Linear Technology LT3081 User manual

LT3081
1
3081fc
For more information www.linear.com/LT3081
Typical applicaTion
FeaTures DescripTion
1.5A Single Resistor
Rugged Linear Regulator
with Monitors
The LT
®
3081 is a 1.5A low dropout linear regulator de-
signed for rugged industrial applications. Key features of
the IC are the extended safe operating area (SOA), output
current monitor, temperature monitor and programmable
current limit. The LT3081 can be paralleled for higher
output current or heat spreading. The device withstands
reverseinputandreverseoutput-to-inputvoltageswithout
reverse current flow.
The LT3081’s precision 50µA reference current source
allows a single resistor to program output voltage to
any level between zero and 34.5V. The current reference
architecture makes load regulation independent of output
voltage. The LT3081 is stable with or without input and
output capacitors.
The output current monitor (IOUT/5000) and die junction
temperature output (1µA/°C) provide system monitoring
and debug capability. In addition, a single resistor pro-
grams current limit.
Internal protection circuitry includes reverse-battery and
reverse-current protection, current limiting and thermal
limiting. The LT3081 is offered in the 16-lead TSSOP (with
exposed pad for improved thermal performance), 7-lead
TO-220, 7-lead DD-Pak, and an 12-lead 4mm ×4mm DFN.
Wide Safe Operating Area Supply
applicaTions
nExtended Safe Operating Area
nMaximum Output Current: 1.5A
nStable with or without Input/Output Capacitors
nWide Input Voltage Range: 1.2V to 36V
nSingle Resistor Sets Output Voltage
nOutput Current Monitor: IMON = IOUT/5000
nJunction Temperature Monitor: 1µA/°C
nOutput Adjustable to 0V
n50µA SET Pin Current: 1% Initial Accuracy
nOutput Voltage Noise: 27µVRMS
nParallel Multiple Devices for Higher Current or
Heat Spreading
nProgrammable Current Limit
nReverse-Battery and Reverse-Current Protection
n<1mV Load Regulation Typical Independent of VOUT
n<0.001%/V Line Regulation Typical
nAvailable in Thermally-Enhanced 12-Lead 4mm ×4mm
DFN and 16-Lead TSSOP, 7-Lead DD-Pak and 7-Lead
TO-220
nAll Surface Mount Power Supply
nRugged Industrial Power Supply
nPost Regulator for Switching Supplies
nLow Output Voltage Supply
nIntrinsic Safety Applications
L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear
Technology Corporation. All other trademarks are the property of their respective owners.
TEMPERATURE (°C)
–50
49.5
SET PIN CURRENT (µA)
49.6
49.8
49.9
50.0
50.5
50.2
050 75
3081 TA01b
49.7
50.3
50.4
50.1
–25 25 100 125 150
IL= 5mA
SET Pin Current
3081 TA01a
IN
1k 4.53k
10µF*
*OPTIONAL
IMON ILIM
OUT
+
–
LT3081
ILOAD/5000
IOUT
1.5V
1A
VIN
300Ω*
1k
1µA/°C
SET
30.1k
TEMP
50µA

LT3081
2
3081fc
For more information www.linear.com/LT3081
absoluTe MaxiMuM raTings
IN Pin to OUT Pin Differential Voltage.....................±40V
SET Pin Current (Note 6) .....................................±25mA
SET Pin Voltage (Relative to OUT, Note 6) .............. ±10V
TEMP Pin Voltage (Relative to OUT).................1V, –40V
ILIM Pin Voltage (Relative to OUT).........................±0.2V
IMON Pin Voltage (Relative to OUT)...................1V, –40V
Output Short-Circuit Duration .......................... Indefinite
(Note 1) All Voltages Relative to VOUT.
TOP VIEW
13
OUT
DF PACKAGE
12-LEAD (4mm ×4mm) PLASTIC DFN
12
11
8
9
10
4
5
3
2
1IN
IN
IN
IN
TEMP
IMON
OUT
OUT
OUT
OUT
ILIM
SET 67
TJMAX = 125°C, θJA = 32°C/W, θJC = 4°C/W
EXPOSED PAD (PIN 13) IS OUT, MUST BE SOLDERED TO PCB
FE PACKAGE
16-LEAD PLASTIC TSSOP
1
2
3
4
5
6
7
8
TOP VIEW
16
15
14
13
12
11
10
9
OUT
OUT
OUT
OUT
OUT
I
LIM
SET
OUT
OUT
IN
IN
IN
IN
TEMP
IMON
OUT
17
OUT
TJMAX = 150°C, θJA = 29°C/W, θJC = 8°C/W
EXPOSED PAD (PIN 17) IS OUT, MUST BE SOLDERED TO PCB
R PACKAGE
7-LEAD PLASTIC DD
FRONT VIEW
TAB IS
OUT
NC
IN
TEMP
OUT
IMON
SET
ILIM
7
6
5
4
3
2
1
TJMAX = 125°C, θJA = 15°C/W, θJC = 3°C/W
T7 PACKAGE
7-LEAD PLASTIC TO-220
TAB IS
OUT
NC
IN
TEMP
OUT
IMON
SET
ILIM
FRONT VIEW
7
6
5
4
3
2
1
TJMAX = 150°C, θJA = 40°C/W, θJC = 3°C/W
pin conFiguraTion
Operating Junction Temperature Range (Note 2)
E-, I-Grades ....................................... –40°C to 125°C
H-Grade ............................................. –40°C to 150°C
MP-Grade .......................................... –55°C to 150°C
Storage Temperature Range .................. –65°C to 150°C
Lead Temperature (Soldering, 10 sec)
FE, R, T7 Packages Only...................................300°C

LT3081
3
3081fc
For more information www.linear.com/LT3081
The ldenotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TJ= 25°C. (Note 2)
elecTrical characTerisTics
orDer inForMaTion
LEAD FREE FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE
LT3081EDF#PBF LT3081EDF#TRPBF 3081 12-Lead (4mm ×4mm) Plastic DFN –40°C to 125°C
LT3081IDF#PBF LT3081IDF#TRPBF 3081 12-Lead (4mm ×4mm) Plastic DFN –40°C to 125°C
LT3081EFE#PBF LT3081EFE#TRPBF 3081FE 16-Lead Plastic TSSOP –40°C to 125°C
LT3081IFE#PBF LT3081IFE#TRPBF 3081FE 16-Lead Plastic TSSOP –40°C to 125°C
LT3081HFE#PBF LT3081HFE#TRPBF 3081FE 16-Lead Plastic TSSOP –40°C to 150°C
LT3081MPFE#PBF LT3081MPFE#TRPBF 3081FE 16-Lead Plastic TSSOP –55°C to 150°C
LT3081ER#PBF LT3081ER#TRPBF LT3081R 7-Lead Plastic DD-Pak –40°C to 125°C
LT3081IR#PBF LT3081IR#TRPBF LT3081R 7-Lead Plastic DD-Pak –40°C to 125°C
LT3081ET7#PBF NA LT3081T7 7-Lead Plastic TO-220 –40°C to 125°C
LT3081IT7#PBF NA LT3081T7 7-Lead Plastic TO-220 –40°C to 125°C
LT3081HT7#PBF NA LT3081T7 7-Lead Plastic TO-220 –40°C to 150°C
LT3081MPT7#PBF NA LT3081T7 7-Lead Plastic TO-220 –55°C to 150°C
Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container.
Consult LTC Marketing for information on nonstandard lead based finish parts.
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/
PARAMETER CONDITIONS MIN TYP MAX UNITS
SET Pin Current ISET VIN = 2V, ILOAD = 5mA
2V ≤ VIN ≤ 36V, 5mA ≤ ILOAD ≤ 1.5A
l
49.5
48.75
50
50
50.5
51.25
µA
µA
Offset Voltage VOS
(VOUT – VSET)
VIN = 2V, ILOAD = 5mA
VIN = 2V, ILOAD = 5mA
l
–1.5
–3.5
0
0
1.5
3.5
mV
mV
ISET Load Regulation ∆ILOAD = 5mA to 1.5A –0.1 nA
VOS Load Regulation ∆ILOAD = 5mA to 1.5A
(Note 7)
DF, FE Packages l–0.5 –3 mV
R, T7 Packages l–1.5 –4 mV
Line Regulation ∆ISET
∆VOS
∆VIN = 2V to 36V, ILOAD = 5mA
∆VIN = 2V to 36V, ILOAD = 5mA
1.5
0.001
nA/V
mV/V
Minimum Load Current (Note 3) 2V ≤ VIN ≤ 36V l1.1 5 mA
Dropout Voltage (Note 4) ILOAD = 100mA
ILOAD = 1.5A
l
1.21
1.23 1.5
V
V
Internal Current Limit VIN = 5V, VSET = 0V, VOUT = –0.1V l1.5 2 A
ILIM Programming Ratio l300 360 500 mA/kΩ
ILIM Minimum Output Current Resistance 450 Ω
IMON Full-Scale Output Current ILOAD = 1.5A 290 300 330 µA
IMON Scale Factor 100mA ≤ ILOAD ≤ 1.5A 200 µA/A
IMON Operating Range lVOUT – 40V VOUT + 0.4V V

LT3081
4
3081fc
For more information www.linear.com/LT3081
elecTrical characTerisTics
The ldenotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TJ= 25°C. (Note 2)
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 LT3081 is tested and specified under pulse load conditions such
that TJ≈ TA. The LT3081E is tested at TA= 25°C and performance is
guaranteed from 0°C to 125°C. Performance of the LT3081E over the
full –40°C and 125°C operating temperature range is assured by design,
characterization, and correlation with statistical process controls. The
LT3081I is guaranteed over the full –40°C to 125°C operating junction
temperature range. The LT3081MP is 100% tested and guaranteed
over the –55°C to 150°C operating junction temperature range. The
LT3081H is tested at 150°C operating junction temperature. High junction
temperatures degrade operating lifetimes. Operating lifetime is degraded at
junction temperatures greater than 125°C.
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 LT3081, dropout is specified as the minimum input-to-
output voltage differential required supplying a given output current.
Note 5: Adding a small capacitor across the reference current resistor
lowers output noise. Adding this capacitor bypasses the resistor shot
noise and reference current noise; output noise is then equal to error
amplifier noise (see Applications Information section).
Note 6: Diodes with series 400Ω resistors clamp the SET pin to the
OUT pin. These diodes and resistors only carry current under transient
overloads.
Note 7: Load regulation is Kelvin sensed at the package.
Note 8: This IC includes overtemperature protection that protects the
device during momentary overload conditions. Junction temperature
exceeds the maximum operating junction temperature when
overtemperature protection is active. Continuous operation above the
specified maximum operating junction temperature may impair device
reliability.
Note 9: The TEMP pin output current represents the average die junction
temperature. Due to power dissipation and thermal gradients across the
die, the TEMP pin output current measurement does not guarantee that
absolute maximum junction temperature is not exceeded.
PARAMETER CONDITIONS MIN TYP MAX UNITS
TEMP Output Current (Note 9) TJ> 5°C 1 µA/°C
TEMP Output Current Absolute Error (Note 9) 0°C <TJ≤ 125°C
125°C <TJ≤ 150°C
–10
–15
10
15
µA
µA
Reference Current RMS Output Noise (Note 5) 10Hz ≤ f ≤ 100kHz 5.7 nARMS
Error Amplifier RMS Output Noise (Note 5) ILOAD = 1.5A, 10Hz ≤ f ≤ 100kHz, COUT =10µF,
CSET = 0.1µF
27 µVRMS
Ripple Rejection
VRIPPLE = 0.5VP-P, ILOAD = 0.1A, CSET = 0.1µF,
COUT=10µF, VIN = VOUT(NOMINAL) + 3V
f = 120Hz
f = 10kHz
f = 1MHz
75 90
75
20
dB
dB
dB
Thermal Regulation, ISET 10ms Pulse 0.003 %/W

LT3081
5
3081fc
For more information www.linear.com/LT3081
Typical perForMance characTerisTics
Offset Voltage Offset Voltage (VOUT – VSET) Offset Voltage (VOUT – VSET)
Load Regulation Minimum Load Current Dropout Voltage
SET Pin Current SET Pin Current
TJ= 25°C unless otherwise specified.
Offset Voltage (VOUT – VSET)
TEMPERATURE (°C)
–50
49.5
SET PIN CURRENT (µA)
49.6
49.8
49.9
50.0
50.5
50.2
050 75
3081 G01
49.7
50.3
50.4
50.1
–25 25 100 125 150
ILOAD = 5mA
SET PIN CURRENT DISTRIBUTION (µA)
49
N = 3195
49.5 50
3081 G02
50.5 51
TEMPERATURE (°C)
–50
OFFSET VOLTAGE (mV)
0
1.0
150
3081 G03
–1.0
–2.0 050 100
–25 25 75 125
2.0
–0.5
0.5
–1.5
1.5
ILOAD = 5mA
VOS DISTRIBUTION (mV)
–2
N = 3195
–1 0
3081 G04
1 2
INPUT-TO-OUTPUT DIFFERENTIAL (V)
0
–1.0
OFFSET VOLTAGE (mV)
–0.6
–0.2
0.2
612 18 24
3081 G05
30
0.6
1.0
–0.8
–0.4
0
0.4
0.8
36
ILOAD = 5mA
LOAD CURRENT (A)
0
OFFSET VOLTAGE (mV)
–0.6
3081 G06
–1.0
–1.4 0.5 1
0.25 0.75 1.25
–0.2
0.2
–0.8
–1.2
–0.4
0
1.5
TJ= 25°C
TJ= 125°C
TEMPERATURE (°C)
–50
0
SET PIN CURRENT LOAD REGULATION (nA)
OFFSET VOLTAGE LOAD REGULATION (mV)
50
100
150
200
0 50 100 150
3081 G07
250
300
–3.0
–2.5
–2.0
–1.5
–1.0
–0.5
0
–25 25 75 125
∆ILOAD = 5mA TO 1.5A
TEMPERATURE (°C)
–50
0
MINIMUM LOAD CURRENT (mA)
0.5
1.0
1.5
2.0
0 50 100 150
3081 G08
2.5
3.0
–25 25 75 125
VIN – VOUT = 36V
VIN – VOUT = 2V
LOAD CURRENT (A)
0
1.0
DROPOUT VOLTAGE (V)
1.1
1.2
1.3
1.4
1.5
0.25 0.5 0.75 1
3081 G09
1.25 1.5
TJ= –50°C
TJ= 25°C
TJ= 125°C

LT3081
6
3081fc
For more information www.linear.com/LT3081
TO-220 Package Maximum Power
Dissipation Programmable Current Limit Programmable Current Limit
Programmable Current Limit TEMP Pin Current IMON Pin Current
Dropout Voltage Internal Current Limit Internal Current Limit
TEMPERATURE (°C)
–50
DROPOUT VOLTAGE (V)
1.3
1.4
1.5
25 75 150
3081 G10
1.2
1.1
1.0 –25 0 50 100
ILOAD = 1.5A
ILOAD = 5mA
125
TEMPERATURE (°C)
–50
0
CURRENT LIMIT (A)
0.5
1.0
1.5
2.0
0 50 100 150
3081 G11
2.5
3.0
–25 25 75 125
VIN = 7V
VOUT = 0V
INPUT-TO-OUTPUT DIFFERENTIAL VOLTAGE (V)
0
0
CURRENT LIMIT (A)
0.4
0.8
1.2
612 18 24
3081 G12
30
1.6
2.0
0.2
0.6
1.0
1.4
1.8
36
TO-220 AND
DD-PAK
TSSOP
AND DFN
CASE TEMPERATURE (°C)
50
POWER (W)
10
20
150
3081 G13
070 90 110
60 80 100 120 130 140
30
5
15
25
VIN – VOUT = 20V
LIMITED BY FOLDBACK
CURRENT LIMIT
VIN – VOUT = 10V
VIN – VOUT = 5V
θJC = 3°C/W
RILIM (kΩ)
0
0
PROGRAMMED CURRENT LIMIT (A)
0.5
1.0
1.5
2.0
1 2 3 4
3081 G14
5 6
TJ= 25°C
VIN = 7V
VOUT = 0V
OUTPUT CURRENT (A)
0
0
OUTPUT VOLTAGE (V)
0.2
0.4
0.6
0.95
1.00
1.05
0.5 1 1.5 2
3081 G15
RILIM
1.5k
RILIM
3.01k
RILIM
4.53k
RSET = 20k
TEMPERATURE (°C)
–50
TEMP PIN CURRENT (µA)
80
120
150
3081 G16
40
0050 100
–25 25 75 125
160
60
100
20
140
LOAD CURRENT (A)
0
250
300
350
1.2
3081 G17
200
150
0.3 0.6 0.9 1.5
100
50
0
IMON PIN CURRENT (µA)
TEMPERATURE (°C)
–50
PROGRAMMED CURRENT LIMIT (A)
0.8
1.2
150
3081 G39
0.4
0050 100
–25 25 75 125
1.6
0.6
1.0
0.2
1.4 RILIM = 4.53k
RILIM = 3.01k
RILIM = 1.50k
VIN = 7V
VOUT = 0V
Typical perForMance characTerisTics
TJ= 25°C unless otherwise specified.

LT3081
7
3081fc
For more information www.linear.com/LT3081
Linear Regulator
Load Transient Response
Linear Regulator
Line Transient Response
Current Source
Line Transient Response
Current Source
Line Transient Response
Linear Regulator
Turn-On Response
IMON Pin Line Regulation
Linear Regulator
Load Transient Response
Linear Regulator
Load Transient Response
Linear Regulator
Load Transient Response
INPUT-TO-OUTPUT DIFFERENTIAL VOLTAGE (V)
0
0
IMON PIN CURRENT (µA)
10
20
30
612 18 24
3791 TA02b
30
40
50
5
15
25
35
45
36
ILOAD = 200mA
TIME (µs)
0
OUTPUT VOLTAGE
DEVIATION (mV)
LOAD
CURRENT (mA)
–50
0
50
160 180
8081 G19
–100
400
040 80 120
20 200
60 100 140
200
150
100
VIN = 3V
VOUT = 1V
CSET = 0.1µF
COUT = 2.2µF
∆ILOAD = 100mA TO 500mA
TIME (µs)
0
OUTPUT VOLTAGE
DEVIATION (mV)
LOAD
CURRENT (mA)
–100
0
100
160 180
3081 G20
–200
2.0
040 80 120
20 200
60 100 140
1.0
300
200
VIN = 3V
VOUT = 1V
CSET = 0.1µF
COUT = 2.2µF
∆ILOAD = 500mA TO 1.5A
TIME (µs)
0
OUTPUT VOLTAGE
DEVIATION (mV)
LOAD
CURRENT (mA)
–200
–100
0
40 45
3081 G21
600
400
010 20 30
5 50
15 25 35
200
200
100
VIN = 3V
VOUT = 1V
CSET = 30pF
COUT = 0
∆ILOAD = 100mA TO 500mA
tr= tf= 1µs
TIME (µs)
0
OUTPUT VOLTAGE
DEVIATION (mV)
LOAD
CURRENT (mA)
–400
–200
0
40 45
3081 G22
1.5
1.0
010 20 30
5 50
15 25 35
0.5
400
200
VIN = 3V
VOUT = 1V
CSET = 30pF
COUT = 0
∆ILOAD = 500mA TO 1.5A
tr= tf= 1µs
TIME (µs)
0
OUTPUT VOLTAGE
DEVIATION (mV) INPUT VOLTAGE (V)
3
4
5
40 45
3081 G23
0.1
0
–0.2 10 20 30
5 50
15 25 35
–0.1
7
6
RSET = 20k
RLOAD = 0.67Ω
COUT = 2.2µF
CSET = 0.1µF
TIME (µs)
0
OUTPUT CURRENT (mA) INPUT VOLTAGE (V)
2
3
4
40 45
3081 G24
150
100
010 20 30
5 50
15 25 35
50
6
5
RSET = 6.04k
ROUT = 3.01Ω
COUT = 0
CSET = 30pF
100mA CURRENT SOURCE CONFIGURATION
TIME (µs)
0
OUTPUT CURRENT (A) INPUT VOLTAGE (V)
2
3
4
40 45
3081 G25
1.2
1.0
0.6 10 20 30
5 50
15 25 35
0.8
6
5
RSET = 6.04k
ROUT = 0.3Ω
COUT = 0
CSET = 30pF
1A CURRENT SOURCE CONFIGURATION
TIME (µs)
0
OUTPUT VOLTAGE (V) INPUT VOLTAGE (V)
0
1
2
40 45
3081 G26
1.0
0.5
–0.5 10 20 30
5 50
15 25 35
0
4
3
RSET = 20k
RLOAD = 0.67Ω
COUT = 2.2µF CERAMIC
CSET = 0
Typical perForMance characTerisTics
TJ= 25°C unless otherwise specified.

LT3081
8
3081fc
For more information www.linear.com/LT3081
Ripple Rejection Ripple Rejection
Output Impedance Ripple Rejection (120Hz)
Residual Output Voltage with
Less Than Minimum Load
Current Source
Turn-On Response
Current Source
Turn-On Response
TIME (µs)
0
OUTPUT CURRENT (mA) INPUT VOLTAGE (V)
0
1
2
160 180
3081 G28
150
100
040 80 120
20 200
60 100 140
50
4
3
RSET = 6.04k
ROUT = 3.01Ω
COUT = 0
CSET = 20pF
100mA CURRENT SOURCE CONFIGURATION
TIME (µs)
0
OUTPUT CURRENT (A) INPUT VOLTAGE (V)
0
1
2
160 180
3081 G29
1.5
1.0
040 80 120
20 200
60 100 140
0.5
4
3
RSET = 6.04k
ROUT = 0.3Ω
COUT = 0
CSET = 20pF
1A CURRENT SOURCE CONFIGURATION
RTEST (Ω)
0
OUTPUT VOLTAGE (mV)
400
500
600
2000
3081 G30
300
200
0500 1000 1500
100
800
700
VIN = 36V
VIN = 5V
VOUT
SET PIN = 0V
RTEST
VIN
FREQUENCY (Hz)
10 100
40
RIPPLE REJECTION (dB)
50
60
70
80
1k 10k 100k 1M 10M
3081 G31
30
20
10
0
90
100
ILOAD = 100mA
ILOAD = 500mA
ILOAD = 1.5A
COUT = 2.2µF CERAMIC
CSET = 0.1µF
VIN = VOUT(NOMINAL) + 2V
FREQUENCY (Hz)
10 100
40
RIPPLE REJECTION (dB)
50
60
70
80
1k 10k 100k 1M 10M
3081 G32
30
20
10
0
90
100
VIN = VOUT + 5V
VIN = VOUT + 2V
VIN = VOUT + 1.5V
COUT = 2.2µF CERAMIC
CSET = 0.1µF
ILOAD = 100mA
FREQUENCY (Hz)
10
1
OUTPUT IMPEDANCE (Ω)
10
100
1k
10k
100k
1M
10M
100 1k 10k 100k 1M 10M
3081 G33
ISOURCE = 10mA
ISOURCE = 100mA
ISOURCE = 1A
CURRENT SOURCE CONFIGURATION
TEMPERATURE (°C)
–50
70
RIPPLE REJECTION (dB)
72
76
78
80
90
84
050 75
3081 G34
74
86
88
82
–25 25 100 125 150
VIN = VOUT(NOMINAL) + 2V
RIPPLE = 500mVP-P
f = 120Hz
ILOAD = 0.1A
COUT = 2.2µF
CSET = 0.1µF
Linear Regulator
Turn-On Response
TIME (ms)
0
OUTPUT VOLTAGE (V) INPUT VOLTAGE (V)
0
1
2
16 18
3081 G27
1.0
0.5
–0.5 4812
2 20
610 14
0
4
3
RSET = 20k
RLOAD = 0.67Ω
COUT = 2.2µF CERAMIC
CSET = 0.1µF
Typical perForMance characTerisTics
TJ= 25°C unless otherwise specified.

LT3081
9
3081fc
For more information www.linear.com/LT3081
Noise Spectral Density
10Hz to 100kHz
Output Voltage Noise
Ripple Rejection (10kHz) Ripple Rejection (1MHz)
TEMPERATURE (°C)
–50
45
RIPPLE REJECTION (dB)
47
51
53
55
65
59
050 75
3081 G34
49
61
63
57
–25 25 100 125 150
VIN = VOUT(NOMINAL) + 2V
RIPPLE = 500mVP-P
f = 10kHz
ILOAD = 0.1A
COUT = 2.2µF
CSET = 0.1µF
TEMPERATURE (°C)
–50
RIPPLE REJECTION (dB)
18
22
150
3081 G36
14
10 050 100
–25 25 75 125
26
16
20
12
24
VIN = VOUT(NOMINAL) + 2V
RIPPLE = 200mVP-P
f = 1MHz
ILOAD = 0.1A
COUT = 2.2µF CERAMIC
CSET = 0.1µF
FREQUENCY (Hz)
10
10
ERROR AMPLIFIER NOISE
SPECTRAL DENSITY (nV/√Hz)
REFERENCE CURRENT NOISE
SPECTRAL DENSITY (pA/√Hz)
100
1000
1
10
100
1k100 10k 100k
3981 G37
TIME 1ms/DIV
VOUT
50µV/DIV
3081 G38
CSET = 0.1µF
COUT = 4.7µF
ILOAD = 1.5A
NOISE INDEPENDENT
OF OUTPUT VOLTAGE
Typical perForMance characTerisTics
TJ= 25°C unless otherwise specified.

LT3081
10
3081fc
For more information www.linear.com/LT3081
block DiagraM
–
+
50µA
IN
IMON
TEMPERATURE
DEPENDENT
CURRENT SOURCE
1µA/°C
SET ILIM OUT
3081 BD
PROGRAMMABLE
CURRENT LIMIT
CURRENT
MONITOR
IMON = ILOAD/5000
TEMP
pin FuncTions
IN: Input. This pin supplies power to regulate internal
circuitry and supply output load current. For the device
to operate properly and regulate, the voltage on this pin
must be between the dropout voltage and 36V above the
OUT pin (depending on output load current, see Dropout
Voltage Specifications).
OUT: Output. This is the power output of the device. The
LT3081 requires a 5mA minimum load current for proper
output regulation.
TEMP: Temperature Output. This pin delivers a current
proportional to the internal average junction temperature.
Current output is 1µA/°C for temperatures above 5°C. The
TEMP pin output current typically equals 25µA at 25°C.
The output of the TEMP pin is valid for voltages from VOUT
+ 0.4V to VOUT – 40V. If unused, connect this pin to OUT.
ILIM:Current Limit Program. A resistor between this pin
and OUT programs output current limit to a level propor-
tional to resistor value. Connect this resistor directly to
OUT at the pins of the package. The typical ratio of current
limit to resistor value is 360mA/kΩ with a 450Ω offset.
If programmable current limit is not used, leave this pin
open; the internal current limit of the LT3081 is still active,
keeping the device inside safe operating limits. External
voltage drops between the current limit resistor and VOUT
will affect the current limit. Keep drops below 1mV.
IMON:Output Current Monitor. The IMON pin sources a
current typically equal to ILOAD/5000 or 200µA per amp of
output current. Terminating this pin with a resistor to GND
produces a voltage proportional to ILOAD. For example,
at ILOAD = 1.5A, IMON typically sources 300µA. With a
1k resistor to GND, this produces 300mV. The output
of the IMON pin is valid for voltages from VOUT + 0.4V to
VOUT – 40V. If unused, connect this pin to OUT.
SET:Set. This pin is the error amplifier’s noninverting
input and also sets the operating bias point of the circuit.
A fixed 50μA current source flows out of this pin. A single
external resistor programs VOUT. Output voltage range is
0V to 34.5V.
Exposed Pad/Tab:Output. The exposed pad of the DF and
FE packages and the tab of the R and T7 packages are tied
internally to OUT. As such, tie them directly to OUT (Pins
1-4/Pins 1-5, 8, 9, 16/Pin 4/Pin 4) at the PCB. The amount
of copper area and planes connected to OUT determine
the effective thermal resistance of the packages.
NC: No Connection. No connect pins have no connection
to internal circuitry and may be tied to IN, OUT, GND or
floated.