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AS2810
1A Low Dropout Voltage Regulator
Adjustable & Fixed Output,
Fast Response
FEATURES
•
Adjustable Output Down To 1.2V
•
Fixed Output Voltages 1.5V, 2.5V, 3.0V, 3.3V, 5.0V
•
Output Current Of 1A
•
Low Dropout Voltage 1.2V Typ.
•
Extremely Tight Load And Line Regulation
•
Current & Thermal Limiting
•
Standard 3-Terminal Low Cost TO-220, TO-263, TO-252 & SOT-223
APPLICATIONS
•
SCSI-II Active Terminator
•
Portable Palmtap/Notebook Computer
•
SMPS Post-Regulator
•
Disk Drives
•
Portable Consumer Equipment
•
Portable Instrumentation
•
Battery charger
PRODUCT DESCRIPTION
The AS2810 is a low power positive voltage regulator designed to meet 1A output current and comply with SCSI-II specifications with
fix output voltage of 2.85V. This device is an excellent choice for use in battery-powered applications and portable computers. The
AS2810 features very low quiescent current and very low dropout voltage of 1.2V at a full load and lower as output current decreases.
This product is available as adjustable or fixed 1.5V, 2.5V, 3.0V, 3.3V, and 5V output voltages.
The AS2810 is offered in a 3-pin surface mount packages SOT-223, TO-220, TO-252 & DD package. The output capacitor of 10µF
or larger is needed for the output stability of AS2810 as required by most other regulator circuits
ORDERING INFORMATION
TO-220
3-PIN
AS2810YU-X
DD PLASTIC
3-PIN
AS2810YT-X
SOT-223
3-PIN
AS2810YM3-X
TO-252
3-PIN
AS2810YR-X
OPEPERATING JUNCTION
TEMP. RANGE
-45 to +125°C
X= Output Voltage (1.5V, 2.5V, 3.0V, 3.3V, 5.0V and Blank for Adj.)
Y= Output Tolerance, A for 1%
Blank for 2%
Consult with factory for other fixed voltages.
PIN CONNECTIONS
SOT-223 (M3)
TO-263-3 (T)
TO-220-3 (U)
TO-252 (R)
AS2810
1
2
3
AS2810
1
2
3
AS2810
1
2
3
AS2810
1
2
3
ADJ/ GND V
OUT
V
IN
Top View
ADJ/GND V
OUT
V
IN
ADJ/GND V
OUT
V
IN
ADJ/GND V
OUT
V
IN
Front View
Top View
Front View
Rev. 10/2/00
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AS2810
ABSOLUTE MAXIMUM RATINGS
Lead Temp. (Soldering, 10 Seconds) .............................. 300°C
Storage Temperature Range ............................ -65° to +150°C
Operating Junction Temperature Range ......................
AS2810 Control Section ............................ -45°C +125°C
AS2810 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)
2.5V Version
Output Voltage (Note 2)
2.85V Version
Output Voltage (Note 2)
3.0V 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≤ Pmax
1.5V≤ (V
IN
-V
OUT
)≤5.75V, 10mA≤I
OUT
≤1A
1.5V≤ (V
IN
–V
OUT
)≤5.75V
2.75V≤V
IN
≤7V,
I
OUT
=10mA, T
J
=25ºC (Note 3)
V
IN
≤7V,
I
OUT
=0mA, T
J
=25ºC (Note 2)
10mA≤I
OUT
≤1A,
(V
IN
-V
OUT
)=3V, T
J
=25ºC
(Note 3)
0≤I
OUT
≤1A,
V
IN
=7V, T
J
=25ºC (Note 2)
∆V
REF
=1%
I
OUT
= 1A (Note 3)
I
OUT
≤
1A (Note 2)
V
IN
=7V
1.4V
≤
(V
IN
- V
OUT
) (Note3)
1.250
5
0.005
0.005
0.05
0.05
1.1
2
1.2
1.225
1.263
1.270
1.225
10
0.2
0.2
0.3
0.3
1.2
1.2
1.225
1.212
1.270
1.288
10
0.2
0.2
0.3
0.3
1.2
A
%
V
mA
%
AS2810-5.0V, 0
≤
I
OUT
≤
1A, 6.5V≤V
IN
≤12V
5
4.950
4.900
5.050
5.100
4.9
4.65
5.1
5.15
V
AS2810-3.3V, 0
≤
I
OUT
≤
1A, 4.8V≤V
IN
≤10V
3.3
3.267
3.234
3.333
3.366
3.234
3.069
3.366
3.399
V
AS2810-3.0V, 0
≤
I
OUT
≤
1A, 4.5V≤V
IN
≤10V
3
2.970
2.940
3.030
3.060
2.94
2.79
3.06
3.09
V
AS2810-2.85V, 0
≤
I
OUT
≤
1A, 4.5V≤V
IN
≤10V
2.85
2.822
2.793
2.879
2.907
2.793
2.650
2.907
2.936
V
CONDITIONS
Typ
AS2810A
Min
AS2810-1.5V, 0 < I
OUT
< 1A, 3.3V<V
IN
<10V
1.5
1.485
1.47
AS2810-2.5V, 0 < I
OUT
< 1A, 4.0V<V
IN
<10V
2.5
2.475
2.45
Max
1.515
1.53
2.525
2.55
AS2810
Min
1.470
1.455
2.450
2.425
Max
1.530
1.545
2.550
2.575
V
V
UNITS
Dropout Voltage
Current Limit
I
OUT
(MAX)
Rev. 10/2/00
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AS2810
ELECTRICAL CHARACTERISTICS (Cont.)
Long Term Stability
Thermal Regulation (∆V
OUT
(Pwr))
Temperature Stability (∆V
OUT
(T))
Output Noise, RMS
Thermal Resistance
T
A
=125ºC, 1000 Hrs.
T
A
=25ºC, 20 ms pulse
10Hz to 10kHz
TO-220
DD Package
SOT-223 Package
T
A
=25ºC
Junction to Tab
Junction to Ambient
Junction to Tab
Junction to Ambient
Junction to Tab
Junction to Ambient
0.3
(Note 2)
0.01
0.25
0.003
3.0
60
3.0
60
15
156
3.0
60
3.0
60
15
156
ºC/W
1
0.020
1
0.020
%
%/W
%
% Vo
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. 10/2/00
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AS2810
APPLICATION HINTS
The AS2810 incorporates protection against over-current
faults, reversed load insertion, over temperature operation, and
positive and negative transient voltage. However, the use of
an output capacitor is required in order to improve the stability
and the performances.
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
operating conditions.
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 as shown in figure 6. 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 capacitor).
If the ADJ pin is not bypass, the value of the output capacitor
can be lowered to 10µF 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 R
1
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:
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 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 AS2810 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 insure the best thermal flow of the
component, a proper mounting 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 thermally 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
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 Sections
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 case reliable operation is insured by adequate junction
temperature.
Rev. 10/2/00
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AS2810
Basic Adjustable Regulator
V
IN
AS2810
V
REF
I
ADJ
50µA
R
2
V
OUT
= V
REF
* ( 1 + R /R
1
) + I
ADJ
* R
2
2
R
1
V
OUT
V
IN
5V
C1
10uF
V
OUT
3.3V
C2
10uF
AS2810
Basic Fixed Regulator
Fig.2 Basic Adjustable 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 ignored.
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.
R
P
Parasitic Line
Resistance
Output Voltage
The fixed voltage LDO voltage regulator 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
AS2810
Connect R
1
to
Case of Regulator
R
1
R
L
R
2
Connect R
2
to Load
Fig.3 Basic Adjustable Regulator
Rev. 10/2/00
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