Alpha Semiconductor Inc. 1031 Serpentine Lane. Pleasanton, CA 94568 Tel: (925) 417-1391 Fax: (925) 417-1390
Rev. 9/14/99
ALPHA
SEMICONDUCTOR
Excellence in Analog Power Products
AS1117
800mA Low Dropout Regulator
SCSI-II Active Terminator
FEATURES
APPLICATIONS
Guaranteed 800mA Output
SCSI-II Active Terminator
Three Terminal Adjustable Or Fixed 1.5V, 2.5V, 2.85V, 3V, 3.3V & 5V
Portable/ Palm Top / Notebook Computers
Very Low Quiescent Current
Battery Chargers
Low Dropout Voltage Of 1.2 Volts At Full Load
Disk Drives
Extremely Tight Load And Line Regulation
Portable Consumer Equipment
Very Low Temperature Coefficient
Portable Instrumentation
Fixed 2.85V Device For SCSI-II Active Terminator
SMPS Post-Regulator
Logic-Controlled Electronic Shutdown
Internal Overcurrent Limiting & Thermal Overload Protection
Surface Mount Package SOT-223, TO-252, TO-220, SOT-89, TO-263, & SO-8
PRODUCT DESCRIPTION
The ALPHA Semiconductor AS1117 is a low power positive-voltage regulator designed to meet 800mA output current and comply
with SCSI-II specifications with a fixed output voltage of 2.85V. This device is an excellent choice for use in battery-powered
applications, as active terminators for the SCSI bus, and portable computers. The AS1117 features very low quiescent current and
very low dropout voltage of 1.2V at a full load and lower as output current decreases. AS1117 is available as an adjustable or fixed
2.85V, 3V, 3.3V, and 5V output voltages.
The AS1117 is offered in a 3-pin surface mount package SOT-223, TO-252, TO-220, SOT-89 & TO-263. The output capacitor of
10
F or larger is needed for output stability of AS1117 as required by most of the other regulator circuits. Use of ALPHA
Semiconductor's design, processing and testing techniques make our AS1117 superior over similar products.
ORDERING INFORMATION
TO-220
3-PIN
TO-263
3-PIN
SOT-223
3-PIN
PLASTIC
SOIC 8 PIN
SOT-89
3-PIN
TO-252
DPAK
Oper. Temp.
Range
AS1117U
AS1117T
AS1117M3
AS1117S
AS1117M1
AS1117R
-40
C to +85
C
AS1117U-X
AS1117T-X
AS1117M3-X
AS1117S-X
AS1117M1-X
AS1117R-X
-40
C to +85
C
X= Output Voltage (X = 1.5V, 2.5V, 2.85V, 3.0V, 3.3V, 5.0, or Blank for Adjustable)
PIN CONNECTIONS
Top View
2
1
3
4
8
7
6
5
ALPHA
AS1117
8-Pin Surface Mount (S)
ALPHA
AS1117
SOT-89 (M1)
1
2
3
ALPHA
AS1117
1
3
2
SOT-223 (M3)
Top View
TO-263-3 (T)
1
ALPHA
AS1117
2
3
Front View
TO-220-3 (U)
ALPHA
AS1117
1
2
3
Front View
TO-252 (R)
ADJ/GND
V
OUT
1
2
3
V
IN
ALPHA
AS1117
ADJ/GND
V
OUT
V
IN
ADJ/GND
V
OUT
V
IN
ADJ/GND
V
OUT
V
IN
GND
N/C
V
OUT
V
OUT
N/C
V
IN
V
IN
V
IN
ADJ/GND
V
OUT
V
IN
Top View
Top View
Alpha Semiconductor Inc. 1031 Serpentine Lane. Pleasanton, CA 94568 Tel: (925) 417-1391 Fax: (925) 417-1390
Rev. 9/14/99
AS1117
ABSOLUTE MAXIMUM RATINGS
Power Dissipation.......................................Internally Limited
Input Supply Voltage.................................... -20V to +20V
Lead Temp. (Soldering, 5 Seconds) .............................. 260C
ESD Rating .........................................................2KV Min
Storage Temperature Range .......................... -65 to +150C
Operating Junction Temperature Range
AS1117 ................................................-40C to +125C
ELECTRICAL CHARACTERISTICS at
V
IN
= V
OUT
+1, Ta=25C, CL =3.3
f, unless otherwise specified. Limits in
Boldface apply over the full operating temperature range.
Parameter
Conditions
Typ
AS1117
Min Max
Units
1.5V Version
Output Voltage
I
OUT
= 10mA, V
IN
= 4.85V
0
I
OUT
800mA, 4.25
V
IN
10V
1.500
1.485
1.470
1.515
1.530
V
2.5V Version
Output Voltage
I
OUT
= 10mA, V
IN
= 4.85V
0
I
OUT
800mA, 4.25
V
IN
10V
2.500
2.475
2.450
2.525
2.550
V
2.85V Version
Output Voltage
I
OUT
= 10mA, V
IN
= 4.85V
0
I
OUT
800mA, 4.25
V
IN
10V
2.850
2.822
2.793
2.879
2.907
V
3.0V Version
Output Voltage
I
OUT
= 10mA, V
IN
= 4.85V
0
I
OUT
800mA, 4.75
V
IN
10V
3.000
2.970
2.940
3.030
3.060
V
3.3V Version
Output Voltage
I
OUT
= 10mA, V
IN
= 5.0V
0
I
OUT
800mA, 4.75
V
IN
10V
3.300
3.267
3.234
3.333
3.366
V
5.0V Version
Output Voltage
I
OUT
= 10mA, V
IN
= 7.0V
0
I
OUT
800mA, 6.50
V
IN
12V
5.000
4.950
4.900
5.050
5.100
V
All Output Options
Reference Voltage
I
OUT
= 10mA, (V
IN
V
OUT
) = 2V
10
I
OUT
800mA, 1.4
(V
IN
-V
IN
)
10V
1.250
1.238
1.225
1.262
1.270
V
Output Voltage
Temperature Stability
(Note 1)
0.05
%
Line Regulation
4.25V
V
IN
10V, V
OUT
= 2.85, I
OUT
= 0
4.50V
V
IN
12V, V
OUT
= 3.00, I
OUT
= 0
4.80V
V
IN
12V, V
OUT
= 3.30, I
OUT
= 0
6.50V
V
IN
15V, V
OUT
= 5.00, I
OUT
= 0
1.00
1.00
1.00
1.00
6.00
7.00
7.00
10.00
mV
Load Regulation
0
I
OUT
800mA, V
IN
= 4.25V, V
OUT
= 2.85
0
I
OUT
800mA, V
IN
= 4.50V, V
OUT
= 3.00
0
I
OUT
800mA, V
IN
= 4.80V, V
OUT
= 3.30
0
I
OUT
800mA, V
IN
= 6.50V, V
OUT
= 5.00
1.00
1.00
1.00
1.00
10.00
12.00
12.00
15.00
mV
Dropout Voltage
( Note 2)
I
L
= 100mA
I
L
= 500mA
I
L
= 800mA
1.00
1.05
1.10
1.10
1.15
1.20
V
Quiescent Current
4.25V
V
IN
6.5V
5.00
10.00
mA
Current Limit
(V
IN
-V
OUT
) = 5V
1000
1200
mA
Thermal Regulation
25
C,30mS Pulse
0.01
0.1
%/W
Ripple Rejection
f
RIPPLE
= 120Hz, (V
in
-V
OUT
) = 3V,
V
RIPPLE
= 1V
p-p
60
75
dB
Long Term Stability
125C, 1000Hrs
0.03
%
RMS Output Noise
% of V
out
, 10Hz
f
10kHz
0.003
%
Thermal Resistance
Junction to case, at tab
15
C/W
Note 1: Output temperature coefficient is defined as the worst case voltage change divided by the total temperature range
Note 2: Dropout voltage is defined as the input to output differential at which the output voltage drops 100mV below its nominal value measured at 1V differential at very low values of programmed
output voltage, the minimum input supply voltage of 2V ( 2.3V over temperature) must be taken into account.
Note 3: Thermal regulation is defined as the change in output voltage at a time T after a change in power dissipation is applied. excluding load or line regulation effect.
Alpha Semiconductor Inc. 1031 Serpentine Lane. Pleasanton, CA 94568 Tel: (925) 417-1391 Fax: (925) 417-1390
Rev. 9/14/99
AS1117
APPLICATION NOTES EXTERNAL
CAPACITOR
To ensure the stability of the AS1117 an output capacitor of
at least 10
F (tantalum)or 50
F (aluminum) is required.
The value may change based on the application
requirements on the output load or temperature range. The
capacitor equivalent series resistance (ESR) will effect the
AS1117 stability. The value of ESR can vary from the type
of capacitor used in the applications. The recommended
value for ESR is 0.5
. The output capacitance could
increase in size to above the minimum value. The larger
value of output capacitance as high as 100
F can improve
the load transient response.
SOLDERING METHODS
The AS1117 SOT-223 package is designed to be compatible
with infrared reflow or vapor-phase reflow soldering
techniques. During soldering the non-active or mildly
active fluxes may be used. The AS1117 die is attached to
the heatsink lead which exits opposite the input, output, and
ground pins.
Hand soldering and wave soldering should be avoided since
these methods can cause damage to the device with
excessive thermal gradients on the package. The SOT-223
recommended soldering method are as follows: vapor phase
reflow and infrared reflow with the component preheated to
within 65
C of the soldering temperature range.
THERMAL CHARACTERISTICS
The thermal resistance of AS1117 is 15
C/W from junction
to tab and 31
C/W from tab to ambient for a total of 46
C/W from junction to ambient. The AS1117 features the
internal thermal limiting to protect the device during
overload conditions. Special care needs to be taken during
continuos load conditions the maximum junction
temperature does not exceed 125
C.
Taking the FR-4 printed circuit board and 1/16 thick with 1
ounce copper foil as an experiment (fig.1 & fig.2), the PCB
material is effective at transmitting heat with the tab
attached to the pad area and a ground plane layer on the
backside of the substrate. Refer to table 1 for the results of
the experiment.
The thermal interaction from other components in the
application can effect the thermal resistance of the AS1117.
The actual thermal resistance can be determined with
experimentation. AS1117 power dissipation is calculated as
follows:
P
D
= (V
IN
- V
OUT
)(I
OUT
)
Maximum Junction Temperature range:
T
J
= T
ambient
(max) + P
D
* thermal resistance (Junction-to-
ambient)
Maximum Junction temperature must not exceed the 125
C.
10uF
+
..
27K
AS1117-2.85
+
10V
10uF
2.85V
50 X 50 mm
35 X 17 mm
16 X 10 mm
P
O
= (10V - 2.85)(105mA) = (7.15)(105mA) = 750mW
Fig. 1. Circuit Layout, Thermal Experiments.
Fig. 2. Substrate Layout for SOT-223
Alpha Semiconductor Inc. 1031 Serpentine Lane. Pleasanton, CA 94568 Tel: (925) 417-1391 Fax: (925) 417-1390
Rev. 9/14/99
AS1117
Table 1.
TOTAL PC BOARD AREA
TOPDIDE COPPER AREA
BACKSIDE COPPER AREA
THERMAL RESISTANCE
JUNCTION TO AMBIENT
2500mm
2500mm
2500mm
2500mm
2500mm
1600mm
2500mm
2500mm
1600mm
900mm
900mm
2500mm
1250mm
950mm
2500mm
1800mm
600mm
1250mm
915mm
600mm
240mm
240mm
2500mm
2500mm
2500mm
0
0
1600mm
0
0
0
900mm
0
46C/W
47C/W
49C/W
51C/W
53C/W
55C/W
58C/W
59C/W
67C/W
72C/W
85C/W
LOAD
ADJ
ALPHA
AS1117
800mA Current output
Regulator
V
IN
C
1
R
1
OUT
IN
IN
OUT
I
ADJ
ALPHA
AS1117
C
1
R
1
R
2
V
OUT
Typical Adjustable Regulator
V
IN
C
2
V
OUT
= V
REF
(1+R
2
/R
1
) +I
ADJ
R
2
v
REF
50uA
ADJ
Alpha Semiconductor Inc. 1031 Serpentine Lane. Pleasanton, CA 94568 Tel: (925) 417-1391 Fax: (925) 417-1390
Rev. 9/14/99
AS1117
PACKAGE DRAWING
TO-263-3L (T)
0.103 BSC
0.050 (1.270)
0.600
+-
0.025
0.405
0.005
0.055 (1.397)
(10.287
0.127)
0.356
0.005
(9.042
0.127)
(15.24 0.635)
(2.616)
0.032
+
-
0.001
(0.813
0.025)
+
-
0.176 0.005
0.050 0.002
0.015
+
-
0.003
0 8
(0.381
0.074)
+
-
0.100
0.010
(2.540
0.254)
(4.470
0.127)
(1.270
0.051)
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