LT1083CK

LT1083/LT1084/LT1085 7.5A, 5A, 3A Low Dropout Positive Adjustable Regulators FEATURES ■ ■ ■ ■ ■ ■ ■ ■ ■ DESCRIPTIO 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 Available in 3-Lead Plastic TO-220, TO-3P and DD Packages APPLICATIO S ■ ■ ■ ■ The LT®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 10µF 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. , LTC and LT are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. 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 APPLICATIO 5V, 7.5A Regulator INPUT/OUTPUT VOLTAGE DIFFERENTIAL (V) 2 Dropout Voltage vs Output Current VIN ≥ 6.5V IN LT1083 ADJ OUT 121Ω 1% 365Ω 1% 5V AT 7.5A + 10µF + 10µF* TANTALUM 1 *REQUIRED FOR STABILITY 1083/4/5 ADJ TA01 0 0 OUTPUT CURRENT U IFULL LOAD 1083/4/5 ADJ TA02 U U 108345fe 1 LT1083/LT1084/LT1085 ABSOLUTE MAXIMUM RATINGS PRECO DITIO I G 100% thermal shutdown functional test. PACKAGE/ORDER INFORMATION FRONT VIEW TAB IS OUTPUT 3 2 1 T PACKAGE 3-LEAD PLASTIC TO-220 θJA = 50°C/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 θJA = 35°C/W BOTTOM VIEW VIN 2 CASE IS OUTPUT 1 ADJ K PACKAGE 2-LEAD TO-3 METAL CAN θJA = 35°C/W LT1083CK LT1083MK LT1084CK LT1084MK LT1085CK LT1085MK FRONT VIEW 3 TAB IS OUTPUT 2 1 M PACKAGE 3-LEAD PLASTIC DD θJA = 30°C/W* *WITH PACKAGE SOLDERED TO 0.5IN2 COPPER AREA OVER BACKSIDE GROUND PLANE OR INTERNAL POWER PLANE. θJA CAN VARY FROM 20°C/W TO > 40°C/W DEPENDING ON MOUNTING TECHNIQUE. OBSOLETE PACKAGE The ● denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. PARAMETER Reference Voltage CONDITIONS IOUT = 10mA, TJ = 25°C, (VIN – VOUT) = 3V 10mA ≤ IOUT ≤ IFULL LOAD 1.5V ≤ (VIN – VOUT) ≤ 25V (Notes 4, 6, 7) ILOAD = 10mA, 1.5V ≤ (VIN – VOUT) ≤ 15V, TJ = 25°C (Notes 2, 3) M Grade: 15V ≤ (VIN – VOUT) ≤ 35V (Notes 2, 3) C, I Grades: 15V ≤ (VIN – VOUT) ≤ 30V (Notes 2, 3) MIN 1.238 ● ● ● ● ELECTRICAL CHARACTERISTICS Line Regulation 2 UU U Power Dissipation ............................... Internally Limited Input-to-Output Voltage Differential “C” Grades .......................................................... 30V “I” Grades ............................................................ 30V “M” Grades (OBSOLETE)............................ 35V Operating Junction Temperature Range “C” Grades: Control Section .................. 0°C to 125°C Power Transistor ............... 0°C to 150°C “I” Grades: Control Section ............. – 40°C to 125°C Power Transistor .......... – 40°C to 150°C U U W WW U W (Note 1) “M” Grades: (OBSOLETE) Control Section ............. – 55°C to 150°C Power Transistor .......... – 55°C to 200°C Storage Temperature Range ................. – 65°C to 150°C Lead Temperature (Soldering, 10 sec).................. 300°C ORDER PART NUMBER VIN VOUT ADJ LT1083CP LT1084CP VIN VOUT ADJ 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 % % % % 108345fe 1.225 LT1083/LT1084/LT1085 The ● denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. PARAMETER Load Regulation CONDITIONS (VIN – VOUT) = 3V 10mA ≤ IOUT ≤ IFULL LOAD TJ = 25°C (Notes 2, 3, 4, 6) ● ELECTRICAL CHARACTERISTICS 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 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 = 25°C, 30ms Pulse ● ● ● ● ● ● ● ● 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 µA µA µA % % % 10 0.010 0.015 0.020 f = 120Hz, CADJ = 25µF, COUT = 25µF Tantalum IOUT = IFULL LOAD, (VIN – VOUT) = 3V (Notes 6, 7, 8) TJ = 25°C 10mA ≤ IOUT ≤ IFULL LOAD 1.5V ≤ (VIN – VOUT) ≤ 25V (Note 6) TA = 125°C, 1000 Hrs TA = 25°C 10Hz = ≤ f ≤ 10kHz Control Circuitry/Power Transistor K Package P Package K Package P Package T Package K Package M, T Packages ● ● ● ● 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 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. 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 – 55°C ≤ TJ < – 40°C and 7.5A for TJ ≥ – 40°C. Note 7: 1.7V ≤ (VIN – VOUT) ≤ 25V for LT1084 at – 55°C ≤ TJ ≤ – 40°C. Note 8: Dropout is 1.7V maximum for LT1084 at – 55°C ≤ TJ ≤ – 40°C. 108345fe 3 LT1083/LT1084/LT1085 TYPICAL PERFORMANCE CHARACTERISTICS LT1083 Dropout Voltage MINIMUM INPUT/OUTPUT DIFFERENTIAL (V) 2 INDICATES GUARANTEED TEST POINT SHORT-CIRCUIT CURRENT (A) OUTPUT VOLTAGE DEVIATION (%) –40°C ≤ TJ ≤ 150°C 0°C ≤ TJ ≤ 125°C 1 TJ = 150°C TJ = 25°C TJ = – 55°C 0 0 1 2 345678 OUTPUT CURRENT (A) LT1084 Dropout Voltage MINIMUN INPUT/OUTPUT DIFFERENTIAL (V) 2 INDICATES GUARANTEED TEST POINT SHORT-CIRCUIT CURRENT (A) –55°C ≤ TJ ≤ 150°C 0°C ≤ TJ ≤ 125°C OUTPUT VOLTAGE DEVIATION (%) 1 TJ = – 55°C TJ = 150°C TJ = 25°C 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 –55°C ≤ TJ ≤ 150°C 0°C ≤ TJ ≤ 125°C SHORT-CIRCUIT CURRENT (A) 5 4 3 –55°C 2 1 0 IFULL LOAD GUARANTEED 25°C 150°C OUTPUT VOLTAGE DEVIATION (%) 1 TJ = 25°C TJ = 150°C TJ = – 55°C 0 0 3 2 1 OUTPUT CURRENT (A) 4 LT1083/4/5 ADJ G07 4 UW 9 LT1083/4/5 ADJ G01 LT1083 Short-Circut Current 12 10 8 6 4 2 0 –55°C 25°C 150°C LT1083 Load Regulation 0.10 ∆I = 7.5A 0.05 0 –0.05 –0.10 –0.15 –0.20 –50 –25 IFULL LOAD GUARANTEED 0 20 30 15 25 5 10 INPUT/OUTPUT DIFFERENTIAL (V) 35 10 0 25 50 75 100 125 150 TEMPERATURE (°C) LT1083/4/5 ADJ G03 LT1083/4/5 ADJ G02 10 9 8 7 6 5 4 3 2 1 0 LT1084 Short-Circut Current 0.10 LT1084 Load Regulation ∆I = 5A 0.05 0 –0.05 –0.10 –0.15 –0.20 –50 –25 150°C 25°C –55°C IFULL LOAD GUARANTEED 0 20 15 10 25 30 5 INPUT/OUTPUT DIFFERENTIAL (V) 35 0 25 50 75 100 125 150 TEMPERATURE (°C) LT1083/4/5 ADJ G06 LT1083/4/5 ADJ G05 LT1085 Short-Circut Current 6 LT1085 Load Regulation 0.10 ∆I = 3A 0.05 0 –0.05 –0.10 –0.15 –0.20 –50 –25 0 20 30 15 25 5 10 INPUT/OUTPUT DIFFERENTIAL (V) 35 0 25 50 75 100 125 150 TEMPERATURE (°C) LT1083/4/5 ADJ G09 LT1083/4/5 ADJ G08 108345fe LT1083/LT1084/LT1085 TYPICAL PERFORMANCE CHARACTERISTICS Minimum Operating Current 10 MINIMUM OPERATING CURRENT (mA) 9 1.26 ADJUST PIN CURRENT (µA) REFERENCE VOLTAGE (V) 8 7 6 5 4 3 2 1 0 0 20 15 10 25 30 5 INPUT/OUTPUT DIFFERENTIAL (V) 35 TJ = – 55°C TJ = 25°C TJ = 150°C LT1083/4/5 ADJ G10 LT1083 Ripple Rejection 100 90 80 RIPPLE REJECTION (dB) 70 60 50 40 30 20 10 0 10 100 1k 10k FREQUENCY (Hz) 100k CADJ = 200µF AT FREQUENCIES < 60Hz CADJ = 25µF AT FREQUENCIES > 60Hz IOUT = 7A VRIPPLE ≤ 3VP-P VRIPPLE ≤ 0.5VP-P RIPPLE REJECTION (dB) (VIN – VOUT) ≥ 3V POWER (W) (VIN – VOUT) ≥ VDROPOUT LT1084 Ripple Rejection 100 90 80 RIPPLE REJECTION (dB) 70 60 50 40 30 20 10 0 10 100 1k 10k FREQUENCY (Hz) 100k CADJ = 200µF AT FREQUENCIES < 60Hz CADJ = 25µF AT FREQUENCIES > 60Hz IOUT = 5A VRIPPLE ≤ 3VP-P VRIPPLE ≤ 0.5VP-P RIPPLE REJECTION (dB) (VIN – VOUT) ≥ 3V (VIN – VOUT) ≥ VDROPOUT 60 50 40 30 20 10 0 0 POWER (W) 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 90 80 70 60 50 40 30 20 10 0 0 1 6 4 3 2 5 OUTPUT CURRENT (A) 7 8 VOUT = 5V CADJ = 25µF COUT = 25µF fR = 20kHz VRIPPLE ≤ 0.5VP-P fR = 120Hz VRIPPLE ≤ 3VP-P 100 90 80 70 60 50 40 30 20 10 0 LT1083 Maximum Power Dissipation* LT1083MK LT1083CP 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 60 50 LT1084 Maximum Power Dissipation* LT1084MK 40 30 LT1084CT 20 LT1084CP VOUT = 5V CADJ = 25µF COUT = 25µF 1 4 3 2 OUTPUT CURRENT (A) 5 10 0 LT1084CK 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 108345fe 5 LT1083/LT1084/LT1085 TYPICAL PERFORMANCE CHARACTERISTICS LT1085 Ripple Rejection 100 90 80 RIPPLE REJECTION (dB) 70 60 50 40 30 20 10 0 10 100 1k 10k FREQUENCY (Hz) 100k CADJ = 200µF AT FREQUENCIES < 60Hz CADJ = 25µF AT FREQUENCIES > 60Hz IOUT = 3A (VIN – VOUT) ≥ VDROPOUT VRIPPLE ≤ 3VP-P VRIPPLE ≤ 0.5VP-P RIPPLE REJECTION (dB) 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 = 25µF COUT = 25µF fR = 120Hz VRIPPLE ≤ 3VP-P (VIN – VOUT) ≥ 3V 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 = 1µF 0.2 0 –0.2 –0.4 –0.6 CADJ = 1µF OUTPUT VOLTAGE DEVIATION (V) 0.4 CIN = 1µF COUT = 10µF 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 (µs) 100 1083/4/5 ADJ G23 LOAD CURRENT (A) 8 50 TIME (µs) LT1083 Line Transient Response 150 OUTPUT VOLTAGE DEVIATION (V) OUTPUT VOLTAGE DEVIATION (mV) 50 0 –50 CADJ = 1µF 20 0 –20 –40 –60 CADJ = 1µF OUTPUT VOLTAGE DEVIATION (mV) 100 CADJ = 0 –100 VOUT = 10V IIN = 0.2A CIN = 1µF TANTALUM COUT = 10µF TANTALUM –150 INPUT DEVIATION (V) INPUT DEVIATION (V) 14 13 12 0 14 13 12 0 INPUT DEVIATION (V) 100 TIME (µs) 6 UW 1083/4/5 ADJ G19 LT1085 Ripple Rejection vs Current 50 LT1085 Maximum Power Dissipation* 40 LT1085MK 30 fR = 20kHz VRIPPLE ≤ 0.5VP-P 20 LT1085CT 10 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 = 1µF CIN = 1µF COUT = 10µF TANTALUM CIN = 1µF COUT = 10µF TANTALUM VOUT = 10V VIN = 13V PRELOAD=100mA VOUT = 10V VIN = 13V PRELOAD=100mA 0 50 TIME (µs) 100 1083/4/5 ADJ G24 100 1083/4/5 ADJ G22 LT1084 Line Transient Response 60 40 CADJ = 0 60 40 20 0 –20 –40 –60 14 13 12 LT1085 Line Transient Response CADJ = 0 CADJ = 1µF VOUT = 10V IIN = 0.2A CIN = 1µF TANTALUM COUT = 10µF TANTALUM VOUT = 10V IIN = 0.2A CIN = 1µF TANTALUM COUT = 10µF TANTALUM 200 1083/4/5 ADJ G25 100 TIME (µs) 200 1083/4/5 ADJ G26 0 100 TIME (µs) 200 1083/4/5 ADJ G27 108345fe 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 165°C. 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 150µF aluminium electrolytic or a 22µF 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 150µF or 22µF 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 22µF tantalum or 150µF 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 10µF 10µF OUTPUT 10µF Tantalum, 50µF Aluminum 22µF Tantalum, 150µF Aluminum ADJUSTMENT None 20µF 108345fe 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 100µF 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 1000µF to 5000µF 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 150µF + CADJ 10µF 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. 108345fe 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 100Ω to 120Ω). The size of the required adjust pin capacitor is a function of the input ripple frequency. At 120Hz the adjust pin capacitor should be 25µF if R1 = 100Ω. At 10kHz only 0.22µF 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 IADJ 50µA VOUT = VREF 1 + R2 R1 OUT VREF R1 VOUT U W U U () 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 × ⎜ ⎟ , RP = Parasitic Line Resistance ⎝ R1 ⎠ RP PARASITIC LINE RESISTANCE VIN IN LT1083 ADJ R1* RL R2* OUT *CONNECT R1 TO CASE CONNECT R2 TO LOAD 1083/4/5 ADJ F02 Figure 2. Connections for Best Load Regulation 108345fe 9 LT1083/LT1084/LT1085 APPLICATIONS INFORMATION Connected as shown, RP is not multiplied by the divider ratio. RP is about 0.004Ω 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 = 75°C, θHEAT SINK = 1°C/W, θCASE-TO-HEAT SINK = 0.2°C/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 (θHEAT SINK + θCASE-TO-HEAT SINK + θJC) For the Control Section: TJ = 75°C + 24W (1°C/W + 0.2°C/W + 0.6°C/W) = 118°C 118°C < 125°C = TJMAX (Control Section Commercial Range) For the Power Transistor: TJ = 75°C + 24W (1°C/W + 0.2°C/W + 1.6°C/W) = 142°C 142°C < 150°C = 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 108345fe LT1083/LT1084/LT1085 TYPICAL APPLICATIONS 7.5A Variable Regulator T1 TRIAD F-269U C30B 20Ω 110VAC 20Ω C30B 1N4003 1N4003 1µF 560Ω 15V 16k* LT1004-1.2 L 1MH IN 3 T2 1N4003 1 2 1N914 2k OUTPUT ADJUST LT1083 ADJ LT1004-1.2 OUT 750Ω* 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 + 1.5k 0V TO 35V OA TO 7.5A 100µF + C1 50,000µF 8 –15V 4 7 200k 16k* 11k* 2.7k –15V + LT1011 – 0.1µF 1 NC 15V 100pF –15V 4 8 2N3904 – + 1 3 8 2 15K 15V 1µF 10k 6 LM301A 7 15V 1 LT1011 + – 4 –15V 3 2 11k* LT1083/4/5 ADJ TA05 108345fe 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 + 10µF RETURN 1083/4/5 ADJ TA07 12 U IN LT1083 ADJ OUT 2 FEET #18 WIRE* 0.015Ω IN LT1083 ADJ R1 120Ω 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 121Ω 1% R2 365Ω 1% VOUT 5V + 10µF + + C1 25µF* 150µF 1083/4/5 ADJ TA04 Remote Sensing RP (MAX DROP 300mV) OUT + 25Ω 121Ω VOUT 5V 2 100µF 6 1 VIN 7 – + 8 4 LM301A 3 1k RL 365Ω 100pF + 5µF 25Ω RETURN 108345fe LT1083/LT1084/LT1085 TYPICAL APPLICATIONS High Efficiency Regulator with Switching Preregulator VIN 28V 10k 1mH U 1k + MR1122 IN 10,000µF 470Ω 1N914 LT1083 ADJ OUT 240Ω VOUT 28V 2k 1M 4N28 10k 1083/4/5 ADJ TA06 + LT1011 – 1N914 10k 28V 1.2V to 15V Adjustable Regulator VOUT† R1 90.9Ω R2 1k VIN IN LT1083 ADJ OUT + C1* 10µF + C2 100µF †V *NEEDED IF DEVICE IS FAR FROM FILTER CAPACITORS R2 OUT = 1.25V 1 + R1 ( ) 1083/4/5 ADJ TA08 5V Regulator with Shutdown* VIN IN LT1083 ADJ OUT 121Ω 1% VOUT 5V + TTL 10µF 1k 1k 2N3904 365Ω 1% + 100µF 1083/4/5 ADJ TA09 *OUTPUT SHUTS DOWN TO 1.3V 108345fe 13 LT1083/LT1084/LT1085 PACKAGE DESCRIPTION K Package 2-Lead TO-3 Metal Can (LTC DWG # 05-08-1310) 1.177 – 1.197 (29.90 – 30.40) 0.320 – 0.350 (8.13 – 8.89) 0.760 – 0.775 (19.30 – 19.69) 0.060 – 0.135 (1.524 – 3.429) 0.655 – 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 0.067 – 0.077 (1.70 – 1.96) 0.490 – 0.510 (12.45 – 12.95) R 0.420 – 0.480 (10.67 – 12.19) 0.038 – 0.043 (0.965 – 1.09) .256 (6.502) .060 (1.524) .060 (1.524) .183 (4.648) .075 (1.905) .300 (7.620) BOTTOM VIEW OF DD PAK HATCHED AREA IS SOLDER PLATED COPPER HEAT SINK RECOMMENDED SOLDER PAD LAYOUT .420 .080 +.012 .143 –.020 +0.305 3.632 –0.508 .100 (2.54) BSC .013 – .023 (0.330 – 0.584) .350 .205 .565 .090 .100 .070 14 U 0.425 – 0.435 (10.80 – 11.05) K2 (TO-3) 1098 OBSOLETE PACKAGE M Package 3-Lead Plastic DD Pak (LTC DWG # 05-08-1460) .060 (1.524) TYP .390 – .415 (9.906 – 10.541) 15° .165 – .180 (4.191 – 4.572) .045 – .055 (1.143 – 1.397) .330 – .370 (8.382 – 9.398) .059 (1.499) ( +.008 .004 –.004 +0.203 0.102 –0.102 ) .095 – .115 (2.413 – 2.921) .050 ± .012 (1.270 ± 0.305) ( ) .050 (1.270) RECOMMENDED SOLDER PAD LAYOUT FOR THICKER SOLDER PASTE APPLICATIONS .420 .276 .325 .565 .320 NOTE: 1. DIMENSIONS IN INCH/(MILLIMETER) 2. DRAWING NOT TO SCALE .100 .070 108345fe .090 M (DD3) 0204 LT1083/LT1084/LT1085 PACKAGE DESCRIPTION P Package 3-Lead Plastic TO-3P (Similar to TO-247) (LTC DWG # 05-08-1450) .560 (14.224) .325 (8.255) .275 (6.985) .620 – .64O (15.75 – 16.26) .187 – .207 (4.75 – 5.26) MOUNTING HOLE 18° – 22° .115 – .145 (2.92 – 3.68) DIA .060 – .080 (1.52 – 2.03) .580 (14.732) .700 (17.780) .830 – .870 (21.08 – 22.10) .580 – .6OO (14.73 – 15.24) .098 (2.489) .124 (3.149) .780 – .800 (19.81 – 20.32) BOTTOM VIEW OF TO-3P HATCHED AREA IS SOLDER PLATED COPPER HEAT SINK .390 – .415 (9.906 – 10.541) .460 – .500 (11.684 – 12.700) .980 – 1.070 (24.892 – 27.178) .520 – .570 (13.208 – 14.478) .100 (2.540) BSC .028 – .038 (0.711 – 0.965) 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 .170 – .2OO (4.32 – 5.08) EJECTOR PIN MARKS .105 – .125 (2.67 – 3.18) DIA 3° – 7° .170 (4.32) MAX .042 – .052 (1.07 – 1.32) .074 – .084 (1.88 – 2.13) .215 (5.46) BSC .113 – .123 (2.87 – 3.12) .087 – .102 (2.21 – 2.59) .020 – .040 (0.51 – 1.02) P3 0801 T Package 3-Lead Plastic TO-220 (LTC DWG # 05-08-1420) .147 – .155 (3.734 – 3.937) DIA .230 – .270 (5.842 – 6.858) .570 – .620 (14.478 – 15.748) .330 – .370 (8.382 – 9.398) .165 – .180 (4.191 – 4.572) .045 – .055 (1.143 – 1.397) .218 – .252 (5.537 – 6.401) .013 – .023 (0.330 – 0.584) .050 (1.270) TYP .095 – .115 (2.413 – 2.921) T3 (TO-220) 0801 108345fe 15 LT1083/LT1084/LT1085 TYPICAL APPLICATIONS Automatic Light Control RELATED PARTS PART NUMBER LT1086 LT1117 LT1580 LT1581 LT1430 LT1575 LT1573 DESCRIPTION 1.5A Low Dropout Regulator 800mA Low Dropout Regulator 7A Very Low Dropout Linear Regulator 10A Very Low Dropout Linear Regulator High Power Step-Down Switching Regulator UltraFastTM Transient Response LDO Controller UltraFast Transient Response LDO Controller COMMENTS Fixed 2.85V, 3.3V, 3.6V, 5V and 12V Output Fixed 2.85V, 3.3V, 5V or Adjustable Output For High Performance Microprocessors 0.54V Dropout at 7A, Fixed 2.5VOUT and Adjustable 0.43V Dropout at 10A, Fixed 2.5VOUT and Adjustable 5V to 3.3V at 10A, >90% Efficiency External MOSFET Pass Element External PNP Pass Element LT1584/LT1585/LT1587 7A/4.6A/3A Fast Response Low Dropout Regulators UltraFast is a trademark of Linear Technology Corporation. 16 Linear Technology Corporation 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408)432-1900 ● FAX: (408) 434-0507 ● www.linear-tech.com U VIN IN LT1083 ADJ OUT 1.2k 100µF + 10µF 1083/4/5 ADJ TA10 Protected High Current Lamp Driver 12V 5A OUT TTL OR CMOS LT1083 ADJ 1083/4/5 ADJ TA11 IN 15V 10k 108345fe LT/LT 0505 REV E • PRINTED IN USA © LINEAR TECHNOLOGY CORPORATION 1994