LINEAR TECHNOLOGY LT3080 Technical data

FEATURES
prop
LT3080
Adjustable1.1A Single
Resistor Low Dropout
Regulator
U
DESCRIPTIO
Outputs May be Paralleled for Higher Current and
Heat Spreading
Output Current: 1.1A
Single Resistor Programs Output Voltage
1% Initial Accuracy of SET Pin Current
Output Adjustable to 0V
Low Output Noise: 40μV
Wide Input Voltage Range: 1.2V to 36V
Low Dropout Voltage: 300mV
<1mV Load Regulation
<0.001%/V Line Regulation
Minimum Load Current: 0.5mA
Stable with 2.2μF Minimum Ceramic Output
(10Hz to 100kHz)
RMS
Capacitor
Current Limit with Foldback and Overtemperature
Protected
Available in 8-Lead MSOP, 3mm × 3mm DFN,
5-Lead TO-220 and 3-Lead SOT-223
U
APPLICATIO S
High Current All Surface Mount Supply
High Effi ciency Linear Regulator
Post Regulator for Switching Supplies
Low Parts Count Variable Voltage Supply
Low Output Voltage Power Supplies
The LT®3080 is a 1.1A low dropout linear regulator that can be paralleled to increase output current or spread heat in surface mounted boards. Architected as a precision cur­rent source and voltage follower allows this new regulator to be used in many applications requiring high current, adjustability to zero, and no heat sink. Also the device brings out the collector of the pass transistor to allow low dropout operation —down to 300 millivolts— when used with multiple supplies.
A key feature of the LT3080 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 36V. The LT3080 is stable with 2.2μF of capacitance on the output, and the IC uses 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 LT3080 regulator is offered in the 8-lead MSOP (with an Exposed Pad for better thermal characteristics), a 3mm × 3mm DFN, 5-lead TO-220 and a simple-to-use 3-lead SOT-223 version.
, LT, LTC and LTM are registered trademarks of Linear Technology Corporation. All other
trademarks are the
erty of their respective owners.
TYPICAL APPLICATIO
Variable Output Voltage 1.1A Supply
SET
LT3080
R
SET
V
OUT
+ –
V
1.2V TO 36V V
CONTROL
1μF
IN
IN
= R
SET
U
• 10μA
OUT
3080 TA01a
V
OUT
2.2μF
Set Pin Current Distribution
N = 13792
9.80
9.90
SET PIN CURRENT DISTRIBUTION (μA)
10.00
10.10
3080 G02
10.20
3080f
1
LT3080
(
WW
W
ABSOLUTE AXI U RATI GS
V
CONTROL
Pin Voltage ..................................... 40V, –0.3V
U
(Note 1)(All Voltages Relative to V
IN Pin Voltage ................................................ 40V, –0.3V
SET Pin Current (Note 7) .....................................±10mA
SET Pin Voltage (Relative to OUT) .........................±0.3V
Output Short-Circuit Duration .......................... Indefi nite
PIN CONFIGURATION
TOP VIEW
1OUT
OUT
2
OUT
3
SET
4
8-LEAD
T
= 125°C, θJA = 64°C/W, θJC = 3°C/W
JMAX
EXPOSED PAD (PIN 9) IS OUT, MUST BE SOLDERED TO PCB
9
DD PACKAGE
3mm × 3mm) PLASTIC DFN
8 7
6 5
IN IN NC V
CONTROL
)
OUT
Operating Junction Temperature Range
(Notes 2, 10) .......................................... –40°C to 125°C
Storage Temperature Range: .................. –65°C to 150°C
Lead Temperature (Soldering, 10 sec)
MS8E, T and ST Packages Only ........................ 300°C
TOP VIEW
8
OUT
1
OUT
2
OUT
SET
T
EXPOSED PAD (PIN 9) IS OUT, MUST BE SOLDERED TO PCB
8-LEAD PLASTIC MSOP
= 125°C, θJA = 60°C/W, θJC = 10°C/W
JMAX
9
3 4
MS8E PACKAGE
IN
7
IN
6
NC
5
V
CONTROL
FRONT VIEW
3
IN*
TAB IS
OUT
ST PACKAGE
3-LEAD PLASTIC SOT-223
AND IN TIED TOGETHER
CONTROL
= 125°C, θJA = 55°C/W, θJC = 15°C/W
JMAX
2
OUT
1
SET
TAB IS
OUT
FRONT VIEW
5 4 3 2 1
T PACKAGE
5-LEAD PLASTIC TO-220
T
= 125°C, θJA = 40°C/W, θJC = 3°C/W
JMAX
IN V
CONTROL
OUT SET NC
*IN IS V
T
ORDER INFORMATION
LEAD FREE FINISH TAPE AND REEL PART MARKING PACKAGE DESCRIPTION TEMPERATURE RANGE
LT3080EDD#PBF LT3080EDD#TRPBF LCBN 8-Lead (3mm × 3mm) Plastic DFN –40°C to 125°C LT3080EMS8E#PBF LT3080EMS8E#TRPBF LTCBM 8-Lead Plastic MSOP –40°C to 125°C LT3080ET#PBF LT3080ET#TRPBF LT3080ET 5-Lead Plastic TO-220 –40°C to 125°C LT3080EST#PBF LT3080EST#TRPBF 3080 3-Lead Plastic SOT-223 –40°C to 125°C
LEAD BASED FINISH TAPE AND REEL PART MARKING PACKAGE DESCRIPTION TEMPERATURE RANGE
LT3080EDD LT3080EDD#TR LCBN 8-Lead (3mm × 3mm) Plastic DFN –40°C to 125°C LT3080EMS8E LT3080EMS8E#TR LTCBM 8-Lead Plastic MSOP –40°C to 125°C LT3080ET LT3080ET#TR LT3080ET 5-Lead Plastic TO-220 –40°C to 125°C LT3080EST LT3080EST#TR 3080 3-Lead Plastic SOT-223 –40°C to 125°C Consult LTC Marketing for parts specifi ed 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 specifi cations, go to: http://www.linear.com/tapeandreel/
3080f
2
LT3080
The ● denotes the specifi cations which apply over the full operating
ELECTRICAL CHARACTERISTICS
temperature range, otherwise specifi cations are at T
PARAMETER CONDITIONS MIN TYP MAX UNITS
SET Pin Currrent I
Output Offset Voltage (V V
= 1V, V
IN
CONTROL
= 2V, I
OUT
OUT
– V
= 1mA
SET
)
V
Load Regulation ΔI
ΔV
Line Regulation (Note 9) DFN and MSOP Package
Line Regulation (Note 9) SOT-223 and TO-220 Package
ΔI ΔV
ΔI ΔV
Minimum Load Current (Notes 3, 9) VIN = V
V
Dropout Voltage (Note 4) I
CONTROL
VIN Dropout Voltage (Note 4) I
CONTROL Pin Current I
Current Limit VIN = 5V, V Error Amplifi er RMS Output Noise (Note 6) I Reference Current RMS Output Noise (Note 6) 10Hz ≤ f ≤ 100kHz 1 nA Ripple Rejection f = 120Hz, V
Thermal Regulation, I
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 2: Unless otherwise specifi ed, all voltages are with respect to V The LT3080 is tested and specifi ed under pulse load conditions such that T
≈ TA. The LT3080 is 100% tested at TA = 25°C. Performance at –40°C
J
and 125°C is assured by design, characterization and correlation with statistical process controls.
Note 3: Minimum load current is equivalent to the quiescent current of the part. Since all quiescent and drive current is delivered to the output of the part, the minimum load current is the minimum current required to maintain regulation.
Note 4: For the LT3080, dropout is caused by either minimum control voltage (V
) or minimum input voltage (VIN). Both parameters are
CONTROL
specifi ed with respect to the output voltage. The specifi cations 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.
Note 6: Output noise is lowered by adding a small capacitor across the voltage setting resistor. Adding this capacitor bypasses the voltage setting
VIN = 1V, V
SET
V
≥ 1V, V
IN
DFN and MSOP Package
OS
SOT-223 and T0-220 Package
ΔI
SET
SET
SET
OS
LOAD =
ΔI
OS
LOAD =
VIN = 1V to 25V, V V
OS
IN
VIN = 1V to 26V, V V
IN
V
IN
V
IN
LOAD
I
LOAD
LOAD
I
LOAD
LOAD
I
LOAD
LOAD
= 1V to 25V, V
= 1V to 26V, V
= V = V
f = 10kHz f = 1MHz
10ms Pulse 0.003 %/W
= 25°C. (Note 11)
A
CONTROL CONTROL
= 2.0V, I ≥ 2.0V, 1mA ≤ I
= 1mA, TJ = 25°C
LOAD
1mA to 1.1A 1mA to 1.1A (Note 8)
=1V to 25V, I
CONTROL
=1V to 25V, I
CONTROL
=1V to 26V, I
CONTROL
=1V to 26V, I
CONTROL
= 10V
CONTROL
= 25V (DFN and MSOP Package)
CONTROL
= 26V (SOT-223 and TO-220 Package)
CONTROL
= 100mA = 1.1A
= 100mA = 1.1A
= 100mA = 1.1A
CONTROL
= 5V, V
SET
= 0V, V
= 1.1A, 10Hz ≤ f ≤ 100kHz, C
RIPPLE
= 0.5V
P-P
, I
LOAD
= 0.2A, C
resistor shot noise and reference current noise; output noise is then equal to error amplifi er noise (see Applications Information section).
Note 7: SET pin is clamped to the output with diodes. These diodes only carry current under transient overloads.
.
OUT
Note 8: Load regulation is Kelvin sensed at the package. Note 9: Current limit may decrease to zero at input-to-output differential
voltages (V (SOT-223 and TO-220 package). Operation at voltages for both IN and V
CONTROL
between input and output voltage is below the specifi ed differential (V V
OUT
when the device is in current limit. Note 10: This IC includes over-temperature protection that is intended
to protect the device during momentary overload conditions. Junction temperature will exceed the maximum operating junction temperature when over-temperature protection is active. Continuous operation above the specifi ed maximum operating junction temperature may impair device reliability.
Note 11: The SOT-223 package connects the IN and V together internally. Therefore, test conditions for this pin follow the V
CONTROL
≤ 1.1A (Note 9)
LOAD
9.90
9.801010 –2
–3.5
–5 –6
10.10
10.20 2
3.5 5
6
–0.1
LOAD LOAD
LOAD LOAD
=1mA =1mA
=1mA =1mA
0.6 1.3
0.1
0.003
0.1
0.003 300 500
0.5 nA/V
0.5 nA/V
1 1
1.2
OUT
= 10μF, C
OUT
= –0.1V
SET
= 0.1μF, C
SET
= 0.1μF 40 μV
= 2.2μF
OUT
1.35 1.6 100
350
17
200 500
4
6
30
1.1 1.4 A
75 55 20
) greater than 25V (DFN and MSOP package) or 26V
IN–VOUT
is allowed up to a maximum of 36V as long as the difference
) voltage. Line and load regulation specifi cations are not applicable
pins
CONTROL
conditions listed in the Electrical Characteristics Table.
μA μA
mV mV
mV mV
nA
mV
mV/V
mV/V
μA mA mA
mV mV
mA mA
RMS
RMS
dB
dB
dB
IN
3080f
V V
3
LT3080
UW
TYPICAL PERFOR A CE CHARACTERISTICS
Set Pin Current
10.20
10.15
10.10
10.05
10.00
9.95
SET PIN CURRENT (μA)
9.90
9.85
9.80 –50
–25
0
50
25
TEMPERATURE (°C)
75
100
125
150
3080 G01
Offset Voltage Distribution
N = 13250
–2
–1
VOS DISTRIBUTION (mV)
Load Regulation Minimum Load Current
0
ΔI
= 1mA TO 1.1A
LOAD
– V
V
–0.1
IN
OUT
–0.2
–0.3
–0.4
–0.5
–0.6
–0.7
CHANGE IN OFFSET VOLTAGE WITH LOAD (mV)
–0.8
CHANGE IN REFERENCE CURRENT
CHANGE IN OFFSET VOLTAGE
–50
–25
0
0
= 2V
(V
– V
OUT
25
TEMPERATURE (°C)
)
SET
50
75
100
125
3080 G04
3080 G07
2
CHANGE IN REFERENCE CURRENT WITH LOAD (nA)
20
10
0
–10
–20
–30
–40
–50
–60
150
1
Set Pin Current Distribution Offset Voltage (V
N = 13792
9.80
9.90
SET PIN CURRENT DISTRIBUTION (μA)
Offset Voltage Offset Voltage
1.00 I
= 1mA
LOAD
0.75
0.50
0.25
0
–0.25
OFFSET VOLTAGE (mV)
–0.50
–0.75
–1.00
0.8
0.7
0.6
0.5
0.4
0.3
0.2
MINIMUM LOAD CURRENT (mA)
0.1
612 24
0
INPUT-TO-OUTPUT VOLTAGE (V)
*SEE NOTE 9 IN ELECTRICAL
CHARACTERISTICS TABLE
V
IN, CONTROL
V
IN, CONTROL
0
–50
–25
0
25
TEMPERATURE (°C)
*SEE NOTE 9 IN ELECTRICAL
CHARACTERISTICS TABLE
– V
– V
10.00
18
OUT
OUT
50
= 36V*
= 1.5V
75
10.10
100
– V
2.0
OUT
IL = 1mA
1.5
1.0
0.5
0
–0.5
OFFSET VOLTAGE (mV)
–1.0
–1.5
36*
–2.0
–50
0.25
0
–0.25
–0.50
–0.75
–1.00
OFFSET VOLTAGE (mV)
–1.25
–1.50
–1.75
–25
0
TEMPERATURE (°C)
TJ = 125°C
0.2 0.4 0.8
0
LOAD CURRENT (A)
25
TJ = 25°C
50
0.6
10.20
3080 G02
30
3080 G05
)
SET
75
100
1.0
125
150
3080 G03
1.2
3080 G06
Dropout Voltage (Minimum IN Voltage)
400
350
125
3080 G08
150
) (mV)
OUT
300
– V
250
IN
200
150
100
50
MINIMUM IN VOLTAGE (V
0
0.2 0.4 0.8
0
OUTPUT CURRENT (A)
TJ = 125°C
0.6
TJ = 25°C
1.0
1.2
3080 G09
4
3080f
UW
TYPICAL PERFOR A CE CHARACTERISTICS
LT3080
Dropout Voltage (Minimum IN Voltage)
400
350
) (mV)
OUT
300
– V
IN
250
I
200
150
100
50
MINIMUM IN VOLTAGE (V
0
–25
–50
0
TEMPERATURE (°C)
LOAD
I
LOAD
50
25
Current Limit
1.6
1.4
1.2
VIN = 7V
1.0
0.8
0.6
CURRENT LIMIT (A)
0.4
0.2
0
–50
V
–25
OUT
= 0V
0
50
25
TEMPERATURE (°C)
I
LOAD
= 500mA
= 100mA
75
75
= 1.1A
100
100
125
125
3080 G10
3080 G13
150
150
Dropout Voltage (Minimum
Pin Voltage)
TJ = –50°C
TJ = 25°C
0.2 0.4 0.8
0.6
OUTPUT CURRENT (A)
) (V)
1.6
OUT
1.4
– V
1.2
CONTROL
1.0
0.8
0.6
0.4
0.2
0
MINIMUM CONTROL VOLTAGE (V
V
CONTROL
0
Current Limit
1.6
1.4
1.2
1.0
0.8
0.6
CURRENT LIMIT (A)
MSOP
0.4
0.2
0
612 24
0
INPUT-TO-OUTPUT DIFFERENTIAL (V)
*SEE NOTE 9 IN ELECTRICAL
CHARACTERISTICS TABLE
SOT-223 AND TO-220
AND
DFN
18
TJ = 125°C
TJ = 25°C
1.0
30
3080 G11
3080 G14
1.2
36*
Dropout Voltage (Minimum
) (V)
1.6
OUT
1.4
– V
1.2
CONTROL
1.0
0.8
0.6
0.4
0.2
0
MINIMUM CONTROL VOLTAGE (V
–50
V
CONTROL
–25
0
Pin Voltage)
I
= 1mA
LOAD
50
25
TEMPERATURE (°C)
Load Transient Response
75
50
25
0
–25
–50
OUTPUT VOLTAGE DEVIATION (mV)LOAD CURRENT (mA)
400
300
200
100
C
OUT
0
105
0
C
OUT
= 2.2μF CERAMIC
2015
25
TIME (μs)
I
= 1.1A
LOAD
75
100
V
= 1.5V
OUT
= 0.1μF
C
SET
= V
V
IN
CONTROL
= 10μF CERAMIC
30 35 45
40
125
150
3080 G12
= 3V
50
3080 G15
Load Transient Response Line Transient Response
150
100
50
0
–50
–100
OUTPUT VOLTAGE DEVIATION (mV)LOAD CURRENT (A)
1.2
0.9
0.6
0.3
0
105
0
VIN = V V C C
2015
25
TIME (μs)
CONTROL
= 1.5V
OUT
= 10μF CERAMIC
OUT
= 0.1μF
SET
30 35 45
40
= 3V
50
3080 G16
75
50
25
0
–25
–50
6
5
4
3
2
2010
0
IN/CONTROL VOLTAGE (V) OUTPUT VOLTAGE DEVIATION (mV)
4030
50
TIME (μs)
V
= 1.5V
OUT
= 10mA
I
LOAD
= 2.2μF
C
OUT
CERAMIC
= 0.1μF
C
SET
CERAMIC
60 70 90
80
3080 G17
100
Turn-On Response
5
4
3
2
1
0
2.0
1.5
1.0
0.5
0
OUTPUT VOLTAGE (V) INPUT VOLTAGE (V)
21
0
C
= 2.2μF CERAMIC
OUT
43
5
TIME (μs)
R
= 100k
SET
= 0
C
SET
= 1Ω
R
LOAD
67 9
8
3080 G27
3080f
5
10
LT3080
UW
TYPICAL PERFOR A CE CHARACTERISTICS
V
CONTROL
25
20
15
10
CONTROL PIN CURRENT (mA)
5
0
0
*SEE NOTE 9 IN ELECTRICAL
CHARACTERISTICS TABLE
Pin Currrent
I
= 1.1A
LOAD
DEVICE IN CURRENT LIMIT
I
= 1mA
LOAD
12 18 24
6
INPUT-TO-OUTPUT DIFFERENTIAL (V)
Ripple Rejection - Single Supply
100
VIN = V
90
80
70
60
50
40
30
RIPPLE REJECTION (dB)
20
10
= 2.2μF CERAMIC
C
OUT
0
CONTROL
I
= 1.1A
LOAD
FREQUENCY (Hz)
= V
OUT (NOMINAL)
RIPPLE = 50mV
10k 100k10010 1k 1M
I
LOAD
30 36*
+ 2V
= 100mA
3080 G18
P–P
3080 G21
V
CONTROL
30
V V
25
20
15
10
CONTROL PIN CURRENT (mA)
5
0
0
Ripple Rejection - Dual Supply
- V
100
90
80
70
60
50
40
VIN = V V
30
RIPPLE REJECTION (dB)
C
20
10
0
Pin Current
– V
CONTROL
– V
= 1V
IN
OUT
0.4 0.6 0.8
0.2 LOAD CURRENT (A)
Pin
CONTROL
I
LOAD
OUT (NOMINAL)
= V
CONTROL
= 2.2μF CERAMIC
OUT
RIPPLE = 50mV
= 2V
OUT
TJ = –50°C
= 125°C
T
J
= 1.1A
+ 1V
OUT (NOMINAL)
P–P
FREQUENCY (Hz)
+2V
10k 100k10010 1k 1M
I
LOAD
T
J
= 25°C
1.0 1.2
3080 G19
= 100mA
3080 G22
Residual Output Voltage with Less Than Minimum Load
0.8 SET PIN = 0V
0.7
0.6
0.5
0.4
0.3
OUTPUT VOLTAGE (V)
0.2
0.1
0
V
IN
V
= 10V
IN
0
V
OUT
R
TEST
= 5V
V
IN
R
(Ω)
TEST
Ripple Rejection - Dual Supply
- IN Pin
100
90
80
70
60
50
VIN = V
40
30
RIPPLE REJECTION (dB)
20
10
V
CONTROL
RIPPLE = 50mV
C
= 2.2μF CERAMIC
OUT
= 1.1A
I
LOAD
0
OUT (NOMINAL)
= V
+ 1V
OUT (NOMINAL)
P–P
FREQUENCY (Hz)
+2V
10k 100k10010 1k 1M
VIN = 20V
2k1k
3080 G20
3080 G23
6
Ripple Rejection (120Hz)
80
79
78
77
76
75
74
73
RIPPLE REJECTION (dB)
72
71
70
–50
SINGLE SUPPLY OPERATION
= V
V
IN
RIPPLE = 500mV
= 1.1A
I
LOAD
= 0.1μF, C
C
SET
–25 25
0
TEMPERATURE (°C)
OUT(NOMINAL)
REFERENCE CURRENT NOISE SPECTRAL DENSITY (pA/ √Hz)
Noise Spectral Density
10k
1k
100
+ 2V
, f=120Hz
P-P
= 2.2μF
OUT
125
50
100
75
150
3080 G24
10
1
ERROR AMPLIFIER NOISE SPECTRAL DENSITY (nV/√Hz)
FREQUENCY (Hz)
10k 100k10010 1k
1k
100
10
1.0
0.1
3080 G25
3080f
UW
TYPICAL PERFOR A CE CHARACTERISTICS
LT3080
Output Voltage Noise
V
OUT
100μV/DIV
3080 G26
V
OUT
R
SET
C
SET
C
OUT
I
LOAD
= 1V
TIME 1ms/DIV
= 100k = O.1μF
= 10μF
= 1.1A
UUU
PI FU CTIO S
V
CONTROL
pin for the control circuitry of the device. The current fl ow 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 specifi cations).
IN (Pins 7, 8/Pins 7, 8/Pin 5/Pin 3): This is the collector to the power device of the LT3080. The output load current is supplied through this pin. For the device to regulate, the voltage at this pin must be more than 0.1V to 0.5V greater than the output voltage (see Dropout specifi cations).
(Pin 5/Pin 5/Pin 4/NA): This pin is the supply
(DD/MS8E/T/ST)
Error Amplifi er Gain and Phase
3080 G28
300
250
200
PHASE (DEGREES)
150
100
50
0
–50
–100
–150
–200
20
15
10
5
0
–5
GAIN (dB)
–10
–15
–20
–25
–30
FREQUENCY (Hz)
10k 100k10010 1k 1M
IL = 1.1A
= 100mA
I
L
IL = 1.1A
IL = 100mA
OUT (Pins 1-3/Pins 1-3/Pin 3/Pin 2): This is the power output of the device. There must be a minimum load cur­rent of 1mA or the output may not regulate.
SET(Pin 4/Pin 4/Pin 2/Pin 1): This pin is the input to the error amplifi er and the regulation set point for the device. A fi xed current of 10μA fl ows 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.
NC (Pin 6/Pin 6/Pin 1/NA): No Connection. No Connect pins have no connection to internal circuitry and may be tied to V
IN
, V
CONTROL
, V
, GND, or fl oated.
OUT
Exposed Pad (Pin 9/Pin 9/NA/NA): OUT on MS8E and DFN packages.
TAB: OUT on TO-220 and SOT-223 packages.
3080f
7
LT3080
BLOCK DIAGRA
W
V
CONTROL
IN
10μA
+
3080 BD
OUTSET
U
WUU
APPLICATIO S I FOR ATIO
The LT3080 regulator is easy to use and has all the pro­tection features expected in high performance regulators. Included are short-circuit protection and safe operating area protection, as well as thermal shutdown.
The LT3080 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.
A precision “0” TC 10μA internal current source is con­nected to the non-inverting input of a power operational amplifi er. The power operational amplifi er provides a low impedance buffered output to the voltage on the non-invert­ing input. A single resistor from the non-inverting input to ground sets the output voltage and if this resistor is set to zero, zero output results. As can be seen, any output voltage can be obtained from zero up to the maximum defi ned by the input power supply.
What is not so obvious from this architecture are the ben­efi ts of using a true internal current source as the reference as opposed to a bootstrapped reference in older regulators. A true current source allows the regulator to have gain and frequency response independent of the impedance on the 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, the loop gain is unchanged by changing the output voltage or bypassing. Output regulation is not fi xed at a percentage of the output voltage but is a fi xed fraction of millivolts. Use of a true current source allows all the gain in the buffer amplifi er to provide regulation and none of that gain is needed to amplify up the reference to a higher output voltage.
The LT3080 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 to reduce dis­sipation: a higher voltage supply for the control circuitry and a lower voltage supply for the collector. This increases effi ciency and reduces dissipation. To further spread the heat, a resistor can be inserted in series with the collector to move some of the heat out of the IC and spread it on the PC board.
The LT3080 can be operated in two modes. Three terminal mode has the control pin connected to the power input pin which gives a limitation of 1.35V dropout. Alternatively, the “control” pin can be tied to a higher voltage and the power IN pin to a lower voltage giving 300mV dropout on the IN pin and minimizing the power dissipation. This allows for a 1.1A supply regulating from 2.5V or 1.8V
to 1.2V
IN
with low dissipation.
OUT
IN
to 1.8V
OUT
3080f
8
LT3080
U
WUU
APPLICATIO S I FOR ATIO
SET
R
LT3080
SET
+ –
C
SET
OUT
3080 F01
V
OUT
C
OUT
IN
V
CONTROL
+
+
V
V
CONTROL
IN
Figure 1. Basic Adjustable Regulator
Output Voltage
The LT3080 generates a 10μA reference current that fl ows out of the SET pin. Connecting a resistor from SET to ground generates a voltage that becomes the reference point for the error amplifi er (see Figure 1). The reference voltage is a straight
multiplication of the SET pin current and the value of the resistor. Any voltage can be generated and there is no minimum output voltage for the regulator. A minimum load current of 1mA is required to maintain regulation regardless of output voltage. For true zero voltage output operation, this 1mA load current must be returned to a negative supply voltage.
With the low level current used to generate the reference voltage, leakage paths to or from the SET pin can create errors in the reference and output voltages. High quality insulation should be used (e.g., Tefl on, Kel-F); cleaning of all insulating surfaces to remove fl uxes and other resi­dues will probably be required. Surface coating may be necessary to provide a moisture barrier in high humidity environments.
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 signifi cant offset voltage and reference drift, especially over the possible operating temperature range.
If guardring techniques are used, this bootstraps any stray capacitance at the SET pin. Since the SET pin is a high impedance node, unwanted signals may couple into the SET pin and cause erratic behavior. This will be most noticeable when operating with minimum output capacitors at full load current. The easiest way to remedy this is to bypass the SET pin with a small amount of capacitance from SET to ground, 10pF to 20pF is suffi cient.
Stability and Output Capacitance
The LT3080 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.
values of output capacitance decrease peak
Larger
deviations and provide improved transient response for larger load current changes. Bypass capacitors, used to decouple individual components powered by the LT3080, 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 (R
in Figure 1)
SET
and SET pin bypass capacitor. Extra consideration must be given to the use of ceramic
capacitors. Ceramic capacitors are manufactured with a variety of dielectrics, each with different behavior across temperature and applied voltage. The most common dielectrics used are specifi ed 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 coeffi cients as shown in Figures 2 and 3. When used with a 5V regulator, a 16V 10μF Y5V capacitor can exhibit an effective value as low as 1μF to 2μF for the DC bias voltage applied and over the operating tempera­ture range. The X5R and X7R dielectrics result in more stable characteristics and are more suitable for use as the output capacitor. The X7R type has better stability across temperature, while the X5R is less expensive and is avail-
3080f
9
LT3080
U
WUU
APPLICATIO S I FOR ATIO
20
0
–20
–40
–60
CHANGE IN VALUE (%)
–80
–100
0
Figure 2. Ceramic Capacitor DC Bias Characteristics
40
20
0
BOTH CAPACITORS ARE 16V, 1210 CASE SIZE, 10μF
X5R
Y5V
26
4
8
DC BIAS VOLTAGE (V)
14
12
10
X5R
16
3080 F02
ceramic capacitor the stress can be induced by vibrations in the system or thermal transients.
Paralleling Devices
LT3080’s may be 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 using a small piece of PC trace as a ballast resistor to equalize the currents. PC trace resistance in milliohms/inch is shown in Table 1. Only a tiny area is needed for ballasting.
Table 1. PC Board Trace Resistance
WEIGHT (oz) 10 mil WIDTH 20 mil WIDTH
1 54.3 27.1 2 27.1 13.6
Trace resistance is measured in mOhms/in
–20
–40
–60
CHANGE IN VALUE (%)
–80
BOTH CAPACITORS ARE 16V, 1210 CASE SIZE, 10μF
–100
–50
–25 0
TEMPERATURE (°C)
Y5V
50 100 125
25 75
3080 F03
Figure 3. Ceramic Capacitor Temperature Characteristics
able 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 signifi cant 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 verifi ed.
Voltage and temperature coeffi cients 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
The worse 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 a small 10 milliohm ballast resistor, which at full output current gives better than 80 percent equalized sharing of the current. The external resistance of 10 milliohms (5
V
4.8V TO 28V
V
IN
V
CONTROL
V
V
CONTROL
IN
IN
1μF
Figure 4. Parallel Devices
SET
SET
165k
LT3080
+ –
LT3080
+ –
OUT
OUT
10mΩ
10mΩ
3080 F04
10μF
V
OUT
3.3V 2A
3080f
10
LT3080
U
WUU
APPLICATIO S I FOR ATIO
milliohms for the two devices in parallel) only adds about 10 millivolts of output regulation drop at an output of 2A. Even with an output voltage as low as 1V, this only adds 1% to the regulation. Of course, more than two LT3080’s can be paralleled for even higher output current. They are spread out on the PC board, spreading the heat. Input resistors can further spread the heat if the input-to-output difference is high.
Thermal Performance
In this example, two LT3080 3mm × 3mm DFN devices are mounted on a 1oz copper 4-layer PC board. They are placed approximately 1.5 inches apart and the board is mounted vertically for convection cooling. Two tests were set up to measure the cooling performance and current sharing of these devices.
The fi rst test was done with approximately 0.7V input­to-output and 1A per device. This gave a 700 milliwatt dissipation in each device and a 2A output current. The temperature rise above ambient is approximately 28°C and both devices were within plus or minus 1°C. Both the thermal and electrical sharing of these devices is excel­lent. The thermograph in Figure 5 shows the temperature distribution between these devices and the PC board reaches ambient temperature within about a half an inch from the devices.
The power is then increased with 1.7V across each device. This gives 1.7 watts dissipation in each device and a device
temperature of about 90°C, about 65°C above ambient as shown in Figure 6. Again, the temperature matching between the devices is within 2°C, showing excellent tracking between the devices. The board temperature has reached approximately 40°C within about 0.75 inches of each device.
While 90°C is an acceptable operating temperature for these devices, this is in 25°C ambient. For higher ambients, the temperature must be controlled to prevent device tempera­ture from exceeding 125°C. A 3-meter-per-second airfl ow across the devices will decrease the device temperature about 20°C providing a margin for higher operating ambi­ent temperatures.
Both at low power and relatively high power levels de­vices can be paralleled for higher output current. Current sharing and thermal sharing is excellent, showing that acceptable operation can be had while keeping the peak temperatures below excessive operating temperatures on a board. This technique allows higher operating current linear regulation to be used in systems where it could never be used before.
Quieting the Noise
The LT3080 offers numerous advantages when it comes to dealing with noise. There are several sources of noise in a linear regulator. The most critical noise source for any LDO is the reference; from there, the noise contribution
Figure 5. Temperature Rise at 700mW Dissipation
Figure 6. Temperature Rise at 1.7W Dissipation
3080f
11
LT3080
U
WUU
APPLICATIO S I FOR ATIO
from the error amplifi er must be considered, and the gain created by using a resistor divider cannot be forgotten.
Traditional low noise regulators bring the voltage refer­ence out to an external pin (usually through a large value resistor) to allow for bypassing and noise reduction of reference noise. The LT3080 does not use a traditional voltage reference like other linear regulators, but instead uses a reference current. That current operates with typi-
cal noise current levels of 3.2pA/√
Hz (1nA 10Hz to 100kHz bandwidth). The voltage noise of this is equal to the noise current multiplied by the resistor value. The resistor generates spot noise equal to √⎯4⎯k⎯T⎯R (k = Boltzmann’s constant, 1.38 • 10
-23
J/°K, and T is absolute temperature) which is RMS summed with the reference current noise. To lower reference noise, the voltage set­ting resistor may be bypassed with a capacitor, though this causes start-up time to increase as a factor of the RC time constant.
The LT3080 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.
over the
RMS
current limit as the input-to-output voltage increases and keeps the power dissipation at safe levels for all values of input-to-output voltage. The LT3080 provides some output current at all values of input-to-output voltage up to the device breakdown. See the Current Limit curve in the Typical Performance Characteristics.
When power is fi rst 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.
The problem occurs with a heavy output load when the input voltage is high and the output voltage is low. Com­mon situations are immediately after the removal of a short circuit. The load line for such a load may intersect the output current curve at two points. If this happens, there are two stable operating points for the regulator. With this double intersection, the input power supply may need to be cycled down to zero and brought up again to make the output recover.
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, the unity-gain follower presents no gain whatsoever from the SET pin to the output, so noise fi gures do not increase accordingly. Error amplifi er noise is typically 125nV/√ (40μV
over the 10Hz to 100kHz bandwidth); this is
RMS
Hz
another factor that is RMS summed in to give a fi nal noise fi gure for the regulator.
Curves in the Typical Performance Characteristics show noise spectral density and peak-to-peak noise character­istics for both the reference current and error amplifi er over the 10Hz to 100kHz bandwidth.
Overload Recovery
Like many IC power regulators, the LT3080 has safe operat­ing area (SOA) protection. The SOA protection decreases
12
Load Regulation
Because the LT3080 is a fl oating 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
SET
LT3080
+ –
R
SET
RESISTANCE
OUT
PARASITIC
R
P
R
P
R
P
LOAD
3080 F07
3080f
IN
V
CONTROL
Figure 7. Connections for Best Load Regulation
LT3080
U
WUU
APPLICATIO S I FOR ATIO
of the connections between the regulator and the load. The data sheet specifi cation 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 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.
Thermal Considerations
The LT3080 has internal power and thermal limiting cir­cuitry designed to protect it under overload conditions. For continuous normal load conditions, maximum junc­tion temperature must not be exceeded. It is important to give consideration to all sources of thermal resistance from junction to ambient. This includes junction-to-case, case-to-heat sink interface, heat sink resistance or circuit board-to-ambient as the application dictates. Additional heat sources nearby must also be considered.
For surface mount devices, heat sinking is accomplished by using the heat spreading capabilities of the PC board and its copper traces. Surface mount heat sinks and plated through-holes can also be used to spread the heat gener­ated by power devices.
Junction-to-case thermal resistance is specifi ed from the IC junction to the bottom of the case directly below the die. This is the lowest resistance path for heat fl ow. Proper mounting is required to ensure the best possible thermal fl ow from this area of the package to the heat sinking material. For the TO-220 package, thermal compound is strongly recommended for mechanical connections to a heat sink. A thermally conductive spacer can be used for electrical isolation as long as the added contribution to thermal resistance is considered. Note that the Tab or
Exposed Pad (depending on package) is electrically connected to the output.
The following tables list thermal resistance for several different copper areas given a fi xed board size. All mea-
surements were taken in still air on two-sided 1/16” FR-4 board with one ounce copper.
Table 2. MSE Package, 8-Lead MSOP
COPPER AREA
TOPSIDE* BACKSIDE BOARD AREA
2500mm 1000mm
*Device is mounted on topside
Table 3. DD Package, 8-Lead DFN
TOPSIDE* BACKSIDE BOARD AREA
2500mm 1000mm
*Device is mounted on topside
Table 4. ST Package, 3-Lead SOT-223
TOPSIDE* BACKSIDE BOARD AREA
2500mm 1000mm
*Device is mounted on topside
2
2
2
225mm
2
100mm
COPPER AREA
2
2
2
225mm
2
100mm
COPPER AREA
2
2
2
225mm
2
100mm
2500mm22500mm 2500mm22500mm 2500mm22500mm 2500mm22500mm
2500mm22500mm 2500mm22500mm 2500mm22500mm 2500mm22500mm
2500mm22500mm 2500mm22500mm 2500mm22500mm 2500mm22500mm
THERMAL RESISTANCE
(JUNCTION-TO-AMBIENT)
2
2
2
2
(JUNCTION-TO-AMBIENT)
2
2
2
2
(JUNCTION-TO-AMBIENT)
2
2
2
2
55°C/W 57°C/W 60°C/W 65°C/W
THERMAL RESISTANCE
60°C/W 62°C/W 65°C/W 68°C/W
THERMAL RESISTANCE
48°C/W 48°C/W 56°C/W 62°C/W
T Package, 5-Lead TO-220
Thermal Resistance (Junction-to-Case) = 3°C/W
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
2
with topside copper area of 500mm
?
board
3080f
13
LT3080
A
U
WUU
APPLICATIO S I FOR ATIO
The power in the drive circuit equals:
DRIVE
CONTROL
= (V
CONTROL
is equal to I
P where I
of output current. A curve of I in the Typical Performance Characteristics curves.
The power in the output transistor equals: P
OUTPUT
= (VIN – V
The total power equals:
TOTAL
= P
DRIVE
P The current delivered to the SET pin is negligible and can
be ignored. V
CONTROL(MAX CONTINUOUS)
V
IN(MAX CONTINUOUS)
= 0.9V, I
V
OUT
OUT
Power dissipation under these conditions is equal to: PDRIVE = (V
I
CONTROL
P
DRIVE
CONTROL
I
OUT
=
60
= (3.630V – 0.9V)(17mA) = 46mW
+ P
– V
OUT
OUTPUT
OUT
OUT
CONTROL
)(I
OUT
)(I
CONTROL
/60. I
)
CONTROL
= 3.630V (3.3V + 10%)
= 1.575V (1.5V + 5%)
= 1A, TA = 50°C
– V
1A
=
OUT
= 17mA
)(I
CONTROL
60
vs I
)
is a function
can be found
OUT
)
Junction Temperature will be equal to:
= TA + P
T
J
= 50°C + 721mW • 64°C/W = 96°C
T
J
θJA (approximated using tables)
TOTAL
In this case, the junction temperature is below the maxi­mum rating, ensuring reliable operation.
Reducing Power Dissipation
In some applications it may be necessary to reduce the power dissipation in the LT3080 package without sacrifi cing output current capability. Two techniques are available. The fi rst technique, illustrated in Figure 8, em­ploys a resistor in series with the regulator’s input. The voltage drop across R
decreases the LT3080’s IN-to-OUT
S
differential voltage and correspondingly decreases the LT3080’s power dissipation.
As an example, assume: VIN = V
and I
OUT(MAX)
= 1A. Use the formulas from the Calculating
CONTROL
= 5V, V
OUT
= 3.3V
Junction Temperature section previously discussed. Without series resistor R
, power dissipation in the LT3080
S
equals:
1A
P
TOTAL
= 5V – 3.3V
()
60
+ 5V – 3.3V
()
•1
P
OUTPUT
P
OUTPUT
= (VIN – V = (1.575V – 0.9V)(1A) = 675mW
OUT
)(I
OUT
)
Total Power Dissipation = 721mW
V
V
C1
Figure 8. Reducing Power Dissipation Using a Series Resistor
CONTROL
LT3080
SET
R
SET
IN
+ –
OUT
R
S
C2
3080 F08
VINʹ
V
IN
OUT
If the voltage differential (V transistor is chosen as 0.5V, then R
RS=
= 1.73W
5V – 3.3V 0.5V
1A
) across the NPN pass
DIFF
equals:
S
= 1.2Ω
Power dissipation in the LT3080 now equals:
1A
P
TOTAL
= 5V – 3.3V
()
+ 0.5V
()
60
•1A= 0.53W
The LT3080’s power dissipation is now only 30% compared to no series resistor. R
dissipates 1.2W of power. Choose
S
appropriate wattage resistors to handle and dissipate the power properly.
3080f
14
LT3080
U
WUU
APPLICATIO S I FOR ATIO
The second technique for reducing power dissipation, shown in Figure 9, uses a resistor in parallel with the LT3080. This resistor provides a parallel path for current fl ow, reducing the current fl owing through the LT3080. 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: V
5.5V, V I
OUT(MIN)
than 90% of I Calculating R
RP=
= 3.3V, V
OUT
OUT(MIN)
= 0.7A. Also, assuming that RP carries no more
OUT(MIN)
yields:
P
5.5V – 3.2V
= 3.65Ω
0.63A
= V
IN
= 3.2V, I
= 630mA.
(5% Standard value = 3.6Ω)
CONTROL
= 5V, V
OUT(MAX)
IN(MAX)
=
= 1A and
The maximum total power dissipation is (5.5V – 3.2V) • 1A = 2.3W. However the LT3080 supplies only:
5.5V – 3.2V
1A –
3.6Ω
= 0.36A
Therefore, the LT3080’s power dissipation is only: P R
= (5.5V – 3.2V) • 0.36A = 0.83W
DIS
dissipates 1.47W of power. As with the fi rst technique,
P
choose appropriate wattage resistors to handle and dis­sipate the power properly. With this confi guration, the LT3080 supplies only 0.36A. Therefore, load current can increase by 0.64A to 1.64A while keeping the LT3080 in its normal operating range.
V
V
C1
Figure 9. Reducing Power Dissipation Using a Parallel Resistor
CONTROL
SET
R
SET
LT3080
+ –
IN
OUT
IN
R
P
V
OUT
C2
3080 F09
3080f
15
LT3080
TYPICAL APPLICATIO S
U
Higher Output Current
50Ω
V
MJ4502
CONTROL
IN
LT3080
V
IN
6V
+
SET
332k
+ –
OUT
4.7μF
V
OUT
3.3V 5A
+
100μF
3080 TA02
ON OFF
100μF
1μF
Adding Shutdown
V
IN
V
CONTROL
Q1 VN2222LL
SHUTDOWN
IN
LT3080
+ –
SET
R1
*
Q2 INSURES ZERO OUTPUT IN THE ABSENCE OF ANY OUTPUT LOAD.
3080 TA04
OUT
Q2* VN2222LL
V
OUT
Current Source
V
10V
V
CONTROL
IN
IN
LT3080
+
1μF
SET
100k
OUT
I
OUT
0A TO 1A
4.7μF
3080 TA03
16
Low Dropout Voltage LED Driver
V
C1
CONTROL
LT3080
D1
IN
+ –
SET
R1
24.9k
OUT
R2
2.49Ω
3080 TA05
V
100mA
IN
3080f
TYPICAL APPLICATIO S
LT3080
U
Using a Lower Value SET Resistor
V
IN
12V
4.8V to 28V
V
CONTROL
C1 1μF
V
IN
IN
LT3080
+
SET
R1
49.9k 1%
R 10k
SET
1mA
OUT
R2 499Ω 1%
3080 TA06
V
OUT
0.5V TO 10V
C
OUT
4.7μF
V
= 0.5V + 1mA • R
OUT
SET
Adding Soft-Start
SET
R1 332k
LT3080
+ –
OUT
3080 TA07
V
OUT
3.3V 1A
C
OUT
4.7μF
C1 1μF
V
CONTROL
D1 1N4148
C2
0.01μF
IN
V
7V TO 28V
Coincident Tracking
SET 169k
C3
4.7μF
LT3080
+ –
V
OUT2
3.3V
OUT
V
OUT3
5V
4.7μF
3080 TA08
3080f
IN
V
CONTROL
SET R2
80.6k
C2
4.7μF
LT3080
+ –
V
OUT1
2.5V 1A
OUT
IN
V
CONTROL
LT3080
V
CONTROL
IN
IN
+
SET
R1 249k
OUT
C1
1.5μF
17
LT3080
TYPICAL APPLICATIO S
U
Lab Supply
V
12V TO 18V
SETSET
LT3080
+ –
R4 1MEG
OUTOUT
4.7μF 100μF
+
V
OUT
0V TO 10V
3080 TA09
IN
V
CONTROL
+
15μF
LT3080
+ –
+
100k
0A TO 1A
V
CONTROL
15μF
ININ
High Voltage Regulator
SET
R
SET
2MEG
6.1V
LT3080
+ –
4.7μF
OUT
V
OUT
1A
3080 TA10
V
OUT
V
OUT
= 20V
= 10μA • R
SET
V
50V
10k
IN
1N4148
IN
BUZ11
V
CONTROL
+
10μF
+
15μF
18
Ramp Generator
SET
LT3080
+ –
1μF
OUT
V
4.7μF
3080 TA12
OUT
3080f
V
IN
5V
1μF
IN
V
CONTROL
VN2222LL VN2222LL
TYPICAL APPLICATIO S
LT3080
U
Reference Buffer
LT3080
V
CONTROL
IN
V
IN
+
LT1019
GND
INPUT
OUTPUT
SET
C1 1μF
OUT
*
V
OUT
C2
4.7μF
3080 TA11
*MIN LOAD 0.5mA
Ground Clamp
5k
LT3080
+ –
1N4148
OUT
20Ω
4.7μF
V
EXT
V
OUT
V
CONTROL
1μF
IN
V
IN
Boosting Fixed Output Regulators
5V
10μF
*4mV DROP ENSURES LT3080 IS OFF WITH NO LOAD
MULTIPLE LT3080’S CAN BE USED
LT1963-3.3
SET
3080 TA13
LT3080
+ –
20mΩ
42Ω* 47μF
33k
OUT
20mΩ
3.3V
2.6A
3080 TA20
OUT
3080f
19
LT3080
TYPICAL APPLICATIO S
Low Voltage, High Current Adjustable High Effi ciency Regulator*
U
2.7V TO 5.5V
100μF
PV
IN
SV
+
2.2MEG 100k
1000pF
IN
LTC3414
PGOOD RUN/SS
SYNC/MODE
SGND PGND
*DIFFERENTIAL VOLTAGE ON LT3080 IS 0.6V SET BY THE V
MAXIMUM OUTPUT VOLTAGE IS 1.5V
BELOW INPUT VOLTAGE
0.47μH
SW
I
TH
12.1k
R
T
294k
V
FB
78.7k
124k
OF THE 2N3906 PNP.
BE
470pF
+
2× 100μF
2N3906
10k
V
CONTROL
V
CONTROL
V
CONTROL
IN
LT3080
+ –
SET
IN
LT3080
OUT
20mΩ
+ –
SET
IN
LT3080
OUT
20mΩ
0V TO 4V 4A
+ –
SET
OUT
20mΩ
20
V
CONTROL
IN
LT3080
+ –
SET
100k
3080 TA18
OUT
20mΩ
+
100μF
3080f
TYPICAL APPLICATIO S
CMDSH-4E
LT3080
U
Adjustable High Effi ciency Regulator*
4.5V TO 25V
10μF
1μF
V
BOOST
IN
100k
0.1μF
*DIFFERENTIAL VOLTAGE ON LT3080 ≈ 1.4V SET BY THE TPO610L P-CHANNEL THRESHOLD.
BELOW INPUT VOLTAGE
LT3493
GND
SW
FB
10k
IN
SHDN
MAXIMUM OUTPUT VOLTAGE IS 2V
0.1μF 10μH
MBRM140
68μF
TP0610L
2 Terminal Current Source
C
*
COMP
LT3080
V
CONTROL
10k
IN
LT3080
+
SET
1MEG
3080 TA19
OUT
4.7μF
0V TO 10V 1A
V
CONTROL
*C
COMP
R1 ≤ 10Ω 10μF R1 ≥ 10Ω 2.2μF
SET
+ –
100k
R1
3080 TA21
I
OUT
1V
=
R1
3080f
21
LT3080
PACKAGE DESCRIPTIO
U
DD Package
8-Lead Plastic DFN (3mm × 3mm)
(Reference LTC DWG # 05-08-1698)
0.675 ±0.05
R = 0.115
TYP
0.38 ± 0.10
85
3.5 ±0.05
5.23
(.206)
MIN
0.42 ± 0.038
(.0165 ± .0015)
TYP
RECOMMENDED SOLDER PAD LAYOUT
1.65 ±0.05 (2 SIDES)2.15 ±0.05
0.25 ± 0.05
RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS
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
BOTTOM VIEW OF
EXPOSED PAD OPTION
1
8
2.794 ± 0.102 (.110 ± .004)
2.38 ±0.05 (2 SIDES)
2.06 ± 0.102
(.081 ± .004)
1.83 ± 0.102 (.072 ± .004)
2.083 ± 0.102
(.082 ± .004)
0.65
(.0256)
BSC
0.50 BSC
0.889 ± 0.127 (.035 ± .005)
(.126 – .136)
3.20 – 3.45
1.65 ± 0.10
0.00 – 0.05
(2 SIDES)
0.25 ± 0.05
BOTTOM VIEW—EXPOSED PAD
PACKAGE OUTLINE
PIN 1
TOP MARK
(NOTE 6)
0.200 REF
3.00 ±0.10 (4 SIDES)
0.75 ±0.05
MS8E Package
8-Lead Plastic MSOP
(Reference LTC DWG # 05-08-1662)
3.00 ± 0.102 (.118 ± .004)
(NOTE 3)
PLANE
4.90 ± 0.152
(.193 ± .006)
0.22 – 0.38
(.009 – .015)
TYP
1.10
(.043)
MAX
0.65
(.0256)
BSC
0.254
(.010)
GAUGE PLANE
0.18
(.007)
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
DETAIL “A”
0° – 6° TYP
0.53 ± 0.152
(.021 ± .006)
DETAIL “A”
SEATING
2.38 ±0.10 (2 SIDES)
8
7
12
6
3
5
4
(DD8) DFN 1203
14
0.50 BSC
0.52
(.0205)
REF
3.00 ± 0.102
(.118 ± .004)
(NOTE 4)
0.86
(.034)
REF
0.127 ± 0.076 (.005 ± .003)
MSOP (MS8E) 0603
22
3080f
PACKAGE DESCRIPTIO
.390 – .415
(9.906 – 10.541)
.460 – .500
(11.684 – 12.700)
U
.147 – .155
(3.734 – 3.937)
.230 – .270
(5.842 – 6.858)
(14.478 – 15.748)
.330 – .370
(8.382 – 9.398)
T Package
5-Lead Plastic TO-220 (Standard)
(Reference LTC DWG # 05-08-1421)
DIA
.570 – .620
.700 – .728
(17.78 – 18.491)
.165 – .180
(4.191 – 4.572)
.620
(15.75)
TYP
LT3080
.045 – .055
(1.143 – 1.397)
BSC
.264 – .287
(6.70 – 7.30)
.067
(1.70)
.130 – .146
(3.30 – 3.71)
.0905
(2.30)
BSC
.028 – .038
(0.711 – 0.965)
.248 – .264
(6.30 – 6.71)
.114 – .124
(2.90 – 3.15)
SEATING PLANE
.152 – .202
.260 – .320
(6.60 – 8.13)
(3.861 – 5.131)
ST Package
3-Lead Plastic SOT-223
(Reference LTC DWG # 05-08-1630)
.059 MAX
.033 – .041
(0.84 – 1.04)
.135 – .165
(3.429 – 4.191)
.129 MAX
.059 MAX
.181 MAX
RECOMMENDED SOLDER PAD LAYOUT
* MEASURED AT THE SEAT
.039 MAX
.095 – .115
(2.413 – 2.921)
.155 – .195*
(3.937 – 4.953)
.013 – .023
(0.330 – 0.584)
.248 BSC
.090 BSC
.071
(1.80)
MAX
10° – 16°
10°
MAX
.024 – .033
(0.60 – 0.84)
.181
(4.60)
BSC
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.
.012
(0.31)
MIN
.0008 – .0040
(0.0203 – 0.1016)
.010 – .014
(0.25 – 0.36)
10° – 16°
ST3 (SOT-233) 0502
3080f
23
LT3080
TYPICAL APPLICATIO
U
Paralleling Regulators
LT3080
V
CONTROL
IN
+
V
4.8V TO 28V
SET
LT3080
V
CONTROL
IN
IN
OUT
20mΩ
+ –
1μF
SET
165k
OUT
20mΩ
10μF
3080 TA14
V
OUT
3.3V 2A
RELATED PARTS
PART NUMBER DESCRIPTION COMMENTS
LDOs
LT1086 1.5A Low Dropout Regulator Fixed 2.85V, 3.3V, 3.6V, 5V and 12V Output LT1117 800mA Low Dropout Regulator 1V Dropout, Adjustable or Fixed Output, DD-Pak, SOT-223 Packages LT1118 800mA Low Dropout Regulator OK for Sinking and Sourcing, S0-8 and SOT-223 Packages LT1963A 1.5A Low Noise, Fast Transient Response LDO 340mV Dropout Voltage, Low Noise: 40μV
TO-220, DD, SOT-223 and SO-8 Packages
LT1965 1.1A Low Noise LDO 290mV Dropout Voltage, Low Noise 40μV
V
= 1.2V to 19.5V, Stable with Ceramic Caps TO-220, DDPak, MSOP
OUT
and 3mm × 3mm DFN packages.
LT C®3026 1.5A Low Input Voltage VLDOTM Regulator VIN: 1.14V to 3.5V (Boost Enabled), 1.14V to 5.5V (with External 5V),
V
= 0.1V, IQ = 950μA, Stable with 10μF Ceramic Capacitors, 10-Lead
DO
MSOP and DFN Packages
Switching Regulators
LT1976 High Voltage, 1.5A Step-Down Switching Regulator f = 200kHz, I LTC3414 4A (I
), 4MHz Synchronous Step-Down DC/DC
OUT
95% Effi ciency, VIN: 2.25V to 5.5V, V
= 100μA, TSSOP-16E Package
Q
OUT(MIN)
Converter
LTC3406/LTC3406B 600mA (I
Converter
LTC3411 1.25A (I
Converter
), 1.5MHz Synchronous Step-Down DC/DC
OUT
), 4MHz Synchronous Step-Down DC/DC
OUT
95% Effi ciency, VIN: 2.5V to 5.5V, V I
< 1μA, ThinSOTTM Package
SD
95% Effi ciency, VIN: 2.5V to 5.5V, V I
< 1μA, 10-Lead MS or DFN Packages
SD
OUT(MIN)
OUT(MIN)
VLDO and ThinSOT are trademarks of Linear Technology Corporation.
, VIN = 2.5V to 20V,
RMS
, VIN = 1.8V to 20V,
RMS
= 0.8V, TSSOP Package
= 0.6V, IQ = 20μA,
= 0.8V, IQ = 60μA,
24
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900 ● FAX: (408) 434-0507
www.linear.com
3080f
LT 1107 • PRINTED IN USA
© LINEAR TECHNOLOGY CORPORATION 2007
Loading...