LINER LT3083EQ Adjustable 3a single resistor low dropout regulator Datasheet

LT3083
Adjustable 3A
Single Resistor Low
Dropout Regulator
DESCRIPTION
FEATURES
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Outputs May be Paralleled for Higher Current and
Heat Spreading
Output Current: 3A
Single Resistor Programs Output Voltage
50μA Set Pin Current: 1% Initial Accuracy
Output Adjustable to 0V
Low Output Noise: 40μVRMS (10Hz to 100kHz)
Wide Input Voltage Range: 1.2V to 23V
(DD-Pak and TO-220 Packages)
Low Dropout Voltage: 310mV
<1mV Load Regulation
<0.001%/V Line Regulation
Minimum Load Current: 1mA
Stable with Minimum 10μF Ceramic Capacitor
Current Limit with Foldback and Overtemperature
Protection
Available in 16-Lead TSSOP, 12-Lead 4mm × 4mm
DFN, 5-Lead TO-220 and 5-Lead Surface Mount
DD-PAK Packages
APPLICATIONS
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High Current All Surface Mount Supply
High Efﬁciency Linear Regulator
Post Regulator for Switching Supplies
Low Parts Count Variable Voltage Supply
Low Output Voltage Power Supplies
The LT®3083 is a 3A low dropout linear regulator that can
be paralleled to increase output current or spread heat on
surface mounted boards. Architected as a precision current
source and voltage follower, this new regulator ﬁnds use
in many applications requiring high current, adjustability
to zero, and no heat sink. The device also brings out the
collector of the pass transistor to allow low dropout operation—down to 310mV—when used with multiple supplies.
A key feature of the LT3083 is the capability to supply a
wide output voltage range. By using a reference current
through a single resistor, the output voltage is programmed
to any level between zero and 23V (DD-PAK and TO-220
packages). The LT3083 is stable with 10μF of capacitance
on the output, and the IC is stable with small ceramic capacitors that do not require additional ESR as is common
with other regulators.
Internal protection circuitry includes current limiting and
thermal limiting. The LT3083 is offered in the 16-lead
TSSOP (with an exposed pad for better thermal characteristics), 12-lead 4mm × 4mm DFN (also with an exposed
pad), 5-lead TO-220, and 5-lead surface mount DD-PAK
packages.
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.
TYPICAL APPLICATION
Set Pin Current Distribution
1.5V to 0.9V at 3A Supply (Using 3.3V VCONTROL)
N = 1052
VCONTROL
3.3V
4.7μF
VCONTROL
VIN
1.5V
IN
10μF
LT3083
VOUT = 0.9V
IMAX = 3A
OUT
10μF
SET
3083 TA01a
RSET
18.2k
1%
0.1μF
*RMIN
909Ω
*OPTIONAL FOR
MINIMUM 1mA LOAD
REQUIREMENT
49
49.5
50
50.5
SET PIN CURRENT DISTRIBUTION (μA)
51
3083 TA01b
3083f
1
LT3083
ABSOLUTE MAXIMUM RATINGS
(Note 1) All Voltages Relative to VOUT
CONTROL Pin Voltage.............................................±28V
IN Pin Voltage (T5, Q Packages) ....................18V, –0.3V
No Overload or Short-Circuit .....................23V, –0.3V
IN Pin Voltage (DF, FE Packages) .....................8V, –0.3V
No Overload or Short-Circuit .....................14V, –0.3V
SET Pin Current (Note 7) .....................................±25mA
SET Pin Voltage (Relative to OUT) .......................... ±10V
Output Short-Circuit Duration .......................... Indeﬁnite
Operating Junction Temperature Range (Notes 2, 10)
E-, I-grades ........................................ –40°C to 125°C
MP-grade ........................................... –55°C to 125°C
Storage Temperature Range .................. –65°C to 150°C
Lead Temperature (Soldering, 10 sec)
T, Q, FE Packages Only ..................................... 300°C
PIN CONFIGURATION
TOP VIEW
OUT
1
16 OUT
OUT
2
15 IN
OUT
3
14 IN
10 IN
OUT
4
9 IN
OUT
5
TOP VIEW
OUT
12 IN
1
11 IN
OUT
2
OUT
3
OUT
4
OUT
5
8 VCONTROL
OUT
6
11 VCONTROL
SET
6
7 VCONTROL
SET
7
10 VCONTROL
OUT
8
9
13
OUT
DF PACKAGE
12-LEAD (4mm s 4mm) PLASTIC DFN
17
OUT
13 IN
12 IN
OUT
FE PACKAGE
16-LEAD PLASTIC TSSOP
TJMAX = 125°C, θJA = 37°C/W, θJC = 8°C/W
EXPOSED PAD (PIN 13) IS OUT, MUST BE SOLDERED TO PCB
TJMAX = 125°C, θJA = 25°C/W, θJC = 8°C/W
EXPOSED PAD (PIN 17) IS OUT, MUST BE SOLDERED TO PCB
FRONT VIEW
TAB IS
OUT
FRONT VIEW
5
IN
5
IN
4
VCONTROL
4
VCONTROL
3
OUT
3
OUT
2
SET
2
SET
NC
1
NC
1
TAB IS
OUT
Q PACKAGE
5-LEAD PLASTIC DD-PAK
T PACKAGE
5-LEAD PLASTIC TO-220
TJMAX = 125°C, θJA = 15°C/W, θJC = 3°C/W
TJMAX = 125°C, θJA = 40°C/W, θJC = 3°C/W
ORDER INFORMATION
LEAD FREE FINISH
TAPE AND REEL
PART MARKING*
PACKAGE DESCRIPTION
TEMPERATURE RANGE
LT3083EDF#PBF
LT3083EDF#TRPBF
3083
12-Lead (4mm × 4mm) Plastic DFN
–40°C to 125°C
LT3083EFE#PBF
LT3083EFE#TRPBF
3083FE
16-Lead Plastic TSSOP
–40°C to 125°C
LT3083EQ#PBF
LT3083EQ#TRPBF
LT3083Q
5-Lead Plastic DD-PAK
–40°C to 125°C
LT3083ET#PBF
LT3083ET#TRPBF
LT3083T
5-Lead Plastic TO-220
–40°C to 125°C
LT3083IDF#PBF
LT3083IDF#TRPBF
3083
12-Lead (4mm × 4mm) Plastic DFN
–40°C to 125°C
LT3083IFE#PBF
LT3083IFE#TRPBF
3083FE
16-Lead Plastic TSSOP
–40°C to 125°C
3083f
2
LT3083
ORDER INFORMATION
LEAD FREE FINISH
TAPE AND REEL
PART MARKING*
PACKAGE DESCRIPTION
TEMPERATURE RANGE
LT3083IQ#PBF
LT3083IQ#TRPBF
LT3083Q
5-Lead Plastic DD-PAK
–40°C to 125°C
LT3083IT#PBF
LT3083IT#TRPBF
LT3083T
5-Lead Plastic TO-220
–40°C to 125°C
LT3083MPDF#PBF
LT3083MPDF#TRPBF
083MP
12-Lead (4mm × 4mm) Plastic DFN
–55°C to 125°C
LT3083MPFE#PBF
LT3083MPFE#TRPBF
3083MPFE
16-Lead Plastic TSSOP
–55°C to 125°C
LT3083MPQ#PBF
LT3083MPQ#TRPBF
LT3083MPQ
5-Lead Plastic DD-PAK
–55°C to 125°C
LT3083MPT#PBF
LT3083MPT#TRPBF
LT3083MPT
5-Lead Plastic TO-220
–55°C to 125°C
LEAD BASED FINISH
TAPE AND REEL
PART MARKING*
PACKAGE DESCRIPTION
TEMPERATURE RANGE
LT3083EDF
LT3083EDF#TR
3083
12-Lead (4mm × 4mm) Plastic DFN
–40°C to 125°C
LT3083EFE
LT3083EFE#TR
3083FE
16-Lead Plastic TSSOP
–40°C to 125°C
LT3083EQ
LT3083EQ#TR
LT3083Q
5-Lead Plastic DD-PAK
–40°C to 125°C
LT3083ET
LT3083ET#TR
LT3083T
5-Lead Plastic TO-220
–40°C to 125°C
LT3083IDF
LT3083IDF#TR
3083
12-Lead (4mm × 4mm) Plastic DFN
–40°C to 125°C
LT3083IFE
LT3083IFE#TR
3083FE
16-Lead Plastic TSSOP
–40°C to 125°C
LT3083IQ
LT3083IQ#TR
LT3083Q
5-Lead Plastic DD-PAK
–40°C to 125°C
LT3083IT
LT3083IT#TR
LT3083T
5-Lead Plastic TO-220
–40°C to 125°C
LT3083MPDF
LT3083MPDF#TR
083MP
12-Lead (4mm × 4mm) Plastic DFN
–55°C to 125°C
LT3083MPFE
LT3083MPFE#TR
3083MPFE
16-Lead Plastic TSSOP
–55°C to 125°C
LT3083MPQ
LT3083MPQ#TR
LT3083MPQ
5-Lead Plastic DD-PAK
–55°C to 125°C
LT3083MPT
LT3083MPT#TR
LT3083MPT
5-Lead Plastic TO-220
–55°C to 125°C
Consult LTC Marketing for parts speciﬁed with wider operating temperature ranges. *The temperature grade is identiﬁed by a label on the shipping container.
For more information on lead free part marking, go to: http://www.linear.com/leadfree/
For more information on tape and reel speciﬁcations, go to: http://www.linear.com/tapeandreel/
ELECTRICAL CHARACTERISTICS
The l denotes the speciﬁcations which apply over the full operating
temperature range, otherwise speciﬁcations are at TA = 25°C (Note 2).
PARAMETER
SET Pin Current
Output Offset Voltage (VOUT – VSET)
VIN = 1V, VCONTROL = 2V, ILOAD = 1mA
CONDITIONS
ISET
VIN = 1V, VCONTROL = 2V, ILOAD = 1mA, TJ = 25°C
VIN ≥ 1V, VCONTROL ≥ 2V, 5mA ≤ ILOAD ≤ 3A (Note 9)
VOS
DF, FE Packages
MIN
TYP
MAX
UNITS
l
49.5
49
50
50
50.5
51
μA
μA
l
–3
–4
0
0
3
4
mV
mV
l
–4
–6
0
0
4
6
mV
mV
T, Q Packages
Load Regulation (DF, FE Packages)
Load Regulation (T, Q Packages)
Line Regulation (DF, FE Packages)
Line Regulation (T, Q Packages)
Minimum Load Current (Notes 3, 9)
ΔISET
ΔVOS
ΔILOAD = 1mA to 3A
ΔILOAD = 5mA to 3A (Note 8)
l
–10
–0.4
–1
nA
mV
ΔISET
ΔVOS
ΔILOAD = 1mA to 3A
ΔILOAD = 5mA to 3A (Note 8)
l
–10
–0.7
–4
nA
mV
ΔISET
ΔVOS
ΔVIN = 1V to 14V, ΔVCONTROL = 2V to 25V, ILOAD = 1mA
ΔVIN = 1V to 14V, ΔVCONTROL = 2V to 25V, ILOAD = 1mA
0.1
0.002
0.01
nA/V
mV/V
ΔISET
ΔVOS
ΔVIN = 1V to 23V, ΔVCONTROL = 2V to 25V, ILOAD = 1mA
ΔVIN = 1V to 23V, ΔVCONTROL = 2V to 25V, ILOAD = 1mA
0.1
0.002
0.01
nA/V
mV/V
500
1
μA
mA
VIN = 1V, VCONTROL = 2V
VIN = 14V (DF/FE) or 23V (T/Q), VCONTROL = 25V
l
l
350
3083f
3
LT3083
ELECTRICAL CHARACTERISTICS
The l denotes the speciﬁcations which apply over the full operating
temperature range, otherwise speciﬁcations are at TA = 25°C (Note 2).
PARAMETER
CONDITIONS
VCONTROL Dropout Voltage (Note 4)
ILOAD = 100mA
ILOAD = 1A
ILOAD = 3A
TYP
MAX
UNITS
l
l
1.2
1.22
1.25
1.55
1.6
V
V
V
ILOAD = 100mA
l
10
25
mV
ILOAD = 1A, Q, T Packages
ILOAD = 1A, DF, FE Packages
l
l
120
90
190
160
mV
mV
ILOAD = 3A, Q, T Packages
ILOAD = 3A, DF, FE Packages
l
l
310
240
510
420
mV
mV
VCONTROL Pin Current (Note 5)
ILOAD = 100mA
ILOAD = 1A
ILOAD = 3A
l
l
l
5.5
18
40
10
35
80
mA
mA
mA
Current Limit
VIN = 5V, VCONTROL = 5V, VSET = 0V, VOUT = –0.1V
l
Error Ampliﬁer RMS Output Noise (Note 6)
ILOAD = 500mA, 10Hz ≤ f ≤ 100kHz, COUT = 10μF, CSET = 0.1μF
VIN Dropout Voltage (Note 4)
MIN
3
3.7
A
40
μVRMS
Reference Current RMS Output Noise (Note 6)
10Hz ≤ f ≤ 100kHz
1
nARMS
Ripple Rejection
VRIPPLE = 0.5VP-P, IL = 0.1A, CSET = 0.1μF,
COUT = 10μF
f = 120Hz
f = 10kHz
f = 1MHz
85
75
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 LT3083 is tested and speciﬁed under pulse load conditions such that
TJ ≅ TA. The LT3083E is 100% tested at TA = 25°C. Performance of the
LT3083E over the full –40°C to 125°C operating junction temperature
range is assured by design, characterization, and correlation with
statistical process controls. The LT3083I regulators are guaranteed
over the full –40°C to 125°C operating junction temperature range. The
LT3083MP is 100% tested and guaranteed over the –55°C to 125°C
operating junction temperature range.
Note 3: Minimum load current is equivalent to the quiescent current of
the part. Since all quiescent and drive current is delivered to the output
of the part, the minimum load current is the minimum current required to
maintain regulation.
Note 4: For the LT3083, 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.
0.003
%/W
Note 5: The VCONTROL pin current is the drive current required for the
output transistor. This current will track output current with roughly a 1:60
ratio. The minimum value is equal to the quiescent current of the device.
Note 6: Output noise is lowered by adding a small capacitor across the
voltage setting resistor. Adding this capacitor bypasses the voltage setting
resistor shot noise and reference current noise; output noise is then equal
to error ampliﬁer noise (see the Applications Information section).
Note 7: The SET pin is clamped to the output with diodes through 1k
resistors. These resistors and diodes will only carry current under
transient overloads.
Note 8: Load regulation is Kelvin sensed at the package.
Note 9: Current limit includes foldback protection circuitry. Current limit
decreases at higher input-to-output differential voltages.
Note 10: This IC includes overtemperature protection that is intended
to protect the device during momentary overload conditions. Junction
temperature will exceed the maximum operating junction temperature
when overtemperature protection is active. Overtemperature protection
(thermal limit) is typically active at junction temperatures of 165°C.
Continuous operation above the speciﬁed maximum operating junction
temperature may impair device reliability.
3083f
4
LT3083
TYPICAL PERFORMANCE CHARACTERISTICS
SET Pin Current
Set Pin Current Distribution
50.5
Offset Voltage (VOUT – VSET)
1.0
N = 1052
50.4
0.8
50.3
0.6
OFFSET VOLTAGE (mV)
SET PIN CURRENT (μA)
TA = 25°C, unless otherwise noted.
50.2
50.1
50.0
49.9
49.8
0.2
0
–0.2
–0.4
–0.6
49.6
–0.8
0
49.5
50
50.5
SET PIN CURRENT DISTRIBUTION (μA)
49
25 50 75 100 125 150
TEMPERATURE (°C)
–1.0
–50 –25
51
Offset Voltage Distribution
ILOAD = 5mA
0.75
0
0.50
–0.25
OFFSET VOLTAGE (mV)
OFFSET VOLTAGE (mV)
Offset Voltage (VOUT – VSET)
0.25
0.25
0
–0.25
–0.50
–0.75
–1
0
1
2
VOS DISTRIBUTION (mV)
–1.00
3
10
15
20
5
INPUT-TO-OUTPUT VOLTAGE (V)
0
–0.4
–0.6
50
0
CHANGE IN REFERENCE CURRENT
–50
–100
–0.8
–1.0
–150
–1.2
–200
–250
–1.4 ΔILOAD = 5mA TO 3A
VIN = VCONTROL = VOUT + 2V
–300
–1.6
–50 –25 0
25 50 75 100 125 150
TEMPERATURE (°C)
3083 G07
–1.00
–1.25
25
–1.75
0
0.5
1
1.5
2
LOAD CURRENT (A)
2.5
1.4
Dropout Voltage, T/Q Packages
(Minimum IN Voltage)
400
VIN = VCONTROL
1.2
1.0
VIN,CONTROL – VOUT = 23V
0.8
0.6
VIN, CONTROL – VOUT = 1.5V
0.4
0.2
0
–50 –25
0
3
3083 G06
Minimum Load Current
MINIMUM LOAD CURRENT (mA)
100
CHANGE IN REFERENCE CURRENT WITH LOAD (nA)
–0.2
–0.75
3083 G05
Load Regulation
CHANGE IN OFFSET VOLTAGE (VOUT – VSET)
TJ = 125°C
–1.50
3083 G04
0
TJ = 25°C
–0.50
MINIMUM VOLTAGE (VIN – VOUT) (mV)
–2
25 50 75 100 125 150
TEMPERATURE (°C)
3083 G03
Offset Voltage (VOUT – VSET)
1.00
N = 1052
–3
0
3083 G02
3083 G01
CHANGE IN OFFSET VOLTAGE WITH LOAD (mV)
0.4
49.7
49.5
–50 –25
ILOAD = 5mA
25 50 75 100 125 150
TEMPERATURE (°C)
3083 G08
350
TJ = 125°C
300
250
TJ = 25°C
200
TJ = –50°C
150
100
50
0
0
0.5
1
1.5
2
LOAD CURRENT (A)
2.5
3
3083 G09
3083f
5
LT3083
TYPICAL PERFORMANCE CHARACTERISTICS
Dropout Voltage, T/Q Packages
(Minimum IN Voltage)
Dropout Voltage, FE/DF Packages
Dropout Voltage, FE/DF Packages
(Minimum IN Voltage)
500
350
TJ = 125°C
300
250
TJ = 25°C
200
150
TJ = –50°C
100
50
0
0.5
1
1.5
2
LOAD CURRENT (A)
2.5
450
400
ILOAD = 3A
350
300
250
ILOAD = 1.5A
200
150
ILOAD = 500mA
100
3
50
ILOAD = 100mA
0
–50 –25
0
25 50 75 100 125 150
TEMPERATURE (°C)
3083 G10
350
ILOAD = 3A
300
250
ILOAD = 1.5A
200
150
100
ILOAD = 500mA
50
ILOAD = 100mA
0
–50 –25
0
25 50 75 100 125 150
TEMPERATURE (°C)
3083 G12
1.6
1.4
MINIMUM VCONTROL PIN VOLTAGE
(VCONTROL – VOUT) (V)
MINIMUM VCONTROL PIN VOLTAGE
(VCONTROL – VOUT) (V)
400
Dropout Voltage (Minimum
VCONTROL Pin Voltage)
1.6
TJ = –50°C
TJ = 25°C
1.2
1.0
TJ = 125°C
0.8
0.6
0.4
0.2
0
0.5
1
1.5
2
LOAD CURRENT (A)
2.5
1.4
ILOAD = 3A
1.2
1.0
0.8
0.6
0.4
0.2
0
–50 –25
3
0
25 50 75 100 125 150
TEMPERATURE (°C)
3083 G13
3083 G14
Current Limit
Current Limit
5.0
4.0
4.5
3.5
TJ = 25°C
4.0
3.0
3.5
CURRENT LIMIT (A)
CURRENT LIMIT (A)
450
3083 G11
Dropout Voltage (Minimum
VCONTROL Pin Voltage)
0
MINIMUM IN VOLTAGE (VIN – VOUT) (mV)
500
MINIMUM IN VOLTAGE (VIN – VOUT) (mV)
MINIMUM VOLTAGE (VIN – VOUT) (mV)
400
0
TA = 25°C, unless otherwise noted.
3.0
2.5
2.0
1.5
2.5
2.0
1.5
1.0
1.0
0.5 VIN = VCONTROL = 7V
VOUT = 0V
0
–50 –25 0
25 50 75 100 125 150
TEMPERATURE (°C)
3083 G15
0.5
0
0
5
10
15
20
IN-TO-OUT DIFFERENTIAL (VIN – VOUT) (V)
3083 G16
3083f
6
LT3083
TYPICAL PERFORMANCE CHARACTERISTICS
150
VIN = 2V
100 VCONTROL = 3V
VOUT = 1V
50 CSET = 0.1μF
COUT = 22μF CERAMIC
0
–50
LOAD CURRENT (A)
Load Transient Response
250
LOAD CURRENT (A) OUTPUT VOLTAGE
DEVIATION (mV)
OUTPUT VOLTAGE
DEVIATION (mV)
Load Transient Response
COUT = 10μF CERAMIC
–100
1.0
0.5
0
ΔILOAD = 100mA TO 1A
0
TA = 25°C, unless otherwise noted.
VIN = 2V
VCONTROL = 3V
VOUT = 1V
CSET = 0.1μF
150
50
COUT = 22μF CERAMIC
–50
–150
4
2
ΔILOAD = 500mA TO 3A
0
0
20 40 60 80 100 120 140 160 180 200
TIME (μs)
20 40 60 80 100 120 140 160 180 200
TIME (μs)
3083 G18
3083 G17
Line Transient Response
Turn-On Response
2
3
1
10
0
0
–10
–20
IN/ VCONTROL
VOLTAGE (V)
3
RSET = 20k
CSET = 0
RLOAD = 0.33Ω
COUT = 10μF CERAMIC
0.5
0
20 40 60 80 100 120 140 160 180 200
TIME (μs)
0
5
70
70
60
50
40
ILOAD = 3A
30
DEVICE IN
CURRENT LIMIT
ILOAD = 1.5A
0
VCONTROL PIN CURRENT (mA)
VCONTROL PIN CURRENT (mA)
80
0
–0.5
0
3083 G22
4
6
8 10 12 14 16 18 20
TIME (ms)
Residual Output Voltage with
Less Than Minimum Load
600
VCONTROL – VOUT = 2V
VIN – VOUT = 1V
VIN = 20V
500
50
TJ = –50°C
40
30
TJ = 25°C
20
TJ = 125°C
0
VIN = 10V
400
VIN = 5V
300
ADD 1N4148 FOR
RTEST < 1k
SET PIN = 0V
VIN
VOUT
200
RTEST
100
10
2
4
6
8 10 12 14 16 18
IN-TO-OUT DIFFERENTIAL (VIN – VOUT) (V)
2
3083 G21
VCONTROL Pin Current
60
RSET = 20k
CSET = 0.1μF
RLOAD = 1Ω
COUT = 10μF CERAMIC
0
3083 G20
VCONTROL Pin Current
10
0.5
10 15 20 25 30 35 40 45 50
TIME (μs)
3083 G19
20
1
1.0
1.0
–0.5
0
2
0
OUTPUT
VOLTAGE (V)
4
3
4
OUTPUT VOLTAGE (mV)
5
4
5
IN/ VCONTROL
VOLTAGE (V)
VOUT = 1V
ILOAD = 10mA
COUT = 10μF CERAMIC
CSET = 0.1μF
6
Turn-On Response
6
OUTPUT
VOLTAGE (V)
OUTPUT VOLTAGE
DEVIATION (mV)
IN/ VCONTROL
VOLTAGE (V)
7
0
0.5
1
1.5
2
LOAD CURRENT (A)
2.5
3
3083 G23
0
0
500
1000
RSET (Ω)
1500
2000
3083 G24
3083f
7
LT3083
TYPICAL PERFORMANCE CHARACTERISTICS
Ripple Rejection, Dual Supply,
VCONTROL Pin
Ripple Rejection, Single Supply
ILOAD = 0.1A
RIPPLE REJECTION (dB)
RIPPLE REJECTION (dB)
80
70
60
50
ILOAD = 1.5A
ILOAD = 0.5A
40
30
COUT = 10μF CERAMIC
20 CSET = 0.1μF CERAMIC
10 RIPPLE = 50mVP-P
VIN – VCONTROL = VOUT(NOMINAL) + 2V
0
10
100
1k
10k 100k
1M
FREQUENCY (Hz)
Ripple Rejection, Dual Supply,
IN Pin
120
120
105
105
ILOAD = 0.1A
90
RIPPLE REJECTION (dB)
100
90
TA = 25°C, unless otherwise noted.
75
60 I
LOAD = 1.5A
45
30
15
10M
0
COUT = 10μF CERAMIC
CSET = 0.1μF
VIN = VOUT(NOMINAL) + 1V
VCONTROL = VOUT(NOMINAL) + 2V
10
100
1M
75
60
3083 G25
ILOAD = 1.5A
45
30
0
10M
ILOAD = 0.5A
90
15
1k
10k 100k
FREQUENCY (Hz)
ILOAD = 0.1A
COUT = 10μF CERAMIC
CSET = 0.1μF
VIN = VOUT(NOMINAL) + 1V
VCONTROL = VOUT(NOMINAL) + 2V
10
100
1k
10k 100k
FREQUENCY (Hz)
3083 G26
Ripple Rejection (120Hz)
1M
10M
3083 G27
Noise Spectral Density
80
1000
100
100
10
RIPPLE REJECTOIN (dB)
78
77
76
75
74
73
72
71
VIN = VCONTROL = VOUT(NOMINAL) + 2V
RIPPLE = 500mVP-P, ƒ = 120Hz
ILOAD = 0.5A
CSET = 0.1μF, COUT = 10μF
70
–50 –25
0
10
25 50 75 100 125 150
TEMPERATURE (°C)
10
100
1
100k
1k
10k
FREQUENCY (Hz)
3083 G28
3083 G29
Output Voltage Noise
Error Ampliﬁer Gain and Phase
21
36
18
0
GAIN (dB)
15
VOUT
100μV/DIV
PHASE
–36
12
–72
9
–108
6
–144
3
–180
0
–3
–216
GAIN
–252
–6
–288
ILOAD = 0.5A
ILOAD = 1.5A
ILOAD = 3A
–9
–12
TIME 1ms/DIV
VOUT = 1V, RSET = 20k
CSET = 0.1μF, COUT = 10μF
ILOAD = 3A
REFERENCE CURRENT NOISE
SPECTRAL DENSITY (pA/√Hz)
ERROR AMPLIFIER NOISE
SPECTRAL DENSITY (nV/√Hz)
79
3083 G30
–15
10
100
1k
10k
FREQUENCY (Hz)
–324
–360
100k
–396
1M
3083 G31
3083f
8
LT3083
PIN FUNCTIONS
(DF/FE/Q/T Packages)
OUT (Pins 1-5,13/Pins 1-6,8,9,16,17/ Pin 3, Tab/Pin 3,
Tab): Output. The exposed pad of the DF package (Pin 13)
and the FE package (Pin 17) and the Tab of the DD-PAK
and TO-220 packages is an electrical connection to OUT.
Connect the exposed pad of the DF and FE packages and
the Tab of the DD-PAK package directly to OUT on the
PCB and the respective OUT pins for each package. There
must be a minimum load current of 1mA or the output
may not regulate.
VCONTROL (Pins 7,8/Pins 10,11/Pin 4/Pin 4): Bias Supply. This is the supply pin for the control circuitry of the
device. Minimum input capacitance is 2.2μF (see Input
Capacitance and Stability in the Applications Information
section). 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 1.4V greater than the output
voltage (see dropout speciﬁcations in the Electrical Characteristics section).
SET (Pin 6/Pin 7/Pin 2/Pin 2): Set Point. This pin is the
non-inverting input to the error ampliﬁer and the regulation set point. A ﬁxed current of 50μA 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 VIN(MAX) – VDROPOUT. Transient performance
can be improved by adding a small capacitor from the
SET pin to ground.
IN (Pins 9-12/Pins 12-15/Pin 5/Pin 5): Power Input. This
is the collector to the power device of the LT3083. The
output load current is supplied through this pin. Minimum
IN capacitance is 10μF (see Input Capacitance and Stability in Applications Information section). 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 in the Electrical Characteristics section).
NC (NA/NA/Pin 1/Pin 1): No Connection. No Connect pins
have no connection to internal circuitry and may be tied
to VIN, VCONTROL, VOUT, GND, or ﬂoated.
3083f
9
LT3083
BLOCK DIAGRAM
IN
VCONTROL
50μA
+
–
3083 BD
SET
OUT
3083f
10
LT3083
APPLICATIONS INFORMATION
The LT3083 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 with hysteresis.
The LT3083 ﬁts well in applications needing multiple rails.
This 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. When the input is pre-regulated,
such as with a 5V or 3.3V input supply, external resistors
can help spread the heat.
A precision “0” TC 50μA reference current source connects
to the noninverting input of a power operational ampliﬁer.
The power operational ampliﬁer provides a low impedance
buffered output to the voltage on the noninverting input.
A single resistor from the noninverting input to ground
sets the output voltage. If this resistor is set to 0Ω, zero
output voltage results. Therefore, any output voltage can
be obtained between zero and the maximum deﬁned by
the input power supply.
The beneﬁt of using a true internal current source as the
reference, as opposed to a bootstrapped reference in older
regulators, is not so obvious in this architecture. A true
reference current source allows the regulator to have gain
and frequency response independent of the impedance on
the positive input. On older adjustable regulators, such as
the LT1086, loop gain changes with output voltage and
bandwidth changes if the adjustment pin is bypassed to
ground. For the LT3083, the loop gain is unchanged with
output voltage changes or bypassing. Output regulation
is not a ﬁxed percentage of output voltage, but is a ﬁxed
fraction of millivolts. Use of a true current source allows
all of 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 LT3083 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 typically only 310mV,
two supplies can be used to power the LT3083 to reduce
dissipation: a higher voltage supply for the control circuitry
and a lower voltage supply for the collector. This increases
efﬁciency and reduces dissipation. To further spread the
heat, a resistor inserted in series with the collector moves
some of the heat out of the IC to spread it on the PC board
(see the section Reducing Power Dissipation).
The LT3083 can be operated in two modes. Three terminal mode has the VCONTROL pin connected to the IN pin
and gives a limitation of 1.25V dropout. Alternatively, the
VCONTROL pin is separately tied to a higher voltage and the
IN pin to a lower voltage giving 310mV dropout on the IN
pin, minimizing total power dissipation. This allows for a
3A supply regulating from 2.5VIN to 1.8VOUT or 1.8VIN to
1.2VOUT with low power dissipation.
Programming Output Voltage
The LT3083 sources a 50μA 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 equals 50μA multiplied by the value of
the SET pin resistor. Any voltage can be generated and
there is no minimum output voltage for the regulator.
LT3083
IN
VCONTROL
50μA
+
+
–
+
VIN
VCONTROL
OUT
VOUT
SET
COUT
RSET
CSET
3083 F01
VOUT = 50μA • RSET
Figure 1. Basic Adjustable Regulator
3083f
11
LT3083
APPLICATIONS INFORMATION
Table 1 lists many common output voltages and the closest standard 1% resistor values used to generate that
output voltage.
OUT
Regulation of the output voltage requires a minimum
load current of 1mA. For a true zero voltage output
operation, return this 1mA load current to a negative
supply voltage.
Table 1. 1% Resistors for Common Output Voltages
VOUT (V)
RSET (k)
1
20
1.2
24.3
1.5
30.1
1.8
35.7
2.5
49.9
3.3
66.5
5
100
With the lower level current used to generate the reference voltage, leakage paths to or from the SET pin can
create errors in the reference and output voltages. High
quality insulation should be used (e.g., Teﬂon, Kel-F);
cleaning of all insulating surfaces to remove ﬂuxes and
other residues will probably be required. Surface coating
may be necessary to provide a moisture barrier in high
humidity environments.
Minimize board leakage by encircling the SET pin and
circuitry with a guard ring operated at a potential close
to itself. Tie the guard ring to the OUT pin. Guard rings
on both sides of the circuit board are required. Bulk leakage reduction depends on the guard ring width. 50nA
of leakage into or out of the SET pin and its associated
circuitry creates a 0.1% reference voltage error. 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.
Figure 2 depicts an example of a guard ring layout.
If guard ring 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
GND
SET PIN
3083 F02
Figure 2. Guard Ring Layout Example
for DF Package
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 Input Capacitance
Typical minimum input capacitance is 10μF for IN and
2.2μF for VCONTROL. These amounts of capacitance work
well using low ESR ceramic capacitors when placed close
to the LT3083 and the circuit is located in close proximity
to the power source. Higher values of input capacitance
may be necessary to maintain stability depending on the
application.
Oscillating regulator circuits are often viewed as a problem
of phase margin and inadequate stability with the output
capacitor used. More and more frequently, the problem
is not the regulator operating without sufﬁcient output
capacitance, but instead with too little input capacitance.
The entire circuit must be analyzed and debugged as a
whole; conditions relating to the input of the regulator
cannot be ignored.
The LT3083 input presents a high impedance to its power
source: the output voltage and load current are independent
of input voltage variations. To maintain stability of the
regulator circuit as a whole, the LT3083 must be powered
from a low impedance supply. When using short supply
lines or powering directly from a large switching supply,
there is no issue—hundreds or thousands of microfarads
of capacitance are available through a low impedance.
3083f
12
LT3083
APPLICATIONS INFORMATION
When longer supply lines, ﬁlters, current sense resistors,
or other impedances exist between the supply and the
input to the LT3083, input bypassing should be reviewed
if stability concerns are seen. Just as output capacitance
supplies the instantaneous changes in load current for
output transients until the regulator is able to respond,
input capacitance supplies local power to the regulator until
the main supply responds. When impedance separates the
LT3083 from its main supply, the local input can droop
so that the output follows. The entire circuit may break
into oscillations, usually characterized by larger amplitude
oscillations on the input and coupling to the output.
Low ESR, ceramic input bypass capacitors are acceptable
for applications without long input leads. However, applications connecting a power supply to an LT3083 circuit’s IN
and GND pins with long input wires combined with low
ESR, ceramic input capacitors are prone to voltage spikes,
reliability concerns and application-speciﬁc board oscillations. The input wire inductance found in many battery
powered applications, combined with the low ESR ceramic
input capacitor, forms a high-Q LC resonant tank circuit. In
some instances this resonant frequency beats against the
output current dependent LDO bandwidth and interferes
with proper operation. Simple circuit modiﬁcations/solutions are then required. This behavior is not indicative of
LT3083 instability, but is a common ceramic input bypass
capacitor application issue.
The self-inductance, or isolated inductance, of a wire is
directly proportional to its length. Wire diameter is not a
major factor on its self-inductance. For example, the selfinductance of a 2-AWG isolated wire (diameter = 0.26") is
about half the self-inductance of a 30-AWG wire (diameter
= 0.01"). One foot of 30-AWG wire has about 465nH of
self-inductance.
One of two ways reduces a wire’s self-inductance. One
method divides the current ﬂowing towards the LT3083
between two parallel conductors. In this case, the farther
apart the wires are from each other, the more the self-inductance is reduced; up to a 50% reduction when placed
a few inches apart. Splitting the wires basically connects
two equal inductors in parallel, but placing them in close
proximity gives the wires mutual inductance adding to
the self-inductance. The second and most effective way
to reduce overall inductance is to place both forward and
return current conductors (the input and GND wires) in
very close proximity. Two 30-AWG wires separated by only
0.02", used as forward- and return- current conductors,
reduce the overall self-inductance to approximately oneﬁfth that of a single isolated wire.
If wiring modiﬁcations are not permissible for the applications, including series resistance between the power supply
and the input of the LT3083 also stabilizes the application.
As little as 0.1Ω to 0.5Ω, often less, is effective in damping
the LC resonance. If the added impedance between the
power supply and the input is unacceptable, adding ESR to
the input capacitor also provides the necessary damping of
the LC resonance. However, the required ESR is generally
higher than the series impedance required.
Stability and Output Capacitance
The LT3083 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 10μF 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 LT3083, 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.
Give extra consideration 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 3 and 4. When used with
a 5V regulator, a 16V 10μF Y5V capacitor can exhibit an
3083f
13
LT3083
APPLICATIONS INFORMATION
20
effective value as low as 1μF to 2μF for the DC bias voltage
applied and over the operating temperature range. The X5R
and X7R dielectrics result in more stable characteristics
and are more suitable for use as the output capacitor.
The X7R type has better stability across temperature,
while the X5R is less expensive and is available in higher
values. Care still must be exercised when using X5R and
X7R capacitors. The X5R and X7R codes only specify
operating temperature range and maximum capacitance
change over temperature. Capacitance change due to DC
bias with X5R and X7R capacitors is better than Y5V and
Z5U capacitors, but can still be signiﬁcant enough 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.
BOTH CAPACITORS ARE 16V,
1210 CASE SIZE, 10μF
0
CHANGE IN VALUE (%)
X5R
–20
–40
–60
Y5V
–80
–100
0
2
4
8
6
10 12
DC BIAS VOLTAGE (V)
14
16
3083 F03
Figure 3. Ceramic Capacitor DC Bias Characteristics
40
CHANGE IN VALUE (%)
20
X5R
0
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. In a
ceramic capacitor, the stress can be induced by vibrations
in the system or thermal transients.
–20
–40
Y5V
–60
–80
BOTH CAPACITORS ARE 16V,
1210 CASE SIZE, 10μF
–100
–50 –25
50
25
75
0
TEMPERATURE (°C)
100
125
Paralleling Devices
3083 F04
Figure 4. Ceramic Capacitor Temperature Characteristics
VIN
LT3083
VCONTROL
+
–
OUT 10mΩ
Table 2. PC Board Trace Resistance
SET
VIN
4.8V
TO 20V
VIN
Higher output current is obtained by paralleling multiple
LT3083s together. Tie the individual SET pins together and
tie the individual IN pins together. Connect the outputs in
common using small pieces of PC trace as ballast resistors
to promote equal current sharing. PC trace resistance in
mΩ/inch is shown in Table 2. Ballasting requires only a
tiny area on the PCB.
LT3083
VCONTROL
WEIGHT (oz)
10mil WIDTH
20mil WIDTH
1
54.3
27.1
2
27.1
13.6
Trace resistance is measured in mΩ/in
+
–
10μF
OUT 10mΩ
SET
VOUT
3.3V
6A
10μF
33k
3083 F05
Figure 5. Parallel Devices
The worst-case room temperature offset, only ±4mV
(DD-PAK, T Packages) between the SET pin and the OUT
pin, allows the use of very small ballast resistors.
As shown in Figure 5, each LT3083 has a small 10mΩ
ballast resistor, which at full output current gives better
than 80% equalized sharing of the current. The external
3083f
14
LT3083
APPLICATIONS INFORMATION
resistance of 10mΩ (5mΩ for the two devices in parallel) only adds about 30mV of output regulation drop at
an output of 6A. With an output voltage of 3.3V, this only
adds 1% to the regulation. Of course, paralleling more
than two LT3083s yields even higher output current.
Spreading the devices on the PC board also spreads the
heat. Series input resistors can further spread the heat if
the input-to-output difference is high.
Quieting the Noise
The LT3083 offers numerous noise performance advantages. Every linear regulator has its sources of noise. In
general, a linear regulator’s critical noise source is the
reference. In addition, consider the error ampliﬁer’s noise
contribution along with the resistor divider’s noise gain.
Many traditional low noise regulators bond out the voltage
reference to an external pin (usually through a large value
resistor) to allow for bypassing and noise reduction. The
LT3083 does not use a traditional voltage reference like
other linear regulators. Instead, it uses a 50μA reference
current. The 50μA current source generates noise current
levels of 3.16pA/√Hz (1nARMS) over the 10Hz to 100kHz
bandwidth). The equivalent voltage noise equals the RMS
noise current multiplied by the resistor value.
The SET pin resistor generates spot noise equal to √4kTR
(k = Boltzmann’s constant, 1.38 • 10–23J/°K, and T is absolute temperature) which is RMS summed with the voltage
noise. If the application requires lower noise performance,
bypass the voltage setting resistor with a capacitor to GND.
Note that this noise-reduction capacitor increases start-up
time as a factor of the RC time constant.
The LT3083 uses a unity-gain follower from the SET pin
to the OUT pin. Therefore, multiple possibilities exist
(besides a SET pin resistor) to set output voltage. For
example, using a high accuracy voltage reference from
SET to GND removes the errors in output voltage due to
reference current tolerance and resistor tolerance. Active
driving of the SET pin is acceptable.
The typical noise scenario for a linear regulator is that the
output voltage setting resistor divider gains up the noise
reference, especially if VOUT is much greater than VREF.
The LT3083’s noise advantage is that the unity gain follower
presents no noise gain whatsoever from the SET pin to the
output. Thus, noise ﬁgures do not increase accordingly.
Error ampliﬁer noise is typically 126.5nV/√Hz (40μVRMS)
over the 10Hz to 100kHz bandwidth). The error ampliﬁer’s
noise is RMS summed with the other noise terms to give
a ﬁnal noise ﬁgure for the regulator.
Curves in the Typical Performance Characteristics section show noise spectral density and peak-to-peak noise
characteristics for both the reference current and error
ampliﬁer over the 10Hz to 100kHz bandwidth.
Load Regulation
The LT3083 is a ﬂoating device. No ground pin exists on
the packages. Thus, the IC delivers all quiescent current
and drive current to the load. Therefore, it is not possible
to provide true remote load sensing. The connection resistance between the regulator and the load determines load
regulation performance. The data sheet’s load regulation
speciﬁcation is Kelvin sensed at the package’s pins. Negative-side sensing is a true Kelvin connection by returning
the bottom of the voltage setting resistor to the negative
side of the load (see Figure 6).
Connected as shown, system load regulation is the sum
of the LT3083’s load regulation and the parasitic line
resistance multiplied by the output current. To minimize
load regulation, keep the positive connection between the
regulator and load as short as possible. If possible, use
large diameter wire or wide PC board traces.
IN
LT3083
VCONTROL
PARASITIC
RESISTANCE
+
–
OUT
SET RSET
RP
RP
LOAD
RP
3080 F06
Figure 6. Connections for Best Load Regulation
3083f
15
LT3083
APPLICATIONS INFORMATION
Thermal Considerations
Table 4. FE Package, 16-Lead TSSOP
The LT3083’s internal power and thermal limiting circuitry
protects itself under overload conditions. For continuous
normal load conditions, do not exceed the 125°C maximum
junction temperature. Carefully consider all sources of
thermal resistance from junction-to-ambient. This includes
(but is not limited to) junction-to-case, case-to-heat sink
interface, heat sink resistance or circuit board-to-ambient
as the application dictates. Consider all additional, adjacent
heat generating sources in proximity on the PCB.
Surface mount packages provide the necessary heat
sinking by using the heat spreading capabilities of the
PC board, copper traces, and planes. Surface mount heat
sinks, plated through-holes and solder-ﬁlled vias can also
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, or the bottom
of the pin most directly in the heat path. This is the lowest
thermal resistance path for heat ﬂow. Only proper device
mounting ensures the best possible thermal ﬂow from this
area of the packages to the heat sinking material.
Note that the exposed pad of the DFN and TSSOP packages and the tab of the DD-PAK and TO-220 packages
are electrically connected to the output (VOUT).
Tables 3 through 5 list thermal resistance as a function
of copper areas on a ﬁxed board size. All measurements
were taken in still air on a 4-layer FR-4 board with 1oz
solid internal planes and 2oz external trace planes with a
total ﬁnished board thickness of 1.6mm. Layers are not
connected electrically or thermally.
Table 3. DF Package, 12-Lead DFN
COPPER AREA
THERMAL RESISTANCE
BOARD AREA (JUNCTION-TO-AMBIENT)
TOPSIDE*
BACKSIDE
2500mm2
2500mm2
2500mm2
18°C/W
1000mm2
2500mm2
2500mm2
22°C/W
225mm2
2500mm2
2500mm2
29°C/W
100mm2
2500mm2
2500mm2
35°C/W
COPPER AREA
THERMAL RESISTANCE
BOARD AREA (JUNCTION-TO-AMBIENT)
TOPSIDE*
BACKSIDE
2500mm2
2500mm2
2500mm2
16°C/W
1000mm2
2500mm2
2500mm2
20°C/W
225mm2
2500mm2
2500mm2
26°C/W
100mm2
2500mm2
2500mm2
32°C/W
*Device is mounted on topside.
Table 5. Q Package, 5-Lead DD-PAK
COPPER AREA
THERMAL RESISTANCE
BOARD AREA (JUNCTION-TO-AMBIENT)
TOPSIDE*
BACKSIDE
2500mm2
2500mm2
2500mm2
13°C/W
1000mm2
2500mm2
2500mm2
14°C/W
125mm2
2500mm2
2500mm2
16°C/W
*Device is mounted on topside.
T Package, 5-Lead TO-220
Thermal Resistance (Junction-to-Case) = 3°C/W
For further information on thermal resistance and using
thermal information, refer to JEDEC standard JESD51,
notably JESD51-12.
PCB layers, copper weight, board layout and thermal vias
affect the resultant thermal resistance. Tables 3 through 5
provide thermal resistance numbers for best-case 4-layer
boards with 1oz internal and 2oz external copper. Modern,
multilayer PCBs may not be able to achieve quite the same
level performance as found in these tables.
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 10mA to 3A and a maximum ambient
temperature of 50°C, what will the maximum junction
temperature be for the DD-PAK on a 2500mm2 board with
topside copper of 1000mm2?
*Device is mounted on topside.
3083f
16
LT3083
APPLICATIONS INFORMATION
The power in the drive circuit equals:
PDRIVE = (VCONTROL – VOUT)(ICONTROL)
where ICONTROL is equal to IOUT/60. ICONTROL is a function
of output current. A curve of ICONTROL vs IOUT can be found
in the Typical Performance Characteristics curves.
The total power equals:
PTOTAL = PDRIVE + POUTPUT
The current delivered to the SET pin is negligible and can
be ignored.
VCONTROL(MAX_CONTINUOUS) = 3.630V (3.3V + 10%)
VIN(MAX_CONTINUOUS) = 1.575V (1.5V + 5%)
VOUT = 0.9V, IOUT = 3A, TA = 50°C
Power dissipation under these conditions is equal to:
PDRIVE = (VCONTROL – VOUT)(ICONTROL)
ICONTROL =
IOUT 3A
=
= 50mA
60 60
PDRIVE = (3.630V – 0.9V)(50mA) = 137mW
POUTPUT = (VIN – VOUT)(IOUT)
As an example, assume: VIN = VCONTROL = 5V, VOUT = 3.3V
and IOUT(MAX) = 2A. Use the formulas from the Calculating
Junction Temperature section previously discussed.
Without series resistor RS, power dissipation in the LT3083
equals:
⎛ 2A ⎞
PTOTAL = (5V − 3.3V ) • ⎜ ⎟ + (5V − 3.3V ) • 2A
⎝ 60 ⎠
= 3.46W
If the voltage differential (VDIFF) across the NPN pass
transistor is chosen as 0.5V, then RS equals:
RS =
5V − 3.3V − 0.5V
= 0.6Ω
2A
Power dissipation in the LT3083 now equals:
⎛ 2A ⎞
PTOTAL = (5V − 3.3V ) • ⎜ ⎟ + 0.5V • 2A = 1.06W
⎝ 60 ⎠
The LT3083’s power dissipation is now only 30% compared
to no series resistor. RS dissipates 2.4W of power. Choose
appropriate wattage resistors or use multiple resistors in
parallel to handle and dissipate the power properly.
POUTPUT = (1.575V – 0.9V)(3A) = 2.03W
Total Power Dissipation = 2.16W
VIN
C1
VCONTROL
RS
LT3083
IN
VINa
Junction Temperature will be equal to:
TJ = TA + PTOTAL • θJA (using tables)
+
–
TJ = 50°C + 2.16W • 16°C/W = 84.6°C
In this case, the junction temperature is below the maximum rating, ensuring reliable operation.
OUT
SET
3083 F07
VOUT
C2
RSET
Reducing Power Dissipation
In some applications it may be necessary to reduce the
power dissipation in the LT3083 package without sacriﬁcing output current capability. Two techniques are available.
The ﬁrst technique, illustrated in Figure 7, employs a
resistor in series with the regulator’s input. The voltage
drop across RS decreases the LT3083’s input-to-output
differential voltage and correspondingly decreases the
LT3083’s power dissipation.
Figure 7. Reducing Power Dissipation Using a Series Resistor
3083f
17
LT3083
APPLICATIONS INFORMATION
The second technique for reducing power dissipation,
shown in Figure 8, uses a resistor in parallel with the
LT3083. This resistor provides a parallel path for current
ﬂow, reducing the current ﬂowing through the LT3083.
This technique works well if input voltage is reasonably
constant and output load current changes are small. This
technique also increases the maximum available output
current at the expense of minimum load requirements.
As an example, assume: VIN = VCONTROL = 5V, VIN(MAX) =
5.5V, VOUT = 3.3V, VOUT(MIN) = 3.2V, IOUT(MAX) = 2A and
IOUT(MIN) = 0.7A. Also, assuming that RP carries no more
than 90% of IOUT(MIN) = 630mA.
Calculating RP yields:
5.5V − 3.2V
= 3.65Ω
0.63A
(5% Standard Value = 3.6Ω)
RP =
VIN
C1
VCONTROL
LT3083
The maximum total power dissipation is (5.5V – 3.2V) •
2A = 4.6W. However, the LT3083 supplies only:
IN
+
–
OUT
SET
2A −
RP
3083 F08
VOUT
C2
RSET
Figure 8. Reducing Power Dissipation Using a Parallel Resistor
5.5V − 3.2V
= 1.36A
3.6Ω
Therefore, the LT3083’s power dissipation is only:
PDISS = (5.5V – 3.2V) • 1.36A = 3.13W
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
LT3083 supplies only 1.36A. Therefore, load current can
increase by 1.64A to a total output current of 3.64A while
keeping the LT3083 in its normal operating range.
3083f
18
LT3083
TYPICAL APPLICATIONS
Adding Shutdown
LT3083
IN
VIN
Current Source
LT3083
IN
VIN
10V
VCONTROL
VCONTROL
+
–
+
–
10μF
OUT
OUT 0.33Ω
VOUT
SET
ON OFF
Q1
VN2222LL
SET
10μF
Q2*
VN2222LL
R1
SHUTDOWN
IOUT
0A TO 3A
20k
3083 TA03
3083 TA02
*Q2 INSURES ZERO OUTPUT
IN THE ABSENCE OF ANY
OUTPUT LOAD.
Low Dropout Voltage LED Driver
VIN
C1
VCONTROL
1A
D1
LT3083
IN
+
–
OUT
SET
R1
20k
R2
1Ω
3083 TA04
DAC-Controlled Regulator
LT3083
IN
VIN
VCONTROL
+
–
150k
SPI
LTC2641
150k
OUT
450k
SET
–
+
VOUT
10μF
3083 TA05
LT1991
GAIN = 4
3083f
19
LT3083
TYPICAL APPLICATIONS
Coincident Tracking
LT3083
IN
VCONTROL
LT3083
IN
+
–
VCONTROL
VIN
7V TO 20V
OUT
LT3083
IN
+
–
VCONTROL
SET
34k
OUT
+
–
C1
10μF
SET
R2
16.2k
OUT
SET
R1
49.9k
VOUT3
5V
10μF
3083 TA06
VOUT2
3.3V
C3
10μF
VOUT1
2.5V
C2
10μF
Adding Soft-Start
LT3083
IN
VIN
4.8V to 20V
VCONTROL
+
–
D1
1N4148
C1
10μF
OUT
SET
C2
0.01μF
VOUT
3.3V
3A
COUT
10μF
R1
66.5k
3083 TA07
Lab Supply
LT3083
IN
VIN
12V TO 18V
LT3083
IN
VCONTROL
VCONTROL
+
–
+
15μF
+
–
OUT 0.33Ω
OUT
+
SET
20k
0A TO 3A
+
SET
15μF
R4
200k
VOUT
0V TO 10V
10μF
100μF
3083 TA08
3083f
20
LT3083
TYPICAL APPLICATIONS
High Voltage Regulator
6.1V
10k
VIN
50V
1N4148
IN
LT3083
BUZ11
VCONTROL
+
+
–
10μF
VOUT
3A
OUT
SET
RSET
402k
+
15μF
VOUT = 20V
VOUT = 50μA • RSET
10μF
3083 TA09
Ramp Generator
LT3083
IN
VIN
5V
Reference Buffer
VCONTROL
VCONTROL
+
–
10μF
+
–
OUT
10μF
VN2222LL
10nF
OUT
VOUT
SET
VN2222LL
LT3083
IN
VIN
INPUT
LT1019
OUTPUT
SET
C1
1μF
GND
VOUT*
C2
10μF
3083 TA11
*MIN LOAD 0.5mA
3083 TA10
Boosting Fixed Output Regulators
LT3083
IN
VCONTROL
+
–
OUT
10mΩ
SET
20mΩ
5V
3.3VOUT
4.5A
LT1963-3.3
10μF
42Ω*
47μF
3083 TA12
33k
*4mV DROP ENSURES LT3083 IS
OFF WITH NO LOAD
MULTIPLE LT3083’S CAN BE USED
3083f
21
LT3083
TYPICAL APPLICATIONS
Low Voltage, High Current Adjustable High Efﬁciency Regulator*
0.47μH
PVIN
2.7V TO 5.5V†
2×
100μF
ITH
SVIN
+
2.2MEG
100k
10k
SW
LTC3610
+
12.1k
RT
470pF
294k
PGOOD
2×
100μF
2N3906
LT3083
IN
VCONTROL
RUN/SS
+
–
VFB
1000pF
OUT
78.7k
SGND
PGND
10mΩ
SET
SYNC/MODE
124k
LT3083
IN
VCONTROL
+
–
*DIFFERENTIAL VOLTAGE ON LT3083
IS 0.6V SET BY THE VBE OF THE 2N3906 PNP.
OUT
†MAXIMUM OUTPUT VOLTAGE IS 1.5V
BELOW INPUT VOLTAGE
10mΩ
SET
0V TO 4V†
12A
LT3083
IN
VCONTROL
+
–
OUT
10mΩ
SET
LT3083
IN
VCONTROL
+
–
OUT
3083 TA13
SET
100k
10mΩ
+
100μF
3083f
22
LT3083
TYPICAL APPLICATIONS
Adjustable High Efﬁciency Regulator*
4.5V TO 25V†
VIN
10μF
1μF
BOOST
0.47μF
BD
LT3680
100k
RUN/SS
4.7μH
0.1μF
68μF
B340A
680pF
RT
63.4k
GND
VCONTROL
TP0610L
VCONTROL
15.4k
LT3083
IN
SW
+
–
FB
200k
OUT
10k
3083 TA14
SET
600kHz
0V TO 10V†
3A
4.7μF
200k
*DIFFERENTIAL VOLTAGE ON LT3083
≈ 1.4V SET BY THE TPO610L P-CHANNEL THRESHOLD.
†MAXIMUM OUTPUT VOLTAGE IS 2V
BELOW INPUT VOLTAGE
10k
2 Terminal Current Source
CCOMP*
IN
LT3083
VCONTROL
+
–
R1
SET
20k
3083 TA15
*CCOMP
R1 ≤ 10Ω 10μF
R1 ≥ 10Ω 2.2μF
IOUT =
1V
R1
3083f
23
LT3083
PACKAGE DESCRIPTION
FE Package
16-Lead Plastic TSSOP (4.4mm)
(Reference LTC DWG # 05-08-1663 Rev H)
Exposed Pad Variation BB
4.90 – 5.10*
(.193 – .201)
3.58
(.141)
3.58
(.141)
16 1514 13 12 1110
6.60 p0.10
9
2.94
(.116)
4.50 p0.10
2.94 6.40
(.116) (.252)
BSC
SEE NOTE 4
0.45 p0.05
1.05 p0.10
0.65 BSC
1 2 3 4 5 6 7 8
RECOMMENDED SOLDER PAD LAYOUT
4.30 – 4.50*
(.169 – .177)
0.09 – 0.20
(.0035 – .0079)
0.50 – 0.75
(.020 – .030)
NOTE:
1. CONTROLLING DIMENSION: MILLIMETERS
MILLIMETERS
2. DIMENSIONS ARE IN
(INCHES)
3. DRAWING NOT TO SCALE
0.25
REF
1.10
(.0433)
MAX
0o – 8o
0.65
(.0256)
BSC
0.195 – 0.30
(.0077 – .0118)
TYP
0.05 – 0.15
(.002 – .006)
FE16 (BB) TSSOP REV G 0910
4. RECOMMENDED MINIMUM PCB METAL SIZE
FOR EXPOSED PAD ATTACHMENT
*DIMENSIONS DO NOT INCLUDE MOLD FLASH. MOLD FLASH
SHALL NOT EXCEED 0.150mm (.006") PER SIDE
3083f
24
LT3083
PACKAGE DESCRIPTION
DF Package
12-Lead Plastic DFN (4mm × 4mm)
(Reference LTC DWG # 05-08-1733 Rev Ø)
2.50 REF
0.70 p0.05
3.38 p0.05
4.50 p 0.05
2.65 p 0.05
3.10 p 0.05
PACKAGE OUTLINE
0.25 p0.05
0.50 BSC
RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS
APPLY SOLDER MASK TO AREAS THAT ARE NOT SOLDERED
4.00 p 0.10
(4 SIDES)
2.50 REF
7
12
0.40 p 0.10
3.38 p0.10
2.65 p 0.10
PIN 1 NOTCH
R = 0.20 TYP OR
0.35 s 45o
CHAMFER
PIN 1
TOP MARK
(NOTE 6)
(DF12) DFN 0806 REV Ø
6
R = 0.115
TYP
0.200 REF
0.75 p 0.05
1
0.25 p 0.05
0.50 BSC
BOTTOM VIEW—EXPOSED PAD
0.00 – 0.05
NOTE:
1. DRAWING IS PROPOSED TO BE MADE A JEDEC PACKAGE OUTLINE MO-220
VARIATION (WGGD-X)—TO BE APPROVED
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 THE TOP AND BOTTOM OF PACKAGE
3083f
25
LT3083
PACKAGE DESCRIPTION
Q Package
5-Lead Plastic DD-PAK
(Reference LTC DWG # 05-08-1461 Rev E)
.256
(6.502)
.060
(1.524)
TYP
.060
(1.524)
.390 – .415
(9.906 – 10.541)
.165 – .180
(4.191 – 4.572)
.045 – .055
(1.143 – 1.397)
15o TYP
.060
(1.524)
.183
(4.648)
+.008
.004 –.004
+0.203
0.102 –0.102
.059
(1.499)
TYP
.330 – .370
(8.382 – 9.398)
.095 – .115
(2.413 – 2.921)
.075
(1.905)
.300
(7.620)
.067
(1.702)
.028 – .038 BSC
(0.711 – 0.965)
TYP
+.012
.143 –.020
+0.305
3.632 –0.508
BOTTOM VIEW OF DD PAK
HATCHED AREA IS SOLDER PLATED
COPPER HEAT SINK
.420
.276
.080
.420
.050 p .012
(1.270 p 0.305)
.013 – .023
(0.330 – 0.584)
.325
.350
.205
.585
.585
.320
.090
.090
.067
.042
RECOMMENDED SOLDER PAD LAYOUT
NOTE:
1. DIMENSIONS IN INCH/(MILLIMETER)
2. DRAWING NOT TO SCALE
.067
.042
RECOMMENDED SOLDER PAD LAYOUT
FOR THICKER SOLDER PASTE APPLICATIONS
Q(DD5) 0610 REV E
3083f
26
LT3083
PACKAGE DESCRIPTION
T Package
5-Lead Plastic TO-220 (Standard)
(Reference LTC DWG # 05-08-1421)
.390 – .415
(9.906 – 10.541)
.165 – .180
(4.191 – 4.572)
.147 – .155
(3.734 – 3.937)
DIA
.045 – .055
(1.143 – 1.397)
.230 – .270
(5.842 – 6.858)
.460 – .500
(11.684 – 12.700)
.570 – .620
(14.478 – 15.748)
.330 – .370
(8.382 – 9.398)
.620
(15.75)
TYP
.700 – .728
(17.78 – 18.491)
SEATING PLANE
.152 – .202
.260 – .320 (3.861 – 5.131)
(6.60 – 8.13)
.095 – .115
(2.413 – 2.921)
.155 – .195*
(3.937 – 4.953)
.013 – .023
(0.330 – 0.584)
BSC
.067
(1.70)
.028 – .038
(0.711 – 0.965)
.135 – .165
(3.429 – 4.191)
* MEASURED AT THE SEATING PLANE
T5 (TO-220) 0801
3083f
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.
27
LT3083
TYPICAL APPLICATION
Paralleling Regulators
IN
LT3083
VCONTROL
+
–
OUT 10mΩ
SET
IN
VIN
4.8V TO 28V
LT3083
VCONTROL
+
–
OUT
10μF
10mΩ
VOUT
3.3V
6A
SET
22μF
33.2k
3083 TA16
RELATED PARTS
PART NUMBER
LT1185
LT1764/
LT1764A
LT1963/A
LT1965
LT3022
DESCRIPTION
3A Negative Low Dropout Regulator
3A, Fast Transient Response,
Low Noise LDO
1.5A Low Noise, Fast Transient
Response LDO
1.1A, Low Noise, Low Dropout
Linear Regulator
1A, Low Voltage, VLDO Linear
Regulator
LT3070
5A, Low Noise, Programmable VOUT,
85mV Dropout Linear Regulator with
Digital Margining
LT3071
5A, Low Noise, Programmable Vout,
85mV Dropout Linear Regulator with
Analog Margining
LT3080/
LT3080-1
1.1A, Parallelable, Low Noise, Low
Dropout Linear Regulator
LT3082
200mA, Parallelable, Single Resistor,
Low Dropout Linear Regulator
LT3085
500mA, Parallelable, Low Noise,
Low Dropout Linear Regulator
LTC3026
1.5A, Low Input Voltage VLDO
Linear Regulator
COMMENTS
VIN: –4.5V to –35V, 0.8V Dropout Voltage, DD-PAK and TO-220 Packages
340mV Dropout Voltage, Low Noise: 40μVRMS, VIN = 2.7V to 20V, TO-220 and DD Packages.
“A” Version Stable Also with Ceramic Capacitors
340mV Dropout Voltage, Low Noise: 40μVRMS, VIN = 2.5V to 20V, “A” Version Stable with
Ceramic Capacitors, TO-220, DD, SOT-223 and SO-8 Packages
290mV Dropout Voltage, Low Noise: 40μVRMS, VIN: 1.8V to 20V, VOUT: 1.2V to 19.5V,
Stable with Ceramic Capacitors, TO-220, DD-PAK, MSOP and 3mm × 3mm DFN Packages
VIN: 0.9V to 10V, Dropout Voltage: 145mV Typical, Adjustable Output (VREF = VOUT(MIN) = 200mV),
Stable with Low ESR, Ceramic Output Capacitors, 16-Pin DFN (5mm × 3mm) and
16-Lead MSOP Packages
Dropout Voltage: 85mV, Digitally Programmable VOUT: 0.8V to 1.8V, Digital Output Margining:
±1%, ±3% or ±5%, Low Output Noise: 25μVRMS (10Hz to 100kHz), Parallelable: Use Two for a
10A Output, Stable with Low ESR Ceramic Output Capacitors (15μF Minimum),
28-Lead 4mm × 5mm QFN Package
Dropout Voltage: 85mV, Digitally Programmable VOUT: 0.8V to 1.8V, Analog Margining: ±10%,
Low Output Noise: 25μVRMS (10Hz to 100kHz), Parallelable: Use Two for a 10A Output, IMON
Output Current Monitor, Stable with Low ESR Ceramic Output Capacitors (15μF Minimum),
28-Lead 4mm × 5mm QFN Package
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, DD-PAK, SOT-223, MS8E and 3mm × 3mm
DFN-8 Packages; “-1” Version Has Integrated Internal Ballast Resistor
Outputs May Be Paralleled for Higher Output, Current or Heat Spreading, Wide Input Voltage
Range: 1.2V to 40V, Low Value Input/Output Capacitors Required: 0.22μF, Single Resistor Sets
Output Voltage, 8-Lead SOT-23, 3-Lead SOT-223 and 8-Lead 3mm × 3mm DFN Packages
275mV 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, MS8E and 2mm × 3mm DFN-6 Packages
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-E and DFN-10 Packages
3083f
28 Linear Technology Corporation
LT 0111 • PRINTED IN USA
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900 ● FAX: (408) 434-0507
●
www.linear.com
© LINEAR TECHNOLOGY CORPORATION 2011

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