Linear Technology LT3081 Datasheet

1.5a single resistor rugged linear regulator with monitors

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FeaTures
Extended Safe Operating Area
n
Maximum Output Current: 1.5A
n
Stable with or without Input/Output Capacitors
n
Wide Input Voltage Range: 1.2V to 36V
n
Single Resistor Sets Output Voltage
n
Output Current Monitor: I
n
Junction Temperature Monitor: 1µA/°C
n
Output Adjustable to 0V
n
50µA SET Pin Current: 1% Initial Accuracy
n
Output Voltage Noise: 27µV
n
Parallel Multiple Devices for Higher Current or
n
Heat Spreading
Programmable Current Limit
n
Reverse-Battery and Reverse-Current Protection
n
<1mV Load Regulation Typical Independent of V
n
<0.001%/V Line Regulation Typical
n
Available in Thermally-Enhanced 12-Lead 4mm × 4mm
n
DFN and 16-Lead TSSOP, 7-Lead DD-Pak and 7-Lead
TO-220
applicaTions
All Surface Mount Power Supply
n
Rugged Industrial Power Supply
n
Post Regulator for Switching Supplies
n
Low Output Voltage Supply
n
Intrinsic Safety Applications
n
Typical applicaTion
Wide Safe Operating Area Supply
LT3081
I
/5000
1µA/°C
LOAD
I
TEMP
SET
MON
1k
1k
30.1k
= I
/5000
MON
OUT
RMS
V
IN
IN
50µA
+
OUT
I
LIM
4.53k
*OPTIONAL
For more information
Rugged Linear Regulator
DescripTion
The
LT
3081
is a 1.5A low dropout linear regulator de-
®
signed for rugged industrial applications. Key features of
the IC are the extended safe operating area (SOA), output
current monitor, temperature monitor and programmable
current limit. The LT3081 can be paralleled for higher
output current or heat spreading. The device withstands
reverse input and reverse output-to-input voltages without
reverse current flow.
The LT3081's precision 50µA reference current source
allows a single resistor to program output voltage to
any level between zero and 34.5V. The current reference
architecture makes load regulation independent of output
voltage. The LT3081 is stable with or without input and
output capacitors.
OUT
The output current monitor (I
temperature output (1µA/°C) provide system monitoring
and debug capability. In addition, a single resistor pro-
grams current limit.
Internal protection circuitry includes reverse-battery and
reverse-current protection, current limiting and thermal
limiting. The LT3081 is offered in the 16-lead TSSOP (with
exposed pad for improved thermal performance), 7-lead
TO-220, 7-lead DD-Pak, and an 12-lead 4mm × 4mm DFN.
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.
I
OUT
1.5V
1A
300 *
10µF*
3081 TA01a
www.linear.com/LT3081
1.5A Single Resistor
with Monitors
/5000) and die junction
OUT
SET Pin Current
50.5
I
= 5mA
L
50.4
50.3
50.2
50.1
50.0
49.9
49.8
49.7
49.6
49.5
–50
–25
0
25
50
75
TEMPERATURE (°C)
LT3081
100 125 150
3081 TA01b
3081fc
1

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Summary of Contents for Linear Technology LT3081

  • Page 1 TO-220, 7-lead DD-Pak, and an 12-lead 4mm × 4mm DFN. Low Output Voltage Supply L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear Intrinsic Safety Applications Technology Corporation. All other trademarks are the property of their respective owners.
  • Page 2: Absolute Maximum Ratings

    LT3081 absoluTe MaxiMuM raTings (Note 1) All Voltages Relative to V IN Pin to OUT Pin Differential Voltage .....±40V Operating Junction Temperature Range (Note 2) SET Pin Current (Note 6) ........±25mA E-, I-Grades ........–40°C to 125°C SET Pin Voltage (Relative to OUT, Note 6) ....±10V H-Grade ..........
  • Page 3: Order Information

    LT3081 orDer inForMaTion LEAD FREE FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE LT3081EDF#PBF LT3081EDF#TRPBF 3081 12-Lead (4mm × 4mm) Plastic DFN –40°C to 125°C LT3081IDF#PBF LT3081IDF#TRPBF 3081 12-Lead (4mm × 4mm) Plastic DFN –40°C to 125°C LT3081EFE#PBF...
  • Page 4 0.003 Note 1: Stresses beyond those listed under Absolute Maximum Ratings Note 4: For the LT3081, dropout is specified as the minimum input-to- may cause permanent damage to the device. Exposure to any Absolute output voltage differential required supplying a given output current.
  • Page 5: Typical Performance Characteristics

    LT3081 Typical perForMance characTerisTics = 25°C unless otherwise specified. SET Pin Current SET Pin Current Offset Voltage (V – V 50.5 = 5mA N = 3195 = 5mA LOAD LOAD 50.4 50.3 50.2 50.1 50.0 49.9 –0.5 49.8 –1.0 49.7 –1.5...
  • Page 6 LT3081 Typical perForMance characTerisTics = 25°C unless otherwise specified. Dropout Voltage Internal Current Limit Internal Current Limit = 7V = 0V TO-220 AND DD-PAK TSSOP = 1.5A LOAD AND DFN = 5mA LOAD –50 –25 –50 –25 TEMPERATURE (°C) INPUT-TO-OUTPUT DIFFERENTIAL VOLTAGE (V) TEMPERATURE (°C)
  • Page 7 LT3081 Typical perForMance characTerisTics = 25°C unless otherwise specified. Linear Regulator Linear Regulator Pin Line Regulation Load Transient Response Load Transient Response = 200mA = 3V = 2.2µF = 3V = 2.2µF LOAD = 1V = 1V = 0.1µF = 0.1µF –50...
  • Page 8 LT3081 Typical perForMance characTerisTics = 25°C unless otherwise specified. Linear Regulator Current Source Current Source Turn-On Response Turn-On Response Turn-On Response 100mA CURRENT SOURCE CONFIGURATION 1A CURRENT SOURCE CONFIGURATION = 6.04k = 6.04k = 3.01 = 0.3 = 20pF = 20pF = 20k = 0.67...
  • Page 9 LT3081 Typical perForMance characTerisTics = 25°C unless otherwise specified. Ripple Rejection (1MHz) Ripple Rejection (10kHz) + 2V OUT(NOMINAL) RIPPLE = 200mV f = 1MHz = 0.1A LOAD = 2.2µF CERAMIC = 0.1µF + 2V OUT(NOMINAL) RIPPLE = 500mV f = 10kHz = 0.1A...
  • Page 10: Pin Functions

    If programmable current limit is not used, leave this pin to internal circuitry and may be tied to IN, OUT, GND or open; the internal current limit of the LT3081 is still active, floated. keeping the device inside safe operating limits. External voltage drops between the current limit resistor and V will affect the current limit.
  • Page 11: Applications Information

    Introduction The LT3081 has many additional features that facilitate monitoring and control. Current limit is externally pro- The LT3081 regulator is easy to use and has all the pro- grammable via a single resistor between the I pin and tection features expected in high performance regulators.
  • Page 12 SET pin can create errors in the reference and output voltages. High quality Setting the LT3081 to operate as a 2-terminal current insulation should be used (e.g., Teflon, Kel-F); cleaning of source is a simple matter. The 50µA reference current from...
  • Page 13 LT3081 applicaTions inForMaTion Again, the lower current levels used in the LT3081 neces- Programming Current Limit Externally sitate attention to board leakages as error sources (see the A resistor placed between I and OUT on the LT3081 Programming Linear Regulator Output Voltage section).
  • Page 14 Splitting the wires basically connects capacitors to frequency compensate the circuit. Figure 3 two equal inductors in parallel, but placing them in close highlights the simplicity of using the LT3081 as a current proximity gives the wires mutual inductance adding to source.
  • Page 15 LT3081 applicaTions inForMaTion In LT3081 applications with long wires or PCB traces, the capacitor’s stored energy to create a spark or arc. For ap- inductive reactance may cause instability. In some cases, plications where a single capacitor is unacceptable, Figure...
  • Page 16 In some extreme cases, capacitors or series RC networks Using Ceramic Capacitors may be required on both the LT3081’s input and output to Give extra consideration to the use of ceramic capacitors. stabilize the circuit. Figure 6 depicts a general application...
  • Page 17 Every linear regulator has its sources of noise. In As shown in Figure 9, each LT3081 has a small 10mΩ general, a linear regulator’s critical noise source is the ballast resistor, which at full output current gives better reference.
  • Page 18 ADC. With a 1k resistor, 0mV to 150mV indicates 0°C to 150°C. The LT3081 is a floating device. No ground pin exists on the packages. Thus, the IC delivers all quiescent current It should be noted that the TEMP pin current represents an and drive current to the load.
  • Page 19 Only proper or cables between the LT3081 and the load. Breaking the device mounting ensures the best possible thermal flow SET resistor into two pieces adjusts the output voltage as a from this area of the packages to the heat sinking material.
  • Page 20 = 1.5V • 1.5A = 2.25W TOTAL = (V – V TOTAL The LT3081’s power dissipation is now only 40% compared The current delivered to the SET pin is negligible and can to no series resistor. R dissipates 3.3W of power. Choose be ignored.
  • Page 21 Figure 13, uses a resistor in parallel with the sipate the power properly. With this configuration, the LT3081. This resistor provides a parallel path for current flow, reducing the current flowing through the LT3081. LT3081 supplies only 0.86A. Therefore, load current can increase by 0.64A to a total output current of 2.14A while...
  • Page 22: Typical Applications

    Clamping diodes and 400Ω limiting resistors protect the second scenario follows improper shutdown techniques LT3081’s SET pin relative to the OUT pin voltage. These in which the SET pin is reset to GND quickly while OUT protection components typically only carry current under is held up by a large output capacitance with light load.
  • Page 23 LT3081 Typical applicaTions Load Sharing Without Ballast Resistors 3V TO 18V 4.5A 22µF 22µF LT3081 LT3081 LT3081 0.1µF 5.1k 0.1µF 0.1µF 100k 100k 1/2 LT1638 1/2 LT1638 5.1k – – 0.47µF 0.47µF 5.1k 5.1k 3081 TA05 Load Current Sharing Without Ballasting 3V TO 36V 4.7µF...
  • Page 24 LT3081 Typical applicaTions 3081fc For more information www.linear.com/LT3081...
  • Page 25 50µA – SET TEMP 3.3V LT1963-3.3 47µF 8.2 * 10µF 47µF 3081 TA08 6.2k *4mV DROP ENSURES LT3081 IS OFF WITH NO LOAD MULTIPLE LT3081s CAN BE USED Reference Buffer LT3081 50µA – SET TEMP 47µF INPUT OUTPUT LT1019 1µF...
  • Page 26 LT3081 Typical applicaTions Using a Lower Value Set Resistor 4.7µF LT3081 50µA – 0.2V TO 10V TEMP 4.7µF 4.02k 40.2 3081 TA11 = 0.2V + 5mA • R Using an External Reference Current 1µF LT3092 LT3081 10µA 50µA – –...
  • Page 27: Package Description

    LT3081 package DescripTion Please refer to http://www.linear.com/designtools/packaging/ for the most recent package drawings. DF Package 12-Lead Plastic DFN (4mm × 4mm) (Reference LTC DWG # 05-08-1733 Rev A) 2.50 REF 0.70 ±0.05 3.38 ±0.05 4.50 ±0.05 2.65 ±0.05 3.10 ±0.05 PACKAGE OUTLINE 0.25 ±0.05...
  • Page 28 LT3081 package DescripTion Please refer to http://www.linear.com/designtools/packaging/ for the most recent package drawings. FE Package 16-Lead Plastic TSSOP (4.4mm) (Reference LTC DWG # 05-08-1663 Rev K) Exposed Pad Variation BB 4.70 DETAIL A 4.90 – 5.10* (.185) 0.56 (.193 – .201) 3.58...
  • Page 29 LT3081 package DescripTion Please refer to http://www.linear.com/designtools/packaging/ for the most recent package drawings. T7 Package 7-Lead Plastic TO-220 (Standard) (Reference LTC DWG # 05-08-1422) .165 – .180 .147 – .155 .390 – .415 (4.191 – 4.572) (3.734 – 3.937) .045 – .055 (9.906 –...
  • Page 30 LT3081 package DescripTion Please refer to http://www.linear.com/designtools/packaging/ for the most recent package drawings. R Package 7-Lead Plastic DD Pak (Reference LTC DWG # 05-08-1462 Rev F) .060 .390 – .415 (1.524) .060 .256 (9.906 – 10.541) (1.524) .165 – .180 (6.502)
  • Page 31: Revision History

    Corrected Formula and Text in Programming Current Limit Section 3081fc 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 representa- For more information www.linear.com/LT3081...
  • Page 32: Typical Application

    (DD-Pak and TO-220), Low Dropout Operation: 310mV (2 Supplies) 3081fc Linear Technology Corporation LT 0315 REV C • PRINTED IN USA 1630 McCarthy Blvd., Milpitas, CA 95035-7417 For more information www.linear.com/LT3081 (408) 432-1900 FAX: (408) 434-0507 www.linear.com/LT3081 ● ●  LINEAR TECHNOLOGY CORPORATION 2014...

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