TO-220, TO-263, TO-252 and SOT-223 package available
AMS317
1A LOW DROPOUT VOLTAGE REGULATOR
APPLICATIONS
•
High Efficiency Linear Regulators
•
Post Regulators for Switching Supplies
•
5V to 3.3V Linear Regulator
•
Battery Chargers
•
Active SCSI Terminators
•
Power Management for Notebook
•
Battery Powered Instrumentation
GENERAL DESCRIPTION
The AMS317 series of adjustable and fixed voltage regulators are designed to provide 1A output current and to operate down
The
to 1V input-to-output differential. The dropout voltage of the device is guaranteed maximum 1.3V at maximum output
current, decreasing at lower load currents.
On-chip trimming adjusts the reference voltage to 1%. Current limit is also trimmed, minimizing the stress under overload
conditions on both the regulator and power source circuitry.
The AMS317 devices are pin compatible with other three-terminal regulators and are offered in 3 lead TO-220 package, in
the 2 & 3 Lead TO-263 (Plastic DD), in the TO-252 (D PAK) and in the low profile surface mount SOT-223 package.
ORDERING INFORMATION:
OUTPUT
PACKAGE TYPE
TO-252
AMS317ACD
AMS317CD
AMS317ACD-X
AMS317CD-X
SOT-223
AMS317A
AMS317
AMS317A-X
AMS317-X
OPERATING JUNCTION
TEMPERATURE RANGE
-40 to +125° C
0 to 125° C
-40 to +125° C
0 to 125° C
3 Lead TO-220 2 &3 Lead TO-263
VOLTAGE
ADJUSTABLE AMS317ACT
AMS317ACM
AMS317CT
AMS317CM
FIXED*
AMS317ACT-X
AMS317ACM-X
AMS317CT-X
AMS317CM-X
X= 1.8V, 2.5V, 2.85V, 3.3V and 5.0V.
*For additional available fixed voltages contact factory.
PIN CONNECTIONS
FIXED VERSION
1- Ground
2- V
OUT
3- V
IN
ADJUSTABLE VERSION
SOT-223 Top View
TO-263 FRONT VIEW
3
2
1
TAB IS
OUTPUT
1- Adjust
2- V
OUT
3- V
IN
TO-220 FRONT VIEW
TAB IS
OUTPUT
1
2
3
TO-252 FRONT VIEW
3
2
1
2L TO-263 FRONT VIEW
3
2
1
3
TAB IS
OUTPUT
2
1
TAB IS
OUTPUT
Advanced Monolithic Systems, Inc.
6680B Sierra Lane, Dublin, CA 94568 Phone (925) 556-9090 Fax (925) 556-9140
AMS317
ABSOLUTE MAXIMUM RATINGS
(Note 1)
Power Dissipation
Internally limited
Input Voltage
25V
Operating Junction Temperature Range
AMS317A
-40°C to +125°C
AMS317
0°C to +125°C
Storage temperature
- 65°C to +150°C
Soldering information
Lead Temperature (10 sec)
300°C
Thermal Resistance
TO-220 package
TO-263 package
TO-252 package
SOT-223 package
ϕ
JA
= 50°C/W
ϕ
JA
= 30°C/W
ϕ
JA
= 80°C/W
ϕ
JA
= 90°C/W*
* With package soldering to copper area over backside ground
plane or internal power plane
ϕ
JA
can vary from 46°C/W to
>90°C/W
(for SOT-223) (20°C/W to
>40°C/W
for TO-263)
depending on mounting technique and the size of the copper
area.
ELECTRICAL CHARACTERISTICS
Electrical Characteristics at I
OUT
= 10 mA, (V
IN
- V
OUT
) = 5V, and T
J
= +25°C unless otherwise specified.
Parameter
Reference Voltage
(Note 2)
Output Voltage
(Note 2)
Device
AMS317
AMS317-1.8
Conditions
Min
I
OUT
= 10 mA
10mA
≤
I
OUT
≤
I
MAX
, 3V≤ (V
IN
- V
OUT
)
≤
25V
0
≤
I
OUT
≤
I
MAX
, 3.3V≤ V
IN
≤
25V
1.238
1.225
1.782
1.764
2.475
2.460
2.82
2.793
3.267
3.235
4.950
4.900
AMS317A
Typ
1.250
1.250
1.800
1.800
2.500
2.500
2.850
2.850
3.300
3.300
5.000
5.000
0.015
0.035
0.1
0.3
1.5
5
0.04
40
100
AMS317
Max
Min
1.225
1.20
1.764
1.746
2.450
2.425
2.793
2.765
3.235
3.201
4.900
4.850
Units
Max
1.270
1.30
1.836
1.854
2.550
2.575
2.907
2.935
3.365
3.399
5.100
5.150
0.2
0.2
0.5
1.0
2.0
10
0.07
100
V
V
V
V
V
V
V
V
V
V
V
V
%
%
%
%
A
mA
%W
µA
µA
µA
%
1
%
dB
%
°C/W
°C/W
°C/W
Typ
1.250
1.250
1.800
1.800
2.500
2.500
2.850
2.850
3.300
3.300
5.000
5.000
0.015
0.035
0.1
0.3
1.5
5
0.04
40
1.262
1.270
1.818
1.836
2.525
2.560
2.88
2.907
3.333
3.365
5.050
5.100
0.2
0.2
0.5
1.0
2.0
10
0.07
AMS317-2.5
0
≤
I
OUT
≤
I
MAX
, 4.0V≤ V
IN
≤
25V
AMS317-2.85
0
≤
I
OUT
≤
I
MAX
, 4.35V≤ V
IN
≤
25V
AMS317-3.3
0
≤
I
OUT
≤
I
MAX
, 4.75V
≤
V
IN
≤
25V
AMS317-5.0
0
≤
I
OUT
≤
I
MAX
, 6.5V
≤
V
IN
≤
25V
Line Regulation
Load Regulation
(Notes 2, 3)
Current Limit
Minimum Load
Current
Thermal Regulation
Adjust Pin Current
Adjust Pin Current
Change
Temperature
Stability
Long Term Stability
Ripple Rejection
RMS Output Noise
(% of V
OUT
)
Thermal Resistance
Junction-to-Case
AMS317
AMS317/-1.8/-
2.5/-2.85/-3.3/-5.0
AMS317
AMS317
AMS317
AMS317
10mA
≤
I
OUT
≤
I
MAX
, 3V≤ (V
IN
- V
OUT
)
≤
25V
T
MIN
≤
T
J
≤
T
MAX
T
A
=125°C, 1000Hrs
f =120Hz , C
OUT
= 25µF Tantalum,
(V
IN
-V
OUT
) = 3V, C
ADJ
=10µF
T
A
= 25°C , 10Hz
≤
f
≤
10kHz
TO-252 Package
SOT-223 Package
TO-220 / TO-263 Package
(V
IN
- V
OUT
) = 5V
(V
IN
- V
OUT
) = 25V
T
A
= 25°C, 20ms pulse
AMS317
AMS317
I
LOAD
= 10 mA , 3V≤ (V
IN
- V
OUT
)
≤
25V
10mA
≤
I
OUT
≤
I
MAX
0.2
1.0
0.3
66
80
0.003
5
23.5
5
5
0.2
1.0
5
1
66
0.3
80
0.003
5
23.5
5
Advanced Monolithic Systems, Inc.
6680B Sierra Lane, Dublin, CA 94568 Phone (925) 556-9090 Fax (925) 556-9140
AMS317
Note 1:
Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. For guaranteed specifications and test conditions, see the
Electrical Characteristics
.
The guaranteed specifications apply only for the test conditions listed. Parameters identified with
boldface type
apply over the full
operating temperature range.
Note 2:
Line and Load regulation are guaranteed up to the maximum power dissipation of 1.2 W. Power dissipation is determined by the input/output differential
and the output current. Guaranteed maximum power dissipation will not be available over the full input/output range.
Note 3:
See thermal regulation specifications for changes in output voltage due to heating effects. Line and load regulation are measured at a constant junction
temperature by low duty cycle pulse testing. Load regulation is measured at the output lead ~1/8” from the package.
Note 4:
Minimum load current is defined as the minimum output current required to maintain regulation. When 3V
≤
(V
IN
- V
OUT
)
≤
25V the device is guaranteed
to regulate if the output current is greater than 10mA.
APPLICATION HINTS
The AMS317 series of adjustable and fixed regulators are easy to
use and are protected against short circuit and thermal overloads.
Thermal protection circuitry will shut-down the regulator should
the junction temperature exceed 165°C at the sense point.
Pin compatible with older three terminal adjustable regulators,
these devices offer the advantage of a lower dropout voltage,
more precise reference tolerance and improved reference stability
with temperature.
output capacitors are used, such as 1000µF to 5000µF and the
input pin is instantaneously shorted to ground, damage can occur.
A diode from output to input is recommended, when a crowbar
circuit at the input of the AMS317 is used (Figure 1).
D1
Stability
The circuit design used in the AMS317 series requires the use of
an output capacitor as part of the device frequency compensation.
The addition of
150
µF
aluminum electrolytic or a 22µF solid
tantalum on the output will ensure stability for all operating
conditions.
When the adjustment terminal is bypassed with a capacitor to
improve the ripple rejection, the requirement for an output
capacitor increases. The value of 22µF tantalum or
150
µF
aluminum covers all cases of bypassing the adjustment terminal.
Without bypassing the adjustment terminal smaller capacitors can
be used with equally good results.
To ensure good transient response with heavy load current
changes capacitor values on the order of 100µF are used in the
output of many regulators. To further improve stability and
transient response of these devices larger values of output
capacitor can be used.
V
IN
AMS317
IN
OUT
ADJ
C
ADJ
10µF
V
OUT
R
1
R
2
+
C
OUT
150µF
Figure 1.
Output Voltage
The AMS317 series develops a 1.25V reference voltage between
the output and the adjust terminal. Placing a resistor between
these two terminals causes a constant current to flow through R1
and down through R2 to set the overall output voltage. This
current is normally the specified minimum load current of 10mA.
Because I
ADJ
is very small and constant it represents a small
error and it can usually be ignored.
AMS317
IN
OUT
ADJ
I
ADJ
50µA
Protection Diodes
Unlike older regulators, the AMS317 family does not need any
protection diodes between the adjustment pin and the output and
from the output to the input to prevent over-stressing the die.
Internal resistors are limiting the internal current paths on the
AMS317 adjustment pin, therefore even with capacitors on the
adjustment pin no protection diode is needed to ensure device
safety under short-circuit conditions.
Diodes between the input and output are not usually needed.
Microsecond surge currents of 50A to 100A can be handled by the
internal diode between the input and output pins of the device. In
normal operations it is difficult to get those values of surge
currents even with the use of large output capacitances. If high
value
V
IN
V
OUT
V
REF
R1
R2
V
OUT
= V
REF
(1+
R2/R1)+I
ADJ
R2
Figure 2. Basic Adjustable Regulator
Advanced Monolithic Systems, Inc.
6680B Sierra Lane, Dublin, CA 94568 Phone (925) 556-9090 Fax (925) 556-9140
AMS317
APPLICATION HINTS
Load Regulation
True remote load sensing it is not possible to provide, because the
AMS317 is a three terminal device. The resistance of the wire
connecting the regulator to the load will limit the load regulation.
The data sheet specification for load regulation is measured at the
bottom of the package. Negative side sensing is a true Kelvin
connection, with the bottom of the output divider returned to the
negative side of the load.
The best load regulation is obtained when the top of the resistor
divider R1 is connected directly to the case not to the load. If R1
were connected to the load, the effective resistance between the
regulator and the load would be:
R
P
x ( R2+R1 ) ,
R1
R
P
= Parasitic Line Resistance
The thermal resistance from the junction to the tab for the
AMS317 is 15
°C/W;
t
hermal resistance from tab to ambient can
be as low as 30°C/W. The total thermal resistance from junction
to ambient can be as low as 45°C/W. This requires a reasonable
sized PC board with at least on layer of copper to spread the heat
across the board and couple it into the surrounding air.
Experiments have shown that the heat spreading copper layer
does not need to be electrically connected to the tab of the device.
The PC material can be very effective at transmitting heat
between the pad area, attached to the pad of the device, and a
ground plane layer either inside or on the opposite side of the
board. Although the actual thermal resistance of the PC material
is high, the Length/Area ratio of the thermal resistance between
layers is small. The data in Table 1, was taken using 1/16” FR-4
board with 1 oz. copper foil, and it can be used as a rough
guideline for estimating thermal resistance.
For the TO-252 package, if the maximum allowable value is
found to be
≥92°C/W,
no heat sink is needed since the package
alone will dissipate enough heat to satisfy these requirements. If
the calculated value for
θ
JA
falls bellow these limits, a heat sink
is required.
For each application the thermal resistance will be affected by
thermal interactions with other components on the board. To
determine the actual value some experimentation will be
necessary.
The power dissipation of the AMS317 is equal to:
P
D
= ( V
IN
- V
OUT
)( I
OUT
)
Maximum junction temperature will be equal to:
R2*
Connected as shown , R
P
is not multiplied by the divider ratio
R
P
PARASITIC
LINE RESISTANCE
V
IN
AMS317
IN
OUT
ADJ
R1*
R
L
T
J
= T
A(MAX)
+ P
D
(Thermal Resistance (junction-to-ambient))
Maximum junction temperature must not exceed 125°C.
Ripple Rejection
*
CONNECT R1 TO CASE
CONNECT R2 TO LOAD
Figure 3. Connections for Best Load Regulation
In the case of fixed voltage devices the top of R1 is connected
Kelvin internally, and the ground pin can be used for negative
side sensing.
Thermal Considerations
The AMS317 series have internal power and thermal limiting
circuitry designed to protect the device under overload conditions.
However maximum junction temperature ratings of 125
°C
should
not be exceeded under continuous normal load conditions.
Careful consideration must be given to all sources of thermal
resistance from junction to ambient. For the surface mount
package SOT-223 additional heat sources mounted near the
device must be considered. The heat dissipation capability of the
PC board and its copper traces is used as a heat sink for the
device.
The ripple rejection values are measured with the adjustment pin
bypassed. The impedance of the adjust pin capacitor at the ripple
frequency should be less than the value of R1 (normally 100Ω to
200Ω) for a proper bypassing and ripple rejection approaching
the values shown. The size of the required adjust pin capacitor is
a function of the input ripple frequency. If R1=100Ω at 120Hz
the adjust pin capacitor should be
>13µF.
At 10kHz only 0.16µF
is needed.
The ripple rejection will be a function of output voltage, in
circuits without an adjust pin bypass capacitor. The output ripple
will increase directly as a ratio of the output voltage to the
reference voltage (V
OUT
/ V
REF
).
Advanced Monolithic Systems, Inc.
6680B Sierra Lane, Dublin, CA 94568 Phone (925) 556-9090 Fax (925) 556-9140
AMS317
Table 1.
COPPER AREA
TOP SIDE*
BACK SIDE
BOARD AREA
2500 Sq. mm
2500 Sq. mm
2500 Sq. mm
1000 Sq. mm
2500 Sq. mm
2500 Sq. mm
225 Sq. mm
2500 Sq. mm
2500 Sq. mm
100 Sq. mm
2500 Sq. mm
2500 Sq. mm
1000 Sq. mm
1000 Sq. mm
1000 Sq. mm
1000 Sq. mm
0
1000 Sq. mm
* Tab of device attached to topside copper.
THERMAL RESISTANCE
(JUNCTION-TO-AMBIENT)
45°C/W
45°C/W
53°C/W
59°C/W
52°C/W
55°C/W
TYPICAL PERFORMANCE CHARACTERISTICS
Minimum Operating Current
(Adjustable Device)
12
MINIMUM OPERATING CURRENT (mA)
1.25
Short-Circuit Current
T
J
= 125°C
9
T
J
=
125°C
SHORT CIRCUIT CURRENT (A)
1.00
T
J
= 25°C
0.75
6
T
J
= 25°C
0.50
3
0.25
0
0
5
10
15
20
INPUT/OUTPUT DIFFERENTIAL (V)
0
0
5
10
15
INPUT/OUTPUT DIFFERENTIAL
Load Regulation
0.10
∆
I
LOAD
= 1A
OUTPUT VOLTAGE DEVIATION (%)
0.05
RIPPLE REJECTION (dB)
100
90
Ripple Rejection vs. Current
f
RIPPLE
= 120Hz
80
70
60
50
40
30
20
f
RIPPLE
= 20Hz
V
RIPPLE
≤0.5Vp-p
V
RIPPLE
≤3Vp-p
0
-0.05
-0.10
-0.15
10
-0.20
-50
-25
0
25
50
75
100
125
TEMPERATURE (°C)
0
0
V
OUT
= 5V
C
ADJ
= 25
µF
C
OUT
= 25µF
0.2
0.4
OUTPUT CURRENT (A)
0.6
0.8
Advanced Monolithic Systems, Inc.
6680B Sierra Lane, Dublin, CA 94568 Phone (925) 556-9090 Fax (925) 556-9140
