LT3080EDD-1-TRPBF [Linear]
Parallelable 1.1A Adjustable Single Resistor Low Dropout Regulator; 并联1.1A可调的单电阻低压差稳压器
| 型号： | LT3080EDD-1-TRPBF |
| 厂家： | 
Linear |
| 描述： | Parallelable 1.1A Adjustable Single Resistor Low Dropout Regulator |
| 文件： | 总24页 (文件大小：301K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
LT3080-1
Parallelable 1.1A
Adjustable Single Resistor
Low Dropout Regulator
DESCRIPTION
FEATURES
n
Internal Ballast Resistor Permits Direct
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.
Connection to Power Plane for Higher Current
and Heat Spreading
n
Output Current: 1.1A
n
Single Resistor Programs Output Voltage
1% Initial Accuracy of SET Pin Current
n
n
Output Adjustable to 0V
Low Output Noise: 40μV
n
(10Hz to 100kHz)
RMS
n
n
n
n
n
n
Wide Input Voltage Range: 1.2V to 36V
Low Dropout Voltage: 350mV
<0.001%/V Line Regulation
The LT3080-1 is capable of supplying a wide output volt-
age 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.
Minimum Load Current: 0.5mA
Stable with 2.2μF Minimum Ceramic Output Capacitor
Current Limit with Foldback and Overtemperature
Protected
n
Available in 8-Lead MSOP and 3mm × 3mm DFN
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.
APPLICATIONS
n
High Current All Surface Mount Supply
n
High Efficiency Linear Regulator
n
Post Regulator for Switching Supplies
, LT, LTC and LTM are registered trademarks of Linear Technology Corporation. All other
trademarks are the property of their respective owners.
n
Low Parts Count Variable Voltage Supply
n
Low Output Voltage Power Supplies
TYPICAL APPLICATION
Paralleling Regulators
Offset Voltage Distribution
IN
LT3080-1
N = 13250
V
CONTROL
+
–
25mΩ
OUT*
SET
IN
LT3080-1
V
IN
4.8V TO 28V
V
CONTROL
+
–
1μF
25mΩ
V
3.3V
2.2A
OUT
OUT*
–2
–1
V
0
1
2
DISTRIBUTION (mV)
OS
SET
165k
30801 TA01b
10μF
*OUTPUTS CAN BE
DIRECTLY MOUNTED
TO POWER PLANE
30801 TA01
30801fa
1
LT3080-1
ABSOLUTE MAXIMUM RATINGS (Note 1) All Voltages Relative to VOUT
V
Pin Voltage.....................................40V, –0.3V
Operating Junction Temperature Range
CONTROL
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
(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
OUT
OUT
SET
1
2
3
4
8
7
6
5
IN
IN
NC
V
OUT
OUT
OUT
SET
1
2
3
4
8 IN
7 IN
6 NC
5 V
9
9
CONTROL
CONTROL
MS8E PACKAGE
8-LEAD PLASTIC MSOP
T
= 125°C, θ = 60°C/W, θ = 10°C/W
JA JC
DD PACKAGE
JMAX
8-LEAD (3mm × 3mm) PLASTIC DFN
EXPOSED PAD (PIN 9) IS OUT, MUST BE SOLDERED TO PCB
T
= 125°C, θ = 64°C/W, θ = 3°C/W
JMAX
JA JC
EXPOSED PAD (PIN 9) IS OUT, MUST BE SOLDERED TO PCB
ORDER INFORMATION
LEAD FREE FINISH
LT3080EDD-1#PBF
LT3080EMS8E-1#PBF
LEAD BASED FINISH
LT3080EDD-1
TAPE AND REEL
PART MARKING
PACKAGE DESCRIPTION
TEMPERATURE RANGE
LT3080EDD-1#TRPBF
LDPM
–40°C to 125°C
–40°C to 125°C
TEMPERATURE RANGE
–40°C to 125°C
–40°C to 125°C
8-Lead (3mm × 3mm) Plastic DFN
8-Lead Plastic MSOP
LT3080EMS8E-1#TRPBF LTDPN
TAPE AND REEL
PART MARKING
PACKAGE DESCRIPTION
LT3080EDD-1#TR
LT3080EMS8E-1#TR
LDPM
LTDPN
8-Lead (3mm × 3mm) Plastic DFN
8-Lead Plastic MSOP
LT3080EMS8E-1
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
SET Pin Current
I
V
V
= 1V, V
≥ 1V, V
= 2.0V, I
= 1mA, T = 25°C
LOAD
9.90
9.80
10
10
10.10
10.20
μA
μA
SET
IN
IN
CONTROL
CONTROL
LOAD
J
●
●
≥ 2.0V, 1mA ≤ I
≤ 1.1A (Note 9)
Output Offset Voltage (V
– V
)
SET
V
V
= 1V, V
= 2V, I = 1mA
OUT
–2
–3.5
2
3.5
mV
mV
OUT
OS
IN
CONTROL
Load Regulation
ΔI
ΔI
ΔI
ΔI
= 1mA to 1.1A
–0.1
27.5
nA
mV
mV
SET
LOAD
LOAD
LOAD
ΔV
ΔV
= 1mA to 1.1A (Note 8)
= 1mA to 1.1A (Note 8)
34
48
OS
OS
●
●
Line Regulation (Note 9)
Minimum Load Current (Notes 3, 9)
ΔI
SET
V
V
= 1V to 22V, V
=1V to 22V, I
=1V to 22V, I
=1mA
LOAD
=1mA
LOAD
0.1
0.003
0.5
nA/V
mV/V
IN
IN
CONTROL
CONTROL
ΔV
= 1V to 22V, V
OS
●
●
V
IN
V
IN
= V
= V
= 10V
= 22V
300
500
1
μA
mA
CONTROL
CONTROL
V
V
Dropout Voltage (Note 4)
I
I
= 100mA
= 1.1A
1.2
V
V
CONTROL
LOAD
LOAD
●
1.35
1.6
●
●
Dropout Voltage (Note 4)
I
I
= 100mA
= 1.1A
100
350
200
500
mV
mV
IN
LOAD
LOAD
●
●
CONTROL Pin Current (Note 5)
Current Limit (Note 9)
I
I
= 100mA
= 1.1A
4
6
30
mA
mA
LOAD
LOAD
17
●
V
= 5V, V
= 5V, V = 0V, V = –0.1V
OUT
1.1
1.4
40
1
A
IN
CONTROL
SET
Error Amplifier RMS Output Noise (Note 6)
I
= 1.1A, 10Hz ≤ f ≤ 100kHz, C
= 10μF, C = 0.1μF
μV
LOAD
OUT
SET
RMS
RMS
Reference Current RMS Output Noise (Note 6) 10Hz ≤ f ≤ 100kHz
nA
Ripple Rejection
f = 120Hz, V
f = 10kHz
f = 1MHz
= 0.5V , I
= 0.2A, C = 0.1μF, C = 2.2μF
75
55
20
dB
dB
dB
RIPPLE
P-P LOAD
SET
OUT
Thermal Regulation, I
10ms Pulse
0.003
%/W
SET
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 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 2: Unless otherwise specified, all voltages are with respect to V
.
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
OUT
The LT3080-1 is tested and specified under pulse load conditions such that
T ≈ T . The LT3080-1 is 100% tested at T = 25°C. Performance at –40°C
J
A
A
and 125°C is assured by design, characterization and correlation with
statistical process controls.
voltages (V – V ) greater than 22V. Operation at voltages for both IN
IN
OUT
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.
and V
is allowed up to a maximum of 36V as long as the difference
CONTROL
between input and output voltage is below the specified differential
(V – V ) voltage. Line and load regulation specifications are not
IN
OUT
applicable when the device is in current limit.
Note 4: For the LT3080-1, dropout is caused by either minimum control
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.
voltage (V
) or minimum input voltage (V ). Both parameters are
CONTROL
IN
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.
30801fa
3
LT3080-1
TYPICAL PERFORMANCE CHARACTERISTICS
Set Pin Current
Set Pin Current Distribution
Offset Voltage (VOUT – VSET
)
10.20
10.15
10.10
10.05
10.00
9.95
2.0
1.5
N = 13792
I
L
= 1mA
1.0
0.5
0
–0.5
–1.0
–1.5
–2.0
9.90
9.85
9.80
10.00
SET PIN CURRENT DISTRIBUTION (μA)
9.80
9.90
10.10
10.20
50 75
TEMPERATURE (°C)
50 75
TEMPERATURE (°C)
–50 –25
150
1.2
1.2
–50 –25
0
25
100 125 150
0
25
100 125
30801 G02
30801 G01
30801 G03
Offset Voltage Distribution
Offset Voltage
Offset Voltage
1.00
0.75
0.50
0.25
5
0
N = 13250
I
= 1mA
LOAD
–5
–10
–15
–20
–25
–30
–35
–40
–45
T
= 25°C
J
0
–0.25
T
= 125°C
J
–0.50
–0.75
–1.00
0
0
6
12
24
30
36*
–2
–1
V
1
2
18
0.2
0.4
0.8
0
1.0
0.6
DISTRIBUTION (mV)
INPUT-TO-OUTPUT VOLTAGE (V)
LOAD CURRENT (A)
OS
*SEE NOTE 9 IN ELECTRICAL
CHARACTERISTICS TABLE
30801 G04
30801 G05
30801 G06
Dropout Voltage
(Minimum IN Voltage)
Load Regulation
Minimum Load Current
0
–5
400
350
300
250
80
70
60
50
40
30
20
10
0
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
ΔI
V
= 1mA TO 1.1A
OUT
LOAD
– V
= 2V
IN
T
= 125°C
J
–10
–15
–20
–25
–30
–35
–40
–45
–50
V
V
– V
– V
= 36V*
= 1.5V
IN, CONTROL
IN, CONTROL
OUT
OUT
T
= 25°C
J
CHANGE IN OFFSET VOLTAGE
– V
200
150
(V
)
SET
OUT
100
50
0
CHANGE IN REFERENCE CURRENT
–10
–20
0.2
0.4
0.8
50 75
25
TEMPERATURE (°C)
–50 –25
50 75
25
TEMPERATURE (°C)
0
0.6
1.0
–50 –25
0
100 125 150
0
100 125 150
OUTPUT CURRENT (A)
30801 G09
30801 G07
*SEE NOTE 9 IN ELECTRICAL
CHARACTERISTICS TABLE
30801 G08
30801fa
4
LT3080-1
TYPICAL PERFORMANCE CHARACTERISTICS
Dropout Voltage
(Minimum IN Voltage)
Dropout Voltage
(Minimum VCONTROL Pin Voltage)
Dropout Voltage
(Minimum VCONTROL Pin Voltage)
1.6
1.4
1.2
1.0
400
350
300
250
200
150
100
50
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0
T
= –50°C
J
I
= 1.1A
LOAD
I
= 1.1A
LOAD
T
= 125°C
J
I
= 1mA
LOAD
T
= 25°C
J
I
I
= 500mA
LOAD
LOAD
0.8
0.6
0.4
0.2
0
= 100mA
0
0.2
0.4
0.8
0
1.0
1.2
50 75
TEMPERATURE (°C)
0.6
50 75
TEMPERATURE (°C)
–50 –25
0
25
100 125 150
–50 –25
0
25
100 125
150
OUTPUT CURRENT (A)
30801 G11
30801 G10
30801 G12
Current Limit
Current Limit
Load Transient Response
60
40
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0
1.6
1.4
1.2
1.0
V
C
V
= 1.5V
OUT
SET
IN
T
= 25°C
J
= 0.1μF
= V
= 3V
CONTROL
20
0
–20
–40
400
300
200
100
0
C
= 10μF CERAMIC
OUT
0.8
0.6
C
= 2.2μF CERAMIC
OUT
0.4
0.2
0
V
V
= 7V
IN
OUT
= 0V
0
5
10 15 20 25 30 35 40 45 50
50 75
25
TEMPERATURE (°C)
0
6
12
24
30
36*
–50 –25
0
100 125 150
18
TIME (μs)
INPUT-TO-OUTPUT DIFFERENTIAL (V)
30801 G15
30801 G13
*SEE NOTE 9 IN ELECTRICAL
CHARACTERISTICS TABLE
30801 G14
Load Transient Response
Line Transient Response
Turn-On Response
150
100
50
75
50
25
0
5
4
3
0
2
–50
–100
1.2
0.9
0.6
0.3
0
–25
–50
6
1
V
= 1.5V
= 10mA
= 2.2μF
OUT
0
I
LOAD
C
2.0
1.5
1.0
0.5
0
OUT
C
= 2.2μF CERAMIC
OUT
V
V
C
C
= V
= 3V
CONTROL
CERAMIC
= 0.1μF
SET
CERAMIC
IN
5
= 1.5V
C
OUT
OUT
SET
= 10μF CERAMIC
= 0.1μF
4
R
C
LOAD
= 100k
SET
SET
R
= 0
3
= 1Ω
2
0
5
10 15 20 25 30 35 40 45 50
0
10 20 30 40 50 60 70 80 90 100
0
1
2
3
4
5
6
7
8
9
10
TIME (μs)
TIME (μs)
TIME (μs)
30801 G16
30801 G17
30801 G18
30801fa
5
LT3080-1
TYPICAL PERFORMANCE CHARACTERISTICS
Residual Output Voltage with
Less Than Minimum Load
VCONTROL Pin Current
VCONTROL Pin Current
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
25
20
15
10
30
25
20
15
10
5
V
V
– V
= 2V
OUT
CONTROL
– V
SET PIN = 0V
= 1V
OUT
IN
V
IN
= 20V
V
IN
V
OUT
I
= 1.1A
LOAD
R
TEST
DEVICE IN
CURRENT LIMIT
T
= –50°C
J
V
IN
= 10V
T
J
= 25°C
V
= 5V
IN
T
= 125°C
J
5
0
I
= 1mA
12
LOAD
6
0
0
1k
2k
0
18
24
30
36*
0
0.4
0.6
0.8
1.0
1.2
0.2
INPUT-TO-OUTPUT DIFFERENTIAL (V)
LOAD CURRENT (A)
R
(Ω)
TEST
30801 G21
30801 G19
30801 G20
*SEE NOTE 9 IN ELECTRICAL
CHARACTERISTICS TABLE
Ripple Rejection - Dual Supply
- VCONTROL Pin
Ripple Rejection - Dual Supply
- IN Pin
Ripple Rejection - Single Supply
100
90
80
70
60
50
40
30
20
10
0
100
90
80
70
60
50
40
30
20
10
0
100
90
80
70
60
50
40
30
20
10
0
V
= V
= V
+ 2V
OUT (NOMINAL)
IN
CONTROL
RIPPLE = 50mV
P–P
I
= 100mA
I
= 100mA
LOAD
LOAD
I
= 1.1A
LOAD
I
= 1.1A
LOAD
V
V
= V
+ 1V
OUT (NOMINAL)
IN
CONTROL
= V
+2V
OUT (NOMINAL)
V
V
C
= V
+ 1V
OUT (NOMINAL)
IN
CONTROL
RIPPLE = 50mV
P–P
= V
+2V
OUT (NOMINAL)
= 2.2μF CERAMIC
OUT
C
I
= 2.2μF CERAMIC
= 1.1A
OUT
LOAD
C
OUT
= 2.2μF CERAMIC
RIPPLE = 50mV
100
P–P
10
100
1k
10k
100k
1M
10
1k
10k
100k
1M
10
100
1k
10k
100k
1M
FREQUENCY (Hz)
FREQUENCY (Hz)
FREQUENCY (Hz)
30801 G22
30801 G23
30801 G24
Ripple Rejection (120Hz)
Noise Spectral Density
10k
1k
80
79
78
77
76
75
74
73
72
1k
100
100
10
1
10
SINGLE SUPPLY OPERATION
1.0
V
= V
+ 2V
IN
OUT(NOMINAL)
RIPPLE = 500mV , f=120Hz
P-P
I
= 1.1A
71 LOAD
C
= 0.1μF, C
= 2.2μF
SET
OUT
0.1
100k
70
–50
10
100
1k
10k
–25
0
25
50
75
100 125
150
FREQUENCY (Hz)
TEMPERATURE (oC)
30801 G26
30801 G25
30801fa
6
LT3080-1
TYPICAL PERFORMANCE CHARACTERISTICS
Error Amplifier Gain and Phase
Output Voltage Noise
20
300
250
200
150
100
50
15
10
V
OUT
I
= 1.1A
5
0
L
100μV/DIV
I
= 100mA
L
–5
I
= 1.1A
L
30801 G27
–10
–15
–20
–25
–30
0
TIME 1ms/DIV
V
= 1V
OUT
SET
SET
–50
–100
–150
R
= 100k
= O.1μF
= 10μF
= 1.1A
I
= 100mA
L
C
C
OUT
LOAD
I
–200
1M
10
100
1k
10k
100k
FREQUENCY (Hz)
30801 G28
PIN FUNCTIONS (DD/MS8E)
V
(Pin 5/Pin 5): This pin is the supply pin for
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.
CONTROL
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).
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.
IN (Pins 7, 8/Pins 7, 8): This is the collector to the power
deviceoftheLT3080-1.Theoutputloadcurrentissupplied
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
Exposed Pad (Pin 9/Pin 9): OUT on MS8E and DFN
packages.
no connection to internal circuitry and may be tied to V ,
IN
V
, V , GND, or floated.
CONTROL OUT
30801fa
7
LT3080-1
BLOCK DIAGRAM
IN
V
CONTROL
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.
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.
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.
TheLT3080-1alsoincorporatesaninternalballastresistor
toallowfordirectparallelingofdeviceswithouttheneedfor
PC board trace resistors or sense resistors. This internal
ballast resistor allows multiple devices to be paralleled
directlyonasurfacemountboardforhigheroutputcurrent
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,outputsofalldevicesaretieddirectlytogether,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.
Aprecision“0”TC10μAinternalcurrentsourceisconnected
tothenon-invertinginputofapoweroperationalamplifier.
Thepoweroperationalamplifierprovidesalowimpedance
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.
Whatisnotsoobviousfromthisarchitecturearethebenefits
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.
IN
LT3080-1
V
CONTROL
+
–
+
+
V
V
CONTROL
IN
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.
25mΩ
OUT
V
C
OUT
OUT
SET
R
C
SET
SET
30801 F01
Figure 1. Basic Adjustable Regulator
dissipation:ahighervoltagesupplyforthecontrolcircuitry
andalowervoltagesupplyforthecollector. Thisincreases
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.
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.
TheLT3080-1canbeoperatedintwomodes.Threeterminal
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
allowsfora1.1Asupplyregulatingfrom2.5V to1.8V
IN
OUT
or 1.8V to 1.2V
with low dissipation.
Stability and Output Capacitance
IN
OUT
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
individualcomponentspoweredbytheLT3080-1,increase
the effective output capacitor value.
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
regulationregardlessofoutputvoltage.Fortruezerovoltage
output operation, this 1mA load current must be returned
to a negative supply voltage.
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
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
to the time constant of the voltage setting resistor (R
in Figure 1) and SET pin bypass capacitor.
SET
30801fa
9
LT3080-1
APPLICATIONS INFORMATION
capacitancechangeovertemperature.Capacitancechange
due to DC bias with X5R and X7R capacitors is better than
Y5VandZ5Ucapacitors,butcanstillbesignificantenough
todropcapacitorvaluesbelowappropriatelevels.Capacitor
DC bias characteristics tend to improve as component
casesizeincreases, butexpectedcapacitanceatoperating
voltage should be verified.
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
characteristiccodesofZ5U,Y5V,X5RandX7R.TheZ5Uand
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
acrosstemperature, whiletheX5Rislessexpensiveandis
availableinhighervalues.Carestillmustbeexercisedwhen
using X5R and X7R capacitors; the X5R and X7R codes
only specify operating temperature range and maximum
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
BOTH CAPACITORS ARE 16V,
1210 CASE SIZE, 10μF
0
X5R
–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
internalballastresistors, whichatfulloutputcurrentgives
–40
–60
Y5V
–80
V
LT3080-1
IN
–100
0
8
12 14
2
4
6
10
16
V
DC BIAS VOLTAGE (V)
CONTROL
30801 F02
+
–
Figure 2. Ceramic Capacitor DC Bias Characteristics
25mΩ
OUT
40
20
SET
V
IN
4.8V TO 28V
V
LT3080-1
IN
X5R
0
–20
V
CONTROL
+
–
1μF
–40
–60
–80
–100
Y5V
25mΩ
V
3.3V
2.2A
OUT
OUT
SET
165k
BOTH CAPACITORS ARE 16V,
1210 CASE SIZE, 10μF
10μF
50
TEMPERATURE (°C)
100 125
–50 –25
0
25
75
30801 F04
3080 F03
Figure 4. Parallel Devices
Figure 3. Ceramic Capacitor Temperature Characteristics
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
absoluteerror 1.3%.Ofcourse,morethantwoLT3080-1’s
can be paralleled for even higher output current. They are
spread out on the PC board, spreading the heat. Input
resistorscanfurtherspreadtheheatiftheinput-to-output
difference is high.
reaches ambient temperature within about a half an inch
from the devices.
Thepoweristhenincreasedwith1.7Vacrosseachdevice.
Thisgives1.7wattsdissipationineachdeviceandadevice
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.
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
mountedverticallyforconvectioncooling. Twotestswere
set up to measure the cooling performance and current
sharing of these devices.
Bothatlowpowerandrelativelyhighpowerlevelsdevices
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
temperaturesbelowexcessiveoperatingtemperatureson
a board. This technique allows higher operating current
linear regulation to be used in systems where it could
never be used before.
The first test was done with approximately 0.7V input-
to-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
thermalandelectricalsharingofthesedevicesisexcellent.
The thermograph in Figure 5 shows the temperature
distribution between these devices and the PC board
Figure 5. Temperature Rise at 700mW Dissipation
Figure 6. Temperature Rise at 1.7W Dissipation
30801fa
11
LT3080-1
APPLICATIONS INFORMATION
Quieting the Noise
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.
TheLT3080-1offersnumerousadvantageswhenitcomes
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.
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
increasesandkeepsthepowerdissipationatsafelevelsfor
allvaluesofinput-to-outputvoltage.TheLT3080-1provides
someoutputcurrentatallvaluesofinput-to-outputvoltage
up to the device breakdown. See the Current Limit curve
in the Typical Performance Characteristics section.
Traditionallownoiseregulatorsbringthevoltagereference
outtoanexternalpin(usuallythroughalargevalueresistor)
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 (1nA
over the 10Hz to
RMS
100kHzbandwidth).Thevoltagenoiseofthisisequaltothe
noise current multiplied by the resistor value. The resistor
generates spot noise equal to √4kTR (k = Boltzmann’s
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.
-23
constant, 1.38•10 J/°K, andTisabsolutetemperature)
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.
The problem occurs with a heavy output load when the
inputvoltageishighandtheoutputvoltageislow.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.
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 (40μV
over the 10Hz to 100kHz
RMS
bandwidth); this is another factor that is RMS summed in
to give a final noise figure for the regulator.
30801fa
12
LT3080-1
APPLICATIONS INFORMATION
Load Regulation
functionofoutputloadcurrent.Outputvoltageissetbased
on the midpoint of the output load current range:
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.
1
2
• IOUT(MIN) +IOUT(MAX)
(
)
As output current decreases below the midpoint, output
voltage increases above the nominal set-point. Corre-
spondingly,asoutputcurrentincreasesabovethemidpoint,
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:
(VOUT +IMID •RBALLAST
)
RSET
=
ISET
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
calledactivevoltagepositioningandisespeciallyusefulfor
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
where
= 1/2 (I
I
+ I
)
MID
OUT(MIN)
OUT(MAX)
R
= 25mΩ
BALLAST
I
= 10μA
SET
Thermal Considerations
The LT3080-1 has internal power and thermal limiting
circuitry designed to protect it under overload conditions.
Forcontinuousnormalloadconditions,maximumjunction
temperature must not be exceeded. It is important to
IN
LT3080-1
V
CONTROL
PARASITIC
+
–
RESISTANCE
25mΩ
R
P
R
P
R
P
OUT
LOAD
R
SET
SET
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.
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
boardwith1ouncecopper,modernmultilayerPCBsprovide
betterperformancethanfoundinthesetables.Forexample,
a 4-layer, 1 ounce copper PCB board with five thermal vias
fromtheDFNorMSOPexposedbacksidepadtoinnerlayers
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.
(connected to V ) achieves 40°C/W thermal resistance.
OUT
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.
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
sinkingmaterial.NotethattheExposedPadiselectrically
connected to the output.
Calculating Junction Temperature
Example: Given an output voltage of 0.9V, a V
CONTROL
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
2
temperature be for the DFN package on a 2500mm board
with topside copper area of 500mm ?
2
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.
The power in the drive circuit equals:
P
DRIVE
= (V
– V )(I
)
CONTROL
OUT CONTROL
where I
is equal to I /60. I
is a function
canbefound
CONTROL
ofoutputcurrent. AcurveofI
OUT
CONTROL
vsI
Table 1. MSE Package, 8-Lead MSOP
CONTROL
OUT
COPPER AREA
in the Typical Performance Characteristics curves.
THERMAL RESISTANCE
(JUNCTION-TO-AMBIENT)
TOPSIDE* BACKSIDE BOARD AREA
The power in the output transistor equals:
2
2
2
2
2
2
2
2
2
2500mm
2500mm
2500mm
2500mm
2500mm
2500mm
2500mm
2500mm
2500mm
55°C/W
2
1000mm
57°C/W
P
= (V – V )(I
)
OUTPUT
IN
OUT OUT
2
225mm
100mm
60°C/W
The total power equals:
= P + P
OUTPUT
2
65°C/W
P
TOTAL
DRIVE
*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
THERMAL RESISTANCE
TOPSIDE* BACKSIDE BOARD AREA
V
V
V
= 3.630V (3.3V + 10%)
(JUNCTION-TO-AMBIENT)
CONTROL(MAX CONTINUOUS)
2
2
2
2
2
2
2
2
2
2500mm
2500mm
2500mm
2500mm
2500mm
2500mm
2500mm
2500mm
2500mm
60°C/W
62°C/W
65°C/W
68°C/W
= 1.575V (1.5V + 5%)
IN(MAX CONTINUOUS)
2
1000mm
= 0.9V, I
= 1A, T = 50°C
A
2
OUT
OUT
225mm
100mm
2
*Device is mounted on topside
30801fa
14
LT3080-1
APPLICATIONS INFORMATION
Power dissipation under these conditions is equal to:
OUT differential voltage and correspondingly decreases
the LT3080-1’s power dissipation.
PDRIVE = (V
– V )(I
)
CONTROL
OUT CONTROL
As an example, assume: V = V
= 5V, V
= 3.3V
IN
CONTROL
OUT
IOUT
1A
ICONTROL
=
=
=17mA
and I
= 1A. Use the formulas from the Calculating
OUT(MAX)
60 60
= (3.630V – 0.9V)(17mA) = 46mW
Junction Temperature section previously discussed.
P
P
P
DRIVE
Without series resistor R , power dissipation in the
S
= (V – V )(I )
OUT OUT
LT3080-1 equals:
OUTPUT
OUTPUT
IN
= (1.575V – 0.9V)(1A) = 675mW
1A
60
⎛
⎝
⎞
⎠
PTOTAL = 5V – 3.3V •
+ 5V – 3.3V •1A =1.73W
(
)
(
)
⎜
⎟
Total Power Dissipation = 721mW
Junction Temperature will be equal to:
If the voltage differential (V ) across the NPN pass
DIFF
transistor is chosen as 0.5V, then R equals:
S
T = T + P
• θ (approximated using tables)
JA
J
A
TOTAL
5V – 3.3V − 0.5V
T = 50°C + 721mW • 64°C/W = 96°C
J
RS =
=1.2Ω
1A
Inthiscase,thejunctiontemperatureisbelowthemaximum
rating, ensuring reliable operation.
Power dissipation in the LT3080-1 now equals:
1A
60
⎛
⎝
⎞
⎠
Reducing Power Dissipation
PTOTAL = 5V – 3.3V •
+ 0.5V •1A = 0.53W
(
)
(
)
⎜
⎟
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-
The LT3080-1’s power dissipation is now only 30%
compared to no series resistor. R dissipates 1.2W of
S
power. Choose appropriate wattage resistors to handle
and dissipate the power properly.
V
V
IN
IN
V
C1
CONTROL
R
S
LT3080-1
IN
a
+
–
25mΩ
OUT
V
OUT
C2
SET
30801 F08
R
SET
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. Thisresistorprovidesaparallelpathforcurrent
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:
5.5V – 3.2V
1A –
= 0.36A
3.6Ω
Therefore, the LT3080-1’s power dissipation is only:
= (5.5V – 3.2V) • 0.36A = 0.83W
P
DIS
R dissipates 1.47W of power. As with the first technique,
As an example, assume: V = V
= 5V, V
OUT(MAX)
=
P
IN
CONTROL
= 3.2V, I
IN(MAX)
= 1A and
choose appropriate wattage resistors to handle and
dissipate the power properly. With this configuration, the
LT3080-1suppliesonly0.36A. Therefore, loadcurrentcan
increase by 0.64A to 1.64A while keeping the LT3080-1 in
its normal operating range.
5.5V, V
= 3.3V, V
OUT
OUT(MIN)
I
= 0.7A. Also, assuming that R carries no more
OUT(MIN)
P
than 90% of I
= 630mA.
OUT(MIN)
Calculating R yields:
P
5.5V – 3.2V
RP =
= 3.65Ω
0.63A
(5% Standard value = 3.6Ω)
V
IN
V
C1
CONTROL
LT3080-1
IN
R
P
+
–
25mΩ
OUT
V
OUT
C2
SET
30801 F09
R
SET
Figure 9. Reducing Power Dissipation Using a Parallel Resistor
30801fa
16
LT3080-1
TYPICAL APPLICATIONS
Adding Shutdown
IN
LT3080-1
V
CONTROL
+
–
25mΩ
OUT
SET
IN
LT3080-1
V
IN
V
CONTROL
+
–
25mΩ
OUT
V
OUT
SET
R1
Q1
VN2222LL
Q2*
VN2222LL
ON OFF
SHUTDOWN
30801 TA02
*Q2 INSURES ZERO OUTPUT IN THE
ABSENCE OF ANY OUTPUT LOAD
Current Source
IN
LT3080-1
V
IN
10V
V
CONTROL
+
–
25mΩ
OUT
SET
LT3080-1
IN
V
CONTROL
+
–
2.2μF
25mΩ
1Ω
I
OUT
OUT
0A TO 2A
SET
100k
10μF
30801 TA03
30801fa
17
LT3080-1
TYPICAL APPLICATIONS
Using a Lower Value SET Resistor
IN
LT3080-1
V
IN
10V
V
CONTROL
+
–
25mΩ
OUT
SET
IN
LT3080-1
V
CONTROL
+
–
C1
2.2μF
V
= 0.5V + 2mA • R
OUT SET
25mΩ
OUT
V
OUT
0.5V TO 10V
SET
R1
24.9k
1%
R2
249Ω
1%
C
2mA
OUT
10μF
R
SET
4.99k
1%
30801 TA04
Adding Soft-Start
V
IN
LT3080-1
IN
4.8V TO 28V
V
CONTROL
+
–
D1
IN4148
V
3.3V
2.2A
25mΩ
OUT
OUT
SET
IN
LT3080-1
V
CONTROL
+
–
C1
2.2μF
25mΩ
OUT
SET
R1
C2
0.01μF
C
OUT
10μF
165k
30801 TA05
30801fa
18
LT3080-1
TYPICAL APPLICATIONS
Lab Supply
IN
LT3080-1
IN
LT3080-1
V
IN
13V TO 18V
V
V
CONTROL
CONTROL
+
–
+
–
25mΩ
25mΩ
OUT
OUT
SET
SET
IN
LT3080-1
IN
LT3080-1
V
V
CONTROL
CONTROL
+
–
+
–
0.5Ω
25mΩ
25mΩ
OUT
OUT
V
OUT
0V TO 10V
SET
50k
0A TO 2A
SET
R4
CURRENT
LIMIT
+
+
+
10μF
15μF
15μF
100μF
500k
3080 TA06
Boosting Fixed Output Regulators
LT3080-1
+
–
25mΩ
OUT
SET
20mΩ
3.3V
OUT
LT1963-3.3
5V
2.6A
10μF
42Ω*
33k
47μF
30801 TA07
*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
12.1k
10k
PV
SV
SW
IN
+
2×
2.7V TO
5.5V
I
TH
LT3080-1
LT3080-1
LT3080-1
LT3080-1
IN
100μF
IN
†
+
2×
100μF
LTC3414
470pF
R
2.2MEG 100k
1000pF
T
2N3906
V
CONTROL
294k
PGOOD
RUN/SS
+
–
V
FB
25mΩ
OUT
78.7k
124k
SYNC/MODE
SGND PGND
SET
IN
V
CONTROL
+
–
*DIFFERENTIAL VOLTAGE ON LT3080-1
IS 0.6V SET BY THE V OF THE 2N3906 PNP
BE
25mΩ
0V TO
OUT
†
†
MAXIMUM OUTPUT VOLTAGE IS 1.5V
BELOW INPUT VOLTAGE
4V
4A
SET
IN
V
CONTROL
+
–
25mΩ
OUT
SET
IN
V
CONTROL
+
–
25mΩ
OUT
SET
+
100μF
100k
30801 TA08
30801fa
20
LT3080-1
TYPICAL APPLICATIONS
Adjustable High Efficiency Regulator*
CMDSH-4E
4.5V TO
25V
V
BOOST
SW
IN
†
LT3493
0.1μF
10μF
1μF
100k
10μH
IN
LT3080-1
SHDN
68μF
0.1μF
V
MBRM140
CONTROL
TP0610L
+
–
FB
GND
0V
TO 10V
1A
25mΩ
OUT
†
10k
SET
4.7μF
1MEG
*DIFFERENTIAL VOLTAGE ON LT3080-1
≈ 1.4V SET BY THE TPO610L P-CHANNEL THRESHOLD.
10k
†
MAXIMUM OUTPUT VOLTAGE IS 2V
BELOW INPUT VOLTAGE
30801 TA09
2 Terminal Current Source
C
*
COMP
IN
LT3080-1
V
CONTROL
+
–
R1
25mΩ
OUT
SET
100k
30801 TA10
CURRENT SET
*C
COMP
1V
R1
R1 ≤ 10Ω 10μF
R1 ≥ 10Ω 2.2μF
I
=
OUT
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
2.15 ±0.05 (2 SIDES)
1.65 ±0.05
PACKAGE
OUTLINE
0.25 ± 0.05
0.50
BSC
2.38 ±0.05
(2 SIDES)
RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS
R = 0.115
0.38 ± 0.10
TYP
5
8
3.00 ±0.10
(4 SIDES)
1.65 ± 0.10
(2 SIDES)
PIN 1
TOP MARK
(NOTE 6)
(DD) DFN 1203
4
1
0.25 ± 0.05
0.75 ±0.05
0.200 REF
0.50 BSC
2.38 ±0.10
(2 SIDES)
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
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
1.83 ± 0.102
(.072 ± .004)
0.889 ± 0.127
(.035 ± .005)
2.794 ± 0.102
(.110 ± .004)
5.23
(.206)
MIN
3.20 – 3.45
(.126 – .136)
2.083 ± 0.102
(.082 ± .004)
8
3.00 ± 0.102
(.118 ± .004)
(NOTE 3)
0.52
(.0205)
REF
0.65
(.0256)
BSC
0.42 ± 0.038
(.0165 ± .0015)
TYP
8
7 6 5
RECOMMENDED SOLDER PAD LAYOUT
3.00 ± 0.102
(.118 ± .004)
(NOTE 4)
4.90 ± 0.152
(.193 ± .006)
DETAIL “A”
0° – 6° TYP
0.254
(.010)
GAUGE PLANE
1
2
3
4
0.53 ± 0.152
(.021 ± .006)
1.10
(.043)
MAX
0.86
(.034)
REF
DETAIL “A”
0.18
(.007)
SEATING
PLANE
0.22 – 0.38
(.009 – .015)
TYP
0.1016 ± 0.0508
(.004 ± .002)
0.65
(.0256)
BSC
MSOP (MS8E) 0307 REV D
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
30801fa
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However,noresponsibilityisassumedforitsuse.LinearTechnologyCorporationmakesnorepresentation
that the interconnection of its circuits as described herein will not infringe on existing patent rights.
23
LT3080-1
TYPICAL APPLICATION
Paralleling Regulators
IN
LT3080-1
V
CONTROL
+
–
25mΩ
OUT
SET
IN
LT3080-1
V
IN
4.8V TO 28V
V
CONTROL
+
–
25mΩ
V
3.3V
2.2A
OUT
OUT
1μF
SET
165k
10μF
30801 TA11
RELATED PARTS
PART NUMBER
LDOs
DESCRIPTION
COMMENTS
LT1086
1.5A Low Dropout Regulator
Fixed 2.85V, 3.3V, 3.6V, 5V and 12V Output
LT1117
800mA Low Dropout Regulator
800mA Low Dropout Regulator
1V Dropout, Adjustable or Fixed Output, DD-Pak, SOT-223 Packages
Okay for Sinking and Sourcing, S0-8 and SOT-223 Packages
LT1118
LT1963A
1.5A Low Noise, Fast Transient
Response LDO
340mV Dropout Voltage, Low Noise = 40μV
, V : 2.5V to 20V,
RMS IN
TO-220, DD, SOT-223 and SO-8 Packages
LT1965
1.1A Low Noise LDO
290mV Dropout Voltage, Low Noise 40μV
, V : 1.8V to 20V,
RMS IN
V
: 1.2V to 19.5V, Stable with Ceramic Caps, TO-220, DDPak, MSOP and 3mm × 3mm
OUT
DFN Packages
LTC®3026
LT3080
1.5A Low Input Voltage VLDOTM
Regulator
V
IN
: 1.14V to 3.5V (Boost Enabled), 1.14V to 5.5V (with External 5V), V = 0.1V, I =
DO
Q
950μA, Stable with 10μF Ceramic Capacitors, 10-Lead MSOP and DFN Packages
1.1A, Parallelable, Low Noise,
Low Dropout Linear Regulator
300mV Dropout Voltage (2-Supply Operation), Low Noise: 40μV , V : 1.2V to 36V,
RMS IN
V
OUT
: 0V to 35.7V, Current-Based Reference with 1-Resistor V
Set, Directly Parallelable
OUT
(No Op Amp Required), Stable with Ceramic Capacitors, TO-220, SOT-223, MSOP and
3mm × 3mm DFN Packages.
Switching Regulators
LTC3414
4A (I ), 4MHz Synchronous
95% Efficiency, V : 2.25V to 5.5V, V
= 0.8V, TSSOP Package
OUT
IN
OUT(MIN)
Step-Down DC/DC Converter
LTC3406/LTC3406B 600mA (I ), 1.5MHz Synchronous
95% Efficiency, V : 2.5V to 5.5V, V
= 0.6V, I = 20μA,
Q
OUT
IN
OUT(MIN)
Step-Down DC/DC Converter
I
< 1μA, ThinSOTTM Package
SD
LTC3411
1.25A (I ), 4MHz Synchronous
95% Efficiency, V : 2.5V to 5.5V, V
SD
= 0.8V, I = 60μA,
Q
OUT
IN
OUT(MIN)
Step-Down DC/DC Converter
I
< 1μA, 10-Lead MS or DFN Packages
VLDO and ThinSOT are trademarks of Linear Technology Corporation.
30801fa
LT 1008 REV A • PRINTED IN USA
LinearTechnology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
24
●
●
© LINEAR TECHNOLOGY CORPORATION 2008
(408) 432-1900 FAX: (408) 434-0507 www.linear.com
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