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LT1086 Series 1.5A Low Dropout Positive Regulators Adjustable and Fixed 2.85V 3.3V, 3.6V, 5V 12V , ,
FEATURES
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DESCRIPTIO
3-Terminal Adjustable or Fixed 2.85V, 3.3V, 3.6V, 5V, 12V Output Current of 1.5A (0.5A for LT1086H) Operates Down to 1V Dropout Guaranteed Dropout Voltage at Multiple Current Levels Line Regulation: 0.015% Load Regulation: 0.1% 100% Thermal Limit Functional Test Ripple Rejection >75dB Available in 3-Pin TO-220 and 3-Pin DD Package
The LT (R)1086 is designed to provide up to 1.5A output current. All internal circuitry is designed to operate down to 1V input-to-output differential and the dropout voltage is fully specified as a function of load current. Dropout is guaranteed at several operating points up to a maximum of 1.5V at maximum output current. Dropout decreases at lower load currents. On-chip trimming adjusts the reference/ouput voltage to 1%. Current limit is also trimmed, minimizing the stress on both the regulator and power source circuitry under overload conditions. The LT1086 is pin compatible with older 3-terminal adjustable regulators. A minimum 10F output capacitor is required on these devices. The LT1086 offers excellent line and load regulation specifications and ripple rejection exceeds 75dB even at the maximum load current of 1.5A. The LT1086 is floating architecture with a composite NPN output stage. All of the quiescent current and the drive current for the output stage flows to the load increasing efficiency. The LT1086 is available in a 3-pin TO-220 package and a space-saving surface mountable 3-pin DD package.
, LTC and LT are registered trademarks of Linear Technology Corporation.
APPLICATIO S
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SCSI-2 Active Terminator High Efficiency Linear Regulators Post Regulators for Switching Supplies Constant Current Regulators Battery Chargers Microprocessor Supply
TYPICAL APPLICATIO
MINIMUM INPUT/OUTPUT DIFFERENTIAL (V)
2 INDICATES GUARANTEED TEST POINT -55C TJ 150C 0C TJ 125C
5V to 3.3V Regulator
VIN 4.75V
IN
LT1086-3.3 OUT GND
3.3V AT 1.5A
10F* TANTALUM
10F TANTALUM
1 TJ = - 55C TJ = 25C TJ = 150C
LT1086 * TA01
*MAY BE OMITTED IF INPUT SUPPLY IS WELL BYPASSED WITHIN 2" OF THE LT1086
0 0 1 0.5 OUTPUT CURRENT (A) 1.5
LT1086 * TA02
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LT1086 Dropout Voltage
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1
LT1086 Series
ABSOLUTE MAXIMUM RATINGS (Note 1)
Power Dissipation ............................... Internally Limited Input Voltage* ......................................................... 30V Operating Input Voltage Adjustable Devices ........................................... 25V 2.85V Devices .................................................. 18V 3.3V, 3.6V, and 5V Devices ............................... 20V 12V Devices ...................................................... 25V Operating Junction Temperature Range "C" Grades Control Section ............................... 0C to 125C Power Transistor ............................. 0C to 150C "I" Grades Control Section .......................... - 40C to 125C Power Transistor ........................ - 40C to 150C "M" Grades Control Section .......................... - 55C to 150C Power Transistor ........................ - 55C to 200C Storage Temperature Range ................. - 65C to 150C Lead Temperature (Soldering, 10 sec).................. 300C
* Although the device's maximum operating voltage is limited, (18V for a 2.85V device, 20V for a 5V device, and 25V for adjustable and12V devices) the devices are guaranteed to withstand transient input voltages up to 30V. For input voltages greater than the maximum operating input voltage some degradation of specifications will occur. For fixed voltage devices operating at input/output voltage differentials greater than 15V, a minimum external load of 5mA is required to maintain regulation.
PRECONDITIONING
100% Thermal Shutdown Functional Test.
PACKAGE/ORDER INFORMATION
BOTTOM VIEW ADJ 2 VIN 1 3 VOUT (CASE)
ORDER PART NUMBER
FRONT VIEW 3 TAB IS OUTPUT 2 1 M PACKAGE 3-LEAD PLASTIC DD VIN VOUT ADJ (GND)
LT1086CH LT1086MH
H PACKAGE 3-LEAD TO-39 METAL CAN
JA = 30C/W** ** WITH PACKAGE SOLDERED TO 0.5IN2 COPPER AREA OVER BACKSIDE GROUND PLANE OR INTERNAL POWER PLANE. JA CAN VARY FROM 20C/W TO > 40C/W DEPENDING ON MOUNTING TECHNIQUE.
JA = 150C/W
ORDER PART NUMBER
BOTTOM VIEW VIN 2 CASE IS OUTPUT
1 ADJ (GND)* K PACKAGE 2-LEAD TO-3 METAL CAN
JA = 35C/W
LT1086CK LT1086CK-5 LT1086CK-12 LT1086IK LT1086IK-5 LT1086IK-12 LT1086MK LT1086MK-5 LT1086MK-12
FRONT VIEW 3 TAB IS OUTPUT 2 1 T PACKAGE 3-LEAD PLASTIC TO-220 VIN VOUT ADJ (GND)
JA = 50C/W
OBSOLETE PACKAGES
Consider the T Package for Alternate Source
For fixed versions. Consult LTC Marketing for parts specified with wider operating temperature ranges.
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ORDER PART NUMBER
LT1086CM LT1086CM-3.3 LT1086CM-3.6 LT1086IM LT1086IM-3.3 LT1086IM-3.6
ORDER PART NUMBER
LT1086CT LT1086CT-2.85 LT1086CT-3.3 LT1086IT LT1086IT-5 LT1086IT-12 LT1086CT-3.6 LT1086CT-5 LT1086CT-12
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LT1086 Series
The q denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25C.
PARAMETER Reference Voltage (Note 3) Output Voltage (Note 3) CONDITIONS LT1086, LT1086H LT1086-2.85 LT1086-3.3 LT1086-3.6 IOUT = 10mA, TJ = 25C, (VIN - VOUT) = 3V 10mA IOUT 1.5A, (0.5A for LT1086H), 1.5V (VIN - VOUT) 15V IOUT = 0mA, TJ = 25C, VIN = 5V 0V IOUT 1.5A, 4.35V VIN 18V VIN = 5V, IOUT = 0mA, TJ = 25C 4.75V VIN 18V, 0V IOUT 1.5A VIN = 5V, IOUT = 0mA, TJ = 25C 5V VIN 18V, 0 IOUT 1.5A 4.75V VIN 18V, 0 IOUT 1A, TJ 0C VIN = 4.75V, IOUT = 1.5A, TJ 0C IOUT = 0mA, TJ = 25C, VIN = 8V 0 IOUT 1.5A, 6.5V VIN 20V IOUT = 0mA, TJ = 25C, VIN = 15V 0 IOUT 1.5A, 13.5V VIN 25V ILOAD = 10mA, 1.5V (VIN - VOUT) 15V, TJ = 25C
q q q q q
ELECTRICAL CHARACTERISTICS
MIN 1.238 1.225 2.82 2.79 3.267 3.235 3.564 3.500 3.500 3.300 4.950 4.900
TYP 1.250 1.250 2.85 2.85 3.300 3.300 3.600
MAX 1.262 1.270 2.88 2.91 3.333 3.365 3.636 3.672 3.672 3.672 5.050 5.100
UNITS V V V V V V V V V V V V V V % % mV mV mV mV mV mV mV mV mV mV % % mV mV mV mV mV mV mV mV mV mV mV mV V V
LT1086-5 LT1086-12 Line Regulation LT1086, LT1086H LT1086-2.85 LT1086-3.3 LT1086-3.6 LT1086-5 LT1086-12 Load Regulation LT1086, LT1086H
q q
5.000 5.000
11.880 12.000 12.120 11.760 12.000 12.240 0.015 0.035 0.3 0.6 0.5 1.0 0.5 1.0 0.5 1.0 1.0 2.0 0.1 0.2 3 6 3 7 3 6 2 4 5 10 12 24 1.3 0.95 0.2 0.2 6 6 10 10 10 10 10 10 25 25 0.3 0.4 12 20 15 25 15 25 15 25 20 35 36 72 1.5 1.25
IOUT = 0mA, TJ = 25C, 4.35V VIN 18V
q
4.5V VIN 18V, IOUT = 0mA, TJ = 25C
q
4.75V VIN 18V, IOUT = 0mA, TJ = 25C
q
IOUT = 0mA, TJ = 25C, 6.5V VIN 20V
q
IOUT = 0mA, TJ = 25C, 13.5V VIN 25V
q
(VIN - VOUT) = 3V, 10mA IOUT 1.5A, (0.5A for LT1086H) TJ = 25C (Notes 2, 3)
q
LT1086-2.85 LT1086-3.3 LT1086-3.6
VIN = 5V, 0 IOUT 1.5A, TJ = 25C (Notes 2, 3)
q
VIN = 5V, 0 IOUT 1.5A, TJ = 25C (Notes 2, 3)
q
VIN = 5.25V, 0 IOUT 1.5A, TJ = 25C (Notes 2, 3)
q
VIN = 5V, 0 IOUT 1A, TJ = 25C
q
LT1086-5 LT1086-12 Dropout Voltage (VIN - VOUT)
VIN = 8V, 0 IOUT 1.5A, TJ = 25C (Notes 2, 3)
q
VIN = 15V, 0 IOUT 1.5A, TJ = 25C (Notes 2, 3)
q
LT1086/-2.85/-3.3/-3.6/-5/-12 LT1086H
VOUT, VREF = 1%, IOUT = 1.5A (Note 4)
q q
VREF = 1%, IOUT = 0.5A (Note 4)
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LT1086 Series
ELECTRICAL CHARACTERISTICS
PARAMETER Current Limit CONDITIONS
The q denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25C.
MIN
q q q q q q q q q q
TYP 2.00 0.15 0.700 0.075 5 5 5 5 5 5 0.008
MAX
UNITS A A A A
LT1086/-2.85/-3.3/-3.6/-5/-12 (VIN - VOUT) = 5V (VIN - VOUT) = 25V LT1086H (VIN - VOUT) = 5V (VIN - VOUT) = 25V (VIN - VOUT) = 25V (Note 5) VIN 18V VIN 18V VIN 18V VIN 20V VIN 25V
1.50 0.05 0.50 0.02
Minimum Load Current Quiescient Current
LT1086/LT1086H LT1086-2.85 LT1086-3.3 LT1086-3.6 LT1086-5 LT1086-12 TA = 25C, 30ms pulse
10 10 10 10 10 10 0.04
mA mA mA mA mA mA %/W dB dB dB dB dB dB
Thermal Regulation Ripple Rejection
f = 120Hz, COUT = 25F Tantalum, IOUT = 1.5A, (IOUT = 0.5A for LT1086H) LT1086, LT1086H CADJ = 25F, (VIN - VOUT) = 3V LT1086-2.85 VIN = 6V LT1086-3.3 VIN = 6.3V LT1086-3.6 VIN = 6.6V LT1086-5 VIN = 8V LT1083-12 VIN = 15V LT1086, LT1086H LT1086, LT1086H TJ = 25C
q q q q q q q
60 60 60 60 60 54
75 72 72 72 68 60 55 120 0.2 0.5 0.3 0.003 15/20 1.7/4.0 1.5/4.0 1.5/4.0 1 5
Adjust Pin Current Adjust Pin Current Change Temperature Stability Long-Term Stability RMS Output Noise (% of VOUT) Thermal Resistance Junction-to-Case
A A A % % % C/W C/W C/W C/W
10mA IOUT 1.5A (0.5A for LT1086H) 1.5V (VIN - VOUT) 15V
q q
TA = 125C, 1000 Hrs. TA = 25C, 10Hz = f 10kHz H Package: Control Circuitry/Power Transistor K Package: Control Circuitry/Power Transistor M Package: Control Circuitry/Power Transistor T Package: Control Circuitry/Power Transistor
Note 1: Absolute Maximum Ratings are those values beyond which the life of a device may be impaired. Note 2: See Thermal Regulation specifications for changes in output voltage due to heating effects. Line and load regulation are measured at a constant junction temperature by low duty cycle pulse testing. Load regulation is measured at the output lead 1/8" from the package. Note 3: Line and load regulation are guaranteed up to the maximum power dissipation of 15W (3W for the LT1086H). Power dissipation is determined
by the input/output differential and the output current. Guaranteed maximum power dissipation will not be available over the full input/output range. See Short-Circuit Current curve for available output current. Note 4: Dropout voltage is specified over the full output current range of the device. Test points and limits are shown on the Dropout Voltage curve. Note 5: Minimum load current is defined as the minimum output current required to maintain regulation. At 25V input/output differential the device is guaranteed to regulate if the output current is greater than 10mA.
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LT1086 Series TYPICAL PERFORMANCE CHARACTERISTICS
LT1086 Short-Circuit Current
2.5 TJ = 150C TJ = 25C TJ = -55C 1.5 OUTPUT VOLTAGE DEVIATION (%) 0.10 0.05 0 -0.05 -0.10 -0.15 -0.20 -50 -25
MINIMUM OPERATING CURRENT (mA)
SHORT-CIRCUIT CURRENT (A)
2.0
1.0
0.5
GUARANTEED OUTPUT CURRENT 0 25 10 15 20 5 INPUT/OUTPUT DIFFERENTIAL (V) 30
0
Temperature Stability
2
OUTPUT VOLTAGE CHANGE (%)
ADJUST PIN CURRENT (A)
1
POWER (W)
0
-1
-2 -50 -25
0
25 50 75 100 125 150 TEMPERATURE (C)
LT1086 * TPC04
LT1086 Ripple Rejection
100 90 80 RIPPLE REJECTION (dB) 70 60 50 40 30 20 10 0 10 100 1k 10k FREQUENCY (Hz) 100k
LT1086 * TPC07
VRIPPLE 3VP-P VRIPPLE 0.5VP-P RIPPLE REJECTION (dB) (VIN - VOUT) 3V (VIN - VOUT) VDROPOUT
70 60 50 40 30 20 10 0 0 0.25 VOUT = 5V CADJ = 25F COUT = 25F
fR = 20kHz VRIPPLE 0.5VP-P
RIPPLE REJECTION (dB)
CADJ = 200F AT FREQUENCIES < 60Hz CADJ = 25F AT FREQUENCIES > 60Hz IOUT = 1.5A
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LT1086 * TPC01
LT1086 Load Regulation
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Minimum Operating Current (Adjustable Device)
9 8 7 6 5 4 3 2 1 0 0 20 15 10 25 30 5 INPUT/OUTPUT DIFFERENTIAL (V) 35 TJ = 150C TJ = 25C TJ = -55C
I = 1.5A
0
25 50 75 100 125 150 TEMPERATURE (C)
LT1086 * TPC02
LT1086 * TPC03
Adjust Pin Current
100 90 80 70 60 50 40 30 20 10 0 -50 -25 0 25 50 75 100 125 150 TEMPERATURE (C)
LT1086 * TPC05
LT1086 Maximum Power Dissipation*
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LT1086MK
LT1086CT 10 LT1086CK
5
50 60 70 80 90 100 110 120 130 140 150 CASE TEMPERATURE (C) *AS LIMITED BY MAXIMUM JUNCTION TEMPERATURE
LT1086 * TPC06
0
LT1086 Ripple Rejection vs Current
100 90 80 fR = 120Hz VRIPPLE 3VP-P
LT1086-5 Ripple Rejection
80 70 60 50 40 30 20 10 0 IOUT = 1.5A 10 100 1k 10k FREQUENCY (Hz) 100k
LT1086 * TPC09
VRIPPLE 3VP-P VRIPPLE 0.5VP-P (VIN - VOUT) 3V
(VIN - VOUT) VDROPOUT
0.75 1.0 1.25 0.5 OUTPUT CURRENT (A)
1.5
LT1086 * TPC08
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LT1086 Series TYPICAL PERFORMANCE CHARACTERISTICS
LT1086-5 Ripple Rejection vs Current
100 90 80 RIPPLE REJECTION (dB) 70 60 50 40 30 20 10 0 0 0.25 1.25 0.75 1.0 0.5 OUTPUT CURRENT (A) 1.5 VOUT = 5V CADJ = 25F COUT = 25F fR = 20kHz VRIPPLE 0.5VP-P RIPPLE REJECTION (dB) fR = 120Hz VRIPPLE 3VP-P
(VIN - VOUT) 3V
RIPPLE REJECTION (dB)
LT1086 Line Transient Response
60 0.3
OUTPUT VOLTAGE DEVIATION (V)
OUTPUT VOLTAGE DEVIATION (mV)
40 20 0 -20 -40 -60 VOUT = 10V IOUT = 0.2A CIN = 1F TANTALUM COUT = 10F TANTALUM CADJ = 0 CADJ = 1F
0.1 0 -0.1 -0.2 -0.3 CADJ = 1F
SHORT-CIRCUIT CURRENT (A)
LOAD CURRENT (A)
INPUT VOLTAGE DEVIATION (V)
14 13 12 11 0
100 TIME (s)
LT1086H Dropout Voltage
MINIMUM INPUT/OUTPUT DIFFERENTIAL (V)
2 INDICATES GUARANTEED TEST POINT
OUTPUT VOLTAGE DEVIATION (%)
RIPPLE REJECTION (dB)
- 55C TJ 150C 0C TJ 125C 1 TJ = - 55C TJ = 25C TJ = 150C
0
0
0.1
0.3 0.4 0.2 OUTPUT CURRENT (A)
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LT1086-12 Ripple Rejection
80 70 60 50 40 30 20 10 0 10 IOUT = 1.5A 100 1k 10k FREQUENCY (Hz) 100k
LT1086 * TPC11
LT1086-12 Ripple Rejection vs Current
100 90 80 70 60 50 40 30 20 10 0 0 0.25 0.75 1.0 1.25 0.5 OUTPUT CURRENT (A) 1.5 VOUT = 5V CADJ = 25F COUT = 25F fR = 20kHz VRIPPLE 0.5VP-P fR = 120Hz VRIPPLE 3VP-P
VRIPPLE 3VP-P VRIPPLE 0.5VP-P
(VIN - VOUT) VDROPOUT
LT1086 * TPC10
LT1086 * TPC12
LT1086 Load Transient Response
1.2
CADJ = 0 0.2
LT1086H Short-Circuit Current
1.0 0.8 0.6 0.4 0.2 0 GUARANTEED OUTPUT CURRENT 0 5 10 15 20 INPUT/OUTPUT DIFFERENTIAL (V) 25
CIN = 1F TANTALUM COUT = 10F TANTALUM VOUT = 10V VIN = 13V PRELOAD = 100mA
1.5 1.0 0.5 0 0
200
LT1086 * TPC13
50 TIME (s)
100
LT1086 * TPC14
LT1086 * TPC15
LT1086H Load Regulation
0.10 I = 0.5A 0.05 0 -0.05 -0.10 -0.15 -0.20 -50 -25 100 90 80 70 60 50 40 30 20 10
0.5
LT1086H Ripple Rejection vs Current
fR = 120Hz VRIPPLE 3VP-P fR = 20kHz VRIPPLE 0.5VP-P
VOUT = 5V CADJ = 25F COUT = 25F 0 0.1 0.3 0.4 0.2 OUTPUT CURRENT (A) 0.5
0
25 50 75 100 125 150 TEMPERATURE (C)
LT1086 * TPC17
0
LT1086 * TPC16
LT1086 * TPC18
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LT1086 Series TYPICAL PERFORMANCE CHARACTERISTICS
LT1086H Ripple Rejection
100 90 80 RIPPLE REJECTION (dB) 70 60 50 40 30 20 10 0 10 100 1k 10k FREQUENCY (Hz) 100k
LT1086 * TPC19
VRIPPLE 3VP-P VRIPPLE 0.5VP-P (VIN - VOUT) 3V
POWER (W)
(VIN - VOUT) VDROPOUT
CADJ = 200F AT FREQUENCIES < 60Hz CADJ = 25F AT FREQUENCIES > 60Hz IOUT = 0.5A
BLOCK DIAGRAM
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VADJ
LT1086H Maximum Power Dissipation*
5
4
3 LT1086MH 2
1
50 60 70 80 90 100 110 120 130 140 150 CASE TEMPERATURE (C) *AS LIMITED BY MAXIMUM JUNCTION TEMPERATURE
LT1086 * TPC20
0
W
VIN
+ -
THERMAL LIMIT
1086 * BD
VOUT
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LT1086 Series
APPLICATIONS INFORMATION
The LT1086 family of 3-terminal regulators is easy to use and has all the protection features that are expected in high performance voltage regulators. They are short-circuit protected and have safe area protection as well as thermal shutdown to turn off the regulator should the temperature exceed about 165C at the sense point. These regulators are pin compatible with older 3-terminal adjustable devices, offer lower dropout voltage and more precise reference tolerance. Further, the reference stability with temperature is improved over older types of regulators. The only circuit difference between using the LT1086 family and older regulators is that they require an output capacitor for stability. Stability The circuit design used in the LT1086 family requires the use of an output capacitor as part of the device frequency compensation. For all operating conditions, the addition of 150F aluminum electrolytic or a 22F solid tantalum on the output will ensure stability. Normally capacitors much smaller than this can be used with the LT1086. Many different types of capacitors with widely varying characteristics are available. These capacitors differ in capacitor tolerance (sometimes ranging up to 100%), equivalent series resistance, and capacitance temperature coefficient. The 150F or 22F values given will ensure stability. When using the LT1086 the adjustment terminal can be bypassed to improve ripple rejection. When the adjustment terminal is bypassed the requirement for an output capacitor increases. The values of 22F tantalum or 150F aluminum cover all cases of bypassing the adjustment terminal. For fixed voltage devices or adjustable devices without an adjust pin bypass capacitor, smaller output capacitors can be used with equally good results. The table below shows approximately what size capacitors are needed to ensure stability.
Recommended Capacitor Values
INPUT 10F 10F OUTPUT 10F Tantalum, 50F Aluminum 22F Tantalum, 150F Aluminum ADJUSTMENT None 20F
Normally, capacitor values on the order of 100F are used in the output of many regulators to ensure good transient
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response with heavy load current changes. Output capacitance can be increased without limit and larger values of output capacitor further improve stability and transient response of the LT1086 regulators. Another possible stability problem that can occur in monolithic IC regulators is current limit oscillations. These can occur because in current limit, the safe area protection exhibits a negative impedance. The safe area protection decreases the current limit as the input-to-output voltage increases.That is the equivalent of having a negitive resistance since increasing voltage causes current to decrease. Negative resistance during current limit is not unique to the LT1086 series and has been present on all power IC regulators. The value of negative resistance is a function of how fast the current limit is folded back as input-to-output voltage increases. This negative resistance can react with capacitors or inductors on the input to cause oscillation during current limiting. Depending on the value of series resistance, the overall circuitry may end up unstable. Since this is a system problem, it is not necessarily easy to solve; however, it does not cause any problems with the IC regulator and can usually be ignored. Protection Diodes In normal operation the LT1086 family does not need any protection diodes. Older adjustable regulators required protection diodes between the adjustment pin and the output and from the output to the input to prevent overstressing the die. The internal current paths on the LT1086 adjustment pin are limited by internal resistors. Therefore, even with capacitors on the adjustment pin, no protection diode is needed to ensure device safety under short-circuit conditions. Diodes between input and output are usually not needed. The internal diode between the input and the output pins of the LT1086 family can handle microsecond surge currents of 10A to 20A. Even with large output capacitances, it is very difficult to get those values of surge currents in normal operation. Only with high value output capacitors such as 1000F to 5000F, and with the input pin instantaneously shorted to ground, can damage occur. A crowbar circuit at the input of the LT1086 can generate those kinds of currents and a diode from output to input is then recommended. Normal power supply cycling or even
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LT1086 Series
APPLICATIONS INFORMATION
plugging and unplugging in the system will not generate current large enough to do any damage. The adjustment pin can be driven on a transient basis 25V, with respect to the output without any device degradation. Of course as with any IC regulator, exceeding the maximum input-to-output voltage differential causes the internal transistors to break down and none of the protection circuitry is functional.
D1 1N4002 (OPTIONAL)
VIN
IN
LT1086 ADJ
OUT R1
+
VOUT COUT 150F
+
CADJ 10F
R2
LT1086 * AI01
Overload Recovery Like any of the IC power regulators, the LT1086 has safe area protection. The safe area protection decreases the current limit as input-to-output voltage increases and keeps the power transistor inside a safe operating region for all values of input-to-output voltage. The LT1086 protection is designed to provide some output current at all values of input-to-output voltage up to the device breakdown. When power is first turned on, as the input voltage rises, the output follows the input, allowing the regulator to start up into very heavy loads. During the start-up, as the input voltage is rising, the input-to-output voltage differential remains small, allowing the regulator to supply large output currents. With high input voltage, a problem can occur wherein removal of an output short will not allow the output voltage to recover. Older regulators such as the 7800 series also exhibited this phenomenon, so it is not unique to the LT1086. The problem occurs with a heavy output load when the input voltage is high and the output voltage is low, such as immediately after a removal of a short. The load line for such a load may intersect the output current curve at two points. If this happens there are two stable output operating points for the regulator. With this double intersection
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the power supply may need to be cycled down to zero and brought up again to make the output recover. Ripple Rejection For the LT1086 the typical curves for ripple rejection reflect values for a bypassed adjust pin. This curve will be true for all values of output voltage. For proper bypassing and ripple rejection approaching the values shown, the impedance of the adjust pin capacitor at the ripple frequency should equal the value of R1, (normally 100 to 120). The size of the required adjust pin capacitor is a function of the input ripple frequency. At 120Hz the adjust pin capacitor should be 13F if R1 = 100; at 10kHz only 0.16F is needed. For circuits without an adjust pin bypass capacitor the ripple rejection will be a function of output voltage. The output ripple will increase directly as a ratio of the output voltage to the reference voltage (VOUT/VREF). For example, with the output voltage equal to 5V and no adjust pin capacitor, the output ripple will be higher by the ratio of 5V/1.25V or four times larger. Ripple rejection will be degraded by 12dB from the value shown on the LT1086 curve. Typical curves are provided for the 5V and 12V devices since the adjust pin is not available. Output Voltage The LT1086 develops a 1.25V reference voltage between the output and the adjust terminal (see Figure 1). By placing resistor R1 between these two terminals, a constant current is caused to flow through R1 and down through R2 to set the overall output voltage. Normally this current is chosen to be the specified minimum load current of 10mA. Because IADJ is very small and constant when compared with the current through R1, it represents a small error and can usually be ignored. For fixed voltage devices R1 and R2 are included in the device.
VIN IN LT1086 ADJ IADJ 50A VOUT = VREF 1 + R2 R1 OUT VREF R1 VOUT 10F TANTALUM
+
(
)
R2 + IADJ R2
1086 * F01
Figure 1. Basic Adjustable Regulator
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LT1086 Series
APPLICATIONS INFORMATION
Load Regulation Because the LT1086 is a 3-terminal device, it is not possible to provide true remote load sensing. Load regulation will be limited by the resistance of the wire connecting the regulator to the load. The data sheet specification for load regulation is measured at the bottom of the package. Negative side sensing is a true Kelvin connection, with the bottom of the output divider returned to the negative side of the load. Although it may not be immediately obvious, best load regulation is obtained when the top of the resistor divider R1 is connected directly to the case not to the load, as illustrated in Figure 2. If R1 were connected to the load, the effective resistance between the regulator and the load would be:
RP R2 + R1 , RP = Parasitic Line Resistance R1
RP PARASITIC LINE RESISTANCE VIN IN LT1086 ADJ R1* RL R2* OUT
(
)
*CONNECT R1 TO CASE CONNECT R2 TO LOAD
1086 * F02
Figure 2. Connections for Best Load Regulation
Connected as shown, RP is not multiplied by the divider ratio. RP is about 0.004 per foot using 16-gauge wire. This translates to 4mV/ft at 1A load current, so it is important to keep the positive lead between regulator and load as short as possible and use large wire or PC board traces. Note that the resistance of the package leads for the H package 0.06/inch. While it is usually not possible to connect the load directly to the package, it is possible to connect larger wire or PC traces close to the case to avoid voltage drops that will degrade load regulation. For fixed voltage devices the top of R1 is internally Kelvin connected and the ground pin can be used for negative side sensing.
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Thermal Considerations The LT1086 series of regulators have internal power and thermal limiting circuitry designed to protect the device under overload conditions. For continuous normal load conditions however, maximum junction temperature ratings must not be exceeded. It is important to give careful consideration to all sources of thermal resistance from junction to ambient. This includes junction-to-case, caseto-heat sink interface and heat sink resistance itself. New thermal resistance specifications have been developed to more accurately reflect device temperature and ensure safe operating temperatures. The data section for these new regulators provides a separate thermal resistance and maximum junction temperature for both the Control Section and the Power Transistor. Previous regulators, with a single junction-to-case thermal resistance specification, used an average of the two values provided here and therefore could allow excessive junction temperatures under certain conditions of ambient temperature and heat sink resistance. To avoid this possibility, calculations should be made for both sections to ensure that both thermal limits are met. For example, using a LT1086CK (TO-3, Commercial) and assuming: VIN(max continuous) = 9V, VOUT = 5V, IOUT = 1A, TA = 75C, HEAT SINK = 3C/W, CASE-TO-HEAT SINK = 0.2C/ W for T package with thermal compound. Power dissipation under these conditions is equal to: PD = (VIN - VOUT)(IOUT) = 4W Junction temperature will be equal to: TJ = TA + PD (HEAT SINK + CASE-TO-HEAT SINK + JC) For the Control Section: TJ = 75C + 4W(3C/W + 0.2C/ W + 1.5C/ W) = 94.6C 95C < 125C = TJMAX (Control Section Commercial Range) For the Power Transistor: TJ = 75C + 4W(3C/ W + 0.2C/ W + 4C/ W) = 103.8C 103.8C < 150C = TJMAX (Power Transistor Commercial Range)
1086ff
LT1086 Series
APPLICATIONS INFORMATION
In both cases the junction temperature is below the maximum rating for the respective sections, ensuring reliable operation. Junction-to-case thermal resistance for the K and T packages is specified from the IC junction to the bottom of the case directly below the die. This is the lowest resistance path for heat flow. While this is also the lowest resistance path for the H package, most available heat sinks for this package are of the clip-on type that attach to the cap of the package. The data sheet specification for thermal resistance for the H package is therefore written to reflect this. In all cases proper mounting is required to ensure the best possible heat flow from the die to the heat sink. Thermal compound at the case-to-heat sink interface is strongly recommended. In the case of the H package, mounting the device so that heat can flow out the bottom of the case will significantly lower thermal resistance ( a factor of 2). If the case of the device must be electrically isolated, a thermally conductive spacer can be used as long as its added contribution to thermal resistance is considered. Note that the case of all devices in this series is electrically connected to the output.
TYPICAL APPLICATIONS
5V, 1.5A Regulator
VIN 6.5V
IN
+
10F
*REQUIRED FOR STABILITY
1N5817 IN LT1086-2.85 OUT GND 4.25V TO 5.25V
+
10F TANTALUM
U
W
U
U
U
LT1086 ADJ
OUT 121 1%
5V AT 1.5A
+
10F* TANTALUM
365 1%
LT1086 * AI02
SCSI-2 Active Termination
TERMPWR 110 2% 110
+
10F TANTALUM
0.1F CERAMIC
110 2%
110
18 TOTAL 110 2% 110
LT1086 * TA03
1086ff
11
LT1086 Series
TYPICAL APPLICATIONS
1.2V to 15V Adjustable Regulator
VIN IN LT1086 ADJ C1* 10F OUT R1 121 R2 5k VOUT
VIN
+
*NEEDED IF DEVICE IS FAR FROM FILTER CAPACITORS R2 V OUT = 1.25V 1 + R1
(
)
Battery Charger
LT1086 VIN IN ADJ VOUT - 1.25 1 + R2 R1 - RS 1 + R2 R1 IF RS OUT VOUT
1.25V R1 R2
LT1086 * TA06
IF =
(
( (
)
) )
(
dIF = dVOUT
)
1 - RS 1 + R2 R1
Regulator with Reference
VIN > 11.5V
+
10F
IN
LT1086-5 OUT GND 5V LT1029
VIN
IN
+
10F
RETURN
12
U
5V Regulator with Shutdown
IN LT1086 ADJ 10F 1k TTL 1k
LT1086 * TA05
OUT 121 1%
5V
+
+
C2 100F
+
100F 2N3904 365 1%
LT1086 * TA04
Adjusting Output Voltage of Fixed Regulators
VIN > 12V
+
10F
IN
LT1086-5 OUT GND
+
5V TO 10V 100F
+
10F* 1k
LT1086 * TA07
*OPTIONAL IMPROVES RIPPLE REJECTION
Protected High Current Lamp Driver
+
10V 100F
TTL OR CMOS 10k
LT1086 * TA08
OUT
LT1086 ADJ
IN 12V 1A
15V
LT1086 * TA10
Remote Sensing
RP (MAX DROP 300mV) LT1086 ADJ OUT VOUT 5V 2
+
100F 25 6 1
VIN 7
- +
8 4
LM301A 3
1k RL 5F
121
365
100pF
+
25 RETURN
LT1086 * TA09
1086ff
LT1086 Series
TYPICAL APPLICATIONS
High Efficiency Dual Linear Supply
L1 285H IN HEAT SINK 2N6667 Q1 DARLINGTON MBR360 10k 1k 1000F LT1086 ADJ 510k 2.4k 30k LT1004-2.5 OUT 124* 12V 1.5A
+
+ +
MDA201 4700F 7 8
-
130VAC TO 90VAC
STANCOR P-8685 HEAT SINK 2N6667 Q2 DARLINGTON MBR360 10k 1k
+
+ +
MDA201 4700F 7 8
-
*1% FILM RESISTORS MDA = MOTOROLA L1 = PULSE ENGINEERING, INC. #PE-92106
VIN
SWITCHING REGULATOR
*1% FILM RESISTORS
LT1086 * TA12
U
+
20k* 30.1k* 1.07k* 100F D1 1N4002
+
LT1011
2
-
4 L1 285H
3
IN 1000F 510k 2.4k 30k 2
LT1086 ADJ
OUT 124*
LT1004-2.5
+
20k* 30.1k* 1.07k* 100F D2 1N4002
+
LT1011
-
4
3 -12V 1.5A
LT1086 * TA11
High Efficiency Dual Supply
FEEDBACK PATH MUR410 5V OUTPUT (TYPICAL)
+
470F
MUR410 IN LT1086 ADJ 470F OUT 124* 12V 1.5A
+
+
10F
+
10F
1N4002
1.07k*
MUR410 IN LT1086 ADJ 470F OUT 124*
+
+
10F
+
10F
1N4002 -12V 1.5A
1086ff
1.07k*
13
LT1086 Series
TYPICAL APPLICATIONS
Battery Backed Up Regulated Supply
VIN IN 10F LT1086-5 OUT GND 50 SELECT FOR CHARGE RATE IN 10F LT1086-5 OUT GND 5.2V LINE 5V BATTERY
+
+
6.5V
Automatic Light Control
VIN IN LT1086 ADJ 10F OUT 1.2k 100F
+
PACKAGE DESCRIPTION
H Package 3-Lead TO-39 Metal Can
(Reference LTC DWG # 05-08-1330)
0.350 - 0.370 (8.890 - 9.398) 0.305 - 0.335 (7.747 - 8.509) 0.050 (1.270) MAX REFERENCE PLANE 0.165 - 0.185 (4.191 - 4.699) * 0.029 - 0.045 (0.737 - 1.143) 0.028 - 0.034 (0.711 - 0.864) 0.016 - 0.021** (0.406 - 0.533) DIA 0.500 (12.700) MIN 0.200 (5.080) TYP 0.100 (2.540)
14
U
U
Improving Ripple Rejection
VIN 6.5V IN LT1086 ADJ 10F OUT R1 121 1% R2 365 1% VOUT = 5V
+
150F
+
C1 10F*
LT1086 * TA14
+
100F
LT1086 * TA13
*C1 IMPROVES RIPPLE REJECTION. XC SHOULD BE R1 AT RIPPLE FREQUENCY
Low Dropout Negative Supply
VIN
IN
LT1086-12 OUT GND
+
10,000F
+
100F VOUT = -12V
LT1086 * TA15
FLOATING INPUT
LT1086 * TA16
PIN 1
0.100 (2.540)
45
H3(TO-39) 1098
*LEAD DIAMETER IS UNCONTROLLED BETWEEN THE REFERENCE PLANE AND 0.045" BELOW THE REFERENCE PLANE 0.016 - 0.024 **FOR SOLDER DIP LEAD FINISH, LEAD DIAMETER IS (0.406 - 0.610)
OBSOLETE PACKAGE
1086ff
LT1086 Series
PACKAGE DESCRIPTION
K Package 2-Lead TO-3 Metal Can
(Reference LTC DWG # 05-08-1310)
0.320 - 0.350 (8.13 - 8.89) 0.760 - 0.775 (19.30 - 19.69) 0.060 - 0.135 (1.524 - 3.429)
0.420 - 0.480 (10.67 - 12.19)
0.210 - 0.220 (5.33 - 5.59)
0.425 - 0.435 (10.80 - 11.05) 0.067 - 0.077 (1.70 - 1.96)
0.256 (6.502)
0.060 (1.524)
0.060 (1.524)
0.183 (4.648)
0.075 (1.905) 0.300 (7.620) BOTTOM VIEW OF DD PAK HATCHED AREA IS SOLDER PLATED COPPER HEAT SINK +0.012 0.143 - 0.020 0.090 - 0.110 (2.286 - 2.794) 0.050 (1.270) BSC 0.013 - 0.023 (0.330 - 0.584)
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.
U
0.038 - 0.043 (0.965 - 1.09) 1.177 - 1.197 (29.90 - 30.40) 0.655 - 0.675 (16.64 - 17.15) 0.151 - 0.161 (3.86 - 4.09) DIA, 2PLCS 0.167 - 0.177 (4.24 - 4.49) R 0.490 - 0.510 (12.45 - 12.95) R
K2 (TO-3) 1098
OBSOLETE PACKAGE
M Package 3-Lead Plastic DD Pak
(Reference LTC DWG # 05-08-1460)
0.060 (1.524) TYP 0.390 - 0.415 (9.906 - 10.541) 15 TYP
0.165 - 0.180 (4.191 - 4.572)
0.045 - 0.055 (1.143 - 1.397) +0.008 0.004 -0.004
0.330 - 0.370 (8.382 - 9.398)
0.059 (1.499) TYP
(
+0.203 0.102 -0.102
)
0.095 - 0.115 (2.413 - 2.921) 0.050 0.012 (1.270 0.305)
(
+0.305 3.632 -0.508
)
M (DD3) 1098
1086ff
15
LT1086 Series
PACKAGE DESCRIPTION
T Package 3-Lead Plastic TO-220
(Reference LTC DWG # 05-08-1420)
0.390 - 0.415 (9.906 - 10.541) 0.147 - 0.155 (3.734 - 3.937) DIA 0.230 - 0.270 (5.842 - 6.858) 0.460 - 0.500 (11.684 - 12.700) 0.570 - 0.620 (14.478 - 15.748) 0.330 - 0.370 (8.382 - 9.398) 0.165 - 0.180 (4.191 - 4.572)
0.980 - 1.070 (24.892 - 27.178)
0.520 - 0.570 (13.208 - 14.478)
0.100 (2.540) BSC
0.028 - 0.038 (0.711 - 0.965)
RELATED PARTS
PART NUMBER LT1129 LT1528 LT1585 LT1761 LT1762 LT1763 DESCRIPTION 700mA, Micropower, LDO 3A LDO for Microprocessor Applications 4.6A LDO , with Fast Transient Response 100mA, Low Noise Micropower, LDO 150mA, Low Noise Micropower, LDO 500mA, Low Noise Micropower, LDO COMMENTS VIN = 4.2V to 30V, VOUT(MIN) = 3.75V, IQ = 50A, ISD = 16A, DD, SOT-223, S8, TO-220, TSSOP-20 Packages VIN = 4V to 15V, VOUT(MIN) = 3.30V, IQ = 400A, ISD = 125A, Fast Transient Response, DD, TO-220 Packages VIN = 2.5V to 7V, VOUT(MIN) = 1.25V, IQ = 8mA, Fast Transient Response, DD, TO-220 Packages VIN = 1.8V to 20V, VOUT(MIN) = 1.22V, IQ = 20A, ISD = <1A, Low Noise < 20VRMS P-P, Stable with 1F Ceramic Capacitors, ThinSOTTM Package VIN = 1.8V to 20V, VOUT(MIN) = 1.22V, IQ = 25A, ISD = <1A, Low Noise < 20VRMS P-P, MSOP Package VIN = 1.8V to 20V, VOUT(MIN) = 1.22V, IQ = 30A, ISD = <1A, Low Noise < 20VRMS P-P, S8 Package VIN = 2.7V to 20V, VOUT(MIN) = 1.21V, IQ = 1mA, ISD = <1A, Low Noise < 40VRMS P-P, "A" Version Stable with Ceramic Capacitor, DD, TO-220 Packages VIN = 1.8V to 20V, VOUT(MIN) = 1.22V, IQ = 30A, ISD = <1A, Low Noise < 20VRMS P-P, MS8 Package VIN = 2.1V to 20V, VOUT(MIN) = 1.21V, IQ = 1mA, ISD = <1A, Low Noise < 40VRMS P-P,"A" Version Stable with Ceramic Capacitor, DD, TO-220, SOT-223, S8 Packages VIN = -0.9V to -20V, VOUT(MIN) = -1.21V, IQ = 30A, ISD = 3A, Low Noise < 30VRMS P-P, Stable with Ceramic Capacitors, ThinSOT Package
1086ff
LT1764/LT1764A 3A, Low Noise, Fast Transient Response, LDOs LT1962 300mA, Low Noise Micropower, LDO
LT1963/LT1963A 1.5A, Low Noise, Fast Transient Response, LDOs
LT1964
200mA, Low Noise Micropower, Negative LDO
ThinSOT is a trademark of Linear Technology Corporation.
16
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900 q FAX: (408) 434-0507
q
U
0.045 - 0.055 (1.143 - 1.397)
0.218 - 0.252 (5.537 - 6.401) 0.013 - 0.023 (0.330 - 0.584) 0.050 (1.270) TYP
0.095 - 0.115 (2.413 - 2.921)
T3 (TO-220) 1098
LT/TP 0703 1K REV F * PRINTED IN USA
www.linear.com
(c) LINEAR TECHNOLOGY CORPORATION 1988

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