Advanced Monolithic Systems, Inc. www.advanced-monolithic.com Phone (925) 443-0722 Fax (925) 443-0723
Advanced AMS2905
Monolithic 500mA LOW DROPOUT VOLTAGE REGULATOR
Systems RoHS compliant
FEATURES APPLICATIONS
• Three Terminal Adjustable or Fixed Voltages* • High Efficiency Linear Regulators
1.5V, 1.8V, 2.5V, 2.85V, 3.3V and 5.0V •Post Re
g
ulators for Switchin
g
Supplies
• Output Current of 500mA • 5V to 3.3V Linear Regulator
• Operates Down to 1V Dropout • Battery Chargers
• Line Regulation: 0.2% Max. • Sound Cards
• Load Regulation: 0.4% Max. • Power Management for Notebook
• TO-252, SOT-223 and SOT-89 packages • Battery Powered Instrumentation
GENERAL DESCRIPTION
The AMS2905 series of adjustable and fixed voltage regulators are designed to provide 500mA output current and to operate
down 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 AMS2905 devices are pin compatible with other three-terminal regulators and are offered in the low profile surface mount
TO-252(DPAK), SOT-223 and SOT-89 packages.
ORDERING INFORMATION:
PACKAGE TYPE OPERATING JUNCTION
SOT-89 TO-252 SOT-223
TEMPERATURE
RANGE
AMS2905CL AMS2905CD AMS2905 -40 to 125° C
AMS2905CL-1.5 AMS2905CD-1.5 AMS2905-1.5 -40 to 125° C
AMS2905CL-1.8 AMS2905CD-1.8 AMS2905-1.8 -40 to 125° C
AMS2905CL-2.5 AMS2905CD-2.5 AMS2905-2.5 -40 to 125° C
AMS2905CL-2.85 AMS2905CD-2.85 AMS2905-2.85 -40 to 125° C
AMS2905CL-3.3 AMS2905CD-3.3 AMS2905-3.3 -40 to 125° C
AMS2905CL-5.0 AMS2905CD-5.0 AMS2905-5.0 -40 to 125° C
*For additional available fixed voltages contact factory.
PIN CONNECTIONS
FIXED VERSION
ADJUSTABLE VERSION
1- VIN
2- Ground
3- VOUT
1- VIN
2- Adjust
3- VOUT
SOT-89 Top View
321
SOT-223 Top View
123
TO-252 Front View
1
2
3
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AMS2905
ABSOLUTE MAXIMUM RATINGS (Note 1)
Power Dissipation Internally limited Thermal Resistance
Input Voltage 15V SOT-89 package ϕ JA= 110°C/W
Operating Junction Temperature TO-252 package ϕ JA= 80°C/W
Control Section -40°C to 125°C SOT-223 package ϕ JA= 90°C/W*
Power Transistor -40°C to 150°C
Storage temperature - 65°C to +150°C
Soldering information
Lead Temperature (25 sec) 265°C
* 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 depending on mounting technique and
the size of the copper area.
ELECTRICAL CHARACTERISTICS
Electrical Characteristics at IOUT = 0 mA, and TJ = +25°C unless otherwise specified.
Parameter
Device Conditions Min Typ Max Units
Reference Voltage
(Note 2) AMS2905 IOUT = 10 mA
10mA ≤ IOUT ≤ 500mA, 1.5V≤ (VIN - VOUT) ≤ 12V 1.238
1.225 1.250
1.250 1.262
1.270 V
V
Output Voltage
(Note 2) AMS2905-1.5 0 ≤ IOUT ≤ 500mA , 4.35V ≤ VIN ≤ 12V 1.485
1.476 1.500
1.500 1.515
1.524 V
V
AMS2905-1.8 0 ≤ IOUT ≤ 500mA , 4.35V≤ VIN ≤ 12V 1.782
1.772 1.800
1.800 1.818
1.828 V
V
AMS2905-2.5 0 ≤ IOUT ≤ 500mA , 4.35V≤ VIN ≤ 12V 2.475
2.460 2.500
2.500 2.525
2.560 V
V
AMS2905-2.85 0 ≤ IOUT ≤ 500mA , 4.35V ≤ VIN ≤ 12V 2.82
2.79 2.850
2.850 2.88
2.91 V
V
AMS2905-3.3 0 ≤ IOUT ≤ 500mA , 4.75V ≤ VIN ≤ 12V 3.267
3.235 3.300
3.300 3.333
3.365 V
V
AMS2905-5.0 0 ≤ IOUT ≤ 500mA , 6.5V ≤ VIN ≤ 12V 4.950
4.900 5.000
5.000 5.050
5.100 V
V
Line Regulation AMS2905 ILOAD = 10 mA , 1.5V≤ (VIN - VOUT) ≤ 12V 0.015
0.035 0.2
0.2 %
%
AMS2905-1.5
3.0V≤ VIN ≤ 12V 0.3
0.6 5
6 mV
mV
AMS2905-1.8
3.0V≤ VIN ≤ 12V 0.3
0.6 5
6 mV
mV
AMS2905-2.5
4.0V≤ VIN ≤ 12V 0.3
0.6 6
6 mV
mV
AMS2905-2.85
4.35V≤ VIN ≤ 12V 0.3
0.6 6
6 mV
mV
AMS2905-3.3
4.75V≤ VIN ≤ 12V 0.5
1.0 10
10 mV
mV
AMS2905-5.0
6.5V≤ VIN ≤ 12V 0.5
1.0 10
10 mV
mV
Load Regulation
(Notes 2, 3)
AMS2905 (VIN - VOUT) =3V, 10mA ≤ IOUT ≤ 500mA 0.1
0.2 0.3
0.4 %
%
AMS2905-1.5
VIN = 5V, 0 ≤ IOUT ≤ 500mA 3
6 10
20 mV
mV
AMS2905-1.8
VIN = 5V, 0 ≤ IOUT ≤ 500mA 3
6 10
20 mV
mV
AMS2905-2.5
VIN = 5V, 0 ≤ IOUT ≤ 500mA 3
6 12
20 mV
mV
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AMS2905
ELECTRICAL CHARACTERISTICS
Electrical Characteristics at IOUT = 0 mA, and TJ = +25°C unless otherwise specified.
Parameter
Device Conditions Min Typ Max Units
Load Regulation
(Notes 2, 3)
AMS2905-2.85 VIN = 5V, 0 ≤ IOUT ≤ 500mA 3
6 12
20 mV
mV
AMS2905-3.3 VIN = 5V, 0 ≤ IOUT ≤ 500mA 3
7 15
25 mV
mV
AMS2905-5.0 VIN = 8V, 0 ≤ IOUT ≤ 500mA 5
10 20
35 mV
mV
Dropout Voltage
(VIN - VOUT) AMS2905-1.5/-1.8/-2.5/-
2.85/-3.3/-5.0 ∆VOUT , ∆VREF = 1%, IOUT = 500mA (Note 4)
1.1 1.3
V
Current Limit
AMS2905-1.5/-1.8/-2.5/-
2.85/-3.3/-5.0 (VIN - VOUT) = 5V
1,000 mA
Minimum Load
Current AMS2905 (VIN - VOUT) = 12V (Note 5) 5 10 mA
Quiescent Current AMS2905-1.5/-1.8/-2.5/-
2.85/-3.3/-5.0 VIN ≤ 12V
5
10
mA
Ripple Rejection AMS2905 f =120Hz , COUT = 25µF Tantalum, IOUT = 500mA,
(VIN-VOUT ) = 3V, CADJ =25µF 60 75 dB
AMS2905-1.5/-1.8/-2.5/-
2.85 f =120Hz , COUT = 25µF Tantalum, IOUT = 500mA,
VIN = 6V 60
72
dB
AMS2905-3.3
f =120Hz , COUT = 25µF Tantalum, IOUT = 500mA
VIN = 6.3V 60 72
dB
AMS2905-5.0
f =120Hz , COUT = 25µF Tantalum, IOUT = 500mA
VIN = 8V 60 68
dB
Thermal Regulation AMS2905 TA = 25°C, 30ms pulse 0.008 0.04 %W
Adjust Pin Current AMS2905 10mA ≤ IOUT ≤ 500mA , 1.5V≤ (VIN - VOUT) ≤ 12V 55
120 µA
µA
Adjust Pin Current
Change AMS2905 10mA ≤ IOUT ≤ 500mA , 1.5V≤ (VIN - VOUT) ≤ 12V 0.2
5
µA
Temperature Stability 0.5 %
Long Term Stability TA =125°C, 1000Hrs 0.3 1 %
RMS Output Noise
(% of VOUT )
TA = 25°C , 10Hz ≤ f ≤ 10kHz 0.003
%
Thermal Resistance
Junction-to-Case
15 °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 for SOT-223 package and 0.9W for SOT-89 package. 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 1.5V ≤ (VIN - VOUT) ≤ 12V the device is
guaranteed to regulate if the output current is greater than 10mA.
Advanced Monolithic Systems, Inc. www.advanced-monolithic.com Phone (925) 443-0722 Fax (925) 443-0723
AMS2905
APPLICATION HINTS
The AMS2905 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 AMS2905 series requires the use of
an output capacitor as part of the device frequency compensation.
The addition of 150µF 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 150µF
aluminum covers all cases of bypassing the adjustment terminal.
Without bypassing the adjustment terminal smaller capacitors can
be used with equally good results.
To further improve stability and transient response of these
devices larger values of output capacitor can be used.
Protection Diodes
Unlike older regulators, the AMS2905 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
AMS2905 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 AMS2905 is used (Figure 1).
AMS2905
IN OUT
ADJ
+
C
OUT
150
µ
F
V
OUT
R
1
R
2
C
ADJ
10
µ
F
D1
V
IN
Figure 1.
Output Voltage
The AMS2905 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
IADJ is very small and constant it represents a small error and it can
usually be ignored.
AMS2905
IN OUT
ADJ R1
R2
V
OUT
V
REF
V
IN
I
ADJ
50
µ
A
VOUT = VREF (1+ R2/R1)+IADJR2
Figure 2. Basic Adjustable Regulator
Load Regulation
True remote load sensing it is not possible to provide, because the
AMS2905 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:
RP x ( R2+R1 ) , RP = Parasitic Line Resistance
R1
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AMS2905
APPLICATION HINTS
Connected as shown , RP is not multiplied by the divider ratio
AMS2905
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 AMS2905 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
AMS2905 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 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 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 AMS2905 is equal to:
PD = ( VIN - VOUT )( IOUT )
Maximum junction temperature will be equal to:
TJ = TA(MAX) + PD(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 100Ω to
200Ω) for a proper by passing 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 (VOUT / VREF).
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.
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AMS2905
TYPICAL PERFORMANCE CHARACTERISTICS
Minimum Operating Current
(Adjustable Device) Short-Circuit Current
Load Regulation Ripple Rejection vs. Current
Adjust Pin CurrentTemperature 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 0.15 0.3 0.45 0.6
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 (
µ
A)
T
J
= 125°C
T
J
= 25°C
f
RIPPLE
= 120Hz
f
RIPPLE
= 20Hz
V
RIPPLE
≤
3Vp-p
V
RIPPLE
≤
0.5Vp-p
∆
I
LOAD
= 500mA
V
OUT
= 5V
C
ADJ
= 25
µ
F
C
OUT
= 25
µ
F
T
J
= 125°C
T
J
= 25°C
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AMS2905
PACKAGE DIMENSIONS inches (millimeters) unless otherwise noted.
TO-252 PLASTIC PACKAGE (D)
0.030
(0.762)
TYP
0.087-0.094
(2.21-2.39) 0.018-0.023
(0.46-0.58)
0.020±0.002
(0.510±0.0508)
0.018-0.023
(0.46-0.58) D (D3) AMS DRW# 011601
0.035-0.050
(0.89-1.27)
0.035-0.045
(0.89-1.14)
0.235-0.245
(5.969-6.223)
0.156-0.204
(3.96-5.18)
0.255-0.265
(6.48-6.73)
0.206-0.214
(5.23-5.44)
0.025
(0.635)
TYP
7.0°
0.380-0.410
(9.65-10.41)
0.045-0.060
(1.14-1.52)
3 LEAD SOT-223 PLASTIC PACKAGE
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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AMS2905
PACKAGE DIMENSIONS inches (millimeters) unless otherwise noted (Continued).
SOT-89 PLASTIC PACKAGE (L)
0.090-0.102
(2.29-2.60)
0.173-0.181
(4.40-4.60)
0.064-0.072
(1.62-1.83)
0.155-0.167
(3.94-4.25)
0.059
(1.50)
BSC
0.035-0.047
(0.89-1.20)
L (SOT-89 ) AMS DRW# 042392
0.118
(3.00)
BSC
0.014-0.019
(0.36-0.48)
0.017-0.022
(0.44-0.56)
0.084-0.090
(2.13-2.29)
0.055-0.063
(1.40-1.60) 0.014-0.017
(0.35-0.44)
