The AMS1085 series of adjustable and fixed voltage regulators are designed to provide 3A output current and to operate
The
down to 1V input-to-output differential. The dropout voltage of the device is guaranteed maximum 1.5V 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 AMS1085 devices are pin compatible with older three-terminal regulators and are offered in 3 lead TO-220 package, 3
and 2 lead TO-263 (Plastic DD) and TO-252 (D PAK) package.
ORDERING INFORMATION:
PACKAGE TYPE
3 LEAD TO-220
AMS1085CT
AMS1085CT-1.5
AMS1085CT-2.5
AMS1085CT-2.85
AMS1085CT-3.0
AMS1085CT-3.3
AMS1085CT-3.5
AMS1085CT-5.0
2&3 LEAD TO-263
AMS1085CM
AMS1085CM-1.5
AMS1085CM-2.5
AMS1085CM-2.85
AMS1085CM-3.0
AMS1085CM-3.3
AMS1085CM-3.5
AMS1085CM-5.0
TO-252
AMS1085CD
AMS1085CD-1.5
AMS1085CD-2.5
AMS1085CD-2.85
AMS1085CD-3.0
AMS1085CD-3.3
AMS1085CD-3.5
AMS1085CD-5.0
OPERATING JUNCTION
TEMPERATURE RANGE
0 to 125° C
0 to 125° C
0 to 125° C
0 to 125° C
0 to 125° C
0 to 125° C
0 to 125° C
0 to 125° C
TO-220 FRONT VIEW
TO-252 FRONT VIEW
3
TAB IS
OUTPUT
3
2
1
TAB IS
OUTPUT
2
1
PIN CONNECTIONS
FIXED VERSION
1- Ground
2- V
OUT
3- V
IN
ADJUSTABLE VERSION
1- Adjust
2- V
OUT
3- V
IN
2L TO-263 FRONT VIEW
3
2
1
TAB IS
OUTPUT
3L TO-263 FRONT VIEW
3
2
1
TAB IS
OUTPUT
Advanced Monolithic Systems, Inc.
6680B Sierra Lane, Dublin, CA 94568 Phone (925) 556-9090 Fax (925) 556-9140
AMS1085
ABSOLUTE MAXIMUM RATINGS
(Note 1)
Power Dissipation
Internally limited
Input Voltage
15V
Operating Junction Temperature Range
Control Section
0°C to 125°C
Power Transistor
0°C to 150°C
Storage temperature
- 65°C to +150°C
Soldering information
Lead Temperature (10 sec)
Thermal Resistance
TO-220 package
TO-263 package
TO-252 package
300°C
ϕ
JA
= 50°C/W
ϕ
JA
= 30°C/W *
ϕ
JA
= 100°C/W
* With package soldering to 0.5in
2
copper area over
backside ground plane or internal power plane
ϕ
JA
can vary
from 20°C/W to
>40°C/W
depending on mounting
technique.
ELECTRICAL CHARACTERISTICS
Electrical Characteristics at I
OUT
= 0 mA, and T
J
= +25°C unless otherwise specified.
Parameter
Reference Voltage
(Note 2)
Output Voltage
(Note 2)
Device
AMS1085
AMS1085-1.5
AMS1085-2.5
AMS1085-2.85
AMS1085-3.0
AMS1085-3.3
AMS1085-3.5
AMS1085-5.0
Conditions
I
OUT
= 10 mA
10mA
≤
I
OUT
≤
3A, 1.5V≤ (V
IN
- V
OUT
)
≤
12V
0
≤
I
OUT
≤
3A , 3V≤ V
IN
≤
12V
0
≤
I
OUT
≤
3A , 4V≤ V
IN
≤
12V
0
≤
I
OUT
≤
3A , 4.35V≤ V
IN
≤
12V
0
≤
I
OUT
≤
3A , 4.5V
≤
V
IN
≤
12V
0
≤
I
OUT
≤
3A , 4.75V
≤
V
IN
≤
12V
0
≤
I
OUT
≤
3A , 5V
≤
V
IN
≤
12V
0
≤
I
OUT
≤
3A , 6.5V
≤
V
IN
≤
12V
I
LOAD
= 10 mA , 1.5V≤ (V
IN
- V
OUT
)
≤
12V
(V
IN
- V
OUT
) =3V, 10mA
≤
I
OUT
≤
3A
V
IN
= 5V, 0
≤
I
OUT
≤
3A
V
IN
= 5V, 0
≤
I
OUT
≤
3A
V
IN
= 5V, 0
≤
I
OUT
≤
3A
V
IN
= 5V, 0
≤
I
OUT
≤
3A
V
IN
= 5V, 0
≤
I
OUT
≤
3A
V
IN
= 5.25V, 0
≤
I
OUT
≤
3A
V
IN
= 8V, 0
≤
I
OUT
≤
3A
∆V
OUT
,
∆V
REF
= 1%, I
OUT
= 3 A (Note 4)
Min
1.238
1.225
1.485
1.470
2.475
2.450
2.82
2.79
2.970
2.940
3.267
3.235
3.465
3.430
4.950
4.900
Typ
1.250
1.250
1.500
1.500
2.500
2.500
2.850
2.850
3.000
3.000
3.300
3.300
3.500
3.500
5.000
5.000
0.3
0.6
0.1
0.2
3
6
3
6
3
6
3
6
3
7
3
6
5
10
1.3
Max
1.262
1.270
1.515
1.530
2.525
2.550
2.88
2.91
3.300
3.360
3.333
3.365
3.535
3.570
5.050
5.100
10
10
.03
.04
12
20
12
20
12
20
12
20
15
25
15
25
20
35
1.5
Units
V
V
V
V
V
V
V
V
V
V
V
V
V
V
V
mV
mV
%
%
mV
mV
mV
mV
mV
mV
mV
mV
mV
mV
mV
mV
mV
mV
V
Line Regulation
Load Regulation
(Notes 2, 3)
AMS1085/-1.5/-2.5/-2.85/
-3.0/-3.3/-3.5/-5.0
AMS1085
AMS1085-1.5
AMS1085-2.5
AMS1085-2.85
AMS1085-3.0
AMS1085-3.3
AMS1085-3.5
AMS1085-5.0
Dropout Voltage
(V
IN
-
V
OUT
)
AMS1085/-1.5/-2.5/-2.85/
-3.0/-3.3/-3.5/-5.0
Advanced Monolithic Systems, Inc.
6680B Sierra Lane, Dublin, CA 94568 Phone (925) 556-9090 Fax (925) 556-9140
AMS1085
ELECTRICAL CHARACTERISTICS
Electrical Characteristics at I
OUT
= 0 mA, and T
J
= +25°C unless otherwise specified.
Parameter
Current Limit
Minimum Load
Current
Quiescent Current
Ripple Rejection
Device
AMS1085/-1.5/-2.5/-2.85/
-3.0/-3.3/-3.5/-5.0
AMS1085
AMS1085/-1.5/-2.5/-2.85/
-3.0/-3.3/-3.5/-5.0
AMS1085
AMS1085-1.5
AMS1085-2.5
AMS1085-2.85
AMS1085-3.0
AMS1085-3.3
AMS1085-3.5
AMS1085-5.0
Conditions
(V
IN
- V
OUT
) = 5V
(V
IN
- V
OUT
) = 12V (Note 5)
V
IN
≤
12V
f =120Hz , C
OUT
= 25µF Tantalum, I
OUT
= 3A,
(V
IN
-V
OUT
) = 3V, C
ADJ
=25µF
f =120Hz , C
OUT
= 25µF Tantalum, I
OUT
= 3A,
V
IN
= 4.5V
f =120Hz , C
OUT
= 25µF Tantalum, I
OUT
= 3A,
V
IN
= 5.5V
f =120Hz , C
OUT
= 25µF Tantalum, I
OUT
= 3A,
V
IN
= 6V
f =120Hz , C
OUT
= 25µF Tantalum, I
OUT
= 3A
V
IN
= 6V
f =120Hz , C
OUT
= 25µF Tantalum, I
OUT
= 3A
V
IN
= 6.3V
f =120Hz , C
OUT
= 25µF Tantalum, I
OUT
= 3A
V
IN
= 6.5V
f =120Hz , C
OUT
= 25µF Tantalum, I
OUT
= 3A
V
IN
= 8V
T
A
= 25°C, 30ms pulse
10mA
≤
I
OUT
≤
3A , 1.5V≤ (V
IN
- V
OUT
)
≤
12V
10mA
≤
I
OUT
≤
3A , 1.5V≤ (V
IN
- V
OUT
)
≤12V
Min
3.00
Typ
3.50
5
5
Max
4.00
10
10
Units
A
mA
mA
dB
dB
dB
dB
dB
dB
dB
dB
60
60
60
60
60
60
60
60
75
72
72
72
72
72
72
68
0.008
55
120
0.2
0.5
5
0.04
Thermal Regulation
Adjust Pin Current
Adjust Pin Current
Change
Temperature Stability
Long Term Stability
RMS Output Noise
(% of V
OUT
)
Thermal Resistance
Junction-to-Case
AMS1085
AMS1085
AMS1085
%W
µA
µA
µA
%
T
A
=125°C, 1000Hrs
T
A
= 25°C , 10Hz
≤
f
≤
10kHz
M Package: Control Circuitry/ Power Transistor
T Package: Control Circuitry/ Power Transistor
0.3
0.003
1
%
%
1.5/4.0
1.5/4.0
°C/W
°C/W
Parameters identified with
boldface type
apply over the full operating temperature range.
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.
Note 2:
Line and Load regulation are guaranteed up to the maximum power dissipation of 15W. 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:
Dropout voltage is specified over the full output current range of the device.
Note 5:
Minimum load current is defined as the minimum output current required to maintain regulation. When (V
IN
- V
OUT
) = 12V the device is guaranteed to
regulate if the output current is greater than 10mA.
Advanced Monolithic Systems, Inc.
6680B Sierra Lane, Dublin, CA 94568 Phone (925) 556-9090 Fax (925) 556-9140
AMS1085
APPLICATION HINTS
The AMS1085 series of adjustable and fixed regulators are easy
to use and have all the protection features expected in high
performance voltage regulators: short circuit protection and
thermal shutdown.
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.
Stability
The circuit design used in the AMS1085 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 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.
Protection Diodes
Unlike older regulators, the AMS1085 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
AMS1085 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 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 AMS1085 is used. Normal
power supply cycling or even plugging and unplugging in the
system will not generate current large enough to do any damage.
The adjustment pin can be driven on a transient basis
±25V,
with
respect to the output without any device degradation. As with any
IC regulator, none the protection circuitry will be functional and
the internal transistors will break down if the maximum input to
output voltage differential is exceeded.
D1
V
IN
AMS1085
IN
OUT
ADJ
C
ADJ
10µF
V
OUT
R
1
R
2
+
C
OUT
150µF
Overload Recovery
When the power is first turned on, as the input voltage rises, the
output follows the input, permitting the regulator to start up into
heavy loads. During the start-up, as the input voltage is rising,
the input-to-output voltage differential remains small, allowing
the regulator to supply large output currents. A problem can occur
with a heavy output load when the input voltage is high and the
output voltage is low, when the removal of an output short will
not permit the output voltage to recover. The load line for such a
load may intersect two points on the output current curve. In this
case, there are two stable output operating points for the
regulator. With this double intersection, the power supply may
need to be cycled down to zero and brought up again to make the
output recover.
Ripple Rejection
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
to120Ω) 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 25µF. At 10kHz only 0.22µF 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
).
Output Voltage
The AMS1085 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.
Advanced Monolithic Systems, Inc.
6680B Sierra Lane, Dublin, CA 94568 Phone (925) 556-9090 Fax (925) 556-9140
AMS1085
APPLICATION HINTS
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.
Connected as shown, R
P is
not multiplied by the divider ratio.
Using 16-gauge wire the parasitic line resistance is about 0.004Ω
per foot, translating to 4mV/ft at 1A load current. It is important
to keep the positive lead between regulator and load as short as
possible and use large wire or PC board traces.
Thermal Considerations
The AMS1085 series have internal power and thermal limiting
circuitry designed to protect the device under overload
conditions. However maximum junction temperature ratings
should not be exceeded under continuous normal load conditions.
Careful consideration must be given to all sources of thermal
resistance from junction to ambient, including junction-to-case,
case-to-heat sink interface and heat sink resistance itself. To
ensure safe operating temperatures and reflect more accurately
the device temperature, new thermal resistance specifications
have been developed. Unlike older regulators with a single
junction-to-case thermal resistance specification, the data section
for these new regulators provides a separate thermal resistance
and maximum junction temperature for both the Control Section
and the Power Transistor. Calculations for both temperatures
under certain conditions of ambient temperature and heat sink
resistance and to ensure that both thermal limits are met.
Junction-to-case thermal resistance is specified from the IC
junction to the bottom of the case directly below the die. This is
the lowest resistance path for the heat flow. In order to ensure the
best possible thermal flow from this area of the package to the
heat sink proper mounting is required. Thermal compound at the
case-to-heat sink interface is recommended. A thermally
conductive spacer can be used, if the case of the device must be
electrically isolated, but its added contribution to thermal
resistance has to be considered.
V
IN
AMS1085
IN
OUT
ADJ
I
ADJ
50µA
V
OUT
V
REF
R1
R2
V
OUT
= V
REF
(1+
R2/R1)+I
ADJ
R2
Figure 1. Basic Adjustable Regulator
Load Regulation
True remote load sensing it is not possible to provide, because the
AMS1085 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
R
P
PARASITIC
LINE RESISTANCE
V
IN
AMS1085
IN
OUT
ADJ
R1*
R
L
R2*
*
CONNECT R1 TO CASE
CONNECT R2 TO LOAD
Figure 2. Connections for Best Load Regulation
Advanced Monolithic Systems, Inc.
6680B Sierra Lane, Dublin, CA 94568 Phone (925) 556-9090 Fax (925) 556-9140
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