View LT1084_289104.PDF datasheet online --- IC-ON-LINE

Datasheet File OCR Text:

LT1083/LT1084/LT1085 7.5A, 5A, 3A Low Dropout Positive Adjustable Regulators
FEATURES
s s s s s s s s
DESCRIPTION
The LT1083 series of positive adjustable regulators are designed to provide 7.5A, 5A and 3A with higher efficiency than currently available devices. 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 a maximum of 1.5V at maximum output current, decreasing at lower load currents. On-chip trimming adjusts the reference voltage to 1%. Current limit is also trimmed, minimizing the stress on both the regulator and power source circuitry under overload conditions. The LT1083/LT1084/LT1085 devices are pin compatible with older three-terminal regulators. A 10F output capacitor is required on these new devices. However, this is included in most regulator designs. Unlike PNP regulators, where up to 10% of the output current is wasted as quiescent current, the LT1083 quiescent current flows into the load, increasing efficiency.
Three-Terminal Adjustable Output Current of 3A, 5A or 7.5A Operates Down to 1V Dropout Guaranteed Dropout Voltage at Multiple Current Levels Line Regulation: 0.015% Load Regulation: 0.01% 100% Thermal Limit Functional Test Fixed Versions Available
APPLICATIONS
s s s s
High Efficiency Linear Regulators Post Regulators for Switching Supplies Constant Current Regulators Battery Chargers
DEVICE LT1083 LT1084 LT1085 OUTPUT CURRENT* 7.5A 5.0A 3.0A
*For a 1.5A low dropout regulator see the LT1086 data sheet.
TYPICAL APPLICATION
5V, 7.5A Regulator
INPUT/OUTPUT VOLTAGE DIFFERENTIAL (V)
Dropout Voltage vs Output Current
2
VIN 6.5V
IN
LT1083 ADJ
OUT 121 1%
5V AT 7.5A
+
10F
+
10F* TANTALUM
1
365 1% *REQUIRED FOR STABILITY
1083/4/5 ADJ TA01
0
0 OUTPUT CURRENT
U
U
U
IFULL LOAD
1083/4/5 ADJ TA02
1
LT1083/LT1084/LT1085
ABSOLUTE MAXIMUM RATINGS
Power Dissipation............................... Internally Limited Input-to-Output Voltage Differential "C" Grades........................................................... 30V "I" Grades ............................................................ 30V "M" Grades .......................................................... 35V 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
PRECONDITIONING
100% thermal shutdown functional test.
PACKAGE/ORDER INFORMATION
FRONT VIEW TAB IS OUTPUT 3 2 1 T PACKAGE 3-LEAD PLASTIC TO-220
JA = 50C/W
VIN VOUT ADJ
ORDER PART NUMBER LT1084CT LT1084IT LT1085CT LT1085IT
TAB IS OUTPUT
FRONT VIEW 3 2 1 P PACKAGE 3-LEAD PLASTIC TO-3P VIN VOUT ADJ
JA = 35C/W
BOTTOM VIEW VIN 2 CASE IS OUTPUT
1 ADJ K PACKAGE 2-LEAD TO-3 METAL CAN
LT1083CK LT1083MK LT1084CK LT1084MK LT1085CK LT1085MK
FRONT VIEW 3 TAB IS OUTPUT 2 1 M PACKAGE 3-LEAD PLASTIC DD VIN VOUT ADJ
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 = 35C/W
ELECTRICAL CHARACTERISTICS
PARAMETER Reference Voltage CONDITIONS IOUT = 10mA, TJ = 25C, (VIN - VOUT) = 3V 10mA IOUT IFULL LOAD 1.5V (VIN - VOUT) 25V (Notes 3, 5, 6) ILOAD = 10mA, 1.5V (VIN - VOUT) 15V, TJ = 25C (Notes 1, 2) M Grade: 15V (VIN - VOUT) 35V (Notes 1, 2) C, I Grades: 15V (VIN - VOUT) 30V (Notes 1, 2) MIN 1.238
q q q q
Line Regulation
2
UU
U
U
U
W
WW
U
W
ORDER PART NUMBER LT1083CP LT1084CP
LT1084CM LT1085CM
TYP 1.250 1.250 0.015 0.035 0.05 0.05
MAX 1.262 1.270 0.2 0.2 0.5 0.5
UNITS V V % % % %
1.225
LT1083/LT1084/LT1085
ELECTRICAL CHARACTERISTICS
PARAMETER Load Regulation CONDITIONS (VIN - VOUT) = 3V 10mA IOUT IFULL LOAD TJ = 25C (Notes 1, 2, 3, 5)
q
MIN
TYP
MAX
UNITS
Dropout Voltage Current Limit LT1083 LT1084 LT1085 Minimum Load Current Thermal Regulation LT1083 LT1084 LT1085 Ripple Rejection Adjust Pin Current Adjust Pin Current Change Temperature Stability Long Term Stability RMS Output Noise (% of VOUT) Thermal Resistance Junction-to-Case LT1083 LT1084
VREF = 1%, IOUT = IFULLLOAD (Notes 4, 5, 7) (VIN - VOUT) = 5V (VIN - VOUT) = 25V (VIN - VOUT) = 5V (VIN - VOUT) = 25V (VIN - VOUT) = 5V (VIN - VOUT) = 25V (VIN - VOUT) = 25V TA = 25C, 30ms Pulse
q q q q q q q q
0.1 0.2 1.3 8.0 0.4 5.5 0.3 3.2 0.2 9.5 1.0 6.5 0.6 4.0 0.5 5 0.002 0.003 0.004
0.3 0.4 1.5
% % V A A A A A A mA %/W %/W %/W dB A A A % % %
10 0.010 0.015 0.020
f = 120Hz, CADJ = 25F, COUT = 25F Tantalum IOUT = IFULL LOAD, (VIN - VOUT) = 3V (Notes 5, 6, 7) TJ = 25C 10mA IOUT IFULL LOAD 1.5V (VIN - VOUT) 25V (Note 5) TA = 125C, 1000 Hrs TA = 25C 10Hz = f 10kHz Control Circuitry/Power Transistor K Package P Package K Package P Package M, T Packages K Package M, T Packages
q q q q
60
75 55 120 0.2 0.5 0.3 0.003 0.6/1.6 0.5/1.6 0.75/2.3 0.65/2.3 0.65/2.7 0.9/3.0 0.7/3.0 5 1
LT1085
C/W C/W C/W C/W C/W C/W C/W
The q denotes the specifications which apply over the full operating temperature range. Note 1: See thermal regulation specifications for changes in output voltage due to heating effects. Load and line regulation are measured at a constant junction temperature by low duty cycle pulse testing. Note 2: Line and load regulation are guaranteed up to the maximum power dissapation (60W for the LT1083, 45W for the LT1084 (K, P), 30W for the LT1084 (T) and 30W for the LT1085). 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 voltage range. Note 3: IFULL LOAD is defined in the current limit curves. The IFULLLOAD curve is defined as the minimum value of current limit as a function of
input-to-output voltage. Note that the 60W power dissipation for the LT1083 (45W for the LT1084 (K, P), 30W for the LT1084 (T), 30W for the LT1085) is only achievable over a limited range of input-to-output voltage. 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: For LT1083 IFULL LOAD is 5A for - 55C TJ < - 40C and 7.5A for TJ -40C. Note 6: 1.7V (VIN - VOUT) 25V for LT1084 at - 55C TJ - 40C. Note 7: Dropout is 1.7V maximum for LT1084 at - 55C TJ - 40C.
3
LT1083/LT1084/LT1085 TYPICAL PERFORMANCE CHARACTERISTICS
LT1083 Dropout Voltage
MINIMUM INPUT/OUTPUT DIFFERENTIAL (V)
2 INDICATES GUARANTEED TEST POINT SHORT-CIRCUIT CURRENT (A) 10 8 6 4 2 GUARANTEED 0 0 0 1 2 345678 OUTPUT CURRENT (A) 9 10 0 20 30 15 25 5 10 INPUT/OUTPUT DIFFERENTIAL (V) 35
-0.20 -50 -25 0 25 50 75 100 125 150 TEMPERATURE (C)
LT1083/4/5 ADJ G03
25C 150C
OUTPUT VOLTAGE DEVIATION (%)
-40C TJ 150C 0C TJ 125C
1
TJ = 150C TJ = 25C TJ = -55C
LT1084 Dropout Voltage
MINIMUN INPUT/OUTPUT DIFFERENTIAL (V)
2 INDICATES GUARANTEED TEST POINT
SHORT-CIRCUIT CURRENT (A)
-55C TJ 150C 0C TJ 125C
OUTPUT VOLTAGE DEVIATION (%)
1 TJ = -55C TJ = 150C TJ = 25C
0 0 1 3 4 2 OUTPUT CURRENT (A) 5 6
LT1083/4/5 ADJ G04
LT1085 Dropout Voltage
MINIMUM INPUT/OUTPUT DIFFERENTIAL (V)
2 INDICATES GUARANTEED TEST POINT
OUTPUT VOLTAGE DEVIATION (%)
-55C TJ 150C 0C TJ 125C
SHORT-CIRCUIT CURRENT (A)
1 TJ = 25C TJ = 150C
TJ = -55C
0 0 3 2 1 OUTPUT CURRENT (A) 4
LT1083/4/5 ADJ G07
4
UW
LT1083/4/5 ADJ G01
LT1083 Short-Circut Current
12
0.10
LT1083 Load Regulation
I = 7.5A 0.05 0 -0.05 -0.10 -0.15
-55C IFULL LOAD
LT1083/4/5 ADJ G02
LT11084 Short-Circut Current
10 9 8 7 6 5 4 3 2 1 0 0 20 15 10 25 30 5 INPUT/OUTPUT DIFFERENTIAL (V) 35 IFULL LOAD GUARANTEED -55C 150C 25C
LT1084 Load Regulation
0.10 I = 5A 0.05 0 -0.05 -0.10 -0.15 -0.20 -50 -25
0
25 50 75 100 125 150 TEMPERATURE (C)
LT1083/4/5 ADJ G06
LT1083/4/5 ADJ G05
LT1085 Short-Circut Current
6 5 4 3 -55C 2 IFULL LOAD 1 GUARANTEED 0 0 20 30 15 25 5 10 INPUT/OUTPUT DIFFERENTIAL (V) 35 25C 150C
0.10
LT1085 Load Regulation
I = 3A 0.05 0 -0.05 -0.10 -0.15 -0.20 -50 -25
0
25 50 75 100 125 150 TEMPERATURE (C)
LT1083/4/5 ADJ G09
LT1083/4/5 ADJ G08
LT1083/LT1084/LT1085 TYPICAL PERFORMANCE CHARACTERISTICS
Minimum Operating Current
10
MINIMUM OPERATING CURRENT (mA)
9
7 6 5 4 3 2 1 0 0 20 15 10 25 30 5 INPUT/OUTPUT DIFFERENTIAL (V) 35 TJ = -55C TJ = 25C TJ = 150C
1.26
ADJUST PIN CURRENT (A)
REFERENCE VOLTAGE (V)
8
LT1083/4/5 ADJ G10
LT1083 Ripple Rejection
100 90 80 VRIPPLE 3VP-P VRIPPLE 0.5VP-P
100 90 80
RIPPLE REJECTION (dB)
RIPPLE REJECTION (dB)
70 60 50 40 30 20 10 0 10 100
(VIN - VOUT) 3V
POWER (W)
(VIN - VOUT) VDROPOUT
CADJ = 200F AT FREQUENCIES < 60Hz CADJ = 25F AT FREQUENCIES > 60Hz IOUT = 7A 1k 10k FREQUENCY (Hz) 100k
LT1084 Ripple Rejection
100 90 80
RIPPLE REJECTION (dB)
VRIPPLE 3VP-P VRIPPLE 0.5VP-P
RIPPLE REJECTION (dB)
70 60 50 40 30 20 10 0 10 100
(VIN - VOUT) 3V
(VIN - VOUT) VDROPOUT
60 50 40 30 20 10
POWER (W)
CADJ = 200F AT FREQUENCIES < 60Hz CADJ = 25F AT FREQUENCIES > 60Hz IOUT = 5A 1k 10k FREQUENCY (Hz) 100k
UW
1083/4/5 ADJ G13 1083/4/5 ADJ G16
Temperature Stability
1.27 100 90 80 70 60 50 40 30 20 10 1.23 -50 -25 0 25 50 75 100 125 150 TEMPERATURE (C)
LT1083/4/5 ADJ G11
Adjust Pin Current
1.25
1.24
0 -50 -25
0
25 50 75 100 125 150 TEMPERATURE (C)
LT1083/4/5 ADJ G12
LT1083 Ripple Rejection vs Current
100
fR = 120Hz VRIPPLE 3VP-P fR = 20kHz VRIPPLE 0.5VP-P
LT1083 Maximum Power Dissipation*
90 80 70 60 50 40 30 LT1083CP LT1083MK
70 60 50 40 30 20 10 0 0
VOUT = 5V CADJ = 25F COUT = 25F 1 6 4 3 2 5 OUTPUT CURRENT (A) 7 8
20 10 0 LT1083CK
1083/4/5 ADJ G14
50 60 70 80 90 100 110 120 130 140 150 CASE TEMPERATURE (C) * AS LIMITED BY MAXIMUM JUNCTION TEMPERATURE
LT1083/4/5 ADJ G15
LT1084 Ripple Rejection vs Current
100 90 80 70 fR = 20kHz VRIPPLE 0.5VP-P fR = 120Hz VRIPPLE 3VP-P
LT1084 Maximum Power Dissipation*
60 50 LT1084MK 40 30 LT1084CT 20 LT1084CP
VOUT = 5V CADJ = 25F COUT = 25F 0 1 4 3 2 OUTPUT CURRENT (A) 5
10 0
LT1084CK
0
1083/4/5 ADJ G17
50 60 70 80 90 100 110 120 130 140 150 CASE TEMPERATURE (C) * AS LIMITED BY MAXIMUM JUNCTION TEMPERATURE
LT1083/4/5 ADJ G18
5
LT1083/LT1084/LT1085 TYPICAL PERFORMANCE CHARACTERISTICS
LT1085 Ripple Rejection
100 90 80 VRIPPLE 3VP-P VRIPPLE 0.5VP-P
RIPPLE REJECTION (dB)
RIPPLE REJECTION (dB)
(VIN - VOUT) 3V
70 60 50 40 30 20 10 0 10 100 1k 10k FREQUENCY (Hz) 100k CADJ = 200F AT FREQUENCIES < 60Hz CADJ = 25F AT FREQUENCIES > 60Hz IOUT = 3A (VIN - VOUT) VDROPOUT
POWER (W)
LT1083 Load Transient Response
0.6
OUTPUT VOLTAGE DEVIATION (V) OUTPUT VOLTAGE DEVIATION (V)
0.2 0 -0.2 -0.4
CADJ = 0
CADJ = 1F
0.2 0 -0.2 -0.4 -0.6
CADJ = 1F
OUTPUT VOLTAGE DEVIATION (V)
0.4
CIN = 1F COUT = 10F TANTALUM VOUT =10V VIN =13V PRELOAD=100mA
LOAD CURRENT (A)
6 4 2 0 0
LOAD CURRENT (A)
6 4 2 0 0 50 TIME (s) 100
1083/4/5 ADJ G23
LOAD CURRENT (A)
8
50 TIME (s)
LT1083 Line Transient Response
150 60
OUTPUT VOLTAGE DEVIATION (V)
OUTPUT VOLTAGE DEVIATION (mV)
50 0 -50
CADJ = 1F
20 0 -20 -40 -60
CADJ = 1F
OUTPUT VOLTAGE DEVIATION (mV)
100
CADJ = 0
-100 VOUT = 10V IIN = 0.2A CIN = 1F TANTALUM COUT = 10F TANTALUM
-150
INPUT DEVIATION (V)
INPUT DEVIATION (V)
14 13 12 0
14 13 12 0
INPUT DEVIATION (V)
100 TIME (s)
6
UW
1083/4/5 ADJ G19
LT1085 Ripple Rejection vs Current
100 90 80 70 60 50 40 30 20 10 0 0 0.5 2.0 1.0 1.5 OUTPUT CURRENT (A) 2.5 3.0 VOUT = 5V CADJ = 25F COUT = 25F
10 50
LT1085 Maximum Power Dissipation*
fR = 120Hz VRIPPLE 3VP-P fR = 20kHz VRIPPLE 0.5VP-P
40 LT1085MK
30
20 LT1085CT
LT1085CK 0 50 60 70 80 90 100 110 120 130 140 150 CASE TEMPERATURE (C) * AS LIMITED BY MAXIMUM JUNCTION TEMPERATURE
LT1083/4/5 ADJ G21
1083/4/5 ADJ G20
LT1084 Load Transient Response
0.6 0.4 CADJ = 0 0.3 0.2 0.1 0 -0.1 -0.2 -0.3 3 2 1 0
LT1085 Load Transient Response
CADJ = 0 CADJ = 1F
CIN = 1F COUT = 10F TANTALUM
CIN = 1F COUT = 10F TANTALUM
VOUT = 10V VIN = 13V PRELOAD=100mA
VOUT = 10V VIN = 13V PRELOAD=100mA 0 50 TIME (s) 100
1083/4/5 ADJ G24
100
1083/4/5 ADJ G22
LT1084 Line Transient Response
60
CADJ = 0 40
LT1085 Line Transient Response
40 20 0 -20 -40 -60 14 13 12 0 100 TIME (s) 200
1083/4/5 ADJ G27
CADJ = 0 CADJ = 1F
VOUT = 10V IIN = 0.2A CIN = 1F TANTALUM COUT = 10F TANTALUM
VOUT = 10V IIN = 0.2A CIN = 1F TANTALUM COUT = 10F TANTALUM
200
1083/4/5 ADJ G25
100 TIME (s)
200
1083/4/5 ADJ G26
LT1083/LT1084/LT1085
BLOCK DIAGRAM
VADJ
APPLICATIONS INFORMATION
The LT1083 family of three-terminal adjustable 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 junction temperature exceed about 165C. These regulators are pin compatible with older threeterminal 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 LT1083 family and older regulators is that this new family requires an output capacitor for stability. Stability The circuit design used in the LT1083 family requires the use of an output capacitor as part of the device frequency compensation. For all operating conditions, the addition of 150F aluminium electrolytic or a 22F solid tantalum on the output will ensure stability. Normally, capacitors much smaller than this can be used with the LT1083. 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 the adjustment terminal is bypassed to improve the ripple rejection, the requirement for an output capacitor increases. The value of 22F tantalum or 150F aluminum covers all cases of bypassing the adjustment terminal. Without bypassing the adjustment terminal, smaller capacitors can be used with equally good results and 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
U
W
W
VIN
+ -
THERMAL LIMIT
VOUT
1083/4/5 ADJ BD
U
U
7
LT1083/LT1084/LT1085
APPLICATIONS INFORMATION
Normally, capacitor values on the order of 100F are used in the output of many regulators to ensure good transient 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 LT1083 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 negative resistance since increasing voltage causes current to decrease. Negative resistance during current limit is not unique to the LT1083 series and has been present on all power IC regulators. The value of the 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 LT1083 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 LT1083 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 LT1083 family can handle microsecond surge currents of 50A to 100A. Even with large output capacitances, it is very difficult to get those values of surge currents in normal operations. Only with a high value of 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 LT1083 can generate those kinds of currents, and a diode from output to input is then recommended. Normal power supply cycling or even 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)
8
U
W
U
U
VIN
IN
LT1083 ADJ
OUT R1
+
VOUT COUT 150F
+
CADJ 10F
R2
1083/4/5 ADJ F00
Overload Recovery Like any of the IC power regulators, the LT1083 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 LT1083 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 LT1083.
LT1083/LT1084/LT1085
APPLICATIONS INFORMATION
The problem occurs with a heavy output load when the input voltage is high and the output voltage is low, such as immediately after 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, the power supply may need to be cycled down to zero and brought up again to make the output recover. Ripple Rejection The typical curves for ripple rejection reflect values for a bypassed adjustment 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 be less than 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 25F if R1 = 100. At 10kHz only 0.22F 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 typical curve. Output Voltage The LT1083 develops a 1.25V reference voltage between the output and the adjust terminal (see Figure 1). By placing a 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 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.
VIN IN LT1083 ADJ R1* RL R2* OUT
U
W
U
U
VIN
IN
LT1083 ADJ IADJ 50A
OUT VREF R1
VOUT
VOUT = VREF 1 + R2 R1
(
)
R2 + IADJ R2
1083/4/5 ADJ F01
Figure 1. Basic Adjustable Regulator
Load Regulation Because the LT1083 is a three-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. This is illustrated in Figure 2. If R1 were connected to the load, the effective resistance between the regulator and the load would be:
R2 + R1 RP x , RP = Parasitic Line Resistance R1
RP PARASITIC LINE RESISTANCE
*CONNECT R1 TO CASE CONNECT R2 TO LOAD
1083/4/5 ADJ F02
Figure 2. Connections for Best Load Regulation
9
LT1083/LT1084/LT1085
APPLICATIONS INFORMATION
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. Thermal Considerations The LT1083 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. Junction-to-case thermal resistance 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. Proper mounting is required to ensure the best possible thermal flow from this area of the package to the heat sink. Thermal compound at the case-to-heat sink interface is strongly recommended. 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. For example, using an LT1083CK (TO-3, Commercial) and assuming: VIN (max continuous) = 9V, VOUT = 5V, IOUT = 6A, TA = 75C, HEAT SINK = 1C/W, CASE-TO-HEAT SINK = 0.2C/W for K package with thermal compound. Power dissipation under these conditions is equal to: PD = (VIN - VOUT )(IOUT) = 24W Junction temperature will be equal to: TJ = TA + PD (HEAT SINK + CASE-TO-HEAT SINK + JC) For the Control Section: TJ = 75C + 24W (1C/W + 0.2C/W + 0.6C/W) = 118C 118C < 125C = TJMAX (Control Section Commercial Range) For the Power Transistor: TJ = 75C + 24W (1C/W + 0.2C/W + 1.6C/W) = 142C 142C < 150C = TJMAX (Power Transistor Commercial Range) In both cases the junction temperature is below the maximum rating for the respective sections, ensuring reliable operation.
10
U
W
U
U
LT1083/LT1084/LT1085
TYPICAL APPLICATIONS
7.5A Variable Regulator
T1 TRIAD F-269U
C30B
20 110VAC 20 C30B 1N4003 1N4003 1F
3
T2 1N4003 1 2
560 15V
82k
15k 2
10k 1N4148
* 1% FILM RESISTOR L: DALE TO-5 TYPE T2: STANCOR 11Z-2003
GENERAL PURPOSE REGULATOR WITH SCR PREREGULATOR TO LOWER POWER DISSIPATION. ABOUT 1.7V DIFFERENTIAL IS MAINTAINED ACROSS THE LT1083 INDEPENDENT OF OUTPUT VOLTAGE AND LOAD CURRENT
U
3 7
L 1MH IN LT1083 ADJ LT1004-1.2 OUT
+
750* 1.5k
0V TO 35V OA TO 7.5A 100F
+ C1
50,000F
1N914 2k OUTPUT ADJUST 16k* LT1004-1.2
8
-15V 4 7
200k
16k* 11k*
2.7k -15V
+
LT1011
-
0.1F 1 NC 15V 100pF
-15V 4
8
2N3904
- +
1
3 8 2 15K 15V 1F 10k 6 LM301A 7 15V
1
LT1011
+ -
4 -15V
3
2 11k*
LT1083/4/5 ADJ TA05
11
LT1083/LT1084/LT1085
TYPICAL APPLICATIONS
Paralleling Regulators
VIN
VIN
*C1 IMPROVES RIPPLE REJECTION. XC SHOULD BE < R1 AT RIPPLE FREQUENCY
VIN
IN
LT1083 ADJ
+
10F
RETURN
1083/4/5 ADJ TA07
12
U
IN
LT1083 ADJ
OUT
2 FEET #18 WIRE*
0.015 IN LT1083 ADJ R1 120 OUT
VOUT = 1.25V 1 + R2 R1 IOUT = 0A TO 15A
()
*THE #18 WIRE ACTS AS BALLAST RESISTANCE INSURING CURRENT SHARING BETWEEN BOTH DEVICES
LT1083/4/5 ADJ TA03
R2
Improving Ripple Rejection
IN
LT1083 ADJ
OUT R1 121 1% R2 365 1%
VOUT 5V
+
10F
+
150F
+
C1 25F*
1083/4/5 ADJ TA04
Remote Sensing
RP (MAX DROP 300mV) OUT
+
100F 25 6 1
VOUT 5V 2
VIN 7
- +
8 4
LM301A 3
1k RL
121
365
100pF
+
5F
25
RETURN
LT1083/LT1084/LT1085
TYPICAL APPLICATIONS
High Efficiency Regulator with Switching Preregulator
VIN 28V 10k
1.2V to 15V Adjustable Regulator
VIN
IN
LT1083 ADJ
OUT R1 90.9
+
C1* 10F
R2 1k
*NEEDED IF DEVICE IS FAR FROM FILTER CAPACITORS V R2 OUT = 1.25V 1 + R1
(
)
Automatic Light Control
VIN
IN
LT1083 ADJ
OUT 1.2k 100F
TTL OR CMOS
+
10F
U
1k
1mH
+
MR1122 10,000F
IN
LT1083 ADJ
OUT 240
VOUT
470 1N914 2k
28V
1M
4N28 10k
1083/4/5 ADJ TA06
+
LT1011
-
1N914
10k
28V
5V Regulator with Shutdown*
VOUT
VIN
IN
LT1083 ADJ
OUT 121 1%
VOUT 5V
+
+
C2 100F
TTL 1k 10F 1k
+
100F 2N3904 365 1%
1083/4/5 ADJ TA09
*OUTPUT SHUTS DOWN TO 1.3V
1083/4/5 ADJ TA08
Protected High Current Lamp Driver
12V 5A OUT LT1083 ADJ
1083/4/5 ADJ TA11
IN
15V
10k
1083/4/5 ADJ TA10
13
LT1083/LT1084/LT1085
PACKAGE DESCRIPTION
1.177 - 1.197 (29.90 - 30.40) 0.655 - 0.675 (16.64 - 17.15) 0.210 - 0.220 (5.33 - 5.59) 0.151 - 0.161 (3.84 - 4.09) DIA, 2 PLACES 0.167 - 0.177 (4.24 - 4.49) R 0.067 - 0.077 (1.70 - 1.96) 0.495 - 0.525 (12.57 - 13.34) R 0.320 - 0.350 (8.13 - 8.89) 0.760 - 0.775 (19.30 - 19.69) 0.060 - 0.135 (1.524 - 3.429)
0.425 - 0.435 (10.80 - 11.05)
0.390 - 0.415 (9.906 - 10.541)
0.460 - 0.500 (11.684 - 12.700)
0.987 - 1.080 (25.070 - 27.432)
0.520 - 0.560 (13.208 - 14.224)
0.090 - 0.110 (2.286 - 2.794) 0.028 - 0.038 (0.711 - 0.965)
14
U
Dimension in inches (millimeters) unless otherwise noted. K Package 2-Lead TO-3 Metal Can
0.420 - 0.480 (10.67 - 12.19)
0.038 - 0.043 (0.965 - 1.09)
K2 0594
T Package 3-Lead Plastic TO-220
0.147 - 0.155 (3.734 - 3.937) DIA 0.230 - 0.270 (5.842 - 6.858) 0.570 - 0.620 (14.478 - 15.748) 0.330 - 0.370 (8.382 - 9.398)
0.165 - 0.180 (4.293 - 4.699)
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 0694
LT1083/LT1084/LT1085
PACKAGE DESCRIPTION
0.060 (1.524) TYP
0.330 - 0.370 (8.382 - 9.398)
(
+0.012 0.143 - 0.020
+0.305 3.632 -0.508
)
0.050 (1.270) TYP
0.620 - 0.64O (15.75 - 16.26) MOUNTING HOLE 0.115 - 0.145 (2.92 - 3.68) DIA 18 - 22
0.830 - 0.870 (21.08 - 22.10) 0.580 - 0.6OO (14.73 - 15.24)
0.780 - 0.800 (19.81 - 20.32)
0.170 (4.32) MAX
0.042 - 0.052 (1.07 - 1.32) 0.074 - 0.084 (1.88 - 2.13)
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
Dimension in inches (millimeters) unless otherwise noted. M Package 3-Lead DD
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
0.059 (1.499) TYP
(
+0.203 0.102 -0.102
)
0.095 - 0.115 (2.413 - 2.921) 0.090 - 0.110 (2.286 - 2.794)
0.013 - 0.023 (0.330 - 0.584)
0.050 0.012 (1.270 0.305)
DD3 0694
P Package 3-Lead TO-3P Plastic
0.187 - 0.207 (4.75 - 5.26) 0.060 - 0.080 (1.52 - 2.03)
0.170 - 0.2OO (4.32 - 5.08) EJECTOR PIN MARKS 0.105 - 0.125 (2.67 - 3.18) DIA
3 - 7
0.215 (5.46) BSC 0.113 - 0.123 (2.87 - 3.12)
0.087 - 0.102 (2.21 - 2.59) 0.020 - 0.040 (0.51 - 1.02)
P3 0892
15
LT1083/LT1084/LT1085
U.S. Area Sales Offices
NORTHEAST REGION Linear Technology Corporation One Oxford Valley 2300 E. Lincoln Hwy.,Suite 306 Langhorne, PA 19047 Phone: (215) 757-8578 FAX: (215) 757-5631 Linear Technology Corporation 266 Lowell St., Suite B-8 Wilmington, MA 01887 Phone: (508) 658-3881 FAX: (508) 658-2701 SOUTHEAST REGION Linear Technology Corporation 17060 Dallas Parkway Suite 208 Dallas, TX 75248 Phone: (214) 733-3071 FAX: (214) 380-5138 CENTRAL REGION Linear Technology Corporation Chesapeake Square 229 Mitchell Court, Suite A-25 Addison, IL 60101 Phone: (708) 620-6910 FAX: (708) 620-6977 SOUTHWEST REGION Linear Technology Corporation 22141 Ventura Blvd. Suite 206 Woodland Hills, CA 91364 Phone: (818) 703-0835 FAX: (818) 703-0517 NORTHWEST REGION Linear Technology Corporation 782 Sycamore Dr. Milpitas, CA 95035 Phone: (408) 428-2050 FAX: (408) 432-6331
International Sales Offices
FRANCE Linear Technology S.A.R.L. Immeuble "Le Quartz" 58 Chemin de la Justice 92290 Chatenay Malabry France Phone: 33-1-41079555 FAX: 33-1-46314613 GERMANY Linear Techonolgy GmbH Untere Hauptstr. 9 D-85386 Eching Germany Phone: 49-89-3197410 FAX: 49-89-3194821 JAPAN Linear Technology KK 5F YZ Bldg. 4-4-12 Iidabashi, Chiyoda-Ku Tokyo, 102 Japan Phone: 81-3-3237-7891 FAX: 81-3-3237-8010 KOREA Linear Technology Korea Branch Namsong Building, #505 Itaewon-Dong 260-199 Yongsan-Ku, Seoul Korea Phone: 82-2-792-1617 FAX: 82-2-792-1619 SINGAPORE Linear Technology Pte. Ltd. 101 Boon Keng Road #02-15 Kallang Ind. Estates Singapore 1233 Phone: 65-293-5322 FAX: 65-292-0398 TAIWAN Linear Technology Corporation Rm. 801, No. 46, Sec. 2 Chung Shan N. Rd. Taipei, Taiwan, R.O.C. Phone: 886-2-521-7575 FAX: 886-2-562-2285 UNITED KINGDOM Linear Technology (UK) Ltd. The Coliseum, Riverside Way Camberley, Surrey GU15 3YL United Kingdom Phone: 44-276-677676 FAX: 44-276-64851
World Headquarters
Linear Technology Corporation 1630 McCarthy Blvd. Milpitas, CA 95035-7487 Phone: (408) 432-1900 FAX: (408) 434-0507
16
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7487
(408) 432-1900 q FAX: (408) 434-0507 q TELEX: 499-3977
LT/GP 0694 REV C 5K * PRINTED IN USA
(c) LINEAR TECHNOLOGY CORPORATION 1994

▲Up To Search▲

Price & Availability of LT1084

	To Download LT1084 Datasheet File
If you can't view the Datasheet, Please click here to try to view without PDF Reader .