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Advanced Monolithic Systems
FEATURES
* Three Terminal Adjustable or Fixed Voltages* 1.5V, 1.8V, 2.5V, 2.85V, 3.3V and 5.0V * Output Current of 500mA * Operates Down to 1V Dropout * Line Regulation: 0.2% Max. * Load Regulation: 0.4% Max. * TO-252, SOT-223 and SOT-89 packages
AMS2905
500mA LOW DROPOUT VOLTAGE REGULATOR
RoHS compliant
APPLICATIONS
* High Efficiency Linear Regulators * Post Regulators for Switching Supplies * 5V to 3.3V Linear Regulator * Battery Chargers * Sound Cards * Power Management for Notebook * 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 SOT-89 TO-252 SOT-223 OPERATING JUNCTION TEMPERATURE RANGE -40 to 125 C -40 to 125 C -40 to 125 C -40 to 125 C -40 to 125 C -40 to 125 C -40 to 125 C
SOT-223 Top View SOT-89 Top View
AMS2905CL AMS2905CD AMS2905 AMS2905CL-1.5 AMS2905CD-1.5 AMS2905-1.5 AMS2905CL-1.8 AMS2905CD-1.8 AMS2905-1.8 AMS2905CL-2.5 AMS2905CD-2.5 AMS2905-2.5 AMS2905CL-2.85 AMS2905CD-2.85 AMS2905-2.85 AMS2905CL-3.3 AMS2905CD-3.3 AMS2905-3.3 AMS2905CL-5.0 AMS2905CD-5.0 AMS2905-5.0 *For additional available fixed voltages contact factory.
PIN CONNECTIONS
1 2 3
FIXED VERSION 1- VIN 2- Ground 3- VOUT
ADJUSTABLE VERSION 1- VIN 2- Adjust 3- VOUT
TO-252 Front View
3 2 1
1
2
3
Advanced Monolithic Systems, Inc.
www.advanced-monolithic.com
Phone (925) 443-0722
Fax (925) 443-0723
AMS2905
ABSOLUTE MAXIMUM RATINGS (Note 1)
Power Dissipation Input Voltage Operating Junction Temperature Control Section Power Transistor Storage temperature Soldering information Lead Temperature (25 sec) Internally limited 15V -40C to 125C -40C to 150C - 65C to +150C 265C Thermal Resistance SOT-89 package TO-252 package SOT-223 package JA= 110C/W JA= 80C/W JA= 90C/W*
* With package soldering to copper area over backside ground plane or internal power plane JA can vary from 46C/W to >90C/W depending on mounting technique and the size of the copper area.
ELECTRICAL CHARACTERISTICS
Electrical Characteristics at IOUT = 0 mA, and TJ = +25C unless otherwise specified. Parameter
Reference Voltage (Note 2) Output Voltage (Note 2)
Device
AMS2905 AMS2905-1.5 AMS2905-1.8 AMS2905-2.5 AMS2905-2.85 AMS2905-3.3 AMS2905-5.0
Conditions
IOUT = 10 mA 10mA IOUT 500mA, 1.5V (VIN - VOUT) 12V 0 IOUT 500mA , 4.35V VIN 12V 0 IOUT 500mA , 4.35V VIN 12V 0 IOUT 500mA , 4.35V VIN 12V 0 IOUT 500mA , 4.35V VIN 12V 0 IOUT 500mA , 4.75V VIN 12V 0 IOUT 500mA , 6.5V VIN 12V ILOAD = 10 mA , 1.5V (VIN - VOUT) 12V 3.0V VIN 12V 3.0V VIN 12V 4.0V VIN 12V 4.35V VIN 12V 4.75V VIN 12V 6.5V VIN 12V (VIN - VOUT) =3V, 10mA IOUT 500mA VIN = 5V, 0 IOUT 500mA VIN = 5V, 0 IOUT 500mA VIN = 5V, 0 IOUT 500mA
Min
1.238 1.225 1.485 1.476 1.782 1.772 2.475 2.460 2.82 2.79 3.267 3.235 4.950 4.900
Typ
1.250 1.250 1.500 1.500 1.800 1.800 2.500 2.500 2.850 2.850 3.300 3.300 5.000 5.000 0.015 0.035 0.3 0.6 0.3 0.6 0.3 0.6 0.3 0.6 0.5 1.0 0.5 1.0 0.1 0.2 3 6 3 6 3 6
Max
1.262 1.270 1.515 1.524 1.818 1.828 2.525 2.560 2.88 2.91 3.333 3.365 5.050 5.100 0.2 0.2 5 6 5 6 6 6 6 6 10 10 10 10 0.3 0.4 10 20 10 20 12 20
Units
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 mV mV
Line Regulation
AMS2905 AMS2905-1.5 AMS2905-1.8 AMS2905-2.5 AMS2905-2.85 AMS2905-3.3 AMS2905-5.0
Load Regulation (Notes 2, 3)
AMS2905 AMS2905-1.5 AMS2905-1.8 AMS2905-2.5
Advanced Monolithic Systems, Inc.
www.advanced-monolithic.com
Phone (925) 443-0722
Fax (925) 443-0723
AMS2905
ELECTRICAL CHARACTERISTICS
Electrical Characteristics at IOUT = 0 mA, and TJ = +25C unless otherwise specified. Parameter
Load Regulation (Notes 2, 3) AMS2905-3.3 AMS2905-5.0 Dropout Voltage (VIN - VOUT) Current Limit Minimum Load Current Quiescent Current Ripple Rejection AMS2905-1.5/-1.8/-2.5/2.85/-3.3/-5.0 AMS2905-1.5/-1.8/-2.5/2.85/-3.3/-5.0 AMS2905 AMS2905-1.5/-1.8/-2.5/2.85/-3.3/-5.0 AMS2905 AMS2905-1.5/-1.8/-2.5/2.85 AMS2905-3.3 AMS2905-5.0 Thermal Regulation Adjust Pin Current Adjust Pin Current Change Temperature Stability Long Term Stability RMS Output Noise (% of VOUT ) Thermal Resistance Junction-to-Case 15 C/W TA =125C, 1000Hrs TA = 25C , 10Hz f 10kHz AMS2905 AMS2905 AMS2905 VIN = 5V, 0 IOUT 500mA VIN = 8V, 0 IOUT 500mA VOUT , VREF = 1%, IOUT = 500mA (Note 4) (VIN - VOUT) = 5V (VIN - VOUT) = 12V (Note 5) VIN 12V f =120Hz , COUT = 25F Tantalum, IOUT = 500mA, (VIN-VOUT ) = 3V, CADJ =25F f =120Hz , COUT = 25F Tantalum, IOUT = 500mA, VIN = 6V f =120Hz , COUT = 25F Tantalum, IOUT = 500mA VIN = 6.3V f =120Hz , COUT = 25F Tantalum, IOUT = 500mA VIN = 8V TA = 25C, 30ms pulse 10mA IOUT 500mA , 1.5V (VIN - VOUT) 12V 10mA IOUT 500mA , 1.5V (VIN - VOUT) 12V 60 60 60 60
Device
AMS2905-2.85
Conditions
VIN = 5V, 0 IOUT 500mA
Min
Typ
3 6 3 7 5 10 1.1 1,000 5 5 75 72 72 68 0.008 55
Max
12 20 15 25 20 35 1.3
Units
mV mV mV mV mV mV V mA
10 10
mA mA dB dB dB dB
0.04 120
%W A A A %
0.2 0.5 0.3 0.003
5
1
% %
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 165C 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.
D1
VIN
AMS2905 IN OUT ADJ CADJ
10F
VOUT R1 R2
+
COUT
150F
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 150F aluminum electrolytic or a 22F 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 22F tantalum or 150F 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.
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.
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 1000F to 5000F 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).
VIN
AMS2905 IN OUT ADJ IADJ 50A
VOUT VREF R1 R2
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 ) , R1 RP = Parasitic Line Resistance
Advanced Monolithic Systems, Inc.
www.advanced-monolithic.com
Phone (925) 443-0722
Fax (925) 443-0723
AMS2905
APPLICATION HINTS
Connected as shown , RP is not multiplied by the divider ratio
RP PARASITIC LINE RESISTANCE
VIN
AMS2905 IN OUT ADJ
R1*
RL
R2*
The total thermal resistance from junction to ambient can be as low as 45C/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 125C.
*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.
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 >13F. At 10kHz only 0.16F 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).
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 125C 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 15C/W. Thermal resistance from tab to ambient can be as low as 30C/W.
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)
45C/W 45C/W 53C/W 59C/W 52C/W 55C/W
Advanced Monolithic Systems, Inc.
www.advanced-monolithic.com
Phone (925) 443-0722
Fax (925) 443-0723
AMS2905
TYPICAL PERFORMANCE CHARACTERISTICS
Minimum Operating Current (Adjustable Device)
12 MINIMUM OPERATING CURRENT (mA) 1.25 TJ = 125C 9 TJ = 125C SHORT CIRCUIT CURRENT (A) 1.00 TJ = 25C 0.75
Short-Circuit Current
6
TJ = 25C
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 ILOAD = 500mA OUTPUT VOLTAGE DEVIATION (%) 0.05 RIPPLE REJECTION (dB) 100 90
Ripple Rejection vs. Current
fRIPPLE = 120Hz 80 70 60 50 40 30 20 10 VOUT = 5V CADJ = 25F COUT = 25F 0 0.15 0.3 0.45 0.6 fRIPPLE = 20Hz VRIPPLE0.5Vp-p VRIPPLE3Vp-p
0
-0.05
-0.10
-0.15
-0.20 -50 -25 0 25 50 75 100 125 TEMPERATURE (C)
0
OUTPUT CURRENT (A)
Temperature Stability
2.0 100 90 OUTPUT VOLTAGE CHANGE (%) 80 ADJUST PIN CURRENT ( A) 1.0 70 60 50 40 30 20 10 -2.0 -50 -25 0 25 50 75 100 125 150 TEMPERATURE (C) 0 -50
Adjust Pin Current
0
-1.0
-25
0
25
50
75
100
125
150
TEMPERATURE (C)
Advanced Monolithic Systems, Inc.
www.advanced-monolithic.com
Phone (925) 443-0722
Fax (925) 443-0723
AMS2905
PACKAGE DIMENSIONS inches (millimeters) unless otherwise noted.
TO-252 PLASTIC PACKAGE (D)
0.255-0.265 (6.48-6.73) 0.206-0.214 (5.23-5.44)
0.087-0.094 (2.21-2.39)
0.018-0.023 (0.46-0.58) 0.035-0.050 (0.89-1.27)
7.0
0.380-0.410 (9.65-10.41)
0.235-0.245 (5.969-6.223)
0.025 (0.635) TYP 0.156-0.204 (3.96-5.18) 0.030 (0.762) TYP
0.045-0.060 (1.14-1.52)
0.035-0.045 (0.89-1.14) 0.0200.002 (0.5100.0508)
0.018-0.023 (0.46-0.58)
D (D3) AMS DRW# 011601
3 LEAD SOT-223 PLASTIC PACKAGE
0.248-0.264 (6.30-6.71) 0.116-0.124 (2.95-3.15)
0.264-0.287 (6.71-7.29) 0.130-0.146 (3.30-3.71)
0.090 (2.29) NOM
0.033-0.041 (0.84-1.04)
10-16 0.071 (1.80) MAX 10 MAX 0.010-0.014 (0.25-0.36) 10-16 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)
(SOT-223 ) AMS DRW# 042292
Advanced Monolithic Systems, Inc.
www.advanced-monolithic.com
Phone (925) 443-0722
Fax (925) 443-0723
AMS2905
PACKAGE DIMENSIONS inches (millimeters) unless otherwise noted (Continued).
SOT-89 PLASTIC PACKAGE (L)
0.173-0.181 (4.40-4.60) 0.064-0.072 (1.62-1.83)
0.055-0.063 (1.40-1.60) 0.014-0.017 (0.35-0.44)
0.155-0.167 (3.94-4.25) 0.090-0.102 (2.29-2.60) 0.084-0.090 (2.13-2.29)
0.035-0.047 (0.89-1.20) 0.059 (1.50) BSC 0.118 (3.00) BSC 0.014-0.019 (0.36-0.48) 0.017-0.022 (0.44-0.56)
L (SOT-89 ) AMS DRW# 042392
Advanced Monolithic Systems, Inc.
www.advanced-monolithic.com
Phone (925) 443-0722
Fax (925) 443-0723

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