AS2886AT-5.0 [ETC]
Analog IC ; 模拟IC\n
| 型号： | AS2886AT-5.0 |
| 厂家： | 
ETC |
| 描述： | Analog IC
|
| 文件： | 总6页 (文件大小：159K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
AS2886
1.5A Low Dropout Voltage Regulator
Adjustable & Fixed Output,
Fast Response
FEATURES
APPLICATIONS
• Adjustable Output Down To 1.2V
• Fixed Output Voltages 1.5, 2.5, 3.3, 5.0V
• Output Current of 1.5A
• Powering VGA & Sound Card
• Power PCSupplies
• SMPS Post-Regulator
• Low Dropout Voltage 1.1V Typ.
• Extremely Tight Load And Line Regulation
• Current & Thermal Limiting
• High Efficiency “Green” Computer Systems
• High Efficiency Linear Power Supplies
• Portable Instrumentation
• Standard 3-Terminal Low Cost TO-220, TO-263 & TO-252
• Similar To Industry Standard LT1086/LT1586
• Constant Current Regulators
• Adjustable Power Supplies
• Battery charger
PRODUCT DESCRIPTION
The AS2886 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 AS2886 is 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 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 AS2886 features low dropout of a maximum 1.2 volts.
The AS2886 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 IQ of this device flows into load which
increases efficiency.
The AS2886 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 AS2830 data sheet.
ORDERING INFORMATION
TO-220
3-PIN
DD PLASTIC
3-PIN
TO-252
DPAK
AS2886YR
AS2886YR-X
AS2886YU
AS2886YU-X
AS2886YT
AS2886YT-X
PIN CONNECTIONS
X = Output Voltage (i.e. 1.5 for 1.5V, 2.5 for 2.5V)
TO-263-3 (T)
TO-220-3 (U)
TO-252 (R)
Y = Output Tolerance, A for 1%
Blank for 2%
Consult with factory for other fixed output voltages
AS2886
AS2886
1
2
3
AS2886
1
3
2
1
2
3
ADJ/GND VOUT VIN
Front View
VIN
ADJ/GND
VOUT
Top View
VIN
V
ADJ/GND
OUT
Front View
Rev. 10/11/00
AS2886
ABSOLUTE MAXIMUM RATINGS
Lead Temp. (Soldering, 10 Seconds) .............................. 300°C
Storage Temperature Range ............................-65° to +150°C
Operating Junction Temperature Range ......................
AS2886 Control Section............................ -45°C +125°C
AS2886 Power Transistor...........................-45°C +150°C
Input Voltage........................................................ 30V
Input to Output Voltage Differential .................... 30V
ELECTRICAL CHARACTERISTICS (NOTE 1) at IOUT = 10mA, Ta=25°C, unless otherwise specified.
AS2886A
AS2886
PARAMETER
CONDITIONS
Typ
Units
Min
Max
Min
Max
1.5V Version
1.5
1.485
1.470
1.515
1.530
1.470
1.455
1.530
1.545
V
AS2886-1.5V, 0 ≤IOUT≤1.5A, 2.75V≤VIN ≤29V
AS2886-2.5V,0 ≤IOUT≤1.5A, 4.0V≤VIN ≤29V
Output Voltage (Note 2)
1.5
2.5V Version
Output Voltage (Note 2)
2.5
2.5
2.475
2.450
2.525
2.550
2.450
2.425
2.550
2.575
V
3.3V Version
Output Voltage (Note 2)
3.3
3.270
3.330
3.230
3.201
3.370
3.399
V
V
V
AS2886-3.3V, 0 ≤IOUT≤1.5A, 4.75V≤VIN ≤29V
AS2886-5.0V, 0 ≤IOUT≤1.5A, 6.5V≤VIN ≤29V
3.3
3.240
3.360
5.0V Version
Output Voltage (Note 2)
5.0
5.0
4.95
4.90
5.05
5.10
4.900
4.850
5.100
5.150
All Voltage Options
V
IN≤ 7V, P≤ PMAX
Reference Voltage (VREF
)
1.250
5
1.225
1.270
10
1.225
1.270
10
1.5V≤ (VIN -VOUT)≤5.75V, 10mA≤IOUT≤1.5A
1.5V≤ (VIN -VOUT)≤5.75V
mA
%
Min. Load Current (Note 3)
0.005
0.005
0.05
0.2
0.2
0.3
0.2
0.2
0.3
2.75V≤VIN ≤29V, IOUT=10mA, TJ=25°C (Note 3)
Line Regulation (∆VREF(VIN))
Load Regulation(∆VREF(IOUT))
%
%
V
IN ≤29V, IOUT=0mA, TJ=25°C (Note 2)
10mA≤IOUT ≤1.5A, (VIN-VOUT)=3V, TJ=25°C
(Note 3)
0.05
0.3
0.3
%
V
0≤IOUT ≤1.5A, VIN=7V, TJ=25°C (Note 2)
1.1
1.2
1.2
∆VREF=1%
IOUT =1.5A (Note 3)
OUT≤ 1.5A (Note 2)
Dropout Voltage
Current Limit
I
VIN=7V
A
%
2.5
1.7
1.7
1.4V≤ (VIN- VOUT) (Note3)
TA=125°C, 1000 Hrs.
IOUT MAX)
(
0.3
1
1
Long Term Stability
(Note 2)
0.01
0.25
0.020
0.020
%/W
%
TA=25°C, 20 ms pulse
Thermal Regulation
(∆VOUT(Pwr))
Temperature Stability
(∆VOUT(T))
0.003
% VO
°C/W
10Hz to 10khz TA=25°C
TO-220
Output Noise, RMS
Thermal Resistance
Junction to Tab
3.0
60
3.0
60
3.0
60
Junction to Ambient
Junction to Tab
DD Package
3.0
60
3.0
60
3.0
60
°C/W
Junction to Ambient
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. 10/11/00
AS2886
APPLICATION HINTS
Reducing parasitic resistance and inductance
The AS2886 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 insure the stability
and the performances.
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.
Stability
Thermal Consideration
The output capacitor is part of the regulator’s frequency
compensation system. Either a 220µF aluminum electrolytic
capacitor or a 47µF solid tantalum capacitor between the
output terminal and ground guarantees stable operation for all
operating conditions.
Although the AS2886 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.
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
bypass, the value of the output capacitor can be lowered to
100µF for an electrolytic aluminum capacitor or 15µF for a
solid tantalum capacitor.
Assuming:
V
IN = 10V, VOUT = 5V, IOUT = 1.5A, TA = 50°C/W,
θHeatsink Case= 6°C/W, θHeatsink 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)
However the value of the ADJ-bypass capacitor should be
chosen with respect to the following equation:
C = 1 / ( 6.28 * FR * R1 )
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.
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.
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 ADJ-
bypass 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. 10/11/00
AS2886
Basic Adjustable Regulator
V IN
VOUT
AS2886
R1
R2
VREF
IADJ
50µA
VOUT = VREF * ( 1 + R/R1) + IADJ * R2
2
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
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.
R
P Parasitic Line
Resistance
VIN
AS2886
Connect R 1 to
Case of Regulator
R1
RL
R2
Connect R 2 to Load
Fig.3 Basic Adjustable Regulator
Rev. 10/11/00
AS2886
TYPICAL APPLICATIONS
VIN
VOUT
VIN
OUT
IN
AS2886
OUT
IN
AS2886
C2
C1
C1
R1
R2
ADJ
R1
ADJ
VOUT = VREF (1 + R ) + IADJ R2
R21
LOAD
Fig. 5 Typical Adjustable Regulator
Fig. 4 1.5A Current output Regulator
(Note A)
VIN
5V
VIN
(Note A)
IN
OUT
5V
IN
OUT
VOUT
AS2886
ADJ
AS2886
+
10µF
121Ω
ADJ
R1
1%
+
121Ω
+
10µF
1k
1%
100µF
TTL
Input
150µF
2N3904
*C1 improves ripple rejection. Xc
should be ~ R 1 at ripple frequency.
365Ω
R2
365Ω
1%
1%
+
C1
10µF*
1k
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. 10/11/00
AS2886
TYPICAL CHARACTERISTICS
Rev. 10/11/00
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