ETC AS2810AR

AS2810
1A Low Dropout Voltage Regulator
Adjustable & Fixed Output,
Fast Response
FEATURES
APPLICATIONS
• 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
• 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
TO-252
3-PIN
OPEPERATING JUNCTION
TEMP. RANGE
AS2810YM3-X
AS2810YR-X
-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)
AS2810
AS2810
1
2
3
TO-220-3 (U)
1
2
3
AS2810
1
ADJ/ GND VOUT VIN
2
TO-252 (R)
AS2810
1
2
3
3
Top View
ADJ/GND VOUT VIN
Front View
ADJ/GND VOUT VIN
Top View
ADJ/GND VOUT VIN
Front View
Rev. 10/2/00
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 IOUT = 10mA, TA=25°C, unless otherwise specified.
PARAMETER
1.5V Version
Output Voltage (Note 2)
2.5V Version
Output Voltage (Note 2)
CONDITIONS
AS2810-1.5V, 0 < IOUT < 1A, 3.3V<VIN<10V
AS2810-2.5V, 0 < IOUT < 1A, 4.0V<VIN<10V
Typ
1.5
2.5
AS2810A
AS2810
UNITS
Min
Max
Min
Max
1.485
1.515
1.470
1.530
1.47
1.53
1.455
1.545
2.475
2.525
2.450
2.550
2.45
2.55
2.425
2.575
V
V
2.85V Version
Output Voltage (Note 2)
AS2810-2.85V, 0 ≤ IOUT ≤ 1A, 4.5V≤VIN≤10V
2.85
2.822
2.793
2.879
2.907
2.793
2.650
2.907
2.936
V
AS2810-3.0V, 0 ≤ IOUT ≤ 1A, 4.5V≤VIN≤10V
3
2.970
3.030
2.94
3.06
V
2.940
3.060
2.79
3.09
3.267
3.333
3.234
3.366
3.234
3.366
3.069
3.399
4.950
5.050
4.9
5.1
4.900
5.100
4.65
5.15
1.225
1.263
1.270
1.225
10
1.225
1.212
1.270
1.288
10
mA
%
3.0V Version
Output Voltage (Note 2)
3.3V Version
Output Voltage (Note 2)
AS2810-3.3V, 0 ≤ IOUT ≤ 1A, 4.8V≤VIN≤10V
3.3
V
5.0V Version
Output Voltage (Note 2)
AS2810-5.0V, 0 ≤ IOUT ≤ 1A, 6.5V≤VIN≤12V
5
V
All Voltage Options
Reference Voltage (VREF)
1.250
Min. Load Current (Note 3)
VIN≤ 7V, P≤ Pmax
1.5V≤ (VIN -VOUT)≤5.75V, 10mA≤IOUT≤1A
1.5V≤ (VIN –VOUT)≤5.75V
Line Regulation (∆VREF(Vin))
2.75V≤VIN ≤7V, IOUT=10mA, TJ=25ºC (Note 3)
0.005
0.2
0.2
VIN≤7V, IOUT=0mA, TJ=25ºC (Note 2)
0.005
0.2
0.2
10mA≤IOUT ≤1A, (VIN-VOUT)=3V, TJ=25ºC
(Note 3)
0≤IOUT ≤1A, VIN=7V, TJ=25ºC (Note 2)
0.05
0.3
0.3
0.05
0.3
0.3
∆VREF=1%
1.1
1.2
1.2
Load Regulation(∆VREF(IOUT))
Dropout Voltage
Current Limit
IOUT(MAX)
IOUT = 1A (Note 3)
IOUT ≤ 1A (Note 2)
VIN=7V
5
2
1.2
1.2
V
%
A
1.4V ≤ (VIN- VOUT) (Note3)
Rev. 10/2/00
AS2810
ELECTRICAL CHARACTERISTICS (Cont.)
Long Term Stability
TA=125ºC, 1000 Hrs.
Thermal Regulation (∆VOUT(Pwr))
TA=25ºC, 20 ms pulse
Temperature Stability (∆VOUT(T))
Output Noise, RMS
10Hz to 10kHz
Thermal Resistance
TO-220
DD Package
SOT-223 Package
0.3
(Note 2)
0.01
1
1
%
0.020
0.020
%/W
0.25
0.003
TA=25ºC
%
% Vo
Junction to Tab
Junction to Ambient
3.0
3.0
60
60
Junction to Tab
Junction to Ambient
3.0
3.0
60
60
Junction to Tab
Junction to Ambient
ºC/W
15
15
156
156
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
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 * FR * R1 )
Where C
= value of the capacitor in Farads (select an
equal or larger standard value),
FR = ripple frequency in Hz,
R1 = value of resistor R1 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 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:
VIN = 10V, VOUT = 5V, IOUT = 1.5A, TA = 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
PD = (VIN – VOUT) * IOUT = 7.5W
Junction Temperature
TJ = TA + PD * (θ Case - HS+ θ HS + θ JC)
For the Control Sections
TJ = 50 + 7.5*(0.5+6=3) = 121.25°C
121.25°C < TJ (max) for the Control & Power Sections.
In both case reliable operation is insured by adequate junction
temperature.
If an ADJ-bypass capacitor is use, the amplitude of the output
ripple will be independent of the output voltage. If an ADJbypass capacitor is not used, the output ripple will be
proportional to the ratio of the output voltage to the reference
voltage:
M = VOUT / VREF
Where M = multiplier for the ripple seen when the ADJ pin
is optimally bypassed.
VREF = Reference Voltage
Rev. 10/2/00
AS2810
Basic Adjustable Regulator
VIN
VOUT
AS2810
VREF
VIN
5V
R1
IADJ
50µA
AS2810
C2
10uF
C1
10uF
R2
VOUT
3.3V
VOUT = VREF * ( 1 + R2/R1) + IADJ * R2
Basic Fixed Regulator
Fig.2 Basic Adjustable Regulator
Output Voltage
Consider Figure 2. The resistance R1 generates a constant
current flow, normally the specified load current of 10mA.
This current will go through the resistance R2 to set the overall
output voltage. The current IADJ is very small and constant.
Therefore its contribution to the overall output voltage is very
small and can generally be ignored.
Output Voltage
The fixed voltage LDO voltage regulator are simple to use
regulators since the VOUT 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.
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 R1 resistance from the resistor divider to the case,
and not to the load. For the same reason, it is best to connect
the resistor R2 to the Negative side of the load.
VIN
AS2810
R P Parasitic Line
Resistance
Connect R 1 to
Case of Regulator
R1
RL
R2
Connect R 2 to Load
Fig.3 Basic Adjustable Regulator
Rev. 10/2/00
AS2810
TYPICAL APPLICATIONS
VIN
IN
AS2810
VIN
OUT
Fig. 5 Typical Adjustable Regulator
Fig. 4 1A Current output Regulator
5V
IN
+
10µF
AS2810
*C 1 improves ripple rejection. Xc
should be ~ R 1 at ripple frequency.
VOUT
OUT
ADJ
VIN
C1
10µF*
AS2810
TTL
Input
5V
OUT
121Ω
1%
ADJ
+
150µF
+
IN
(Note A)
R1
121Ω
1%
R2
365Ω
1%
R2
VOUT = VREF (1 + R2 ) + IADJ R2
R1
LOAD
(Note A)
R1
ADJ
R1
ADJ
VOUT
OUT
C2
C1
C1
VIN
AS2810
IN
+
10µF
100µF
1k
2N3904
1k
365Ω
1%
Note A: VIN(MIN) = (Intended VOUT) + (VDROPOUT (MAX))
Note A: VIN(MIN)= (Intended VOUT) + (VDROPOUT (MAX))
Fig. 6
Improving Ripple Rejection
Fig.7 5V Regulator with Shutdown
Rev. 10/2/00
AS2810
TYPICAL CHARACTERISTICS
Rev. 10/2/00