Advanced Monolithic Systems, Inc. 6680B Sierra Lane, Dublin, CA 94568 Phone (925) 556-9090 Fax (925) 556-9140
Advanced
AMS2911
Monolithic
1A LOW DROPOUT VOLTAGE REGULATOR
Systems
FEATURES
APPLICATIONS
Three Terminal Adjustable or Fixed Voltages*
High Efficiency Linear Regulators
1.5V, 2.5V, 2.85V, 3.3V, and 5.0V
Post Regulators for Switching Supplies
Output Current of 1A
5V to 3.3V Linear Regulator
Operates Down to 1V Dropout
Battery Chargers
Line Regulation: 0.2% Max.
Active SCSI Terminators
Load Regulation: 0.4% Max.
Power Management for Notebook
Available in TO-220, TO-263, TO-252 and SOT-223
packages
Battery Powered Instrumentation
GENERAL DESCRIPTION
The
The AMS2911 series of adjustable and fixed voltage regulators are designed to provide 1A output current and to operate
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 AMS2911 devices are pin compatible with other three-terminal regulators and are offered in the 3 lead TO-220 package,
in the 3Lead TO-263 (Plastic DD), in the TO-252 (DPAK) and in the low profile surface mount SOT-223 package.
ORDERING INFORMATION:
PACKAGE TYPE
OPERATING JUNCTION
3 LEAD TO-220
3 LEAD TO-263
TO-252
SOT-223
TEMPERATURE RANGE
AMS2911CT
AMS2911CM
AMS2911CD
AMS2911
0 to 125
C
AMS2911CT-1.5
AMS2911CM-1.5
AMS2911CD-1.5
AMS2911-1.5
0 to 125
C
AMS2911CT-2.5
AMS2911CM-2.5
AMS2911CD-2.5
AMS2911-2.5
0 to 125
C
AMS2911CT-2.85
AMS2911CM-2.85
AMS2911CD-2.85
AMS2911-2.85
0 to 125
C
AMS2911CT-3.3
AMS2911CM-3.3
AMS2911CD-3.3
AMS2911-3.3
0 to 125
C
AMS2911CT-5.0
AMS2911CM-5.0
AMS2911CD-5.0
AMS2911-5.0
0 to 125
C
*For additional available fixed voltages contact factory.
PIN CONNECTIONS
FIXED VERSION
ADJUSTABLE VERSION
1- V
IN
2- Ground
3- V
OUT
1- V
IN
2- Adjust
3- V
OUT
1
2
3
TO-220 FRONT VIEW
1
2
3
TO-263 FRONT VIEW
SOT-223 Top View
1
2
3
TO-252 FRONT VIEW
1
2
3
Advanced Monolithic Systems, Inc. 6680B Sierra Lane, Dublin, CA 94568 Phone (925) 556-9090 Fax (925) 556-9140
AMS2911
ABSOLUTE MAXIMUM RATINGS
(Note 1)
Power Dissipation
Internally limited
Thermal Resistance
Input Voltage
15V
TO-220 package
JA
= 50
C/W
Operating Junction Temperature Range
TO-263 package
JA
=
30
C/W
Control Section
0
C to 125
C
TO-252 package
JA
=
80
C/W
Power Transistor
0
C to 150
C
SOT-223 package
JA
= 90
C/W*
Storage temperature
- 65
C to +150
C
Soldering information
Lead Temperature (10 sec)
300
C
* With package soldering to copper area over backside
ground plane or internal power plane
JA
can vary from
46
C/W to
>
90
C/W depending on mounting technique and
the size of the copper area.
ELECTRICAL CHARACTERISTICS
Electrical Characteristics at I
OUT
= 0 mA, and T
J
= +25C unless otherwise specified.
Parameter
Device
Conditions
Min Typ Max
Units
Reference Voltage
(Note 2)
AMS2911
I
OUT
= 10 mA
10mA
I
OUT
1A, 1.5V
(V
IN
- V
OUT
)
12V
1.238
1.225
1.250
1.250
1.262
1.270
V
V
Output Voltage
(Note 2)
AMS2911-1.5
0
I
OUT
1A , 4.35V
V
IN
12V
1.485
1.476
1.500
1.500
1.515
1.524
V
V
AMS2911-2.5
0
I
OUT
1A , 4.35V
V
IN
12V
2.475
2.460
2.500
2.500
2.525
2.540
V
V
AMS2911-2.85
0
I
OUT
1A , 4.35V
V
IN
12V
2.82
2.79
2.850
2.850
2.88
2.91
V
V
AMS2911-3.3
0
I
OUT
1A , 4.75V
V
IN
12V
3.267
3.235
3.300
3.300
3.333
3.365
V
V
AMS2911-5.0
0
I
OUT
1A , 6.5V
V
IN
12V
4.950
4.900
5.000
5.000
5.050
5.100
V
V
Line Regulation
AMS2911
I
LOAD
= 10 mA , 1.5V
(V
IN
- V
OUT
)
12V
0.015
0.035
.02
.02
%
%
AMS2911-1.5
4.35V
V
IN
12V
0.3
0.6
5
6
mV
mV
AMS2911-2.5
4.35V
V
IN
12V
0.3
0.6
6
6
mV
mV
AMS2911-2.85
4.35V
V
IN
12V
0.3
0.6
6
6
mV
mV
AMS2911-3.3
4.75V
V
IN
12V
0.5
1.0
10
10
mV
mV
AMS2911-5.0
6.5V
V
IN
12V
0.5
1.0
10
10
mV
mV
Load Regulation
(Notes 2, 3)
AMS2911
(V
IN
- V
OUT
) =3V, 10mA
I
OUT
1A
0.1
0.2
0.3
0.4
%
%
AMS2911-1.5
V
IN
= 5V, 0
I
OUT
1A
3
6
10
20
mV
mV
AMS2911-2.5
V
IN
= 5V, 0
I
OUT
1A
3
6
12
20
mV
mV
AMS2911-2.85
V
IN
= 5V, 0
I
OUT
1A
3
6
12
20
mV
mV
AMS2911-3.3
V
IN
= 5V, 0
I
OUT
1A
3
7
15
25
mV
mV
AMS2911-5.0
V
IN
= 8V, 0
I
OUT
1A
5
10
20
35
mV
mV
Advanced Monolithic Systems, Inc. 6680B Sierra Lane, Dublin, CA 94568 Phone (925) 556-9090 Fax (925) 556-9140
AMS2911
ELECTRICAL CHARACTERISTICS
Electrical Characteristics at I
OUT
= 0 mA, and T
J
= +25C unless otherwise specified.
Parameter
Device
Conditions
Min Typ Max
Units
Dropout Voltage
(V
IN
-
V
OUT
)
AMS2911/-1.5/-2.5/-2.85/
-3.3/-5.0
V
OUT
,
V
REF
= 1%, I
OUT
= 1A (Note 4)
1.3
1.5
V
Current Limit
AMS2911/-1.5/-2.5/2.85/
-3.3/-5.0
(V
IN
- V
OUT
) = 5V
.9
1.1
1.5
A
Minimum Load
Current
AMS2911
(V
IN
- V
OUT
) = 12V (Note 5)
5
10
mA
Quiescent Current
AMS2911/-1.5/-2.5/-2.85/
-3.3/-5.0
V
IN
12V
5
10
mA
Ripple Rejection
AMS2911
f =120Hz , C
OUT
= 25
F Tantalum, I
OUT
= 1A,
(V
IN
-V
OUT
) = 3V, C
ADJ
=25
F
60
75
dB
AMS2911-1.5
f =120Hz , C
OUT
= 25
F Tantalum, I
OUT
= 1A,
V
IN
= 6V
60
72
dB
AMS2911-2.5
f =120Hz , C
OUT
= 25
F Tantalum, I
OUT
= 1A,
V
IN
= 6V
60
72
dB
AMS2911-2.85
f =120Hz , C
OUT
= 25
F Tantalum, I
OUT
= 1A,
V
IN
= 6V
60
72
dB
AMS2911-3.3
f =120Hz , C
OUT
= 25
F Tantalum, I
OUT
= 1A
V
IN
= 6.3V
60
72
dB
AMS2911-5
f =120Hz , C
OUT
= 25
F Tantalum, I
OUT
= 1A
V
IN
= 8V
60
68
dB
Thermal Regulation
AMS2911
T
A
= 25C, 30ms pulse
0.008
0.04
%W
Adjust Pin Current
AMS2911
10mA
I
OUT
1A , 1.5V
(V
IN
- V
OUT
)
12V
55
120
A
A
Adjust Pin Current
Change
AMS2911
10mA
I
OUT
1A , 1.5V
(V
IN
- V
OUT
)
12V
0.2
5
A
Temperature Stability
0.5
%
Long Term Stability
T
A
=125C, 1000Hrs
0.3
1
%
RMS Output Noise
(% of V
OUT
)
T
A
= 25C , 10Hz
f
10kHz
0.003
%
Thermal Resistance
Junction-to-Case
M Package: Control Circuitry/ Power Transistor
T Package: Control Circuitry/ Power Transistor
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 1.2W. 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 1.5
(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
AMS2911
APPLICATION HINTS
The AMS2911 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.
Stability
The circuit design used in the AMS2911 series requires the use of
an output capacitor as part of the device frequency compensation.
The addition of
150
F aluminum electrolytic or a 22
F 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 22
F tantalum or
150
F
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 100
F 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 AMS2911 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
AMS2911 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 1000
F to 5000
F 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 AMS2911 is used (Figure 1).
AMS2911
IN OUT
ADJ
+
C
OUT
150
F
V
OUT
R
1
R
2
C
ADJ
10
F
D1
V
IN
Figure 1.
Output Voltage
The AMS2911 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.
AMS2911
IN OUT
ADJ
R1
R2
V
OUT
V
REF
V
IN
I
ADJ
50
A
V
OUT
= V
REF
(
1+ R2/R1)+I
ADJ
R2
Figure 2. Basic Adjustable Regulator
Load Regulation
True remote load sensing it is not possible to provide, because
the AMS2911 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 ) , R
P
= Parasitic Line Resistance
R1
Advanced Monolithic Systems, Inc. 6680B Sierra Lane, Dublin, CA 94568 Phone (925) 556-9090 Fax (925) 556-9140
AMS2911
APPLICATION HINTS
Connected as shown , R
P
is not multiplied by the divider ratio
AMS2911
IN OUT
ADJ
R
L
R1*
R2*
V
IN
R
P
PARASITIC
LINE RESISTANCE
*
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 AMS2911 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 thermal resistance from the junction to the tab for the
AMS2911 is 15
C/W.
Thermal 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 resistor 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 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 AMS2911 is equal to:
P
D
= ( V
IN
- V
OUT
)( I
OUT
)
Maximum junction temperature will be equal to:
T
J
= T
A(MAX)
+ P
D
( Thermal Resistance(junction-to-ambient))
Maximum junction temperature must not exceed 125
C.
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 100
to
200
) 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=100
at 120Hz
the adjust pin capacitor should be
>
13
F. At 10kHz only 0.16
F
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
).
Table 1.
COPPER AREA
THERMAL RESISTANCE
TOP SIDE*
BACK SIDE
BOARD AREA
(JUNCTION-TO-AMBIENT)
2500 Sq. mm
2500 Sq. mm
2500 Sq. mm
45
C/W
1000 Sq. mm
2500 Sq. mm
2500 Sq. mm
45
C/W
225 Sq. mm
2500 Sq. mm
2500 Sq. mm
53
C/W
100 Sq. mm
2500 Sq. mm
2500 Sq. mm
59
C/W
1000 Sq. mm
1000 Sq. mm
1000 Sq. mm
52
C/W
1000 Sq. mm
0
1000 Sq. mm
55
C/W
* Tab of device attached to topside copper.
Advanced Monolithic Systems, Inc. 6680B Sierra Lane, Dublin, CA 94568 Phone (925) 556-9090 Fax (925) 556-9140
AMS2911
TYPICAL PERFORMANCE CHARACTERISTICS
Minimum Operating Current
(Adjustable Device)
Short-Circuit Current
Load Regulation
Ripple Rejection vs. Current
Adjust Pin Current
Temperature Stability
0
5
10
15
20
0
3
6
9
12
INPUT/OUTPUT DIFFERENTIAL (V)
0
5
10
15
MINIMUM OPERATING CURRENT (mA)
INPUT/OUTPUT DIFFERENTIAL
0
0.25
0.50
0.75
1.00
1.25
SHORT CIRCUIT CURRENT (A)
-50
-25
0
25
50
75
100
125
-0.20
-0.15
-0.10
-0.05
0
0.05
0.10
TEMPERATURE (C)
OUTPUT VOLTAGE DEVIATION (%)
0
0.25
0.5
0.75
1.0
0
10
20
30
40
50
60
70
80
90
100
OUTPUT CURRENT (A)
RIPPLE REJECTION (dB)
-50
-25
0
25
50
75
100
125
150
-2.0
-1.0
0
1.0
2.0
TEMPERATURE (C)
OUTPUT VOLTAGE CHANGE (%)
TEMPERATURE (C)
-50
-25
0
25
50
75
100
125
150
0
10
20
30
40
50
60
70
80
90
100
ADJUST PIN CURRENT (
A)
T
J
= 125C
T
J
= 25C
f
RIPPLE
= 120Hz
f
RIPPLE
= 20Hz
V
RIPPLE
3Vp-p
V
RIPPLE
0.5Vp-p
I
LOAD
= 1A
V
OUT
= 5V
C
ADJ
= 25
F
C
OUT
= 25
F
T
J
= 125C
T
J
= 25C
Advanced Monolithic Systems, Inc. 6680B Sierra Lane, Dublin, CA 94568 Phone (925) 556-9090 Fax (925) 556-9140
AMS2911
PACKAGE DIMENSIONS
inches (millimeters) unless otherwise noted.
3 LEAD TO-220 PLASTIC PACKAGE (T)
3 LEAD TO-263 PLASTIC DD (M)
0.330-0.370
0.050
(8.382-9.398)
0.090-0.110
(2.286-2.794)
(1.270)
TYP
0.390-0.415
(9.906-10.541)
0.165-0.180
(4.191-4.572)
0.045-0.055
(1.143-1.397)
0.095-0.115
(2.413-2.921)
0.013-0.023
(0.330-0.584)
T (TO-220) AMS DRW# 042193
0.147-0.155
(3.734-3.937)
DIA
0.230-0.270
(5.842-6.858)
0.460-0.500
(11.684-12.700)
0.570-0.620
(14.478-15.748)
0.218-0.252
(5.537-6.401)
0.520-0.570
(13.208-14.478)
0.980-1.070
(24.892-27.178)
0.028-0.038
(0.711-0.965)
0.330-0.370
0.032
0.060
(1.524)
TYP
(8.382-9.398)
(5.05-5.54 )
0.090-0.110
(2.286-2.794)
0.199-0.218
(0.81)
TYP
0.390-0.415
(9.906-10.541)
0.165-0.180
(4.191-4.572)
0.045-0.055
(1.143-1.397)
0.095-0.115
(2.413-2.921)
0.90-0.110
(2.29-2.79)
0.013-0.023
(0.330-0.584)
0.108
(2.74)
TYP
(
0.102
)
+0.203
-0.102
0.004 +0.008
-0.004
M (DD3) AMS DRW# 042191R1
Advanced Monolithic Systems, Inc. 6680B Sierra Lane, Dublin, CA 94568 Phone (925) 556-9090 Fax (925) 556-9140
AMS2911
PACKAGE DIMENSIONS
inches (millimeters) unless otherwise noted (Continued).
TO-252 PLASTIC PACKAGE (D)
3 LEAD SOT-223 PLASTIC PACKAGE
0.030
(0.762)
TYP
0.085-0.095
(2.159-2.413)
0.030-0.034
(0.762-0.863)
0.0240.002
(0.6100.0508)
0.018-0.022
(0.451-0.558)
0.038
(0.965)
TYP
D (D3) AMS DRW# 042891
0.038-0.042
(0.965-1.066)
0.038-0.042
(0.965-1.066)
0.235-0.245
(5.969-6.223)
0.088-0.092
(2.235-2.336)
0.099-0.103
(2.514-2.615)
0.175-0.180
(4.191-4.445)
0.023-0.027
(0.584-0.685)
0.020-0.030
(0.508-0.762)
0.258-0.262
(6.553-6.654)
0.033-0.037
(0.838-0.939)
0.020-0.030
(0.508-0.762)
0.208-0.212
(5.283-5.384)
0.025
(0.635)
TYP
0.057-0.067
(0.144-0.170)
DIA
45.0
7.0
0.130-0.146
(3.30-3.71)
0.248-0.264
(6.30-6.71)
0.116-0.124
(2.95-3.15)
0.264-0.287
(6.71-7.29)
0.090
(2.29)
NOM
0.071
(1.80)
MAX
0.033-0.041
(0.84-1.04)
0.025-0.033
(0.64-0.84)
0.181
(4.60)
NOM
0.012
(0.31)
MIN
0.025-0.033
(0.64-0.84)
10
MAX
10-16
10-16
0.010-0.014
(0.25-0.36)
(SOT-223 ) AMS DRW# 042292
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