LT3080-1 - Parallelable 1.1A Adjustable Single Resistor Low Dropout Regulator

LT3080-1
Parallelable 1.1A
Adjustable Single Resistor
Low Dropout Regulator
Description
Features
Internal Ballast Resistor Permits Direct
Connection to Power Plane for Higher Current
and Heat Spreading
n Output Current: 1.1A
n Single Resistor Programs Output Voltage
n 1% Initial Accuracy of SET Pin Current
n Output Adjustable to 0V
n Low Output Noise: 40µV
RMS (10Hz to 100kHz)
n Wide Input Voltage Range: 1.2V to 36V
n Low Dropout Voltage: 350mV
n <0.001%/ V Line Regulation
n Minimum Load Current: 0.5mA
n Stable with 2.2µF Minimum Ceramic Output Capacitor
n Current Limit with Foldback and Overtemperature
Protected
n Available in 8-Lead MSOP and 3mm × 3mm DFN
The LT®3080-1 is a 1.1A low dropout linear regulator that
incorporates an internal ballast resistor to allow direct
paralleling of devices without the need for PC board trace
resistors. The internal ballast resistor allows multiple devices to be paralleled directly on a surface mount board
for higher output current and power dissipation while
keeping board layout simple and easy. The device brings
out the collector of the pass transistor to allow low dropout
operation—down to 350mV—when used with multiple
input supplies.
Applications
Internal protection includes current limiting and thermal
limiting. The LT3080-1 regulator is offered in the 8-lead
MSOP (with an Exposed Pad for better thermal characteristics) and 3mm × 3mm DFN packages.
n
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
The LT3080-1 is capable of supplying a wide output voltage range. A reference current through a single resistor
programs the output voltage to any level between zero
and 36V. The LT3080-1 is stable with 2.2µF of ceramic
capacitance on the output, not requiring additional ESR
as is common with other regulators.
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.
Typical Application
Paralleling Regulators
IN
Offset Voltage Distribution
LT3080-1
N = 13250
VCONTROL
+
–
25mΩ
OUT*
25mΩ
OUT*
SET
IN
VIN
4.8V TO 28V
LT3080-1
VCONTROL
+
–
1µF
SET
VOUT
3.3V
2.2A
10µF
165k
30801 TA01
–2
*OUTPUTS CAN BE
DIRECTLY MOUNTED
TO POWER PLANE
0
–1
1
VOS DISTRIBUTION (mV)
2
30801 TA01b
30801fc
For more information www.linear.com/LT3080-1
1
LT3080-1
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)
E-, I-grades......................................... –40°C to 125°C
Storage Temperature Range...................–65°C to 150°C
Lead Temperature (Soldering, 10 sec)
MS8E Package Only........................................... 300°C
Pin Configuration
TOP VIEW
OUT 1
OUT 2
OUT 3
9
OUT
SET 4
TOP VIEW
8
IN
7
IN
6
NC
5
VCONTROL
OUT
OUT
OUT
SET
1
2
3
4
9
OUT
8
7
6
5
IN
IN
NC
VCONTROL
MS8E PACKAGE
8-LEAD PLASTIC MSOP
DD PACKAGE
8-LEAD (3mm × 3mm) PLASTIC DFN
TJMAX = 125°C, θJA = 64°C/W, θJC = 3°C/W
EXPOSED PAD (PIN 9) IS OUT, MUST BE SOLDERED TO PCB
TJMAX = 125°C, θJA = 60°C/W, θJC = 10°C/W
EXPOSED PAD (PIN 9) IS OUT, MUST BE SOLDERED TO PCB
Order Information
LEAD FREE FINISH
TAPE AND REEL
PART MARKING*
PACKAGE DESCRIPTION
TEMPERATURE RANGE
LT3080EDD-1#PBF
LT3080EDD-1#TRPBF
LDPM
8-Lead (3mm × 3mm) Plastic DFN
–40°C to 125°C
LT3080IDD-1#PBF
LT3080IDD-1#TRPBF
LDPM
8-Lead (3mm × 3mm) Plastic DFN
–40°C to 125°C
LT3080EMS8E-1#PBF
LT3080EMS8E-1#TRPBF
LTDPN
8-Lead Plastic MSOP
–40°C to 125°C
LT3080IMS8E-1#PBF
LT3080IMS8E-1#TRPBF
LTDPN
8-Lead Plastic MSOP
–40°C to 125°C
LEAD BASED FINISH
TAPE AND REEL
PART MARKING*
PACKAGE DESCRIPTION
TEMPERATURE RANGE
LT3080EDD-1
LT3080EDD-1#TR
LDPM
8-Lead (3mm × 3mm) Plastic DFN
–40°C to 125°C
LT3080IDD-1
LT3080IDD-1#TR
LDPM
8-Lead (3mm × 3mm) Plastic DFN
–40°C to 125°C
LT3080EMS8E-1
LT3080EMS8E-1#TR
LTDPN
8-Lead Plastic MSOP
–40°C to 125°C
LT3080IMS8E-1
LT3080IMS8E-1#TR
LTDPN
8-Lead Plastic MSOP
–40°C to 125°C
Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container.
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/
2
30801fc
For more information www.linear.com/LT3080-1
LT3080-1
Electrical
Characteristics
The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C.
PARAMETER
SET Pin Current
Output Offset Voltage (VOUT – VSET)
Load Regulation
Line Regulation (Note 9)
CONDITIONS
ISET
VOS
VIN = 1V, VCONTROL = 2.0V, ILOAD = 1mA, TJ = 25°C
VIN ≥ 1V, VCONTROL ≥ 2.0V, 1mA ≤ ILOAD ≤ 1.1A (Note 9)
VIN = 1V, VCONTROL = 2V, IOUT = 1mA
∆ISET
∆VOS
∆VOS
∆ILOAD = 1mA to 1.1A
∆ILOAD = 1mA to 1.1A (Note 8)
∆ILOAD = 1mA to 1.1A (Note 8)
∆ISET
∆VOS
VIN = 1V to 22V,
VIN = 1V to 22V,
MIN
TYP
MAX
UNITS
l
9.90
9.80
10
10
10.10
10.20
µA
µA
l
–2
–3.5
2
3.5
mV
mV
34
48
nA
mV
mV
–0.1
27.5
l
VCONTROL=1V to 22V,
VCONTROL=1V to 22V,
ILOAD=1mA
ILOAD=1mA
l
0.1
0.003
0.5
nA/V
mV/V
300
500
1
µA
mA
Minimum Load Current (Notes 3, 9)
VIN = VCONTROL = 10V
VIN = VCONTROL = 22V
l
l
VCONTROL Dropout Voltage (Note 4)
ILOAD = 100mA
ILOAD = 1.1A
l
1.2
1.35
1.6
V
V
VIN Dropout Voltage (Note 4)
ILOAD = 100mA
ILOAD = 1.1A
l
l
100
350
200
500
mV
mV
CONTROL Pin Current (Note 5)
ILOAD = 100mA
ILOAD = 1.1A
l
l
4
17
6
30
mA
mA
Current Limit (Note 9)
VIN = 5V, VCONTROL = 5V, VSET = 0V, VOUT = –0.1V
ILOAD = 1.1A, 10Hz ≤ f ≤ 100kHz, COUT = 10µF, CSET = 0.1µF
l
1.1
1.4
A
40
µVRMS
Reference Current RMS Output Noise (Note 6) 10Hz ≤ f ≤ 100kHz
1
nARMS
Ripple Rejection
f = 120Hz, VRIPPLE = 0.5VP-P, ILOAD = 0.2A, CSET = 0.1µF, COUT = 2.2µF
f = 10kHz
f = 1MHz
75
55
20
dB
dB
dB
Thermal Regulation, ISET
10ms Pulse
Error Amplifier RMS Output Noise (Note 6)
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 LT3080-1 is tested and specified under pulse load conditions such
that TJ ≅ TA. The LT3080E-1 is tested at TA = 25°C. Performance of the
LT3080E-1 over the full –40°C and 125°C operating temperature range
is assured by design, characterization, and correlation with statistical
process controls. The LT3080I-1 is guaranteed over the full –40°C to
125°C operating junction temperature range.
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 LT3080-1, 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 CONTROL 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.
0.003
%/W
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 the 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 22V. 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 over-temperature protection that is intended
to protect the device during momentary overload conditions. Junction
temperature will exceed the maximum operating junction temperature
when over-temperature protection is active. Continuous operation above
the specified maximum operating junction temperature may impair device
reliability.
30801fc
For more information www.linear.com/LT3080-1
3
LT3080-1
Typical Performance Characteristics
Set Pin Current
Offset Voltage (VOUT – VSET)
Set Pin Current Distribution
10.20
2.0
N = 13792
10.10
1.0
OFFSET VOLTAGE (mV)
1.5
SET PIN CURRENT (µA)
10.15
10.05
10.00
9.95
9.90
0.5
0
–0.5
–1.0
–1.5
9.85
9.80
–50 –25
0
9.80
25 50 75 100 125 150
TEMPERATURE (°C)
–2.0
–50 –25
10.00
10.20
9.90
10.10
SET PIN CURRENT DISTRIBUTION (µA)
Offset Voltage Distribution
Offset Voltage
0
–5
0.50
OFFSET VOLTAGE (mV)
OFFSET VOLTAGE (mV)
5
ILOAD = 1mA
0.75
0.25
0
–0.25
–0.50
–1.00
80
∆ILOAD = 1mA TO 1.1A
VIN – VOUT = 2V
70
–10
60
–15
50
–20
–25
–30
40
CHANGE IN OFFSET VOLTAGE
30
20
(VOUT – VSET)
–35
–40
–45
10
0
CHANGE IN REFERENCE CURRENT
–50
–50 –25
0
–10
–20
25 50 75 100 125 150
TEMPERATURE (°C)
30801 G07
4
0
6
12
24
30
18
INPUT-TO-OUTPUT VOLTAGE (V)
36*
0.4
0.8
0.6
LOAD CURRENT (A)
1.2
1.0
30801 G06
400
VIN, CONTROL – VOUT = 36V*
0.5
0.3
0.2
Dropout Voltage
(Minimum IN Voltage)
0.7
0.4
0
30801 G05
0.8
0.6
TJ = 125°C
–30
Minimum Load Current
MINIMUM LOAD CURRENT (mA)
CHANGE IN OFFSET VOLTAGE WITH LOAD (mV)
0
CHANGE IN REFERENCE CURRENT WITH LOAD (nA)
Load Regulation
–20
–25
–40
*SEE NOTE 9 IN ELECTRICAL
CHARACTERISTICS TABLE
30801 G04
TJ = 25°C
–15
–45
MINIMUM IN VOLTAGE (VIN – VOUT) (mV)
2
–10
–35
–0.75
0
–1
1
VOS DISTRIBUTION (mV)
25 50 75 100 125 150
TEMPERATURE (°C)
30801 G03
Offset Voltage
1.00
N = 13250
–2
0
30801 G02
30801 G01
–5
IL = 1mA
VIN, CONTROL – VOUT = 1.5V
0.2
0.1
0
–50 –25
0
25 50 75 100 125 150
TEMPERATURE (°C)
*SEE NOTE 9 IN ELECTRICAL
CHARACTERISTICS TABLE
30801 G08
350
TJ = 125°C
300
250
TJ = 25°C
200
150
100
50
0
0
0.2
0.4
0.8
0.6
OUTPUT CURRENT (A)
1.0
1.2
30801 G09
30801fc
For more information www.linear.com/LT3080-1
LT3080-1
ILOAD = 1.1A
300
250
ILOAD = 500mA
150
100
ILOAD = 100mA
50
0
–50 –25
0
25 50 75 100 125 150
TEMPERATURE (°C)
1.4
1.2
TJ = 125°C
1.0
TJ = 25°C
0.8
0.6
0.4
0.2
0
0
0.2
0.4
0.8
0.6
OUTPUT CURRENT (A)
Current Limit
1.4
1.2
1.2
1.0
0.8
0.6
1.0
0.6
0
25 50 75 100 125 150
TEMPERATURE (°C)
100
50
OUTPUT VOLTAGE
DEVIATION (mV)
75
0
–50
–100
1.2
0.6
0.3
0
5
10 15 20 25 30 35 40 45 50
TIME (µs)
30801 G16
6
12
24
30
18
INPUT-TO-OUTPUT DIFFERENTIAL (V)
0.6
0.4
0.2
0
–50 –25
0
25 50 75 100 125 150
TEMPERATURE (°C)
60
36*
20
0
COUT = 10µF CERAMIC
–20
0
VOUT = 1.5V
ILOAD = 10mA
COUT = 2.2µF
CERAMIC
CSET = 0.1µF
CERAMIC
–50
5
4
3
0
COUT = 2.2µF CERAMIC
400
300
200
100
0
0
5
10 15 20 25 30 35 40 45 50
TIME (µs)
30801 G15
Turn-On Response
–25
2
VOUT = 1.5V
CSET = 0.1µF
VIN = VCONTROL = 3V
40
30801 G14
25
6
IN/CONTROL
VOLTAGE (V)
VIN = VCONTROL = 3V
VOUT = 1.5V
COUT = 10µF CERAMIC
CSET = 0.1µF
ILOAD = 1mA
0.8
Line Transient Response
Load Transient Response
50
0
*SEE NOTE 9 IN ELECTRICAL
CHARACTERISTICS TABLE
150
0.9
1.0
–40
0.8
30801 G13
OUTPUT VOLTAGE
DEVIATION (mV)
TJ = 25°C
0.2
VIN = 7V
VOUT = 0V
0
1.2
Load Transient Response
0.4
0.4
0
–50 –25
ILOAD = 1.1A
1.4
30801 G12
LOAD CURRENT (mA)
CURRENT LIMIT (A)
CURRENT LIMIT (A)
1.4
0.2
1.6
Current Limit
1.6
1.6
LOAD CURRENT (A)
1.2
Dropout Voltage
(Minimum VCONTROL Pin Voltage)
30801 G11
30801 G10
0
1.0
OUTPUT VOLTAGE
DEVIATION (mV)
200
TJ = –50°C
10 20 30 40 50 60 70 80 90 100
TIME (µs)
30801 G17
INPUT VOLTAGE (V)
350
1.6
5
4
3
2
1
0
OUTPUT VOLTAGE (V)
MINIMUM IN VOLTAGE (VIN – VOUT) (mV)
400
Dropout Voltage
(Minimum VCONTROL Pin Voltage)
MINIMUM CONTROL VOLTAGE (VCONTROL – VOUT) (V)
Dropout Voltage
(Minimum IN Voltage)
MINIMUM CONTROL VOLTAGE (VCONTROL – VOUT) (V)
Typical Performance Characteristics
2.0
COUT = 2.2µF CERAMIC
1.5
1.0
RSET = 100k
CSET = 0
RLOAD = 1Ω
0.5
0
0
1
2
3
4 5 6
TIME (µs)
7
8
9
10
30801 G18
30801fc
For more information www.linear.com/LT3080-1
5
LT3080-1
Typical Performance Characteristics
VCONTROL Pin Current
30
CONTROL PIN CURRENT (mA)
CONTROL PIN CURRENT (mA)
ILOAD = 1.1A
DEVICE IN
CURRENT LIMIT
15
10
5
0.8
VCONTROL – VOUT = 2V
VIN – VOUT = 1V
25
20
TJ = –50°C
15
TJ = 25°C
10
TJ = 125°C
5
30
12
18
24
6
INPUT-TO-OUTPUT DIFFERENTIAL (V)
*SEE NOTE 9 IN ELECTRICAL
CHARACTERISTICS TABLE
0
36*
0
RIPPLE REJECTION (dB)
ILOAD = 100mA
ILOAD = 1.1A
60
50
40
30
0
100
1k
10k
FREQUENCY (Hz)
100k
VIN = 10V
0.3
VIN = 5V
0.2
0
1.2
0
1k
RTEST (Ω)
Ripple Rejection - Dual Supply IN Pin
100
90
80
70
1M
ILOAD = 1.1A
ILOAD = 100mA
60
50
40
30
0
2k
30801 G21
80
10
COUT = 2.2µF CERAMIC
10
0.4
90
20
20
10
1.0
100
RIPPLE = 50mVP–P
70
VIN = 20V
0.5
Ripple Rejection - Dual Supply VCONTROL Pin
VIN = VCONTROL = VOUT (NOMINAL) + 2V
80
VOUT
RTEST
30801 G20
RIPPLE REJECTION (dB)
90
0.4
0.6
0.8
LOAD CURRENT (A)
30801 G19
Ripple Rejection - Single Supply
100
0.2
RIPPLE REJECTION (dB)
0
VIN
0.6
0.1
ILOAD = 1mA
0
SET PIN = 0V
0.7
OUTPUT VOLTAGE (V)
25
20
Residual Output Voltage with
Less Than Minimum Load
VCONTROL Pin Current
VIN = VOUT (NOMINAL) + 1V
VCONTROL = VOUT (NOMINAL) +2V
COUT = 2.2µF CERAMIC
RIPPLE = 50mVP–P
10
100
1k
10k
FREQUENCY (Hz)
100k
1M
70
60
50
40 VIN = VOUT (NOMINAL) + 1V
VCONTROL = VOUT (NOMINAL) +2V
30
RIPPLE = 50mVP–P
20
10 COUT = 2.2µF CERAMIC
ILOAD = 1.1A
0
10
100
1k
10k
100k
FREQUENCY (Hz)
30801 G24
30801 G23
30801 G22
Ripple Rejection (120Hz)
1M
Noise Spectral Density
80
10k
1k
1k
100
79
ERROR AMPLIFIER NOISE
SPECTRAL DENSITY (nV/√Hz)
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 = 0.1µF, COUT = 2.2µF
70
–50 –25
0
25 50 75 100 125 150
TEMPERATURE (°C)
100
10
10
1.0
1
10
100
30801 G25
6
1k
10k
FREQUENCY (Hz)
REFERENCE CURRENT NOISE
SPECTRAL DENSITY (pA/ √Hz)
78
0.1
100k
30801 G26
30801fc
For more information www.linear.com/LT3080-1
LT3080-1
Typical Performance Characteristics
Error Amplifier Gain and Phase
Output Voltage Noise
20
300
15
250
200
10
IL = 1.1A
VOUT = 1V
RSET = 100k
CSET = O.1µF
COUT = 10µF
ILOAD = 1.1A
TIME 1ms/DIV
30801 G27
GAIN (dB)
5
150
100
0
IL = 100mA
–5
50
IL = 1.1A
–10
–15
0
–50
IL = 100mA
–20
–100
–150
–25
–30
10
PHASE (DEGREES)
VOUT
100µV/DIV
100
1k
10k
FREQUENCY (Hz)
100k
–200
1M
30801 G28
Pin Functions (DD/MS8E)
VCONTROL (Pin 5/Pin 5): 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): This is the collector to the power
device of the LT3080-1. 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): 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): 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): This pin is the input to the error amplifier and the regulation set point for the device. A fixed
current of 10µA 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): OUT on MS8E and DFN
packages.
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For more information www.linear.com/LT3080-1
7
LT3080-1
Block Diagram
IN
VCONTROL
10µA
+
–
25mΩ
30801 BD
SET
OUT
Applications Information
The LT3080-1 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 LT3080-1 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.
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 LT3080-1, 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.
A precision “0” TC 10µA internal current source is connected to the non-inverting 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 non-inverting
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.
The LT3080-1 also incorporates an internal ballast resistor
to allow for direct paralleling of devices without the need for
PC board trace resistors or sense resistors. This internal
ballast resistor allows multiple devices to be paralleled
directly on a surface mount board for higher output current
and higher power dissipation while keeping board layout
simple and easy. It is not difficult to add more regulators
for higher output current; inputs of devices are all tied
together, outputs of all devices are tied directly together,
and SET pins of all devices are tied directly together. Because of the internal ballast resistor, devices automatically
share the load and the power dissipation.
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 LT3080-1 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 300mV, two
supplies can be used to power the LT3080-1 to reduce
dissipation: a higher voltage supply for the control circuitry
8
30801fc
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LT3080-1
Applications Information
probably be required. Surface coating may be necessary to
provide a moisture barrier in high humidity environments.
LT3080-1
IN
VCONTROL
+
VIN
+
+
–
VCONTROL
25mΩ OUT
SET
RSET
VOUT
COUT
CSET
30801 F01
Figure 1. Basic Adjustable Regulator
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 LT3080-1 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 300mV 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.
Output Voltage
The LT3080-1 generates a 10µA 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
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.
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 LT3080-1 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 2.2µF with an ESR of 0.5Ω
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 LT3080-1, increase
the effective output capacitor value.
For improvement in transient performance, place a capacitor across the voltage setting resistor. Capacitors up to
1µF 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
30801fc
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9
LT3080-1
Applications Information
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 10µF Y5V capacitor
can exhibit an effective value as low as 1µF to 2µF 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 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
20
CHANGE IN VALUE (%)
X5R
–20
–40
–60
Y5V
–80
–100
0
2
4
14
8
6
10 12
DC BIAS VOLTAGE (V)
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
ceramic capacitor the stress can be induced by vibrations
in the system or thermal transients.
Paralleling Devices
LT3080-1’s may be directly 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; the internal ballast
resistor equalizes the currents.
The worst-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
internal ballast resistors, which at full output current gives
better than 90 percent equalized sharing of the current.
The internal resistance of 25 milliohms (per device) only
adds about 25 millivolts of output regulation drop at an
BOTH CAPACITORS ARE 16V,
1210 CASE SIZE, 10µF
0
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.
VIN
16
LT3080-1
VCONTROL
30801 F02
+
–
Figure 2. Ceramic Capacitor DC Bias Characteristics
40
CHANGE IN VALUE (%)
OUT
25mΩ
OUT
SET
20
VIN
4.8V TO 28V
X5R
0
VIN
LT3080-1
VCONTROL
–20
– 40
+
–
1µF
Y5V
– 60
– 80
SET
BOTH CAPACITORS ARE 16V,
1210 CASE SIZE, 10µF
–100
–50 –25
50
25
75
0
TEMPERATURE (°C)
VOUT
3.3V
2.2A
10µF
165k
100
125
30801 F04
3080 F03
Figure 3. Ceramic Capacitor Temperature Characteristics
10
25mΩ
For more information www.linear.com/LT3080-1
Figure 4. Parallel Devices
30801fc
LT3080-1
Applications Information
output of 2A. At low output voltage, 1V, this adds 2.5%
regulation. The output can be set 19mV high for lower absolute error ±1.3%. Of course, more than two LT3080-1’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.
Thermal Performance
In this example, two LT3080-1 3mm × 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 power is then increased with 1.7V across each device. This gives 1.7 watts dissipation in each device and
a device temperature of about 90°C, about 65°C above
ambient as shown in Figure 6. Again, the temperature
matching between the devices is within 2°C, showing
excellent tracking between the devices. The board temperature has reached approximately 40°C within about
0.75 inches of each device.
While 90°C is an acceptable operating temperature for
these devices, this is in 25°C ambient. For higher ambients, the temperature must be controlled to prevent
device temperature from exceeding 125°C. A three meter
per second airflow across the devices will decrease the
device temperature about 20°C providing a margin for
higher operating ambient temperatures.
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 28°C
and both devices were within plus or minus 1°C. 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.
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.
Figure 5. Temperature Rise at 700mW Dissipation
Figure 6. Temperature Rise at 1.7W Dissipation
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11
LT3080-1
Applications Information
Quieting the Noise
The LT3080-1 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
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 LT3080-1 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 LT3080-1 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 LT3080-1, 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 (40µVRMS over the 10Hz to 100kHz
bandwidth); this is another factor that is RMS summed
in to give a final noise figure for the regulator.
12
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 LT3080-1 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 LT3080-1 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 section.
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 LT3080-1.
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.
30801fc
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LT3080-1
Applications Information
Load Regulation
Because the LT3080-1 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 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 LT3080-1 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.
RSET =
(VOUT + IMID • RBALLAST )
where
ISET
IMID = 1/2 (IOUT(MIN) + IOUT(MAX))
RBALLAST = 25mΩ
ISET = 10µA
LT3080-1
IN
Thermal Considerations
VCONTROL
+
–
PARASITIC
RESISTANCE
25mΩ
SET RSET
OUT
RP
RP
LOAD
RP
30801 F07
Figure 7. Connections for Best Load Regulation
The internal 25mΩ ballast resistor is outside of the
LT3080-1’s feedback loop. Therefore, the voltage drop
across the ballast resistor appears as additional DC load
regulation. However, this additional load regulation can
actually improve transient response performance by decreasing peak-to-peak output voltage deviation and even
save on total output capacitance. This technique is called
active voltage positioning and is especially useful for applications that must withstand large output load current
transients. For more information, see Design Note 224,
“Active Voltage Positioning Reduces Output Capacitors.”
The basic principle uses the fact that output voltage is
a function of output load current. Output voltage is set
based on the midpoint of the output load current range:
1
• IOUT(MIN) + IOUT(MAX)
2
(
As output current decreases below the midpoint, output
voltage increases above the nominal set-point. Correspondingly, as output current increases above the midpoint,
output voltage decreases below the nominal set-point.
During a large output load transient, output voltage
perturbation is contained within a window that is tighter
than what would result if active voltage positioning is not
employed. Choose the SET pin resistor value by using the
formula below:
The LT3080-1 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. Note that the Exposed Pad is electrically
connected to the output.
)
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13
LT3080-1
Applications Information
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 1. MSE Package, 8-Lead MSOP
COPPER AREA
TOPSIDE*
BACKSIDE
BOARD AREA
2500mm2
2500mm2
2500mm2
THERMAL RESISTANCE
(JUNCTION-TO-AMBIENT)
55°C/W
1000mm2
2500mm2
2500mm2
57°C/W
225mm2
2500mm2
2500mm2
60°C/W
100mm2
2500mm2
2500mm2
65°C/W
*Device is mounted on topside
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.
Table 2. DD Package, 8-Lead DFN
COPPER AREA
The power in the drive circuit equals:
VCONTROL(MAX CONTINUOUS) = 3.630V (3.3V + 10%)
TOPSIDE*
BACKSIDE
BOARD AREA
2500mm2
2500mm2
2500mm2
THERMAL RESISTANCE
(JUNCTION-TO-AMBIENT)
60°C/W
1000mm2
2500mm2
2500mm2
62°C/W
VOUT = 0.9V, IOUT = 1A, TA = 50°C
225mm2
2500mm2
2500mm2
65°C/W
100mm2
2500mm2
2500mm2
68°C/W
Power dissipation under these conditions is equal to:
*Device is mounted on topside
PCB layers, copper weight, board layout and thermal vias
affect the resultant thermal resistance. Although Tables 1
and 2 provide thermal resistance numbers for a 2-layer
board with 1 ounce copper, modern multilayer PCBs provide better performance than found in these tables. For
example, a 4-layer, 1 ounce copper PCB board with five
thermal vias from the DFN or MSOP exposed backside pad
to inner layers (connected to VOUT) achieves 40°C/W thermal resistance. Demo circuit 995A’s board layout achieves
this 40°C/W performance. This is approximately a 33%
improvement over the numbers shown in Tables 1 and 2.
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 50°C, what will the maximum junction
temperature be for the DFN package on a 2500mm2 board
with topside copper area of 500mm2?
14
VIN(MAX CONTINUOUS) = 1.575V (1.5V + 5%)
PDRIVE = (VCONTROL – VOUT)(ICONTROL)
ICONTROL =
IOUT 1A
=
= 17mA
60 60
PDRIVE = (3.630V – 0.9V)(17mA) = 46mW
POUTPUT = (VIN – VOUT)(IOUT)
POUTPUT = (1.575V – 0.9V)(1A) = 675mW
Total Power Dissipation = 721mW
Junction Temperature will be equal to:
TJ = TA + PTOTAL • θJA (approximated using tables)
TJ = 50°C + 721mW • 64°C/W = 96°C
In this case, the junction temperature is below the maximum rating, ensuring reliable operation.
30801fc
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LT3080-1
Applications Information
C1
VIN
VCONTROL
LT3080-1
+
–
IN
25mΩ
SET
RSET
RS
VIN′
OUT
VOUT
C2
The second technique for reducing power dissipation,
shown in Figure 9, uses a resistor in parallel with the
LT3080-1. This resistor provides a parallel path for current
flow, reducing the current flowing through the LT3080-1.
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.
VIN
30801 F08
C1
VCONTROL
LT3080-1
IN
Figure 8. Reducing Power Dissipation Using a Series Resistor
Reducing Power Dissipation
In some applications it may be necessary to reduce
the power dissipation in the LT3080-1 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 LT3080-1’s IN-toOUT differential voltage and correspondingly decreases
the LT3080-1’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
LT3080-1 equals:
⎛ 1A ⎞
PTOTAL = ( 5V – 3.3V ) • ⎜ ⎟ + ( 5V – 3.3V ) • 1A = 1.73W
⎝ 60 ⎠
If the voltage differential (VDIFF) across the NPN pass
transistor is chosen as 0.5V, then RS equals:
RS =
5V – 3.3V − 0.5V
= 1.2Ω
1A
PTOTAL
⎛ 1A ⎞
= ( 5V – 3.3V ) • ⎜ ⎟ + ( 0.5V ) • 1A = 0.53W
⎝ 60 ⎠
The LT3080-1’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.
RP
25mΩ
OUT
SET
RSET
VOUT
C2
30801 F09
Figure 9. Reducing Power Dissipation Using a Parallel Resistor
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:
RP =
5.5V – 3.2V
= 3.65Ω
0.63A
(5% Standard value = 3.6Ω)
The maximum total power dissipation is (5.5V – 3.2V) •
1A = 2.3W. However, the LT3080-1 supplies only:
Power dissipation in the LT3080-1 now equals:
+
–
1A –
5.5V – 3.2V
= 0.36A
3.6Ω
Therefore, the LT3080-1’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
LT3080-1 supplies only 0.36A. Therefore, load current can
increase by 0.64A to 1.64A while keeping the LT3080-1
in its normal operating range.
30801fc
For more information www.linear.com/LT3080-1
15
LT3080-1
Typical Applications
Adding Shutdown
LT3080-1
IN
VCONTROL
+
–
25mΩ
OUT
25mΩ
OUT
SET
LT3080-1
IN
VIN
VCONTROL
+
–
VOUT
SET
Q2*
VN2222LL
1N4148
Q1
VN2222LL
ON OFF
R1
SHUTDOWN
30801 TA02
*Q2 INSURES ZERO OUTPUT IN THE
ABSENCE OF ANY OUTPUT LOAD
Current Source
LT3080-1
IN
VIN
10V
VCONTROL
+
–
25mΩ
OUT
25mΩ
OUT
SET
LT3080-1
IN
VCONTROL
+
–
2.2µF
SET
1Ω
IOUT
0A TO 2A
100k
10µF
30801 TA03
16
30801fc
For more information www.linear.com/LT3080-1
LT3080-1
Typical Applications
Using a Lower Value SET Resistor
LT3080-1
IN
VIN
10V
VCONTROL
+
–
25mΩ
OUT
25mΩ
OUT
SET
LT3080-1
IN
VCONTROL
+
–
C1
2.2µF
VOUT = 0.5V + 2mA • RSET
VOUT
0.5V TO 10V
SET
R1
24.9k
1%
2mA
R2
249Ω
1%
COUT
10µF
RSET
4.99k
1%
30801 TA04
Adding Soft-Start
VIN
4.8V TO 28V
LT3080-1
IN
VCONTROL
+
–
D1
IN4148
25mΩ
OUT
25mΩ
OUT
SET
VOUT
3.3V
2.2A
LT3080-1
IN
VCONTROL
+
–
C1
2.2µF
SET
C2
0.01µF
R1
165k
COUT
10µF
30801 TA05
30801fc
For more information www.linear.com/LT3080-1
17
LT3080-1
Typical Applications
Lab Supply
LT3080-1
IN
VIN
13V TO 18V
VCONTROL
VCONTROL
+
–
25mΩ
+
–
OUT
SET
25mΩ
OUT
25mΩ
OUT
SET
LT3080-1
IN
LT3080-1
IN
VCONTROL
VCONTROL
+
–
25mΩ
OUT
+
–
0.5Ω
50k
0A TO 2A
SET
+
LT3080-1
IN
CURRENT
LIMIT
15µF
VOUT
0V TO 10V
SET
+
R4
500k
15µF
10µF
+
100µF
3080 TA06
Boosting Fixed Output Regulators
LT3080-1
+
–
25mΩ
OUT
SET
LT1963-3.3
5V
10µF
20mΩ
42Ω*
3.3VOUT
2.6A
47µF
30801 TA07
33k
*4mV DROP ENSURES LT3080-1 IS OFF WITH NO-LOAD
MULTIPLE LT3080-1’S CAN BE USED IN PARALLEL
18
30801fc
For more information www.linear.com/LT3080-1
LT3080-1
Typical Applications
Low Voltage, High Current Adjustable High Efficiency Regulator*
0.47µH
2.7V TO
5.5V †
2× +
100µF
2.2MEG
100k
PVIN
SW
SVIN
ITH
LTC3414
10k
+
12.1k
470pF
RT
2×
100µF
2N3906
294k
PGOOD
LT3080-1
IN
VCONTROL
RUN/SS
+
–
VFB
1000pF
78.7k
PGND
OUT
25mΩ
OUT
25mΩ
OUT
25mΩ
OUT
SET
SYNC/MODE
SGND
25mΩ
124k
IN
LT3080-1
VCONTROL
+
–
* DIFFERENTIAL VOLTAGE ON LT3080-1
IS 0.6V SET BY THE VBE OF THE 2N3906 PNP
† MAXIMUM OUTPUT VOLTAGE IS 1.5V
BELOW INPUT VOLTAGE
SET
0V TO
4V †
4A
LT3080-1
IN
VCONTROL
+
–
SET
IN
LT3080-1
VCONTROL
+
–
SET
+
100k
100µF
30801 TA08
30801fc
For more information www.linear.com/LT3080-1
19
LT3080-1
Typical Applications
Adjustable High Efficiency Regulator*
CMDSH-4E
4.5V TO
25V †
VIN
10µF
1µF
100k
BOOST
LT3493
SHDN
0.1µF
10µH
0.1µF
LT3080-1
IN
SW
68µF
MBRM140
VCONTROL
TP0610L
GND
+
–
FB
10k
25mΩ
OUT
SET
4.7µF
0V
TO 10V †
1A
1MEG
*DIFFERENTIAL VOLTAGE ON LT3080-1
≈ 1.4V SET BY THE TPO610L P-CHANNEL THRESHOLD.
† MAXIMUM OUTPUT VOLTAGE IS 2V
BELOW INPUT VOLTAGE
10k
30801 TA09
2 Terminal Current Source
CCOMP*
IN
LT3080-1
VCONTROL
+
–
SET
25mΩ
OUT
R1
100k
30801 TA10
*CCOMP
R1 ≤ 10Ω 10µF
R1 ≥ 10Ω 2.2µF
20
CURRENT SET
IOUT =
1V
R1
30801fc
For more information www.linear.com/LT3080-1
LT3080-1
Package Description
Please refer to http://www.linear.com/designtools/packaging/ for the most recent package drawings.
DD Package
8-Lead Plastic DFN (3mm × 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
PIN 1
TOP MARK
(NOTE 6)
0.200 REF
3.00 ±0.10
(4 SIDES)
R = 0.125
TYP
5
0.40 ± 0.10
8
1.65 ± 0.10
(2 SIDES)
0.75 ±0.05
4
0.25 ± 0.05
1
(DD8) DFN 0509 REV C
0.50 BSC
2.38 ±0.10
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
30801fc
For more information www.linear.com/LT3080-1
21
LT3080-1
Package Description
Please refer to http://www.linear.com/designtools/packaging/ for the most recent package drawings.
MS8E Package
MS8E
Package
8-Lead Plastic
MSOP
, Exposed Die Pad
8-Lead
Plastic
MSOP,
Exposed Die
(Reference LTC DWG # 05-08-1662
Rev Pad
K)
(Reference LTC DWG # 05-08-1662 Rev K)
BOTTOM VIEW OF
EXPOSED PAD OPTION
1.88
(.074)
1
1.88 ±0.102
(.074 ±.004)
0.29
REF
1.68
(.066)
0.889 ±0.127
(.035 ±.005)
0.05 REF
5.10
(.201)
MIN
DETAIL “B”
CORNER TAIL IS PART OF
DETAIL “B” THE LEADFRAME FEATURE.
FOR REFERENCE ONLY
NO MEASUREMENT PURPOSE
1.68 ±0.102 3.20 – 3.45
(.066 ±.004) (.126 – .136)
8
3.00 ±0.102
(.118 ±.004)
(NOTE 3)
0.65
(.0256)
BSC
0.42 ±0.038
(.0165 ±.0015)
TYP
8
7 6 5
0.52
(.0205)
REF
RECOMMENDED SOLDER PAD LAYOUT
0.254
(.010)
3.00 ±0.102
(.118 ±.004)
(NOTE 4)
4.90 ±0.152
(.193 ±.006)
DETAIL “A”
0° – 6° TYP
GAUGE PLANE
0.53 ±0.152
(.021 ±.006)
DETAIL “A”
1
2 3
4
1.10
(.043)
MAX
0.86
(.034)
REF
0.18
(.007)
SEATING
PLANE
0.22 – 0.38
(.009 – .015)
TYP
0.65
(.0256)
BSC
0.1016 ±0.0508
(.004 ±.002)
MSOP (MS8E) 0213 REV K
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 INCLUDE MOLD FLASH. MOLD FLASH ON E-PAD
SHALL NOT EXCEED 0.254mm (.010") PER SIDE.
22
30801fc
For more information www.linear.com/LT3080-1
LT3080-1
Revision History
(Revision history begins at Rev B)
REV
DATE
DESCRIPTION
PAGE NUMBER
B
9/11
Updated the Absolute Maximum Ratings, Order Information, and Note 2 in the Electrical Characteristics sections to
include I-grade parts.
2, 3
C
5/15
Added diode to shutdown application circuit.
16
30801fc
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.
For more
information
www.linear.com/LT3080-1
23
LT3080-1
Typical Application
Paralleling Regulators
LT3080-1
IN
VCONTROL
+
–
25mΩ
OUT
25mΩ
OUT
SET
LT3080-1
IN
VIN
4.8V TO 28V
VCONTROL
+
–
1µF
VOUT
3.3V
2.2A
SET
165k
10µF
30801 TA11
Related Parts
PART NUMBER
DESCRIPTION
COMMENTS
LT1086
1.5A Low Dropout Regulator
Fixed 2.85V, 3.3V, 3.6V, 5V and 12V Output
LT1117
800mA Low Dropout Regulator
1V Dropout, Adjustable or Fixed Output, DD-Pak, SOT-223 Packages
LDOs
LT1118
800mA Low Dropout Regulator
Okay for Sinking and Sourcing, S0-8 and SOT-223 Packages
LT1963A
1.5A Low Noise, Fast Transient
Response LDO
340mV Dropout Voltage, Low Noise = 40µVRMS , VIN : 2.5V to 20V,
TO-220, DD, SOT-223 and SO-8 Packages
LT1965
1.1A Low Noise LDO
290mV Dropout Voltage, Low Noise 40µVRMS , VIN : 1.8V to 20V,
VOUT : 1.2V to 19.5V, Stable with Ceramic Caps, TO-220, DDPak, MSOP and 3mm × 3mm
DFN Packages
LTC®3026
1.5A Low Input Voltage VLDO™
Regulator
VIN : 1.14V to 3.5V (Boost Enabled), 1.14V to 5.5V (with External 5V), VDO = 0.1V,
IQ = 950µA, Stable with 10µF Ceramic Capacitors, 10-Lead MSOP and DFN Packages
LT3080
1.1A, Parallelable, Low Noise,
Low Dropout Linear Regulator
300mV Dropout Voltage (2-Supply Operation), Low Noise: 40µVRMS , VIN : 1.2V to
36V, VOUT : 0V to 35.7V, Current-Based Reference with 1-Resistor VOUT Set, Directly
Parallelable (No Op Amp Required), Stable with Ceramic Capacitors, TO-220, SOT-223,
MSOP and 3mm × 3mm DFN Packages.
4A (IOUT), 4MHz Synchronous
Step-Down DC/DC Converter
95% Efficiency, VIN: 2.25V to 5.5V, VOUT(MIN) = 0.8V, TSSOP Package
Switching Regulators
LTC3414
LTC3406/LTC3406B 600mA (IOUT), 1.5MHz Synchronous
Step-Down DC/DC Converter
LTC3411
24
1.25A (IOUT), 4MHz Synchronous
Step-Down DC/DC Converter
95% Efficiency, VIN: 2.5V to 5.5V, VOUT(MIN) = 0.6V, IQ = 20µA,
ISD < 1µA, ThinSOT™ Package
95% Efficiency, VIN: 2.5V to 5.5V, VOUT(MIN) = 0.8V, IQ = 60µA,
ISD < 1µA, 10-Lead MS or DFN Packages
30801fc
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
For more information www.linear.com/LT3080-1
(408) 432-1900 ● FAX: (408) 434-0507
●
www.linear.com/LT3080-1
LT 0515 REV C • PRINTED IN USA
 LINEAR TECHNOLOGY CORPORATION 2008