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LT3080 Adjustable1.1A Single Resistor Low Dropout Regulator FEATURES
n n n n n n n n n n n n n n
DESCRIPTION
The LT(R)3080 is a 1.1A low dropout linear regulator that can be paralleled to increase output current or spread heat in surface mounted boards. Architected as a precision current source and voltage follower allows this new regulator to be used in many applications requiring high current, adjustability to zero, and no heat sink. Also the device brings out the collector of the pass transistor to allow low dropout operation --down to 350 millivolts-- when used with multiple supplies. A key feature of the LT3080 is the capability to supply a wide output voltage range. By using a reference current through a single resistor, the output voltage is programmed to any level between zero and 36V. The LT3080 is stable with 2.2F of capacitance on the output, and the IC uses small ceramic capacitors that do not require additional ESR as is common with other regulators. Internal protection circuitry includes current limiting and thermal limiting. The LT3080 regulator is offered in the 8-lead MSOP (with an exposed pad for better thermal characteristics), a 3mm x 3mm DFN, 5-lead DD-Pak, TO-220 and a simple-to-use 3-lead SOT-223 version.
L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks and VLDO and ThinSOT are trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners.
Outputs May be Paralleled for Higher Current and Heat Spreading Output Current: 1.1A Single Resistor Programs Output Voltage 1% Initial Accuracy of SET Pin Current Output Adjustable to 0V Low Output Noise: 40VRMS (10Hz to 100kHz) Wide Input Voltage Range: 1.2V to 36V Low Dropout Voltage: 350mV (Except SOT-223 Package) <1mV Load Regulation <0.001%/V Line Regulation Minimum Load Current: 0.5mA Stable with 2.2F Minimum Ceramic Output Capacitor Current Limit with Foldback and Overtemperature Protected Available in 8-Lead MSOP 3mm x 3mm DFN, , 5-Lead DD-Pak, TO-220 and 3-Lead SOT-223
APPLICATIONS
n n n n n
High Current All Surface Mount Supply High Efficiency Linear Regulator Post Regulator for Switching Supplies Low Parts Count Variable Voltage Supply Low Output Voltage Power Supplies
TYPICAL APPLICATION
Variable Output Voltage 1.1A Supply
VIN 1.2V TO 36V IN VCONTROL LT3080
Set Pin Current Distribution
N = 13792
1F SET
+ -
OUT VOUT 2.2F 9.80 10.00 10.20 9.90 10.10 SET PIN CURRENT DISTRIBUTION (A)
3080 G02
RSET VOUT = RSET * 10A
3080 TA01a
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LT3080 ABSOLUTE MAXIMUM RATINGS (Note 1)(All Voltages Relative to VOUT)
VCONTROL Pin Voltage ..................................... 40V, -0.3V IN Pin Voltage ................................................ 40V, -0.3V SET Pin Current (Note 7) .....................................10mA SET Pin Voltage (Relative to OUT) .........................0.3V Output Short-Circuit Duration .......................... Indefinite Operating Junction Temperature Range (Notes 2, 10) .......................................... -40C to 125C Storage Temperature Range:.................. -65C to 150C Lead Temperature (Soldering, 10 sec) MS8E, Q, T and ST Packages Only.................... 300C
PIN CONFIGURATION
TOP VIEW FRONT VIEW OUT 1 OUT 2 OUT 3 SET 4 9 8 7 6 5 IN IN NC VCONTROL TOP VIEW OUT OUT OUT SET 1 2 3 4 8 7 6 5 IN IN NC VCONTROL 5 4 TAB IS OUT 3 2 1 Q PACKAGE 5-LEAD PLASTIC DD-PAK TJMAX = 125C, JA = 30C/W, JC = 3C/W IN VCONTROL OUT SET NC
9
MS8E PACKAGE 8-LEAD PLASTIC MSOP TJMAX = 125C, JA = 60C/W, JC = 10C/W EXPOSED PAD (PIN 9) IS OUT, MUST BE SOLDERED TO PCB
DD PACKAGE 8-LEAD (3mm x 3mm) PLASTIC DFN TJMAX = 125C, JA = 64C/W, JC = 3C/W EXPOSED PAD (PIN 9) IS OUT, MUST BE SOLDERED TO PCB FRONT VIEW 5 TAB IS OUT 4 3 2 1 T PACKAGE 5-LEAD PLASTIC TO-220
FRONT VIEW IN VCONTROL OUT SET NC ST PACKAGE 3-LEAD PLASTIC SOT-223 *IN IS VCONTROL AND IN TIED TOGETHER TJMAX = 125C, JA = 55C/W, JC = 15C/W TAB IS OUT 3 2 1 IN* OUT SET
TJMAX = 125C, JA = 40C/W, JC = 3C/W
ORDER INFORMATION
LEAD FREE FINISH TAPE AND REEL PART MARKING LT3080EDD#PBF LT3080EDD#TRPBF LCBN LT3080EMS8E#PBF LT3080EMS8E#TRPBF LTCBM LT3080EQ#PBF LT3080EQ#TRPBF LT3080EQ LT3080ET#PBF LT3080ET#TRPBF LT3080ET LT3080EST#PBF LT3080EST#TRPBF 3080 LEAD BASED FINISH TAPE AND REEL PART MARKING LT3080EDD LT3080EDD#TR LCBN LT3080EMS8E LT3080EMS8E#TR LTCBM LT3080EQ LT3080EQ#TR LT3080EQ LT3080ET LT3080ET#TR LT3080ET LT3080EST LT3080EST#TR 3080 Consult LTC Marketing for parts specified with wider operating temperature ranges. PACKAGE DESCRIPTION 8-Lead (3mm x 3mm) Plastic DFN 8-Lead Plastic MSOP 5-Lead Plastic DD-Pak 5-Lead Plastic TO-220 3-Lead Plastic SOT-223 PACKAGE DESCRIPTION 8-Lead (3mm x 3mm) Plastic DFN 8-Lead Plastic MSOP 5-Lead Plastic DD-Pak 5-Lead Plastic TO-220 3-Lead Plastic SOT-223 TEMPERATURE RANGE -40C to 125C -40C to 125C -40C to 125C -40C to 125C -40C to 125C TEMPERATURE RANGE -40C to 125C -40C to 125C -40C to 125C -40C to 125C -40C to 125C
For more information on lead free part marking, go to: http://www.linear.com/leadfree/ For more information on tape and reel specifications, go to: http://www.linear.com/tapeandreel/
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LT3080 ELECTRICAL CHARACTERISTICS
PARAMETER SET Pin Current Output Offset Voltage (VOUT - VSET) VIN = 1V, VCONTROL = 2V, IOUT = 1mA CONDITIONS ISET VIN = 1V, VCONTROL = 2.0V, ILOAD = 1mA, TJ = 25C VIN 1V, VCONTROL 2.0V, 1mA ILOAD 1.1A (Note 9) VOS DFN and MSOP Package SOT-223, DD-Pak and T0-220 Package Load Regulation Line Regulation (Note 9) DFN and MSOP Package Line Regulation (Note 9) SOT-223, DD-Pak and T0-220 Package Minimum Load Current (Notes 3, 9) ISET ILOAD = 1mA to 1.1A VOS ILOAD = 1mA to 1.1A (Note 8) ISET VIN = 1V to 25V, VCONTROL = 2V to 25V, ILOAD = 1mA VOS VIN = 1V to 25V, VCONTROL = 2V to 25V, ILOAD = 1mA ISET VIN = 1V to 26V, VCONTROL = 2V to 26V, ILOAD = 1mA VOS VIN = 1V to 26V, VCONTROL = 2V to 26V, ILOAD = 1mA VIN = VCONTROL = 10V VIN = VCONTROL = 25V (DFN and MSOP Package) VIN = VCONTROL = 26V (SOT-223, DD-Pak and T0-220 Package) ILOAD = 100mA ILOAD = 1.1A ILOAD = 100mA ILOAD = 1.1A ILOAD = 100mA ILOAD = 1.1A VIN = 5V, VCONTROL = 5V, VSET = 0V, VOUT = -0.1V ILOAD = 1.1A, 10Hz f 100kHz, COUT = 10F, CSET = 0.1F 10Hz f 100kHz f = 120Hz, VRIPPLE = 0.5VP-P, ILOAD = 0.2A, CSET = 0.1F, COUT = 2.2F f = 10kHz f = 1MHz 10ms Pulse
l l l l l l l l l l l l l l l
The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25C. (Note 11)
MIN 9.90 9.80 -2 -3.5 -5 -6 -0.1 0.6 0.1 0.003 0.1 0.003 300 TYP 10 10 MAX 10.10 10.20 2 3.5 5 6 1.3 0.5 0.5 500 1 1 1.6 200 500 6 30 UNITS A A mV mV mV mV nA mV nA/V mV/V nA/V mV/V A mA mA V V mV mV mA mA A VRMS nARMS dB dB dB %/W
VCONTROL Dropout Voltage (Note 4) VIN Dropout Voltage (Note 4) VCONTROL Pin Current Current Limit Error Amplifier RMS Output Noise (Note 6) Reference Current RMS Output Noise (Note 6) Ripple Rejection
1.2 1.35 100 350 4 17 1.1 1.4 40 1 75 55 20 0.003
Thermal Regulation, ISET
Note 1: Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. Exposure to any Absolute Maximum Rating condition for extended periods may affect device reliability and lifetime. Note 2: Unless otherwise specified, all voltages are with respect to VOUT. The LT3080 is tested and specified under pulse load conditions such that TJ TA. The LT3080 E-Grade is 100% tested at TA = 25C. Performance at -40C and 125C is assured by design, characterization and correlation with statistical process controls. Note 3: Minimum load current is equivalent to the quiescent current of the part. Since all quiescent and drive current is delivered to the output of the part, the minimum load current is the minimum current required to maintain regulation. Note 4: For the LT3080, dropout is caused by either minimum control voltage (VCONTROL) or minimum input voltage (VIN). Both parameters are specified with respect to the output voltage. The specifications represent the minimum input-to-output differential voltage required to maintain regulation. Note 5: The VCONTROL pin current is the drive current required for the output transistor. This current will track output current with roughly a 1:60 ratio. The minimum value is equal to the quiescent current of the device. Note 6: Output noise is lowered by adding a small capacitor across the voltage setting resistor. Adding this capacitor bypasses the voltage setting
resistor shot noise and reference current noise; output noise is then equal to error amplifier noise (see Applications Information section). Note 7: SET pin is clamped to the output with diodes. These diodes only carry current under transient overloads. Note 8: Load regulation is Kelvin sensed at the package. Note 9: Current limit may decrease to zero at input-to-output differential voltages (VIN-VOUT) greater than 25V (DFN and MSOP package) or 26V (SOT-223, DD-Pak and T0-220 Package). Operation at voltages for both IN and VCONTROL is allowed up to a maximum of 36V as long as the difference between input and output voltage is below the specified differential (VIN-VOUT) voltage. Line and load regulation specifications are not applicable when the device is in current limit. Note 10: This IC includes overtemperature protection that is intended to protect the device during momentary overload conditions. Junction temperature will exceed the maximum operating junction temperature when overtemperature protection is active. Continuous operation above the specified maximum operating junction temperature may impair device reliability. Note 11: The SOT-223 package connects the IN and VCONTROL pins together internally. Therefore, test conditions for this pin follow the VCONTROL conditions listed in the Electrical Characteristics Table.
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LT3080 TYPICAL PERFORMANCE CHARACTERISTICS
Set Pin Current
10.20 10.15 SET PIN CURRENT (A) 10.10 10.05 10.00 9.95 9.90 9.85 9.80 -50 -25 0 25 50 75 100 125 150 TEMPERATURE (C)
3080 G01
Set Pin Current Distribution
2.0 N = 13792 OFFSET VOLTAGE (mV) 1.5 1.0 0.5 0 -0.5 -1.0 -1.5 9.80 10.00 10.20 9.90 10.10 SET PIN CURRENT DISTRIBUTION (A)
3080 G02
Offset Voltage (VOUT - VSET)
IL = 1mA
-2.0 -50 -25
0
25 50 75 100 125 150 TEMPERATURE (C)
3080 G03
Offset Voltage Distribution
1.00 N = 13250 OFFSET VOLTAGE (mV) 0.75
Offset Voltage
ILOAD = 1mA 0.50 0.25 0 -0.25 -0.50 -0.75 -1.00 0.25 0 OFFSET VOLTAGE (mV) -0.25 -0.50
Offset Voltage
TJ = 25C
TJ = 125C -0.75 -1.00 -1.25 -1.50
-2
0 -1 1 VOS DISTRIBUTION (mV)
2
3080 G04
0
24 30 18 INPUT-TO-OUTPUT VOLTAGE (V) *SEE NOTE 9 IN ELECTRICAL CHARACTERISTICS TABLE
6
12
36*
3080 G05
-1.75
0
0.2
0.4 0.8 0.6 LOAD CURRENT (A)
1.0
1.2
3080 G06
Load Regulation
CHANGE IN OFFSET VOLTAGE WITH LOAD (mV) 0 -0.1 -0.2 -0.3 -0.4 -0.5 -0.6 -0.7 -0.8 -50 -25 0 CHANGE IN OFFSET VOLTAGE (VOUT - VSET) ILOAD = 1mA TO 1.1A VIN - VOUT = 2V CHANGE IN REFERENCE CURRENT 20 10 0 -10 -20 -30 -40 -50 -60 25 50 75 100 125 150 TEMPERATURE (C)
3080 G07
Minimum Load Current
0.8 MINIMUM IN VOLTAGE (VIN - VOUT) (mV) MINIMUM LOAD CURRENT (mA) 0.7 0.6 0.5 0.4 VIN, CONTROL - VOUT = 1.5V 0.3 0.2 0.1 0 -50 -25 0 25 50 75 100 125 150 TEMPERATURE (C)
3080 G08
Dropout Voltage (Minimum IN Voltage)
400 350 TJ = 125C 300 250 200 150 100 50 0 0 0.2 0.4 0.8 0.6 OUTPUT CURRENT (A) 1.0 1.2
3080 G09
CHANGE IN REFERENCE CURRENT WITH LOAD (nA)
VIN, CONTROL - VOUT = 36V*
TJ = 25C
*SEE NOTE 9 IN ELECTRICAL CHARACTERISTICS TABLE
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LT3080 TYPICAL PERFORMANCE CHARACTERISTICS
MINIMUM CONTROL VOLTAGE (VCONTROL - VOUT) (V) 400 MINIMUM IN VOLTAGE (VIN - VOUT) (mV) 350 300 250 200 150 100 50 0 -50 -25 0 25 50 75 100 125 150 TEMPERATURE (C)
3080 G10
1.6 TJ = -50C 1.4 1.2 TJ = 125C 1.0 0.8 0.6 0.4 0.2 0 0 0.2 0.8 0.6 OUTPUT CURRENT (A) 0.4 1.0 1.2
3080 G11
MINIMUM CONTROL VOLTAGE (VCONTROL - VOUT) (V)
Dropout Voltage (Minimum IN Voltage)
Dropout Voltage (Minimum VCONTROL Pin Voltage)
Dropout Voltage (Minimum VCONTROL Pin Voltage)
1.6 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0 -50 -25 0 25 50 75 100 125 150 TEMPERATURE (C)
3080 G12
ILOAD = 1.1A
ILOAD = 1.1A
ILOAD = 500mA
TJ = 25C
ILOAD = 1mA
ILOAD = 100mA
Current Limit
1.6 1.4 CURRENT LIMIT (A) CURRENT LIMIT (A) 1.2 1.0 0.8 0.6 0.4 0.2 VIN = 7V VOUT = 0V 0 25 50 75 100 125 150 TEMPERATURE (C)
3080 G13
Current Limit
1.6 1.4 1.2 1.0 0.8 LOAD CURRENT (mA) 0.6 0.4 0.2 0 0 24 30 18 INPUT-TO-OUTPUT DIFFERENTIAL (V) 6 12 36* MSOP AND DFN SOT-223, DD-PAK AND TO-220 OUTPUT VOLTAGE DEVIATION (mV) TJ = 25C 75 50 25 0 -25 -50 400 300 200 100 0
Load Transient Response
VOUT = 1.5V CSET = 0.1F VIN = VCONTROL = 3V
COUT = 10F CERAMIC COUT = 2.2F CERAMIC
0 -50 -25
0
5
10 15 20 25 30 35 40 45 50 TIME (s)
3080 G15
*SEE NOTE 9 IN ELECTRICAL CHARACTERISTICS TABLE
3080 G14
Load Transient Response
150 OUTPUT VOLTAGE DEVIATION (mV) OUTPUT VOLTAGE DEVIATION (mV) 100 50 0 -50 75 50 25 0 -25 -50 6 5 4 3 2
Line Transient Response
INPUT VOLTAGE (V) 5 4 3 2 1 0 OUTPUT VOLTAGE (V) 2.0 1.5 1.0 0.5 0
Turn-On Response
LOAD CURRENT (A)
1.2 0.9 0.6 0.3 0 0 5 VIN = VCONTROL = 3V VOUT = 1.5V COUT = 10F CERAMIC CSET = 0.1F
IN/CONTROL VOLTAGE (V)
-100
VOUT = 1.5V ILOAD = 10mA COUT = 2.2F CERAMIC CSET = 0.1F CERAMIC
RSET = 100k CSET = 0 RLOAD = 1 COUT = 2.2F CERAMIC
10 15 20 25 30 35 40 45 50 TIME (s)
3080 G16
0
10 20 30 40 50 60 70 80 90 100 TIME (s)
3080 G17
0
1
2
3
456 TIME (s)
7
8
9
10
3080 G27
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LT3080 TYPICAL PERFORMANCE CHARACTERISTICS
VCONTROL Pin Current
25 30 25 20 15 10 5 0 TJ = 125C TJ = 25C VCONTROL - VOUT = 2V VIN - VOUT = 1V OUTPUT VOLTAGE (V)
VCONTROL Pin Current
0.8 0.7 0.6 0.5 0.4 0.3
Residual Output Voltage with Less Than Minimum Load
SET PIN = 0V VIN VOUT RTEST
CONTROL PIN CURRENT (mA)
20
ILOAD = 1.1A DEVICE IN CURRENT LIMIT
CONTROL PIN CURRENT (mA)
15
TJ = -50C
VIN = 10V VIN = 20V VIN = 5V
10
0.2 0.1 0 0 1k RTEST () 2k
3080 G20
5 ILOAD = 1mA 0 0 30 12 18 24 6 INPUT-TO-OUTPUT DIFFERENTIAL (V) 36*
0
0.2
0.4 0.6 0.8 LOAD CURRENT (A)
1.0
1.2
3080 G19
*SEE NOTE 9 IN ELECTRICAL CHARACTERISTICS TABLE
3080 G18
Ripple Rejection, Single Supply
100 90 80 RIPPLE REJECTION (dB) RIPPLE REJECTION (dB) 70 60 50 40 30 20 V = V IN CONTROL = VOUT (NOMINAL) + 2V 10 RIPPLE = 50mVP-P COUT = 2.2F CERAMIC 0 10 100 1k 10k 100k FREQUENCY (Hz) ILOAD = 100mA ILOAD = 1.1A 100 90 80
Ripple Rejection, Dual Supply, VCONTROL Pin
100 90 80 RIPPLE REJECTION (dB) ILOAD = 100mA ILOAD = 1.1A 70 60 50 40 30 20 10 0 1M
3080 G22
Ripple Rejection, Dual Supply, IN Pin
70 60 50 40 30
1M
3080 G21
VIN = VOUT (NOMINAL) + 1V 20 V CONTROL = VOUT (NOMINAL) +2V 10 COUT = 2.2F CERAMIC RIPPLE = 50mVP-P 0 10 100 1k 10k 100k FREQUENCY (Hz)
VIN = VOUT (NOMINAL) + 1V VCONTROL = VOUT (NOMINAL) +2V RIPPLE = 50mVP-P COUT = 2.2F CERAMIC ILOAD = 1.1A 10 100 1k 10k FREQUENCY (Hz) 100k 1M
3080 G23
Ripple Rejection (120Hz)
80 79 10k
Noise Spectral Density
1k
REFERENCE CURRENT NOISE SPECTRAL DENSITY (pA/ Hz)
ERROR AMPLIFIER NOISE SPECTRAL DENSITY (nV/Hz)
78 RIPPLE REJECTION (dB) 77 76 75 74 73 72 71 SINGLE SUPPLY OPERATION VIN = VOUT(NOMINAL) + 2V RIPPLE = 500mVP-P, f = 120Hz ILOAD = 1.1A CSET = 0.1F, COUT = 2.2F 0 25 50 75 100 125 150 TEMPERATURE (C)
3080 G24
1k
100
100
10
10
1.0
70 -50 -25
1 10
100
1k 10k FREQUENCY (Hz)
0.1 100k
3080 G25
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LT3080 TYPICAL PERFORMANCE CHARACTERISTICS
Output Voltage Noise
20 15 VOUT 100V/DIV GAIN (dB) 10 5 0 -5 -10 -15 -20 -25 -30 10 100 1k 10k FREQUENCY (Hz) 100k IL = 100mA IL = 1.1A IL = 100mA IL = 1.1A
Error Amplifier Gain and Phase
300 250 200 150 100 50 0 -50 -100 -150 -200 1M
3080 G28
PHASE (DEGREES)
VOUT = 1V RSET = 100k CSET = O.1F COUT = 10F ILOAD = 1.1A
TIME 1ms/DIV
3080 G26
PIN FUNCTIONS
(DD/MS8E/Q/T/ST)
VCONTROL (Pin 5/Pin 5/Pin 4/Pin 4/NA): This pin is the supply pin for the control circuitry of the device. The current flow into this pin is about 1.7% of the output current. For the device to regulate, this voltage must be more than 1.2V to 1.35V greater than the output voltage (see dropout specifications). IN (Pins 7, 8/Pins 7, 8/Pin 5/Pin 5/Pin 3): This is the collector to the power device of the LT3080. The output load current is supplied through this pin. For the device to regulate, the voltage at this pin must be more than 0.1V to 0.5V greater than the output voltage (see dropout specifications). NC (Pin 6/Pin 6/Pin 1/Pin 1/NA): No Connection. No connect pins have no connection to internal circuitry and may be tied to VIN, VCONTROL, VOUT, GND or floated.
OUT (Pins 1-3/Pins 1-3/Pin 3/Pin 3/Pin 2): This is the power output of the device. There must be a minimum load current of 1mA or the output may not regulate. SET (Pin 4/Pin 4/Pin 2/Pin 2/Pin 1): This pin is the input to the error amplifier and the regulation set point for the device. A fixed current of 10A flows out of this pin through a single external resistor, which programs the output voltage of the device. Output voltage range is zero to the absolute maximum rated output voltage. Transient performance can be improved by adding a small capacitor from the SET pin to ground. Exposed Pad (Pin 9/Pin 9/NA/NA/NA): OUT on MS8E and DFN packages. TAB: OUT on DD-Pak, TO-220 and SOT-223 packages.
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LT3080 BLOCK DIAGRAM
IN VCONTROL 10A
+ -
3080 BD
SET
OUT
APPLICATIONS INFORMATION
The LT3080 regulator is easy to use and has all the protection features expected in high performance regulators. Included are short-circuit protection and safe operating area protection, as well as thermal shutdown. The LT3080 is especially well suited to applications needing multiple rails. The new architecture adjusts down to zero with a single resistor handling modern low voltage digital IC's as well as allowing easy parallel operation and thermal management without heat sinks. Adjusting to "zero" output allows shutting off the powered circuitry and when the input is pre-regulated--such as a 5V or 3.3V input supply --external resistors can help spread the heat. A precision "0" TC 10A internal current source is connected to the noninverting input of a power operational amplifier. The power operational amplifier provides a low impedance buffered output to the voltage on the noninverting input. A single resistor from the noninverting input to ground sets the output voltage and if this resistor is set to zero, zero output results. As can be seen, any output voltage can be obtained from zero up to the maximum defined by the input power supply. What is not so obvious from this architecture are the benefits of using a true internal current source as the reference as opposed to a bootstrapped reference in older regulators. A true current source allows the regulator to have gain and frequency response independent of the impedance on the positive input. Older adjustable regulators, such as the LT1086 have a change in loop gain with output voltage as well as bandwidth changes when the adjustment pin is bypassed to ground. For the LT3080, the loop gain is unchanged by changing the output voltage or bypassing. Output regulation is not fixed at a percentage of the output voltage but is a fixed fraction of millivolts. Use of a true current source allows all the gain in the buffer amplifier to provide regulation and none of that gain is needed to amplify up the reference to a higher output voltage. The LT3080 has the collector of the output transistor connected to a separate pin from the control input. Since the dropout on the collector (IN pin) is only 350mV, two supplies can be used to power the LT3080 to reduce dissipation: a higher voltage supply for the control circuitry and a lower voltage supply for the collector. This increases efficiency and reduces dissipation. To further spread the heat, a resistor can be inserted in series with the collector to move some of the heat out of the IC and spread it on the PC board. The LT3080 can be operated in two modes. Three-terminal mode has the control pin connected to the power input pin which gives a limitation of 1.35V dropout. Alternatively, the "control" pin can be tied to a higher voltage and the power IN pin to a lower voltage giving 350mV dropout on the IN pin and minimizing the power dissipation. This allows for a 1.1A supply regulating from 2.5VIN to 1.8VOUT or 1.8VIN to 1.2VOUT with low dissipation.
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LT3080 APPLICATIONS INFORMATION
IN VCONTROL LT3080
+
VIN
+
VCONTROL
+ -
OUT SET COUT RSET CSET
3080 F01
VOUT
If guardring techniques are used, this bootstraps any stray capacitance at the SET pin. Since the SET pin is a high impedance node, unwanted signals may couple into the SET pin and cause erratic behavior. This will be most noticeable when operating with minimum output capacitors at full load current. The easiest way to remedy this is to bypass the SET pin with a small amount of capacitance from SET to ground, 10pF to 20pF is sufficient. Stability and Output Capacitance The LT3080 requires an output capacitor for stability. It is designed to be stable with most low ESR capacitors (typically ceramic, tantalum or low ESR electrolytic). A minimum output capacitor of 2.2F with an ESR of 0.5 or less is recommended to prevent oscillations. Larger values of output capacitance decrease peak deviations and provide improved transient response for larger load current changes. Bypass capacitors, used to decouple individual components powered by the LT3080, increase the effective output capacitor value.
For improvement in transient performance, place a capacitor across the voltage setting resistor. Capacitors up to 1F can be used. This bypass capacitor reduces system noise as well, but start-up time is proportional to the time constant of the voltage setting resistor (RSET in Figure 1) and SET pin bypass capacitor. Extra consideration must be given to the use of ceramic capacitors. Ceramic capacitors are manufactured with a variety of dielectrics, each with different behavior across temperature and applied voltage. The most common dielectrics used are specified with EIA temperature characteristic codes of Z5U, Y5V, X5R and X7R. The Z5U and Y5V dielectrics are good for providing high capacitances in a small package, but they tend to have strong voltage and temperature coefficients as shown in Figures 2 and 3. When used with a 5V regulator, a 16V 10F Y5V capacitor can exhibit an effective value as low as 1F to 2F for the DC bias voltage applied and over the operating temperature range. The X5R and X7R dielectrics result in more stable characteristics and are more suitable for use as the output capacitor. The X7R type has better stability across temperature, while the X5R is less expensive and is
3080fb
Figure 1. Basic Adjustable Regulator
Output Voltage The LT3080 generates a 10A reference current that flows out of the SET pin. Connecting a resistor from SET to ground generates a voltage that becomes the reference point for the error amplifier (see Figure 1). The reference voltage is a straight multiplication of the SET pin current and the value of the resistor. Any voltage can be generated and there is no minimum output voltage for the regulator. A minimum load current of 1mA is required to maintain regulation regardless of output voltage. For true zero voltage output operation, this 1mA load current must be returned to a negative supply voltage.
With the low level current used to generate the reference voltage, leakage paths to or from the SET pin can create errors in the reference and output voltages. High quality insulation should be used (e.g., Teflon, Kel-F); cleaning of all insulating surfaces to remove fluxes and other residues will probably be required. Surface coating may be necessary to provide a moisture barrier in high humidity environments. Board leakage can be minimized by encircling the SET pin and circuitry with a guard ring operated at a potential close to itself; the guard ring should be tied to the OUT pin. Guarding both sides of the circuit board is required. Bulk leakage reduction depends on the guard ring width. Ten nanoamperes of leakage into or out of the SET pin and associated circuitry creates a 0.1% error in the reference voltage. Leakages of this magnitude, coupled with other sources of leakage, can cause significant offset voltage and reference drift, especially over the possible operating temperature range.
9
LT3080 APPLICATIONS INFORMATION
20 0 CHANGE IN VALUE (%) X5R -20 -40 -60 Y5V -80 -100 BOTH CAPACITORS ARE 16V, 1210 CASE SIZE, 10F
ceramic capacitor the stress can be induced by vibrations in the system or thermal transients.
Paralleling Devices
LT3080's may be paralleled to obtain higher output current. The SET pins are tied together and the IN pins are tied together. This is the same whether it's in three terminal mode or has separate input supplies. The outputs are connected in common using a small piece of PC trace as a ballast resistor to equalize the currents. PC trace resistance in milliohms/inch is shown in Table 1. Only a tiny area is needed for ballasting.
Table 1. PC Board Trace Resistance
WEIGHT (oz) 10 mil WIDTH 54.3 27.1 20 mil WIDTH 27.1 13.6 1 2
X5R
0
2
4
8 6 10 12 DC BIAS VOLTAGE (V)
14
16
3080 F02
Figure 2. Ceramic Capacitor DC Bias Characteristics
40 20 CHANGE IN VALUE (%) 0 -20 -40 -60 -80 BOTH CAPACITORS ARE 16V, 1210 CASE SIZE, 10F 50 25 75 0 TEMPERATURE (C) 100 125 Y5V
Trace resistance is measured in mOhms/in
-100 -50 -25
The worse case offset between the set pin and the output of only 2 millivolts allows very small ballast resistors to be used. As shown in Figure 4, the two devices have a small 10 milliohm ballast resistor, which at full output current gives better than 80 percent equalized sharing of the current. The external resistance of 10 milliohms
VIN VCONTROL LT3080
3080 F03
Figure 3. Ceramic Capacitor Temperature Characteristics
available in higher values. Care still must be exercised when using X5R and X7R capacitors; the X5R and X7R codes only specify operating temperature range and maximum capacitance change over temperature. Capacitance change due to DC bias with X5R and X7R capacitors is better than Y5V and Z5U capacitors, but can still be significant enough to drop capacitor values below appropriate levels. Capacitor DC bias characteristics tend to improve as component case size increases, but expected capacitance at operating voltage should be verified. Voltage and temperature coefficients are not the only sources of problems. Some ceramic capacitors have a piezoelectric response. A piezoelectric device generates voltage across its terminals due to mechanical stress, similar to the way a piezoelectric microphone works. For a
+ -
SET
OUT 10m
VIN 4.8V TO 28V
VIN VCONTROL
LT3080
1F
+ -
SET 165k
OUT 10m
VOUT 3.3V 2A 10F
3080 F04
Figure 4. Parallel Devices
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10
LT3080 APPLICATIONS INFORMATION
(5 milliohms for the two devices in parallel) only adds about 10 millivolts of output regulation drop at an output of 2A. Even with an output voltage as low as 1V, this only adds 1% to the regulation. Of course, more than two LT3080's can be paralleled for even higher output current. They are spread out on the PC board, spreading the heat. Input resistors can further spread the heat if the input-to-output difference is high. temperature of about 90C, about 65C above ambient as shown in Figure 6. Again, the temperature matching between the devices is within 2C, showing excellent tracking between the devices. The board temperature has reached approximately 40C within about 0.75 inches of each device. While 90C is an acceptable operating temperature for these devices, this is in 25C ambient. For higher ambients, the temperature must be controlled to prevent device temperature from exceeding 125C. A 3-meter-per-second airflow across the devices will decrease the device temperature about 20C providing a margin for higher operating ambient temperatures. Both at low power and relatively high power levels devices can be paralleled for higher output current. Current sharing and thermal sharing is excellent, showing that acceptable operation can be had while keeping the peak temperatures below excessive operating temperatures on a board. This technique allows higher operating current linear regulation to be used in systems where it could never be used before.
Thermal Performance
In this example, two LT3080 3mm x 3mm DFN devices are mounted on a 1oz copper 4-layer PC board. They are placed approximately 1.5 inches apart and the board is mounted vertically for convection cooling. Two tests were set up to measure the cooling performance and current sharing of these devices. The first test was done with approximately 0.7V inputto-output and 1A per device. This gave a 700 milliwatt dissipation in each device and a 2A output current. The temperature rise above ambient is approximately 28C and both devices were within plus or minus 1C. Both the thermal and electrical sharing of these devices is excellent. The thermograph in Figure 5 shows the temperature distribution between these devices and the PC board reaches ambient temperature within about a half an inch from the devices. The power is then increased with 1.7V across each device. This gives 1.7 watts dissipation in each device and a device
Quieting the Noise The LT3080 offers numerous advantages when it comes to dealing with noise. There are several sources of noise in a linear regulator. The most critical noise source for any LDO is the reference; from there, the noise contribution
Figure 5. Temperature Rise at 700mW Dissipation
Figure 6. Temperature Rise at 1.7W Dissipation
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LT3080 APPLICATIONS INFORMATION
from the error amplifier must be considered, and the gain created by using a resistor divider cannot be forgotten. Traditional low noise regulators bring the voltage reference out to an external pin (usually through a large value resistor) to allow for bypassing and noise reduction of reference noise. The LT3080 does not use a traditional voltage reference like other linear regulators, but instead uses a reference current. That current operates with typical noise current levels of 3.2pA/Hz (1nARMS over the 10Hz to 100kHz bandwidth). The voltage noise of this is equal to the noise current multiplied by the resistor value. The resistor generates spot noise equal to 4kTR (k = Boltzmann's constant, 1.38 * 10-23 J/K, and T is absolute temperature) which is RMS summed with the reference current noise. To lower reference noise, the voltage setting resistor may be bypassed with a capacitor, though this causes start-up time to increase as a factor of the RC time constant. The LT3080 uses a unity-gain follower from the SET pin to drive the output, and there is no requirement to use a resistor to set the output voltage. Use a high accuracy voltage reference placed at the SET pin to remove the errors in output voltage due to reference current tolerance and resistor tolerance. Active driving of the SET pin is acceptable; the limitations are the creativity and ingenuity of the circuit designer. One problem that a normal linear regulator sees with reference voltage noise is that noise is gained up along with the output when using a resistor divider to operate at levels higher than the normal reference voltage. With the LT3080, the unity-gain follower presents no gain whatsoever from the SET pin to the output, so noise figures do not increase accordingly. Error amplifier noise is typically 125nV/Hz (40VRMS over the 10Hz to 100kHz bandwidth); this is another factor that is RMS summed in to give a final noise figure for the regulator. Curves in the Typical Performance Characteristics show noise spectral density and peak-to-peak noise characteristics for both the reference current and error amplifier over the 10Hz to 100kHz bandwidth. Overload Recovery Like many IC power regulators, the LT3080 has safe operating area (SOA) protection. The SOA protection decreases current limit as the input-to-output voltage increases and keeps the power dissipation at safe levels for all values of input-to-output voltage. The LT3080 provides some output current at all values of input-to-output voltage up to the device breakdown. See the Current Limit curve in the Typical Performance Characteristics. When power is first turned on, the input voltage rises and the output follows the input, allowing the regulator to start into very heavy loads. During start-up, as the input voltage is rising, the input-to-output voltage differential is small, allowing the regulator to supply large output currents. With a high input voltage, a problem can occur wherein removal of an output short will not allow the output voltage to recover. Other regulators, such as the LT1085 and LT1764A, also exhibit this phenomenon so it is not unique to the LT3080. The problem occurs with a heavy output load when the input voltage is high and the output voltage is low. Common situations are immediately after the removal of a short circuit. The load line for such a load may intersect the output current curve at two points. If this happens, there are two stable operating points for the regulator. With this double intersection, the input power supply may need to be cycled down to zero and brought up again to make the output recover. Load Regulation Because the LT3080 is a floating device (there is no ground pin on the part, all quiescent and drive current is delivered to the load), it is not possible to provide true remote load sensing. Load regulation will be limited by the resistance
IN VCONTROL LT3080
+ -
OUT SET RSET
PARASITIC RESISTANCE RP RP RP
3080 F07
LOAD
Figure 7. Connections for Best Load Regulation
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12
LT3080 APPLICATIONS INFORMATION
of the connections between the regulator and the load. The data sheet specification for load regulation is Kelvin sensed at the pins of the package. Negative side sensing is a true Kelvin connection, with the bottom of the voltage setting resistor returned to the negative side of the load (see Figure 7). Connected as shown, system load regulation will be the sum of the LT3080 load regulation and the parasitic line resistance multiplied by the output current. It is important to keep the positive connection between the regulator and load as short as possible and use large wire or PC board traces. Thermal Considerations The LT3080 has internal power and thermal limiting circuitry designed to protect it under overload conditions. For continuous normal load conditions, maximum junction temperature must not be exceeded. It is important to give consideration to all sources of thermal resistance from junction to ambient. This includes junction-to-case, case-to-heat sink interface, heat sink resistance or circuit board-to-ambient as the application dictates. Additional heat sources nearby must also be considered. For surface mount devices, heat sinking is accomplished by using the heat spreading capabilities of the PC board and its copper traces. Surface mount heat sinks and plated through-holes can also be used to spread the heat generated by power devices. 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 heat flow. Proper mounting is required to ensure the best possible thermal flow from this area of the package to the heat sinking material. For the TO-220 package, thermal compound is strongly recommended for mechanical connections to a heat sink. A thermally conductive spacer can be used for electrical isolation as long as the added contribution to thermal resistance is considered. Note that the Tab or Exposed Pad (depending on package) is electrically connected to the output. The following tables list thermal resistance for several different copper areas given a fixed board size. All measurements were taken in still air on two-sided 1/16" FR-4 board with one ounce copper.
Table 2. MSE Package, 8-Lead MSOP
COPPER AREA TOPSIDE* 2500mm2 1000mm2 225mm2 100mm2 BACKSIDE 2500mm2 2500mm2 2500mm2 2500mm2 BOARD AREA 2500mm2 2500mm2 2500mm2 2500mm2 THERMAL RESISTANCE (JUNCTION-TO-AMBIENT) 55C/W 57C/W 60C/W 65C/W
*Device is mounted on topside
Table 3. DD Package, 8-Lead DFN
COPPER AREA TOPSIDE* 2500mm2 1000mm2 225mm2 100mm2 BACKSIDE 2500mm2 2500mm2 2500mm2 2500mm2 BOARD AREA 2500mm2 2500mm2 2500mm2 2500mm2 THERMAL RESISTANCE (JUNCTION-TO-AMBIENT) 60C/W 62C/W 65C/W 68C/W
*Device is mounted on topside
Table 4. ST Package, 3-Lead SOT-223
COPPER AREA TOPSIDE* 2500mm2 1000mm2 225mm2 100mm2 BACKSIDE 2500mm2 2500mm2 2500mm2 2500mm2 BOARD AREA 2500mm2 2500mm2 2500mm2 2500mm2 THERMAL RESISTANCE (JUNCTION-TO-AMBIENT) 48C/W 48C/W 56C/W 62C/W
*Device is mounted on topside
Table 5. Q Package, 5-Lead DD-Pak
COPPER AREA TOPSIDE* 2500mm2 1000mm2 125mm2 BACKSIDE 2500mm2 2500mm2 2500mm2 BOARD AREA 2500mm2 2500mm2 2500mm2 THERMAL RESISTANCE (JUNCTION-TO-AMBIENT) 25C/W 30C/W 35C/W
*Device is mounted on topside
T Package, 5-Lead TO-220 Thermal Resistance (Junction-to-Case) = 3C/W Calculating Junction Temperature Example: Given an output voltage of 0.9V, a VCONTROL voltage of 3.3V 10%, an IN voltage of 1.5V 5%, output current range from 1mA to 1A and a maximum ambient temperature of 50C, what will the maximum junction temperature be for the DFN package on a 2500mm2 board with topside copper area of 500mm2?
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13
LT3080 APPLICATIONS INFORMATION
The power in the drive circuit equals: PDRIVE = (VCONTROL - VOUT)(ICONTROL) where ICONTROL is equal to IOUT/60. ICONTROL is a function of output current. A curve of ICONTROL vs IOUT can be found in the Typical Performance Characteristics curves. The power in the output transistor equals: POUTPUT = (VIN - VOUT)(IOUT) The total power equals: PTOTAL = PDRIVE + POUTPUT The current delivered to the SET pin is negligible and can be ignored. VCONTROL(MAX CONTINUOUS) = 3.630V (3.3V + 10%) VIN(MAX CONTINUOUS) = 1.575V (1.5V + 5%) VOUT = 0.9V, IOUT = 1A, TA = 50C Power dissipation under these conditions is equal to: PDRIVE = (VCONTROL - VOUT)(ICONTROL) ICONTROL = IOUT 1A = = 17mA 60 60 Reducing Power Dissipation In some applications it may be necessary to reduce the power dissipation in the LT3080 package without sacrificing output current capability. Two techniques are available. The first technique, illustrated in Figure 8, employs a resistor in series with the regulator's input. The voltage drop across RS decreases the LT3080's IN-to-OUT differential voltage and correspondingly decreases the LT3080's power dissipation. As an example, assume: VIN = VCONTROL = 5V, VOUT = 3.3V and IOUT(MAX) = 1A. Use the formulas from the Calculating Junction Temperature section previously discussed. Without series resistor RS, power dissipation in the LT3080 equals: PTOTAL = (5V - 3.3V ) * =1.73W If the voltage differential (VDIFF) across the NPN pass transistor is chosen as 0.5V, then RS equals: RS =
VIN C1 VCONTROL LT3080 IN RS VIN
Junction Temperature will be equal to: TJ = TA + PTOTAL * JA (approximated using tables) TJ = 50C + 721mW * 64C/W = 96C In this case, the junction temperature is below the maximum rating, ensuring reliable operation.
PDRIVE = (3.630V - 0.9V)(17mA) = 46mW POUTPUT = (VIN - VOUT)(IOUT) POUTPUT = (1.575V - 0.9V)(1A) = 675mW Total Power Dissipation = 721mW
1A + (5V - 3.3V ) * 1A 60
5V - 3.3V -0.5V =1.2 1A
Power dissipation in the LT3080 now equals: PTOTAL = (5V - 3.3V ) * 1A + (0.5V ) * 1A = 0.53W 60
+ -
OUT SET RSET C2
3080 F08
VOUT
The LT3080's power dissipation is now only 30% compared to no series resistor. RS dissipates 1.2W of power. Choose appropriate wattage resistors to handle and dissipate the power properly.
Figure 8. Reducing Power Dissipation Using a Series Resistor
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14
LT3080 APPLICATIONS INFORMATION
The second technique for reducing power dissipation, shown in Figure 9, uses a resistor in parallel with the LT3080. This resistor provides a parallel path for current flow, reducing the current flowing through the LT3080. This technique works well if input voltage is reasonably constant and output load current changes are small. This technique also increases the maximum available output current at the expense of minimum load requirements. As an example, assume: VIN = VCONTROL = 5V, VIN(MAX) = 5.5V, VOUT = 3.3V, VOUT(MIN) = 3.2V, IOUT(MAX) = 1A and IOUT(MIN) = 0.7A. Also, assuming that RP carries no more than 90% of IOUT(MIN) = 630mA. Calculating RP yields: 5.5V - 3.2V = 3.65 0.63A (5% Standard value = 3.6) RP =
VIN C1 VCONTROL LT3080 IN
The maximum total power dissipation is (5.5V - 3.2V) * 1A = 2.3W. However the LT3080 supplies only: 1A - 5.5V - 3.2V = 0.36A 3.6
Therefore, the LT3080's power dissipation is only: PDIS = (5.5V - 3.2V) * 0.36A = 0.83W RP dissipates 1.47W of power. As with the first technique, choose appropriate wattage resistors to handle and dissipate the power properly. With this configuration, the LT3080 supplies only 0.36A. Therefore, load current can increase by 0.64A to 1.64A while keeping the LT3080 in its normal operating range.
+ -
OUT SET RSET
RP
VOUT C2
3080 F09
Figure 9. Reducing Power Dissipation Using a Parallel Resistor
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15
LT3080 TYPICAL APPLICATIONS
Higher Output Current
VIN 6V MJ4502 VIN 50 IN LT3080
Adding Shutdown
IN LT3080
VCONTROL
+
100F
VCONTROL
1F SET
+ -
OUT
+ -
VOUT 3.3V 5A 100F SHUTDOWN
3080 TA02
OUT VOUT
SET ON OFF Q1 VN2222LL R1 1N4148 Q2* VN2222LL
3080 TA04
+
4.7F
332k
*Q2 INSURES ZERO OUTPUT IN THE ABSENCE OF ANY OUTPUT LOAD.
Current Source
VIN 10V IN VCONTROL LT3080
Low Dropout Voltage LED Driver
VIN C1 VCONTROL LT3080 IN D1 100mA
1F
+ -
SET 100k
OUT 1
IOUT 0A TO 1A 4.7F
+ -
OUT SET R1 24.9k
3080 TA03
R2 2.49
3080 TA05
Using a Lower Value SET Resistor
VIN 12V IN VCONTROL LT3080
C1 1F
+ -
OUT SET R1 49.9k 1% RSET 10k
3080 TA06
VOUT 0.5V TO 10V R2 499 1% VOUT = 0.5V + 1mA * RSET COUT 4.7F
1mA
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16
LT3080 TYPICAL APPLICATIONS
Coincident Tracking
IN VCONTROL IN VCONTROL VIN 7V TO 28V IN VCONTROL LT3080 LT3080 LT3080
+ -
OUT SET 169k OUT VOUT2 3.3V C3 4.7F VOUT3 5V 4.7F
3080 TA08
+ -
SET R2 80.6k C2 4.7F
C1 1.5F
+ -
OUT SET R1 249k
VOUT1 2.5V 1A
Adding Soft-Start
VIN 4.8V to 28V IN VCONTROL C1 1F D1 1N4148 LT3080
+ -
OUT SET
VOUT 3.3V 1A COUT 4.7F
C2 0.01F
R1 332k
3080 TA07
Lab Supply
IN VCONTROL LT3080 IN VCONTROL LT3080
VIN 12V TO 18V
+
15F
+ -
SET
OUT 1
+ -
OUT VOUT 0V TO 10V
+
100k 0A TO 1A 15F
SET R4 1MEG 4.7F
+
100F
3080 TA09
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17
LT3080 TYPICAL APPLICATIONS
High Voltage Regulator
VIN 50V 10k 1N4148 IN BUZ11 VCONTROL 6.1V
LT3080
+
10F
+ -
OUT
VOUT 1A VOUT = 20V VOUT = 10A * RSET
+
15F
SET RSET 2MEG
4.7F
3080 TA10
Ramp Generator
IN VCONTROL 1F LT3080 IN VCONTROL
Reference Buffer
LT3080
VIN 5V
VIN
+ -
SET VN2222LL 1F 1N4148
OUT
+ -
VOUT 4.7F OUT INPUT LT1019 GND
3080 TA12
OUTPUT
SET C1 1F
VOUT* C2 4.7F
3080 TA11
VN2222LL
*MIN LOAD 0.5mA
Ground Clamp
Boosting Fixed Output Regulators
LT3080
VIN
IN VCONTROL
LT3080
VEXT
+ -
1F 1N4148 OUT
20
+ -
OUT SET VOUT 5V LT1963-3.3 42* 47F
3080 TA20
20m 20m 3.3VOUT 2.6A
4.7F 5k
3080 TA13
10F
33k *4mV DROP ENSURES LT3080 IS OFF WITH NO LOAD MULTIPLE LT3080'S CAN BE USED
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18
LT3080 TYPICAL APPLICATIONS
Low Voltage, High Current Adjustable High Efficiency Regulator*
0.47H PVIN 2.7V TO 5.5V 2x + SVIN 2.2MEG 100k LTC3414 PGOOD RUN/SS 1000pF VFB 78.7k SYNC/MODE SGND PGND 124k SW ITH RT 294k 12.1k
10k
+
470pF
2x 100F 2N3906
IN VCONTROL
LT3080
100F
+ -
SET IN VCONTROL LT3080
OUT 20m
*DIFFERENTIAL VOLTAGE ON LT3080 IS 0.6V SET BY THE VBE OF THE 2N3906 PNP .
MAXIMUM OUTPUT VOLTAGE IS 1.5V
+ -
SET
OUT 20m
BELOW INPUT VOLTAGE
0V TO 4V 4A
IN VCONTROL
LT3080
+ -
SET
OUT 20m
IN VCONTROL
LT3080
+ -
SET 100k
3080 TA18
OUT 20m
+
100F
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19
LT3080 TYPICAL APPLICATIONS
Adjustable High Efficiency Regulator*
CMDSH-4E
4.5V TO 25V 10F 1F 100k
VIN
BOOST LT3493 0.1F 10H SW MBRM140 68F 200k
SHDN 0.1F
IN TP0610L VCONTROL
LT3080
GND
FB 10k SET
+ -
OUT
3080 TA19
0V TO 10V 1A 4.7F
1MEG *DIFFERENTIAL VOLTAGE ON LT3080 1.4V SET BY THE TPO610L P-CHANNEL THRESHOLD.
MAXIMUM OUTPUT VOLTAGE IS 2V
10k
BELOW INPUT VOLTAGE
2 Terminal Current Source
CCOMP*
IN VCONTROL
LT3080
+ -
SET 100k
R1
3080 TA21
*CCOMP R1 10 10F R1 10 2.2F
IOUT =
1V R1
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20
LT3080 PACKAGE DESCRIPTION
DD Package 8-Lead Plastic DFN (3mm x 3mm)
(Reference LTC DWG # 05-08-1698 Rev C)
0.70 0.05
3.5 0.05 1.65 0.05 2.10 0.05 (2 SIDES) PACKAGE OUTLINE 0.25 0.05 0.50 BSC 2.38 0.05 RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS APPLY SOLDER MASK TO AREAS THAT ARE NOT SOLDERED R = 0.125 TYP 5 0.40 8 0.10
3.00 0.10 (4 SIDES) PIN 1 TOP MARK (NOTE 6)
1.65 0.10 (2 SIDES)
(DD8) DFN 0509 REV C
0.200 REF
0.75 0.05
0.25
4 0.05 2.38 0.10
1 0.50 BSC
0.00 - 0.05
BOTTOM VIEW--EXPOSED PAD
NOTE: 1. DRAWING TO BE MADE A JEDEC PACKAGE OUTLINE M0-229 VARIATION OF (WEED-1) 2. DRAWING NOT TO SCALE 3. ALL DIMENSIONS ARE IN MILLIMETERS 4. DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED 0.15mm ON ANY SIDE 5. EXPOSED PAD SHALL BE SOLDER PLATED 6. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION ON TOP AND BOTTOM OF PACKAGE
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21
LT3080 PACKAGE DESCRIPTION
MS8E Package 8-Lead Plastic MSOP Exposed Die Pad ,
(Reference LTC DWG # 05-08-1662 Rev F)
BOTTOM VIEW OF EXPOSED PAD OPTION 1 1.88 (.074) 1.68 (.066) 0.29 REF
1.88 0.102 (.074 .004)
0.889 (.035
0.127 .005)
0.05 REF 5.23 (.206) MIN 1.68 0.102 3.20 - 3.45 (.066 .004) (.126 - .136) 8 DETAIL "B" CORNER TAIL IS PART OF DETAIL "B" THE LEADFRAME FEATURE. FOR REFERENCE ONLY NO MEASUREMENT PURPOSE 0.52 (.0205) REF
0.42 0.038 (.0165 .0015) TYP
0.65 (.0256) BSC
3.00 0.102 (.118 .004) (NOTE 3)
8
7 65
RECOMMENDED SOLDER PAD LAYOUT
DETAIL "A" 0 - 6 TYP 4.90 0.152 (.193 .006) 3.00 0.102 (.118 .004) (NOTE 4)
0.254 (.010) GAUGE PLANE
1 0.53 0.152 (.021 .006) DETAIL "A" 0.18 (.007) SEATING PLANE 0.22 - 0.38 (.009 - .015) TYP 1.10 (.043) MAX
23
4 0.86 (.034) REF
NOTE: 1. DIMENSIONS IN MILLIMETER/(INCH) 2. DRAWING NOT TO SCALE 3. DIMENSION DOES NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS. MOLD FLASH, PROTRUSIONS OR GATE BURRS SHALL NOT EXCEED 0.152mm (.006") PER SIDE 4. DIMENSION DOES NOT INCLUDE INTERLEAD FLASH OR PROTRUSIONS. INTERLEAD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.152mm (.006") PER SIDE 5. LEAD COPLANARITY (BOTTOM OF LEADS AFTER FORMING) SHALL BE 0.102mm (.004") MAX 6. EXPOSED PAD DIMENSION DOES NOT INCLUDE MOLD FLASH. MOLD FLASH ON E-PAD SHALL NOT EXCEED 0.254mm (.010") PER SIDE.
0.65 (.0256) BSC
0.1016 (.004
0.0508 .002)
MSOP (MS8E) 0210 REV F
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22
LT3080 PACKAGE DESCRIPTION
Q Package 5-Lead Plastic DD-Pak
(Reference LTC DWG # 05-08-1461)
.256 (6.502)
.060 (1.524)
.060 (1.524) TYP
.390 - .415 (9.906 - 10.541) 15 TYP
.165 - .180 (4.191 - 4.572)
.045 - .055 (1.143 - 1.397) +.008 .004 -.004 +0.203 0.102 -0.102 .095 - .115 (2.413 - 2.921)
.060 (1.524)
.183 (4.648)
.330 - .370 (8.382 - 9.398)
.059 (1.499) TYP
.075 (1.905) .300 (7.620) BOTTOM VIEW OF DD-PAK HATCHED AREA IS SOLDER PLATED COPPER HEAT SINK +.012 .143 -.020 +0.305 3.632 -0.508 .067 (1.702) .028 - .038 BSC (0.711 - 0.965) TYP
.013 - .023 (0.330 - 0.584)
.050 (1.270
.012 0.305)
Q(DD5) 0502
.420
.080
.420 .276
.350 .205 .565
.325 .565
.320 .090 .067 .042 .067 .090 .042
RECOMMENDED SOLDER PAD LAYOUT NOTE: 1. DIMENSIONS IN INCH/(MILLIMETER) 2. DRAWING NOT TO SCALE
RECOMMENDED SOLDER PAD LAYOUT FOR THICKER SOLDER PASTE APPLICATIONS
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23
LT3080 PACKAGE DESCRIPTION
T Package 5-Lead Plastic TO-220 (Standard)
(Reference LTC DWG # 05-08-1421)
.390 - .415 (9.906 - 10.541) .147 - .155 (3.734 - 3.937) DIA .230 - .270 (5.842 - 6.858) .460 - .500 (11.684 - 12.700) .570 - .620 (14.478 - 15.748) .330 - .370 (8.382 - 9.398) .700 - .728 (17.78 - 18.491) .620 (15.75) TYP .165 - .180 (4.191 - 4.572)
.045 - .055 (1.143 - 1.397)
SEATING PLANE .152 - .202 .260 - .320 (3.861 - 5.131) (6.60 - 8.13)
.095 - .115 (2.413 - 2.921) .155 - .195* (3.937 - 4.953) .013 - .023 (0.330 - 0.584)
BSC
.067 (1.70)
.028 - .038 (0.711 - 0.965)
.135 - .165 (3.429 - 4.191)
* MEASURED AT THE SEATING PLANE
T5 (TO-220) 0801
ST Package 3-Lead Plastic SOT-223
(Reference LTC DWG # 05-08-1630)
.248 - .264 (6.30 - 6.71) .114 - .124 (2.90 - 3.15) .059 MAX .129 MAX
.264 - .287 (6.70 - 7.30) .130 - .146 (3.30 - 3.71)
.248 BSC
.039 MAX
.059 MAX .090 BSC
.181 MAX .0905 (2.30) BSC .033 - .041 (0.84 - 1.04)
RECOMMENDED SOLDER PAD LAYOUT
10 - 16 .071 (1.80) MAX 10 MAX
.010 - .014 (0.25 - 0.36)
10 - 16 .024 - .033 (0.60 - 0.84) .181 (4.60) BSC .012 (0.31) MIN .0008 - .0040 (0.0203 - 0.1016)
ST3 (SOT-233) 0502
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24
LT3080 REVISION HISTORY
REV B DATE 6/10 DESCRIPTION Made minor updates to Features and Description sections Revised Line Regulation Conditions and Note 2 Made minor text edits in Applications Information section Added 200k resistor to drawing 3080 TA19 in Typical Applications section Updated Package Description drawings
(Revision history begins at Rev B)
PAGE NUMBER 1 3 9 20 21, 22
3080fb
Information furnished by Linear Technology Corporation is believed to be accurate and reliable. However, no responsibility is assumed for its use. Linear Technology Corporation makes no representation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
25
LT3080 TYPICAL APPLICATION
Paralleling Regulators
IN VCONTROL LT3080
+ -
SET
OUT 20m
VIN 4.8V TO 28V
IN VCONTROL
LT3080
+ -
1F SET 165k
OUT 20m
VOUT 3.3V 2A 10F
3080 TA14
RELATED PARTS
PART NUMBER LDOs LT1086 LT1117 LT1118 LT1963A LT1965 1.5A Low Dropout Regulator 800mA Low Dropout Regulator 800mA Low Dropout Regulator 1.5A Low Noise, Fast Transient Response LDO 1.1A Low Noise LDO Fixed 2.85V, 3.3V, 3.6V, 5V and 12V Output 1V Dropout, Adjustable or Fixed Output, DD-Pak, SOT-223 Packages OK for Sinking and Sourcing, S0-8 and SOT-223 Packages 340mV Dropout Voltage, Low Noise: 40VRMS, VIN = 2.5V to 20V, TO-220, DD-Pak, SOT-223 and SO-8 Packages 290mV Dropout Voltage, Low Noise 40VRMS, VIN = 1.8V to 20V, VOUT = 1.2V to 19.5V, Stable with Ceramic Caps TO-220, DD-Pak, MSOP and 3mm x 3mm DFN packages. VIN: 1.14V to 3.5V (Boost Enabled), 1.14V to 5.5V (with External 5V), VDO = 0.1V, IQ = 950A, Stable with 10F Ceramic Capacitors, 10-Lead MSOP and DFN Packages f = 200kHz, IQ = 100A, TSSOP-16E Package 95% Efficiency, VIN: 2.25V to 5.5V, VOUT(MIN) = 0.8V, TSSOP Package 95% Efficiency, VIN: 2.5V to 5.5V, VOUT(MIN) = 0.6V, IQ = 20A, ISD < 1A, ThinSOTTM Package 95% Efficiency, VIN: 2.5V to 5.5V, VOUT(MIN) = 0.8V, IQ = 60A, ISD < 1A, 10-Lead MS or DFN Packages DESCRIPTION COMMENTS
LTC(R)3026
1.5A Low Input Voltage VLDOTM Regulator
Switching Regulators LT1976 LTC3414 LTC3406/LTC3406B LTC3411 High Voltage, 1.5A Step-Down Switching Regulator 4A (IOUT), 4MHz Synchronous Step-Down DC/DC Converter 600mA (IOUT), 1.5MHz Synchronous Step-Down DC/DC Converter 1.25A (IOUT), 4MHz Synchronous Step-Down DC/DC Converter
3080fb
26
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900 FAX: (408) 434-0507
LT 0610 REV B * PRINTED IN USA
www.linear.com
(c) LINEAR TECHNOLOGY CORPORATION 2007

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