LT1083/LT1084/LT1085 7.5A, 5A, 3A Low Dropout Positive Adjustable Regulators U DESCRIPTIO FEATURES 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: 0.1% 100% Thermal Limit Functional Test Fixed Versions Available U APPLICATIO S High Efficiency Linear Regulators Post Regulators for Switching Supplies Constant Current Regulators Battery Chargers The LT(R)1083 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. DEVICE OUTPUT CURRENT* LT1083 LT1084 LT1085 7.5A 5.0A 3.0A 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. , LTC and LT are registered trademarks of Linear Technology Corporation. *For a 1.5A low dropout regulator see the LT1086 data sheet. U TYPICAL APPLICATIO 5V, 7.5A Regulator IN LT1083 ADJ + 5V AT 7.5A OUT 121 1% 10F + 10F* TANTALUM 365 1% *REQUIRED FOR STABILITY 1083/4/5 ADJ TA01 INPUT/OUTPUT VOLTAGE DIFFERENTIAL (V) VIN 6.5V Dropout Voltage vs Output Current 2 1 0 0 IFULL LOAD OUTPUT CURRENT 1083/4/5 ADJ TA02 1 LT1083/LT1084/LT1085 (Note 1) "M" Grades: Control Section ............. - 55C to 150C Power Transistor .......... - 55C to 200C Storage Temperature Range ................. - 65C to 150C Lead Temperature (Soldering, 10 sec).................. 300C U W 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 UU W W U ABSOLUTE MAXIMUM RATINGS PRECO DITIO I G 100% thermal shutdown functional test. W U U PACKAGE/ORDER INFORMATION FRONT VIEW TAB IS OUTPUT 3 VIN 2 VOUT 1 ADJ T PACKAGE 3-LEAD PLASTIC TO-220 ORDER PART NUMBER TAB IS OUTPUT LT1084CT LT1084IT LT1085CT LT1085IT CASE IS OUTPUT 1 VIN 2 VOUT 1 ADJ LT1083CP LT1084CP JA = 35C/W BOTTOM VIEW 2 3 P PACKAGE 3-LEAD PLASTIC TO-3P JA = 50C/W VIN ORDER PART NUMBER FRONT VIEW LT1083CK LT1083MK LT1084CK LT1084MK LT1085CK LT1085MK FRONT VIEW TAB IS OUTPUT 3 VIN 2 VOUT 1 ADJ LT1085CM M PACKAGE 3-LEAD PLASTIC DD ADJ JA = 30C/W* K PACKAGE 2-LEAD TO-3 METAL CAN *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 The denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25C. PARAMETER Reference Voltage Line Regulation CONDITIONS IOUT = 10mA, TJ = 25C, (VIN - VOUT) = 3V 10mA IOUT IFULL LOAD 1.5V (VIN - VOUT) 25V (Notes 4, 6, 7) ILOAD = 10mA, 1.5V (VIN - VOUT) 15V, TJ = 25C (Notes 2, 3) M Grade: 15V (VIN - VOUT) 35V (Notes 2, 3) C, I Grades: 15V (VIN - VOUT) 30V (Notes 2, 3) 2 MIN TYP MAX UNITS 1.238 1.250 1.262 V 1.225 1.250 0.015 0.035 0.05 0.05 1.270 0.2 0.2 0.5 0.5 V % % % % LT1083/LT1084/LT1085 ELECTRICAL CHARACTERISTICS The denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25C. PARAMETER Load Regulation CONDITIONS (VIN - VOUT) = 3V 10mA IOUT IFULL LOAD TJ = 25C (Notes 2, 3, 4, 6) MIN Dropout Voltage Current Limit LT1083 LT1084 LT1085 Minimum Load Current Thermal Regulation LT1083 LT1084 LT1085 Ripple Rejection Adjust Pin Current VREF = 1%, IOUT = IFULLLOAD (Notes 5, 6, 8) (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 8.0 0.4 5.5 0.3 3.2 0.2 f = 120Hz, CADJ = 25F, COUT = 25F Tantalum IOUT = IFULL LOAD, (VIN - VOUT) = 3V (Notes 6, 7, 8) TJ = 25C 60 TYP MAX UNITS 0.1 0.2 1.3 0.3 0.4 1.5 % % V 9.5 1.0 6.5 0.6 4.0 0.5 5 10 A A A A A A mA 0.002 0.003 0.004 0.010 0.015 0.020 %/W %/W %/W 75 55 120 Adjust Pin Current Change Temperature Stability Long Term Stability RMS Output Noise (% of VOUT) Thermal Resistance Junction-to-Case LT1083 LT1084 LT1085 10mA IOUT IFULL LOAD 1.5V (VIN - VOUT) 25V (Note 6) TA = 125C, 1000 Hrs TA = 25C 10Hz = f 10kHz Control Circuitry/Power Transistor K Package P Package K Package P Package T Package K Package M, T Packages 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. Load and line regulation are measured at a constant junction temperature by low duty cycle pulse testing. Note 3: 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. 0.2 0.5 0.3 5 1 0.003 dB A A A % % % 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 C/W C/W C/W C/W C/W C/W C/W Note 4: 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 5: 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 6: For LT1083 IFULL LOAD is 5A for - 55C TJ < - 40C and 7.5A for TJ -40C. Note 7: 1.7V (VIN - VOUT) 25V for LT1084 at - 55C TJ - 40C. Note 8: Dropout is 1.7V maximum for LT1084 at - 55C TJ - 40C. 3 LT1083/LT1084/LT1085 U W TYPICAL PERFORMANCE CHARACTERISTICS LT1083 Dropout Voltage LT1083 Short-Circut Current 12 MINIMUM INPUT/OUTPUT DIFFERENTIAL (V) 2 0.10 INDICATES GUARANTEED TEST POINT SHORT-CIRCUIT CURRENT (A) 0C TJ 125C 1 TJ = 150C TJ = 25C TJ = -55C OUTPUT VOLTAGE DEVIATION (%) I = 7.5A -40C TJ 150C 25C 10 150C 8 6 -55C 4 2 IFULL LOAD GUARANTEED 0 0 1 2 3 4 5 6 7 8 OUTPUT CURRENT (A) 9 0 10 20 30 15 25 5 10 INPUT/OUTPUT DIFFERENTIAL (V) LT1084 Dropout Voltage INDICATES GUARANTEED TEST POINT SHORT-CIRCUIT CURRENT (A) 0C TJ 125C 1 TJ = -55C TJ = 25C 0 25 50 75 100 125 150 TEMPERATURE (C) LT1083/4/5 ADJ G03 LT1084 Load Regulation I = 5A 8 7 150C 25C 6 -55C 5 4 3 2 IFULL LOAD GUARANTEED 0 0 5 -0.15 0.10 1 3 4 2 OUTPUT CURRENT (A) -0.10 9 -55C TJ 150C 1 -0.05 LT1084 Short-Circut Current 10 2 0 0 LT1083/4/5 ADJ G02 LT1083/4/5 ADJ G01 TJ = 150C 0.05 -0.20 -50 -25 35 OUTPUT VOLTAGE DEVIATION (%) 0 MINIMUN INPUT/OUTPUT DIFFERENTIAL (V) LT1083 Load Regulation 0 6 20 15 10 25 30 5 INPUT/OUTPUT DIFFERENTIAL (V) 0.05 0 -0.05 -0.10 -0.15 -0.20 -50 -25 35 0 25 50 75 100 125 150 TEMPERATURE (C) LT1083/4/5 ADJ G05 LT1083/4/5 ADJ G06 LT1083/4/5 ADJ G04 LT1085 Short-Circut Current LT1085 Load Regulation 6 2 0.10 INDICATES GUARANTEED TEST POINT -55C TJ 150C 0C TJ 125C 1 TJ = -55C TJ = 25C TJ = 150C 5 25C 4 150C 3 -55C 2 IFULL LOAD GUARANTEED 1 0 0 0 3 2 1 OUTPUT CURRENT (A) 4 LT1083/4/5 ADJ G07 4 OUTPUT VOLTAGE DEVIATION (%) I = 3A SHORT-CIRCUIT CURRENT (A) MINIMUM INPUT/OUTPUT DIFFERENTIAL (V) LT1085 Dropout Voltage 0 20 30 15 25 5 10 INPUT/OUTPUT DIFFERENTIAL (V) 35 LT1083/4/5 ADJ G08 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/LT1084/LT1085 U W TYPICAL PERFORMANCE CHARACTERISTICS Minimum Operating Current Temperature Stability 100 9 7 6 5 TJ = 150C 4 TJ = 25C 3 ADJUST PIN CURRENT (A) 90 8 1.26 1.25 1.24 2 TJ = -55C 0 20 15 10 25 30 5 INPUT/OUTPUT DIFFERENTIAL (V) 35 0 40 30 CADJ = 200F AT FREQUENCIES < 60Hz CADJ = 25F AT FREQUENCIES > 60Hz IOUT = 7A 20 10 100 1k 10k FREQUENCY (Hz) 60 70 50 40 VOUT = 5V CADJ = 25F COUT = 25F 10 7 6 4 3 2 5 OUTPUT CURRENT (A) 1 LT1083/4/5 ADJ G15 LT1084 Maximum Power Dissipation* 60 100 30 CADJ = 200F AT FREQUENCIES < 60Hz CADJ = 25F AT FREQUENCIES > 60Hz IOUT = 5A 10 10 100 1k 10k FREQUENCY (Hz) 60 1083/4/5 ADJ G16 40 50 40 30 LT1084CT LT1084CP 20 30 VOUT = 5V CADJ = 25F COUT = 25F 10 100k LT1084MK fR = 20kHz VRIPPLE 0.5VP-P 70 20 0 50 POWER (W) RIPPLE REJECTION (dB) 40 20 fR = 120Hz VRIPPLE 3VP-P 90 80 (VIN - VOUT) VDROPOUT 50 LT1083CK 50 60 70 80 90 100 110 120 130 140 150 CASE TEMPERATURE (C) * AS LIMITED BY MAXIMUM JUNCTION TEMPERATURE 8 LT1084 Ripple Rejection vs Current (VIN - VOUT) 3V LT1083CP 10 1083/4/5 ADJ G14 VRIPPLE 3VP-P VRIPPLE 0.5VP-P 60 40 0 0 100 70 50 20 0 100k LT1083MK 60 30 30 LT1084 Ripple Rejection 80 25 50 75 100 125 150 TEMPERATURE (C) 80 1083/4/5 ADJ G13 90 0 90 fR = 20kHz VRIPPLE 0.5VP-P 70 20 0 10 20 100 80 (VIN - VOUT) VDROPOUT 50 30 LT1083 Maximum Power Dissipation* fR = 120Hz VRIPPLE 3VP-P 90 RIPPLE REJECTION (dB) RIPPLE REJECTION (dB) 60 40 LT1083/4/5 ADJ G12 100 VRIPPLE 0.5VP-P (VIN - VOUT) 3V 70 50 LT1083 Ripple Rejection vs Current VRIPPLE 3VP-P 80 60 LT1083/4/5 ADJ G11 LT1083 Ripple Rejection 90 70 0 -50 -25 25 50 75 100 125 150 TEMPERATURE (C) LT1083/4/5 ADJ G10 100 80 10 1.23 -50 -25 POWER (W) 1 0 RIPPLE REJECTION (dB) Adjust Pin Current 1.27 REFERENCE VOLTAGE (V) MINIMUM OPERATING CURRENT (mA) 10 10 LT1084CK 0 0 0 1 4 3 2 OUTPUT CURRENT (A) 5 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 U W TYPICAL PERFORMANCE CHARACTERISTICS LT1085 Ripple Rejection 90 80 70 60 (VIN - VOUT) VDROPOUT 50 40 30 CADJ = 200F AT FREQUENCIES < 60Hz CADJ = 25F AT FREQUENCIES > 60Hz IOUT = 3A 100 1k 10k FREQUENCY (Hz) 50 40 10 VOUT = 5V CADJ = 25F COUT = 25F LT1085CK 0 0 0 0.5 2.5 2.0 1.0 1.5 OUTPUT CURRENT (A) 1083/4/5 ADJ G19 0.4 OUTPUT VOLTAGE DEVIATION (V) 0.4 CADJ = 1F 0 CIN = 1F COUT = 10F TANTALUM LOAD CURRENT (A) -0.4 8 VOUT =10V VIN =13V PRELOAD=100mA 6 4 2 0 0 50 TIME (s) 100 0.3 CADJ = 1F 0.2 0 -0.2 CIN = 1F COUT = 10F TANTALUM -0.4 6 VOUT = 10V VIN = 13V PRELOAD=100mA 4 2 0 0 50 TIME (s) OUTPUT VOLTAGE DEVIATION (V) CADJ = 1F 50 0 -50 -100 VOUT = 10V IIN = 0.2A CIN = 1F TANTALUM COUT = 10F TANTALUM 14 13 12 0 100 TIME (s) -0.1 200 1083/4/5 ADJ G25 CIN = 1F COUT = 10F TANTALUM -0.2 -0.3 3 VOUT = 10V VIN = 13V PRELOAD=100mA 2 1 0 0 50 TIME (s) 100 LT1085 Line Transient Response 60 CADJ = 0 40 CADJ = 1F 20 0 -20 -40 VOUT = 10V IIN = 0.2A CIN = 1F TANTALUM COUT = 10F TANTALUM -60 INPUT DEVIATION (V) -150 0 1083/4/5 ADJ G24 60 CADJ = 0 100 CADJ = 1F 0.1 LT1084 Line Transient Response 150 OUTPUT VOLTAGE DEVIATION (mV) 100 CADJ = 0 0.2 1083/4/5 ADJ G23 LT1083 Line Transient Response INPUT DEVIATION (V) LT1085 Load Transient Response CADJ = 0 1083/4/5 ADJ G22 6 LT1083/4/5 ADJ G21 -0.6 LOAD CURRENT (A) OUTPUT VOLTAGE DEVIATION (V) 0.6 -0.2 50 60 70 80 90 100 110 120 130 140 150 CASE TEMPERATURE (C) * AS LIMITED BY MAXIMUM JUNCTION TEMPERATURE LT1084 Load Transient Response 0.6 0.2 3.0 1083/4/5 ADJ G20 LT1083 Load Transient Response CADJ = 0 20 LT1085CT 10 100k LT1085MK 30 30 20 0 10 fR = 20kHz VRIPPLE 0.5VP-P OUTPUT VOLTAGE DEVIATION (mV) 10 60 14 13 12 0 100 TIME (s) CADJ = 0 40 CADJ = 1F 20 0 -20 -40 VOUT = 10V IIN = 0.2A CIN = 1F TANTALUM COUT = 10F TANTALUM -60 INPUT DEVIATION (V) 20 40 fR = 120Hz VRIPPLE 3VP-P 70 POWER (W) (VIN - VOUT) 3V RIPPLE REJECTION (dB) RIPPLE REJECTION (dB) 80 50 100 VRIPPLE 0.5VP-P OUTPUT VOLTAGE DEVIATION (V) VRIPPLE 3VP-P 90 LT1085 Maximum Power Dissipation* LOAD CURRENT (A) 100 LT1085 Ripple Rejection vs Current 200 1083/4/5 ADJ G26 14 13 12 0 100 TIME (s) 200 1083/4/5 ADJ G27 LT1083/LT1084/LT1085 W BLOCK DIAGRAM VIN + - THERMAL LIMIT VOUT 1083/4/5 ADJ BD VADJ U W U U 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 7 LT1083/LT1084/LT1085 U W U U 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. 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. 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. 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. 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 8 D1 1N4002 (OPTIONAL) VIN IN LT1083 OUT ADJ + R1 CADJ 10F + VOUT COUT 150F 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 U W U U 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. IN VIN OUT LT1083 ADJ VOUT VREF R1 IADJ 50A ( VOUT = VREF 1 + R2 R1 ) R2 + IADJ R2 1083/4/5 ADJ F01 Figure 1. Basic Adjustable Regulator Ripple Rejection Load Regulation 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. 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: 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. R2 + R1 RP x , RP = Parasitic Line Resistance R1 RP PARASITIC LINE RESISTANCE VIN IN LT1083 OUT ADJ R1* RL R2* *CONNECT R1 TO CASE CONNECT R2 TO LOAD 1083/4/5 ADJ F02 Figure 2. Connections for Best Load Regulation 9 LT1083/LT1084/LT1085 U W U U 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. 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. Thermal Considerations For example, using an LT1083CK (TO-3, Commercial) and assuming: 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 10 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. LT1083/LT1084/LT1085 U TYPICAL APPLICATIONS 7.5A Variable Regulator T1 TRIAD F-269U L 1MH C30B IN 20 3 110VAC 20 T2 1 + 750* 100F 50,000F 2 1N914 2k OUTPUT ADJUST 1N4003 1F 16k* 560 15V 82k 15k -15V 8 2 + 3 10k LT1004-1.2 16k* 200k 11k* 7 -15V 0.1F - 1 1N4148 NC 15V 100pF 2N3904 8 -15V 4 7 2.7k 4 LT1011 * 1% FILM RESISTOR L: DALE TO-5 TYPE T2: STANCOR 11Z-2003 1.5k 0V TO 35V OA TO 7.5A LT1004-1.2 C30B 1N4003 OUT ADJ + C1 1N4003 LT1083 - 3 1 8 LT1011 + 10k 2 6 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 3 - 2 LM301A 1 15K + 7 15V 4 -15V 11k* 15V 1F LT1083/4/5 ADJ TA05 11 LT1083/LT1084/LT1085 U TYPICAL APPLICATIONS Paralleling Regulators VIN IN LT1083 2 FEET #18 WIRE* OUT ( ) ADJ VOUT = 1.25V 1 + R2 R1 IOUT = 0A TO 15A 0.015 IN LT1083 OUT *THE #18 WIRE ACTS AS BALLAST RESISTANCE INSURING CURRENT SHARING BETWEEN BOTH DEVICES ADJ R1 120 LT1083/4/5 ADJ TA03 R2 Improving Ripple Rejection VIN IN LT1083 R1 121 1% ADJ + VOUT 5V OUT 10F + 150F R2 365 1% + C1 25F* *C1 IMPROVES RIPPLE REJECTION. XC SHOULD BE < R1 AT RIPPLE FREQUENCY 1083/4/5 ADJ TA04 Remote Sensing RP (MAX DROP 300mV) VIN IN LT1083 + ADJ 10F VIN 100F 25 + VOUT 5V OUT 121 7 6 - LM301A 1 + 3 100pF 1k RL 8 4 365 2 5F + 25 RETURN RETURN 1083/4/5 ADJ TA07 12 LT1083/LT1084/LT1085 U TYPICAL APPLICATIONS High Efficiency Regulator with Switching Preregulator 1mH VIN 28V IN + LT1083 ADJ 10,000F MR1122 VOUT OUT 240 470 10k 1N914 28V 1k 1M 2k 4N28 10k + 1083/4/5 ADJ TA06 LT1011 10k - 28V 1N914 1.2V to 15V Adjustable Regulator VIN IN LT1083 R1 90.9 ADJ + C1* 10F VOUT OUT + C2 100F R2 1k *NEEDED IF DEVICE IS FAR FROM FILTER CAPACITORS R2 OUT = 1.25V 1 + R1 ( V ) 1083/4/5 ADJ TA08 5V Regulator with Shutdown* VIN IN LT1083 ADJ + VOUT 5V OUT 121 1% + 10F 100F 1k 2N3904 TTL 365 1% 1k 1083/4/5 ADJ TA09 *OUTPUT SHUTS DOWN TO 1.3V 13 LT1083/LT1084/LT1085 U PACKAGE DESCRIPTION Dimension in inches (millimeters) unless otherwise noted. K Package 2-Lead TO-3 Metal Can (LTC DWG # 05-08-1310) 0.760 - 0.775 (19.30 - 19.69) 0.320 - 0.350 (8.13 - 8.89) 0.060 - 0.135 (1.524 - 3.429) 0.420 - 0.480 (10.67 - 12.19) 0.038 - 0.043 (0.965 - 1.09) 1.177 - 1.197 (29.90 - 30.40) 0.655 - 0.675 (16.64 - 17.15) 0.210 - 0.220 (5.33 - 5.59) 0.151 - 0.161 (3.86 - 4.09) DIA, 2PLCS 0.167 - 0.177 (4.24 - 4.49) R 0.425 - 0.435 (10.80 - 11.05) 0.067 - 0.077 (1.70 - 1.96) 0.490 - 0.510 (12.45 - 12.95) R K2 (TO-3) 1098 M Package 3-Lead Plastic DD Pak (LTC DWG # 05-08-1460) 0.256 (6.502) 0.060 (1.524) 0.060 (1.524) TYP 0.390 - 0.415 (9.906 - 10.541) 0.165 - 0.180 (4.191 - 4.572) 15 TYP 0.060 (1.524) 0.183 (4.648) 0.059 (1.499) TYP 0.330 - 0.370 (8.382 - 9.398) BOTTOM VIEW OF DD PAK HATCHED AREA IS SOLDER PLATED COPPER HEAT SINK 14 ( +0.008 0.004 -0.004 +0.203 0.102 -0.102 ) 0.095 - 0.115 (2.413 - 2.921) 0.075 (1.905) 0.300 (7.620) 0.045 - 0.055 (1.143 - 1.397) ( +0.012 0.143 - 0.020 +0.305 3.632 -0.508 ) 0.090 - 0.110 (2.286 - 2.794) 0.050 (1.270) BSC 0.013 - 0.023 (0.330 - 0.584) 0.050 0.012 (1.270 0.305) M (DD3) 1098 LT1083/LT1084/LT1085 U PACKAGE DESCRIPTION Dimension in inches (millimeters) unless otherwise noted. P Package 3-Lead Plastic TO-3P (Similar to TO-247) (LTC DWG # 05-08-1450) 0.560 (14.224) 0.325 (8.255) 0.187 - 0.207 (4.75 - 5.26) 0.620 - 0.64O (15.75 - 16.26) 0.275 (6.985) 0.580 (14.732) 0.830 - 0.870 (21.08 - 22.10) 0.700 (17.780) 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 0.580 - 0.6OO (14.73 - 15.24) 0.098 (2.489) 0.124 (3.149) MOUNTING HOLE 18 - 22 0.115 - 0.145 (2.92 - 3.68) DIA 3 - 7 0.170 (4.32) MAX 0.780 - 0.800 (19.81 - 20.32) 0.042 - 0.052 (1.07 - 1.32) BOTTOM VIEW OF TO-3P HATCHED AREA IS SOLDER PLATED COPPER HEAT SINK 0.215 (5.46) BSC 0.074 - 0.084 (1.88 - 2.13) 0.087 - 0.102 (2.21 - 2.59) 0.020 - 0.040 (0.51 - 1.02) 0.113 - 0.123 (2.87 - 3.12) P3 0996 T Package 3-Lead Plastic TO-220 (LTC DWG # 05-08-1420) 0.147 - 0.155 (3.734 - 3.937) DIA 0.390 - 0.415 (9.906 - 10.541) 0.165 - 0.180 (4.191 - 4.572) 0.045 - 0.055 (1.143 - 1.397) 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) 0.980 - 1.070 (24.892 - 27.178) 0.520 - 0.570 (13.208 - 14.478) 0.100 (2.540) BSC 0.218 - 0.252 (5.537 - 6.401) 0.013 - 0.023 (0.330 - 0.584) 0.028 - 0.038 (0.711 - 0.965) 0.050 (1.270) TYP 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. 0.095 - 0.115 (2.413 - 2.921) T3 (TO-220) 1098 15 LT1083/LT1084/LT1085 U TYPICAL APPLICATIONS Automatic Light Control VIN IN LT1083 OUT ADJ + 1.2k 100F 10F 1083/4/5 ADJ TA10 Protected High Current Lamp Driver 12V 5A OUT LT1083 IN 15V ADJ TTL OR CMOS 1083/4/5 ADJ TA11 10k RELATED PARTS PART NUMBER DESCRIPTION COMMENTS LT1086 1.5A Low Dropout Regulator Fixed 2.85V, 3.3V, 3.6V, 5V and 12V Output LT1117 800mA Low Dropout Regulator Fixed 2.85V, 3.3V, 5V or Adjustable Output LT1584/LT1585/LT1587 7A/4.6A/3A Fast Response Low Dropout Regulators For High Performance Microprocessors LT1580 7A Very Low Dropout Linear Regulator 0.54V Dropout at 7A, Fixed 2.5VOUT and Adjustable LT1581 10A Very Low Dropout Linear Regulator 0.43V Dropout at 10A, Fixed 2.5VOUT and Adjustable LT1430 High Power Step-Down Switching Regulator 5V to 3.3V at 10A, >90% Efficiency LT1575 UltraFastTM Transient Response LDO Controller External MOSFET Pass Element LT1573 UltraFast Transient Response LDO Controller External PNP Pass Element UltraFast is a trademark of Linear Technology Corporation. 16 Linear Technology Corporation 1083fds, sn1083 LT/TP 0200 2K REV D * PRINTED IN USA 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408)432-1900 FAX: (408) 434-0507 www.linear-tech.com LINEAR TECHNOLOGY CORPORATION 1994