AS2884
8A Low DropOut Voltage Regulator
Adjustable & Fixed 3.3V
FEATURES
•
Adjustable Output Down to 1.2V or Fixed 3.3V & 5V
•
Output Current of 8A
•
Low Dropout Voltage
•
Extremely Tight Load and Line Regulation
•
Current & Thermal Limiting
•
Standard 3-Terminal Low Cost TO-220
•
Similar to Industry Standard LT1083/LT1584
APPLICATIONS
•
Powering Intel Pentium
µP
from +5V Supplies
•
Power PCSupplies
•
SMPS Post-Regulator
•
High Efficiency “Green” Computer Systems
•
High Efficiency Linear Power Supplies
•
Portable Instrumentation
•
Constant Current Regulators
•
Adjustable Power Supplies
•
Battery Charger
PRODUCT DESCRIPTION
The AS2884 is a low power 8A Adjustable Voltage Regulator that is very easy to use. It requires only 2 external resistors to set the
output voltage. This device is an excellent choice when using Powering Intel Microprocessor to convert from +5V to 3.3V supplies,
and as a post regulator for switching supplies applications. The AS2884 features low dropout of a maximum 1.5 volts.
The AS2884 offers full protection against over-current faults, reversed input polarity, reversed load insertion, over temperature
operation, 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 AS2884 is offered in a 3-pin TO-220 package compatible with older 3-terminal regulators. For a 5A low dropout regulator refer
to the AS2850 datasheet.
ORDERING INFORMATION
TO-220
3-PIN
AS2884AU
X = Output Voltage (i.e. 3.3 for 3.3V, 5.0 for 5.0V etc.)
Y = Output Tolerance, A for 1%
Blank for 2%
Consult with factory for fixed output voltage
PIN CONNECTIONS
TO-220-3 (U)
AS2884
1
2
3
ADJ/GND V
OUT
V
IN
Front View
Rev. 9/29/00
AS2884
ABSOLUTE MAXIMUM RATINGS
Power Dissipation..........................................Internally Limited
Lead Temp. (Soldering, 10 Seconds) .............................. 300°C
Storage Temperature Range ............................ -65° to +150°C
Operating Junction Temperature Range
AS2884 Control Section ............................0C° to +125°C
AS2884 Power Transistor..........................0C° to +150°C
Input Supply Voltage ...................................................... 30V
Input to Output Voltage Differential ............................... 30V
ELECTRICAL CHARACTERISTICS
(Note 1) at I
OUT
= 10mA, T
A
= 25°C, unless otherwise specified.
Parameter
3.3V Version
Output Voltage (Note 2)
5.0V Version
Output Voltage (Note 2)
All Voltage Options
Reference Voltage
Mid Load Current
Line Regulation
Load Regulation
Dropout Voltage
Current Limit
Long Term Stability
Adjust Pin Current
Adjust Pin Current
Change
Thermal Regulation
Temperature Stability
Ripple Rejection Ratio
V
IN
- V
OUT
=3V
I
OUT
=3A, C
OUT
= 25µF, C
ADJ
= 25µF,
f= 120Hz
10Hz to 10kHz
TO-220
Junction to Tab
Junction to Ambient
AS2884-3.3V, 0≤I
OUT
≤8A,
4.75V≤V
IN
≤25V
AS2884-3.3V, 0≤I
OUT
≤8A,
6.5V≤V
IN
≤25V
10 mA
≤
I
OUT
≤
I
FULLLOAD
3.3V≤(V
IN
- V
OUT
)≤ V
IN MAX
– V
OUT MAX
(V
IN
- V
OUT
) = V
IN MAX
– V
OUT MAX
29V
≤V
IN
- V
OUT
≤
V
IN MAX
– V
OUT MAX
I
LOAD
= 10mA
10mA
≤
I
OUT
≤
I
FULLLOAD
(V
IN
- V
OUT
)=3V
I
OUT
=I
FULLLOAD
,
∆V
REF
=1%
V
IN
- V
OUT
=5V
T
A
=125°C, 1000Hrs.
T
A
=25°C
3.3
3.3
5.0
5.0
1.250
1.250
5
0.015
0.05
0.1
0.2
1.1
9.5
0.3
55
0.2
30ms pulse
0.003
0.5
75
60
60
3.270
3.240
4.950
4.900
1.238
1.225
3.330
3.360
5.050
5.100
1.262
1.270
10
0.2
0.5
0.3
0.4
1.2
3.230
3.201
4.900
4.650
1.238
1.225
3.370
3.399
5.100
5.150
1.262
1.270
10
0.2
0.5
0.3
0.4
1.2
V
mA
%
%
V
A
1
90
5
0.01
%
µA
µA
%/W
%
dB
V
Conditions
Typ
AS2884A
Min
Max
AS2884
Min
Max
Units
8.0
1
90
5
0.01
8.0
Output Noise, RMS
Thermal Resistance
Junction-to-Case
0.003
2.7
0.65
2.7
0.65
% V
O
°C/W
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: A 10µF output capacitor is required on AS2884
Rev. 9/29/00
AS2884
TYPICAL CHARACTERISTICS
DROPOUT VOLTAGE
LOAD REGULATION
SHORT CIRCUIT CURRENT
2
MINIMUM INPUT/OUTPUT DIFFERENTIAL (V)
OUTPUT VOLTAGE DEVIATION (%)
0.05
0
-0.05
-0.10
-0.15
-0.20
SHORT CIRCUIT CURRENT (A)
INDICATES GUARANTEED TEST
POINT
-40ºC T
J
150ºC
0ºC T
J
120ºC
0.10
12
10
8
6
4
2
0
-25
0
25
50
75 100 125 150
0
5
10
15
20
25
30 35
INPUT/OUTPUT DIFFERENTIAL (V)
ADJUSTMENT PIN CURRENT
INPUT/OUTPUT DIFFERENTIAL (V)
TEMPERATURE STABILITY
-55ºC
I
FULLLOAD
25ºC
150ºC
1
T
J
=25ºC
T
J
=150ºC
T
J
= -55ºC
0
0 1
2
3
4
5
6 7
8
9
10
-50
OUTPUT CURRENT (A)
MINIMUM OPERATING CURRENT
10
9
MINIMUM OPERATING CURRENT
ADJUSTMENT PIN CURRENT (µA)
100
90
REFERENCE VOLTAGE (V)
1.270
8
7
6
5
4
3
2
1
0
0
5
10
15 20
25
30
35
INPUT/OUTPUT DIFFERENTIAL (V)
T
J
=-55ºC
T
J
=25ºC
T
J
=150ºC
80
70
60
50
40
30
20
10
0
-50
-25
0
25
50
75
100 125 150
1.260
1.250
1.240
1.230
-50
-25
0
25
50
75
100 125 150
TEMPERATURE (ºC)
TEMPERATURE (ºC)
Rev. 9/29/00
AS2884
TYPICAL APPLICATIONS
V
IN
C
1
IN
AS2884
ADJ
OUT
R
1
V
IN
C
1
OUT
IN
AS2884
ADJ
V
REF
C
2
R
1
V
OUT
LOAD
V
OUT
= V
REF
(1 + R
2
) + I
ADJ
R
2
R
1
R
2
Fig. 4 8A Current output Regulator
Fig. 5 Typical Adjustable Regulator
Intel Pentium
TM
3.45V
V
IN
+5V
C
1
ADJ
R
1
IN
AS2884
V
CC
C
2
OUT
R
2
TM
Powering Intel Pentium with AS2884
Pentium Processor is a trademark of Intel Corp. Power PC is a trademark of IBM Corp.
Rev. 9/29/00
嵌入式系统
