LINER LT3080EDD-1-PBF Parallelable 1.1a adjustable single resistor low dropout regulator Datasheet

LT3080-1
Parallelable 1.1A
Adjustable Single Resistor
Low Dropout Regulator
DESCRIPTION
FEATURES
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Internal Ballast Resistor Permits Direct
Connection to Power Plane 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: 40μVRMS (10Hz to 100kHz)
Wide Input Voltage Range: 1.2V to 36V
Low Dropout Voltage: 350mV
<0.001%/ V Line Regulation
Minimum Load Current: 0.5mA
Stable with 2.2μF Minimum Ceramic Output Capacitor
Current Limit with Foldback and Overtemperature
Protected
Available in 8-Lead MSOP and 3mm × 3mm DFN
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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.
Internal protection includes current limiting and thermal
limiting. The LT3080-1 regulator is offered in the 8lead MSOP (with an Exposed Pad for better thermal
characteristics) and 3mm × 3mm DFN packages.
APPLICATIONS
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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.
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
, LT, LTC and LTM are registered 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
0
–1
1
VOS DISTRIBUTION (mV)
2
30801 TA01b
*OUTPUTS CAN BE
DIRECTLY MOUNTED
TO POWER PLANE
30801fa
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)......................................–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
TOP VIEW
OUT 1
OUT 2
OUT 3
9
SET 4
8
IN
7
IN
6
NC
5
VCONTROL
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
OUT
OUT
OUT
SET
1
2
3
4
9
8
7
6
5
IN
IN
NC
VCONTROL
MS8E PACKAGE
8-LEAD PLASTIC MSOP
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
LT3080EMS8E-1#PBF
LT3080EMS8E-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
LT3080EMS8E-1
LT3080EMS8E-1#TR
LTDPN
8-Lead Plastic MSOP
–40°C to 125°C
Consult LTC Marketing for parts specified with wider operating temperature ranges.
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/
30801fa
2
LT3080-1
ELECTRICAL CHARACTERISTICS
The ● denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C.
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
●
9.90
9.80
10
10
10.10
10.20
μA
μA
●
–2
–3.5
2
3.5
mV
mV
34
48
nA
mV
mV
Output Offset Voltage (VOUT – VSET)
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
Load Regulation
ΔISET
ΔVOS
ΔVOS
ΔILOAD = 1mA to 1.1A
ΔILOAD = 1mA to 1.1A (Note 8)
ΔILOAD = 1mA to 1.1A (Note 8)
ΔISET
ΔVOS
VIN = 1V to 22V, VCONTROL=1V to 22V, ILOAD=1mA
VIN = 1V to 22V, VCONTROL=1V to 22V, ILOAD=1mA
●
0.1
0.003
0.5
nA/V
mV/V
Minimum Load Current (Notes 3, 9)
VIN = VCONTROL = 10V
VIN = VCONTROL = 22V
●
●
300
500
1
μA
mA
VCONTROL Dropout Voltage (Note 4)
ILOAD = 100mA
ILOAD = 1.1A
●
1.2
1.35
1.6
V
V
VIN Dropout Voltage (Note 4)
ILOAD = 100mA
ILOAD = 1.1A
●
●
100
350
200
500
mV
mV
CONTROL Pin Current (Note 5)
ILOAD = 100mA
ILOAD = 1.1A
●
●
4
17
6
30
mA
mA
Current Limit (Note 9)
VIN = 5V, VCONTROL = 5V, VSET = 0V, VOUT = –0.1V
●
Error Amplifier RMS Output Noise (Note 6)
ILOAD = 1.1A, 10Hz ≤ f ≤ 100kHz, COUT = 10μF, CSET = 0.1μF
SET Pin Current
Line Regulation (Note 9)
ISET
–0.1
27.5
●
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
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 LT3080-1 is 100% tested at TA = 25°C. Performance at – 40°C
and 125°C 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 LT3080-1, 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.
30801fa
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LT3080-1
TYPICAL PERFORMANCE CHARACTERISTICS
Set Pin Current
Offset Voltage (VOUT – VSET)
Set Pin Current Distribution
10.20
2.0
N = 13792
IL = 1mA
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)
0
25 50 75 100 125 150
TEMPERATURE (°C)
30801 G02
30801 G01
Offset Voltage Distribution
30801 G03
Offset Voltage
Offset Voltage
1.00
N = 13250
5
ILOAD = 1mA
0
–5
0.50
OFFSET VOLTAGE (mV)
OFFSET VOLTAGE (mV)
0.75
0.25
0
–0.25
–0.50
–10
TJ = 25°C
–15
–20
–25
TJ = 125°C
–30
–35
–0.75
2
30801 G04
80
ΔILOAD = 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
10
0
CHANGE IN REFERENCE CURRENT
–10
–45
–50
–50 –25
0
–20
25 50 75 100 125 150
TEMPERATURE (°C)
30801 G07
12
24
36*
30
18
INPUT-TO-OUTPUT VOLTAGE (V)
*SEE NOTE 9 IN ELECTRICAL
30801 G05
CHARACTERISTICS TABLE
0
6
0.2
0.4
0.8
0.6
LOAD CURRENT (A)
1.0
1.2
Dropout Voltage
(Minimum IN Voltage)
400
0.8
0.7
0.6
0
30801 G06
Minimum Load Current
MINIMUM LOAD CURRENT (mA)
CHANGE IN OFFSET VOLTAGE WITH LOAD (mV)
0
–5
CHANGE IN REFERENCE CURRENT WITH LOAD (nA)
Load Regulation
–40
–45
MINIMUM IN VOLTAGE (VIN – VOUT) (mV)
0
–1
1
VOS DISTRIBUTION (mV)
–2
–1.00
VIN, CONTROL – VOUT = 36V*
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)
*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
30801fa
4
LT3080-1
ILOAD = 1.1A
300
250
ILOAD = 500mA
200
150
100
ILOAD = 100mA
50
0
–50 –25
0
25 50 75 100 125 150
TEMPERATURE (°C)
TJ = –50°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
0.6
0
25 50 75 100 125 150
TEMPERATURE (°C)
0
–100
1.2
0
5
10 15 20 25 30 35 40 45 50
TIME (μs)
30801 G16
IN/CONTROL
VOLTAGE (V)
0.3
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)
20
0
COUT = 10μF CERAMIC
–20
300
200
100
0
VOUT = 1.5V
ILOAD = 10mA
COUT = 2.2μF
CERAMIC
CSET = 0.1μF
CERAMIC
5
4
3
0
0
5
10 15 20 25 30 35 40 45 50
TIME (μs)
30801 G15
Turn-On Response
0
–50
COUT = 2.2μF CERAMIC
400
30801 G14
–25
2
VOUT = 1.5V
CSET = 0.1μF
VIN = VCONTROL = 3V
40
36*
25
6
VIN = VCONTROL = 3V
VOUT = 1.5V
COUT = 10μF CERAMIC
CSET = 0.1μF
6
INPUT VOLTAGE (V)
50
OUTPUT VOLTAGE
DEVIATION (mV)
100
0.6
0.8
Line Transient Response
75
–50
0
*SEE NOTE 9 IN ELECTRICAL
CHARACTERISTICS TABLE
150
50
ILOAD = 1mA
–40
0.8
Load Transient Response
OUTPUT VOLTAGE
DEVIATION (mV)
TJ = 25°C
1.0
30801 G13
0.9
1.0
Load Transient Response
0.2
VIN = 7V
VOUT = 0V
0
1.2
60
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)
350
1.6
10 20 30 40 50 60 70 80 90 100
TIME (μs)
30801 G17
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
30801fa
5
LT3080-1
TYPICAL PERFORMANCE CHARACTERISTICS
VCONTROL Pin Current
25
0.8
30
ILOAD = 1.1A
20
DEVICE IN
CURRENT LIMIT
15
10
5
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
RIPPLE REJECTION (dB)
ILOAD = 100mA
ILOAD = 1.1A
60
50
40
30
10
100
100k
VIN = 5V
0.2
0
1.2
1k
RTEST (Ω)
30801 G21
Ripple Rejection - Dual Supply
- IN Pin
90
80
ILOAD = 100mA
70
ILOAD = 1.1A
60
50
40
30
1M
2k
100
VIN = VOUT (NOMINAL) + 1V
VCONTROL = VOUT (NOMINAL) +2V
COUT = 2.2μF CERAMIC
RIPPLE = 50mVP–P
0
1k
10k
FREQUENCY (Hz)
VIN = 10V
0.3
80
10
COUT = 2.2μF CERAMIC
0
0.4
90
20
20
10
1.0
0.4
0.6
0.8
LOAD CURRENT (A)
100
RIPPLE = 50mVP–P
70
0.5
Ripple Rejection - Dual Supply
- VCONTROL Pin
VIN = VCONTROL = VOUT (NOMINAL) + 2V
80
VIN = 20V
30801 G20
RIPPLE REJECTION (dB)
90
0.2
30801 G19
Ripple Rejection - Single Supply
100
VOUT
RTEST
0
0
36*
RIPPLE REJECTION (dB)
0
VIN
0.6
0.1
ILOAD = 1mA
0
SET PIN = 0V
0.7
OUTPUT VOLTAGE (V)
CONTROL PIN CURRENT (mA)
CONTROL PIN CURRENT (mA)
Residual Output Voltage with
Less Than Minimum Load
VCONTROL Pin Current
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 (oC)
30801 G25
100
10
10
1.0
1
10
100
1k
10k
FREQUENCY (Hz)
REFERENCE CURRENT NOISE
SPECTRAL DENSITY (pA/ √Hz)
78
0.1
100k
30801 G26
30801fa
6
LT3080-1
TYPICAL PERFORMANCE CHARACTERISTICS
Error Amplifier Gain and Phase
Output Voltage Noise
20
300
15
250
200
10
IL = 1.1A
TIME 1ms/DIV
30801 G27
VOUT = 1V
RSET = 100k
CSET = O.1μF
COUT = 10μF
ILOAD = 1.1A
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.
30801fa
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.
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 LT3080-1, 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 non-inverting 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
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
30801fa
8
LT3080-1
APPLICATIONS INFORMATION
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.
LT3080-1
IN
VCONTROL
+
+
–
+
VIN
VCONTROL
25mΩ OUT
VOUT
SET
COUT
RSET
CSET
30801 F01
Figure 1. Basic Adjustable Regulator
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 LT3080-1 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
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.
30801fa
9
LT3080-1
APPLICATIONS INFORMATION
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 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
20
BOTH CAPACITORS ARE 16V,
1210 CASE SIZE, 10μF
CHANGE IN VALUE (%)
0
X5R
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
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.
–20
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
–40
–60
Y5V
–80
–100
VIN
0
2
4
14
8
6
10 12
DC BIAS VOLTAGE (V)
LT3080-1
16
VCONTROL
30801 F02
+
–
Figure 2. Ceramic Capacitor DC Bias Characteristics
25mΩ
OUT
25mΩ
OUT
40
SET
CHANGE IN VALUE (%)
20
VIN
4.8V TO 28V
X5R
0
VIN
LT3080-1
VCONTROL
–20
+
–
1μF
–40
Y5V
–60
SET
–80
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
Figure 4. Parallel Devices
30801fa
10
LT3080-1
APPLICATIONS INFORMATION
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
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.
reaches ambient temperature within about a half an inch
from the devices.
Thermal Performance
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.
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 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
Figure 5. Temperature Rise at 700mW Dissipation
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.
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 6. Temperature Rise at 1.7W Dissipation
30801fa
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.
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.
30801fa
12
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.
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:
(V
+I
•R
)
R SET = OUT MID BALLAST
ISET
where
IMID = 1/2 (IOUT(MIN) + IOUT(MAX))
RBALLAST = 25mΩ
ISET = 10μA
Thermal Considerations
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
LT3080-1
IN
VCONTROL
+
–
SET RSET
PARASITIC
RESISTANCE
25mΩ
OUT
RP
RP
LOAD
RP
30801 F07
Figure 7. Connections for Best Load Regulation
30801fa
13
LT3080-1
APPLICATIONS INFORMATION
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.
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
THERMAL RESISTANCE
(JUNCTION-TO-AMBIENT)
2500mm2
2500mm2
2500mm2
55°C/W
1000mm2
2500mm2
2500mm2
57°C/W
225mm2
2500mm2
2500mm2
60°C/W
100mm2
2500mm2
2500mm2
65°C/W
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?
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
*Device is mounted on topside
The current delivered to the SET pin is negligible and can
be ignored.
Table 2. DD Package, 8-Lead DFN
COPPER AREA
TOPSIDE*
BACKSIDE
BOARD AREA
THERMAL RESISTANCE
(JUNCTION-TO-AMBIENT)
2500mm2
2500mm2
2500mm2
60°C/W
1000mm2
2500mm2
2500mm2
62°C/W
225mm2
2500mm2
2500mm2
65°C/W
100mm2
2500mm2
2500mm2
68°C/W
VCONTROL(MAX CONTINUOUS) = 3.630V (3.3V + 10%)
VIN(MAX CONTINUOUS) = 1.575V (1.5V + 5%)
VOUT = 0.9V, IOUT = 1A, TA = 50°C
*Device is mounted on topside
30801fa
14
LT3080-1
APPLICATIONS INFORMATION
Power dissipation under these conditions is equal to:
PDRIVE = (VCONTROL – VOUT)(ICONTROL)
OUT 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.
I
1A
ICONTROL = OUT = = 17mA
60 60
PDRIVE = (3.630V – 0.9V)(17mA) = 46mW
Without series resistor RS , power dissipation in the
LT3080-1 equals:
POUTPUT = (VIN – VOUT)(IOUT)
POUTPUT = (1.575V – 0.9V)(1A) = 675mW
⎛ 1A ⎞
PTOTAL = ( 5V – 3.3V ) • ⎜ ⎟ + ( 5V – 3.3V ) • 1A = 1.773W
⎝ 60 ⎠
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.
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-to-
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
Power dissipation in the LT3080-1 now equals:
⎛ 1A ⎞
PTOTAL = ( 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.
VIN
C1
VCONTROL
RS
LT3080-1
+
–
SET
RSET
IN
25mΩ
VINa
OUT
VOUT
C2
30801 F08
Figure 8. Reducing Power Dissipation Using a Series Resistor
30801fa
15
LT3080-1
APPLICATIONS INFORMATION
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.
The maximum total power dissipation is (5.5V – 3.2V) •
1A = 2.3W. However, the LT3080-1 supplies only:
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.
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.
Calculating RP yields:
1A –
5.5V – 3.2V
= 0.36 A
3.6Ω
Therefore, the LT3080-1’s power dissipation is only:
PDIS = (5.5V – 3.2V) • 0.36A = 0.83W
5.5V – 3.2V
= 3.65Ω
0.63A
(5% Standard value = 3.6Ω)
RP =
VIN
C1
VCONTROL
LT3080-1
+
–
SET
RSET
IN
RP
25mΩ
OUT
VOUT
C2
30801 F09
Figure 9. Reducing Power Dissipation Using a Parallel Resistor
30801fa
16
LT3080-1
TYPICAL APPLICATIONS
Adding Shutdown
LT3080-1
IN
VCONTROL
+
–
25mΩ
OUT
25mΩ
OUT
SET
LT3080-1
IN
VIN
VCONTROL
+
–
VOUT
SET
Q1
VN2222LL
ON OFF
Q2*
VN2222LL
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
30801fa
17
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
30801fa
18
LT3080-1
TYPICAL APPLICATIONS
Lab Supply
LT3080-1
IN
VIN
13V TO 18V
LT3080-1
IN
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
+
CURRENT
LIMIT
15μF
VOUT
0V TO 10V
SET
+
+
R4
500k
15μF
10μF
100μF
3080 TA06
Boosting Fixed Output Regulators
LT3080-1
+
–
25mΩ
OUT
SET
20mΩ
3.3VOUT
2.6A
LT1963-3.3
5V
10μF
42Ω*
47μF
30801 TA07
33k
*4mV DROP ENSURES LT3080-1 IS OFF WITH NO-LOAD
MULTIPLE LT3080-1’S CAN BE USED IN PARALLEL
30801fa
19
LT3080-1
TYPICAL APPLICATIONS
Low Voltage, High Current Adjustable High Efficiency Regulator*
0.47μH
2.7V TO
5.5V †
PVIN
SW
SVIN
ITH
10k
+
12.1k
2× +
100μF
2.2MEG
100k
LTC3414
470pF
RT
294k
PGOOD
2×
100μF
2N3906
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
30801fa
20
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
CURRENT SET
IOUT =
1V
R1
30801fa
21
LT3080-1
PACKAGE DESCRIPTION
DD Package
8-Lead Plastic DFN (3mm × 3mm)
(Reference LTC DWG # 05-08-1698)
0.675 ±0.05
3.5 ±0.05
1.65 ±0.05
2.15 ±0.05 (2 SIDES)
PACKAGE
OUTLINE
0.25 ± 0.05
0.50
BSC
2.38 ±0.05
(2 SIDES)
RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS
R = 0.115
TYP
5
3.00 ±0.10
(4 SIDES)
0.38 ± 0.10
8
1.65 ± 0.10
(2 SIDES)
PIN 1
TOP MARK
(NOTE 6)
(DD) DFN 1203
0.200 REF
0.75 ±0.05
0.00 – 0.05
4
0.25 ± 0.05
1
0.50 BSC
2.38 ±0.10
(2 SIDES)
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
30801fa
22
LT3080-1
PACKAGE DESCRIPTION
MS8E Package
8-Lead Plastic MSOP
(Reference LTC DWG # 05-08-1662)
BOTTOM VIEW OF
EXPOSED PAD OPTION
2.06 ± 0.102
(.081 ± .004)
1
5.23
(.206)
MIN
1.83 ± 0.102
(.072 ± .004)
0.889 ± 0.127
(.035 ± .005)
2.794 ± 0.102
(.110 ± .004)
2.083 ± 0.102 3.20 – 3.45
(.082 ± .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
1
0.53 ± 0.152
(.021 ± .006)
DETAIL “A”
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)
NOTE:
BSC
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
0.1016 ± 0.0508
(.004 ± .002)
MSOP (MS8E) 0307 REV D
30801fa
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.
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
10μF
165k
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
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 VLDOTM
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.
LTC3414
4A (IOUT), 4MHz Synchronous
Step-Down DC/DC Converter
95% Efficiency, VIN: 2.25V to 5.5V, VOUT(MIN) = 0.8V, TSSOP Package
LTC3406/LTC3406B
600mA (IOUT), 1.5MHz Synchronous
Step-Down DC/DC Converter
95% Efficiency, VIN: 2.5V to 5.5V, VOUT(MIN) = 0.6V, IQ = 20μA,
ISD < 1μA, ThinSOTTM Package
LTC3411
1.25A (IOUT), 4MHz Synchronous
Step-Down DC/DC Converter
95% Efficiency, VIN: 2.5V to 5.5V, VOUT(MIN) = 0.8V, IQ = 60μA,
ISD < 1μA, 10-Lead MS or DFN Packages
LDOs
Switching Regulators
VLDO and ThinSOT are trademarks of Linear Technology Corporation.
30801fa
24 Linear Technology Corporation
LT 1008 REV A • PRINTED IN USA
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900 ● FAX: (408) 434-0507
●
www.linear.com
© LINEAR TECHNOLOGY CORPORATION 2008
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