current Limit
Iout(MAX)
Long Term Stability
Thermal Regulation
(∆Vout(Pwr))
Temperature Stability
(∆Vout(T))
Output Noise, RMS
Thermal Resistance
∆V
REF
=1%
V
IN
=7V
1.4V
≤
(V
IN
- V
OUT
) (Note3)
T
A
=125ºC, 1000 Hrs.
T
A
=25ºC, 20 ms pulse
0.3
(Note 2)
0.01
0.25
10Hz to 10kHz
TO-220
T
A
=25ºC
Junction to Tab
Junction to Ambient
Junction to Tab
Junction to Ambient
0.003
3.0
60
3.0
60
3.0
60
3.0
60
1
0.020
1
0.020
%
%/W
%
% Vo
ºC/W
I
OUT
= 5A (Note 3)
I
OUT
< 5A (Note 2)
1.250
5
0.005
0.005
0.05
0.05
1.1
6
5.2
1.225
1.270
10
0.2
0.2
0.3
0.3
1.2
5.2
1.225
1.270
10
0.2
0.2
0.3
0.3
1.2
A
%
V
V
%
Load Regulation(∆Vref(Iout))
DD Package
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
Date:
05/14/04
SPX1585
APPLICATION HINTS
The SPX1585 incorporates protection against over-current
faults, reversed load insertion, over temperature operation, and
positive and negative transient voltages. However, the use of an
output capacitor is required in order to insure the stability and
the performance
of the device.
Stability
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 operat-
ing conditions.
The recommended value for ESR is 0.5Ohms or
less.
However, in order to minimize overshoot and undershoot, and
therefore optimize the design, please refer to the section ‘Ripple
Rejection’.
Ripple Rejection
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
(220µF for an aluminum electrolytic capacitor, or 47µF for a
solid tantalum capacitor). If the ADJ pin is not bypassed, the
value of the output capacitor can be lowered to 10µF for an elec-
trolytic 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
F
R
R
1
= value of the capacitor in Farads
(select an equal or larger standard value),
= ripple frequency in Hz,
= value of resistor R
1
in Ohms.
Reducing parasitic resistance and inductance
One solution to minimize parasitic resistance and inductance is
to connect in parallel capacitors. This arrangement will
improve the transient response of the power supply if your
system requires rapidly changing current load condition.
Thermal Consideration
Although the SPX1585 offers some limiting circuitry for
overload conditions, it is necessary not to exceed the maximum
junction temperature, 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 in-
sure the best thermal flow of the component, a proper mounting
is required. Note that the case of the device is electrically con-
nected to the output. If the case must be electrically isolated, a
thermally conductive spacer can be used. However do not for-
get 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
Heatsink Case
= 0.5°C/W,
θ
JC
= 3°C/W
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 the Control Section
T
J
= 50 + 7.5*(0.5 + 6=3) = 121.25°C
121.25°C < T
J (max)
for the Control & Power Sections.
In both
conditions,
reliable operation is insured by adequate
junction temperature.
If an ADJ-bypass capacitor is used, 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:
M = V
OUT
/ V
REF
Where M
V
REF
= multiplier for the ripple seen when the ADJ pin
is optimally bypassed.
= Reference Voltage
D
ate: 05/14/04
SPX1585
Basic Adjustable Regulator
V
IN
V
OUT
V
REF
R
1
SPX1585
ADJ
I
ADJ
50uA
R
2
V
OUT
= V
REF
* ( 1 + R /R
1
) + I
ADJ
* R
2
2
Load Regulation
Parasitic line resistance can degrade load regulation. 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,
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.
V
IN
5V
SPX1585
Fig.2 Basic Adjustable Regulator
C1
10uF
V
OUT
3.3V
C2
10uF
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 ignored.
Basic Fixed Regulator
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 stability and improvement. For most operating conditions a
capacitance of 22uF tantalum or 100uF electrolytic will ensure
stability and prevent oscillation.
V
IN
R
P
Parasitic Line
Resistance
V
OUT
SPX1585
ADJ
Connect R
1
to
Case of Regulator
R
1
R
L
R
2
Connect R
2
to Load
Fig.3 Basic Adjustable Regulator
D
ate: 05/14/04
SPX1585
TYPICAL APPLICATIONS
V
IN
C
1
IN
SPX1585
ADJ
OUT
R
1
V
IN
C
1
IN
SPX1585
ADJ
OUT
C
2
R
1
V
OUT
LOAD
V
OUT
= V
REF
(1 + R
2
) + I
ADJ
R
2
R
1
R
2
Fig. 4 5A Current output Regulator
Fig. 5 Typical Adjustable Regulator
(Note A)
V
IN
IN
5V
+
10µF
SPX1585
ADJ
OUT
V
OUT
R
1
121Ω
1%
150µF
V
IN
(Note A)
+
IN
SPX1585
ADJ
OUT
5V
121Ω
1%
+
100µF
10µF
1k
2N3904
1k
365Ω
1%
*C
1
improves ripple rejection. Xc
should be ~ R
1
at ripple frequency.
R
2
365Ω
1%
TTL
Input
+
C
1
10µF*
Note A: V
IN(MIN)
= (Intended V
OUT
) + (V
DROPOUT (MAX)
)
Note A: V
IN(MIN)
= (Intended V ) + (V
DROPOUT (MAX)
)
OUT
Fig. 6
Improving Ripple Rejection
Fig.7 5V Regulator with Shutdown
D
ate: 05/14/04
