LT1086 Series 1.5A Low Dropout Positive Regulators Adjustable and Fixed 2.85V, 3.3V, 3.6V, 5V, 12V U FEATURES ■ ■ ■ ■ ■ ■ ■ ■ ■ DESCRIPTIO 3-Terminal Adjustable or Fixed 2.85V, 3.3V, 3.6V, 5V, 12V Output Current of 1.5A (0.5A for LT1086H) Operates Down to 1V Dropout Guaranteed Dropout Voltage at Multiple Current Levels Line Regulation: 0.015% Load Regulation: 0.1% 100% Thermal Limit Functional Test Ripple Rejection >75dB Available in 3-Pin TO-220 and 3-Pin DD Packages The LT1086 is pin compatible with older 3-terminal adjustable regulators. A minimum 10µF output capacitor is required on these devices. U APPLICATIO S ■ ■ ■ ■ ■ ■ The LT ®1086 is designed to provide up to 1.5A output current. All internal circuitry is designed to operate down to 1V input-to-output differential and the dropout voltage is fully specified as a function of load current. Dropout is guaranteed at several operating points up to a maximum of 1.5V at maximum output current. Dropout decreases at lower load currents. On-chip trimming adjusts the reference/ouput voltage to 1%. Current limit is also trimmed, minimizing the stress on both the regulator and power source circuitry under overload conditions. SCSI-2 Active Terminator High Efficiency Linear Regulators Post Regulators for Switching Supplies Constant Current Regulators Battery Chargers Microprocessor Supply The LT1086 offers excellent line and load regulation specifications and ripple rejection exceeds 75dB even at the maximum load current of 1.5A. The LT1086 is floating architecture with a composite NPN output stage. All of the quiescent current and the drive current for the output stage flows to the load increasing efficiency. The LT1086 is available in a 3-pin TO-220 package and a space-saving surface mountable 3-pin DD package. , LTC and LT are registered trademarks of Linear Technology Corporation. U TYPICAL APPLICATIO 5V to 3.3V Regulator VIN ≥ 4.75V IN LT1086-3.3 OUT 3.3V AT 1.5A GND 10µF* TANTALUM 10µF TANTALUM LT1086 • TA01 *MAY BE OMITTED IF INPUT SUPPLY IS WELL BYPASSED WITHIN 2" OF THE LT1086 MINIMUM INPUT/OUTPUT DIFFERENTIAL (V) LT1086 Dropout Voltage 2 INDICATES GUARANTEED TEST POINT –55°C ≤ TJ ≤ 150°C 0°C ≤ TJ ≤ 125°C 1 TJ = – 55°C TJ = 25°C TJ = 150°C 0 0 1 0.5 OUTPUT CURRENT (A) 1.5 LT1086 • TA02 sn1086 1086ffs 1 LT1086 Series W W U W ABSOLUTE MAXIMUM RATINGS (Note 1) “M” Grades 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 * Although the device’s maximum operating voltage is limited, (18V for a 2.85V device, 20V for a 5V device, and 25V for adjustable and12V devices) the devices are guaranteed to withstand transient input voltages up to 30V. For input voltages greater than the maximum operating input voltage some degradation of specifications will occur. For fixed voltage devices operating at input/output voltage differentials greater than 15V, a minimum external load of 5mA is required to maintain regulation. UU U Power Dissipation ............................... Internally Limited Input Voltage* ......................................................... 30V Operating Input Voltage Adjustable Devices ........................................... 25V 2.85V Devices .................................................. 18V 3.3V, 3.6V, and 5V Devices ............................... 20V 12V Devices ...................................................... 25V Operating Junction Temperature Range “C” Grades Control Section ............................... 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 PRECONDITIONING 100% Thermal Shutdown Functional Test. U W U PACKAGE/ORDER INFORMATION ORDER PART NUMBER BOTTOM VIEW ADJ LT1086CH LT1086MH 2 VIN 1 3 VOUT (CASE) ORDER PART NUMBER FRONT VIEW TAB IS OUTPUT 3 VIN 2 VOUT 1 ADJ (GND)† M PACKAGE 3-LEAD PLASTIC DD θJA = 30°C/W** H PACKAGE 3-LEAD TO-39 METAL CAN ** 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. θJA = 150°C/W ORDER PART NUMBER ORDER PART NUMBER BOTTOM VIEW CASE IS OUTPUT VIN 2 1 ADJ (GND)* K PACKAGE 2-LEAD TO-3 METAL CAN θJA = 35°C/W LT1086CK LT1086CK-5 LT1086CK-12 LT1086IK LT1086IK-5 LT1086IK-12 LT1086MK LT1086MK-5 LT1086MK-12 LT1086CM LT1086CM-3.3 LT1086CM-3.6 LT1086IM LT1086IM-3.3 FRONT VIEW TAB IS OUTPUT 3 VIN 2 VOUT 1 ADJ (GND)† T PACKAGE 3-LEAD PLASTIC TO-220 θJA = 50°C/W LT1086CT LT1086CT-2.85 LT1086CT-3.3 LT1086IT LT1086IT-5 LT1086IT-12 LT1086CT-3.6 LT1086CT-5 LT1086CT-12 OBSOLETE PACKAGES Consider the T Package for Alternate Source † For fixed versions. Consult LTC Marketing for parts specified with wider operating temperature ranges. sn1086 1086ffs 2 LT1086 Series ELECTRICAL CHARACTERISTICS The ● denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. PARAMETER CONDITIONS Reference Voltage (Note 3) LT1086, LT1086H Output Voltage (Note 3) LT1086-2.85 LT1086-3.3 LT1086-3.6 LT1086-5 LT1086-12 Line Regulation LT1086, LT1086H LT1086-2.85 LT1086-3.3 LT1086-3.6 LT1086-5 LT1086-12 Load Regulation LT1086, LT1086H LT1086-2.85 LT1086-3.3 LT1086-3.6 MIN TYP MAX UNITS ● 1.238 1.225 1.250 1.250 1.262 1.270 V V IOUT = 0mA, TJ = 25°C, VIN = 5V 0V ≤ IOUT ≤ 1.5A, 4.35V ≤ VIN ≤ 18V ● 2.82 2.79 2.85 2.85 2.88 2.91 V V VIN = 5V, IOUT = 0mA, TJ = 25°C 4.75V ≤ VIN ≤ 18V, 0V ≤ IOUT ≤ 1.5A ● 3.267 3.235 3.300 3.300 3.333 3.365 V V 3.564 3.500 3.500 3.300 3.600 3.636 3.672 3.672 3.672 V V V V 5.000 5.000 IOUT = 10mA, TJ = 25°C, (VIN – VOUT) = 3V 10mA ≤ IOUT ≤ 1.5A, (0.5A for LT1086H), 1.5V ≤ (VIN – VOUT) ≤ 15V VIN = 5V, IOUT = 0mA, TJ = 25°C 5V ≤ VIN ≤ 18V, 0 ≤ IOUT ≤ 1.5A 4.75V ≤ VIN ≤ 18V, 0 ≤ IOUT ≤ 1A, TJ ≥ 0°C VIN = 4.75V, IOUT = 1.5A, TJ ≥ 0°C ● IOUT = 0mA, TJ = 25°C, VIN = 8V 0 ≤ IOUT ≤ 1.5A, 6.5V ≤ VIN ≤ 20V ● 4.950 4.900 5.050 5.100 V V IOUT = 0mA, TJ = 25°C, VIN = 15V 0 ≤ IOUT ≤ 1.5A, 13.5V ≤ VIN ≤ 25V ● 11.880 12.000 12.120 11.760 12.000 12.240 V V ● 0.015 0.035 0.2 0.2 % % ● 0.3 0.6 6 6 mV mV ● 0.5 1.0 10 10 mV mV ● 0.5 1.0 10 10 mV mV ● 0.5 1.0 10 10 mV mV ● 1.0 2.0 25 25 mV mV ● 0.1 0.2 0.3 0.4 % % ● 3 6 12 20 mV mV ● 3 7 15 25 mV mV ● 3 6 2 4 15 25 15 25 mV mV mV mV ● 5 10 20 35 mV mV ● 12 24 36 72 mV mV ● 1.3 1.5 V ● 0.95 1.25 V ILOAD = 10mA, 1.5V ≤ (VIN – VOUT) ≤ 15V, TJ = 25°C IOUT = 0mA, TJ = 25°C, 4.35V ≤ VIN ≤ 18V 4.5V ≤ VIN ≤ 18V, IOUT = 0mA, TJ = 25°C 4.75V ≤ VIN ≤ 18V, IOUT = 0mA, TJ = 25°C IOUT = 0mA, TJ = 25°C, 6.5V ≤ VIN ≤ 20V IOUT = 0mA, TJ = 25°C, 13.5V ≤ VIN ≤ 25V (VIN – VOUT) = 3V, 10mA ≤ IOUT ≤ 1.5A, (0.5A for LT1086H) TJ = 25°C (Notes 2, 3) VIN = 5V, 0 ≤ IOUT ≤ 1.5A, TJ = 25°C (Notes 2, 3) VIN = 5V, 0 ≤ IOUT ≤ 1.5A, TJ = 25°C (Notes 2, 3) VIN = 5.25V, 0 ≤ IOUT ≤ 1.5A, TJ = 25°C (Notes 2, 3) ● VIN = 5V, 0 ≤ IOUT ≤ 1A, TJ = 25°C LT1086-5 LT1086-12 Dropout Voltage (VIN – VOUT) VIN = 8V, 0 ≤ IOUT ≤ 1.5A, TJ = 25°C (Notes 2, 3) VIN = 15V, 0 ≤ IOUT ≤ 1.5A, TJ = 25°C (Notes 2, 3) LT1086/-2.85/-3.3/-3.6/-5/-12 LT1086H ∆VOUT, ∆VREF = 1%, IOUT = 1.5A (Note 4) ∆VREF = 1%, IOUT = 0.5A (Note 4) sn1086 1086ffs 3 LT1086 Series ELECTRICAL CHARACTERISTICS The ● denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. PARAMETER CONDITIONS Current Limit LT1086/-2.85/-3.3/-3.6/-5/-12 (VIN – VOUT) = 5V (VIN – VOUT) = 25V LT1086H Minimum Load Current Quiescient Current Thermal Regulation TA = 25°C, 30ms pulse Ripple Rejection f = 120Hz, COUT = 25µF Tantalum, IOUT = 1.5A, (IOUT = 0.5A for LT1086H) LT1086, LT1086H CADJ = 25µF, (VIN – VOUT) = 3V LT1086-2.85 VIN = 6V LT1086-3.3 VIN = 6.3V LT1086-3.6 VIN = 6.6V LT1086-5 VIN = 8V LT1083-12 VIN = 15V Adjust Pin Current MIN TYP ● ● 1.50 0.05 2.00 0.15 A A (VIN – VOUT) = 5V (VIN – VOUT) = 25V ● ● 0.50 0.02 0.700 0.075 A A LT1086/LT1086H (VIN – VOUT) = 25V (Note 5) ● 5 10 mA LT1086-2.85 LT1086-3.3 LT1086-3.6 LT1086-5 LT1086-12 VIN ≤ 18V VIN ≤ 18V VIN ≤ 18V VIN ≤ 20V VIN ≤ 25V ● ● ● ● ● 5 5 5 5 5 10 10 10 10 10 mA mA mA mA mA 0.008 0.04 %/W LT1086, LT1086H ● ● ● ● ● ● TJ = 25°C 60 60 60 60 60 54 75 72 72 72 68 60 LT1086, LT1086H 10mA ≤ IOUT ≤ 1.5A (0.5A for LT1086H) 1.5V ≤ (VIN – VOUT) ≤ 15V Temperature Stability ● ● Long-Term Stability TA = 125°C, 1000 Hrs. RMS Output Noise (% of VOUT) TA = 25°C, 10Hz = ≤ f ≤ 10kHz Thermal Resistance Junction-to-Case H Package: Control Circuitry/Power Transistor K Package: Control Circuitry/Power Transistor M Package: Control Circuitry/Power Transistor T Package: Control Circuitry/Power Transistor Note 1: Absolute Maximum Ratings are those values beyond which the life of a device may be impaired. Note 2: See Thermal Regulation specifications for changes in output voltage due to heating effects. Line and load regulation are measured at a constant junction temperature by low duty cycle pulse testing. Load regulation is measured at the output lead ≈1/8" from the package. Note 3: Line and load regulation are guaranteed up to the maximum power dissipation of 15W (3W for the LT1086H). Power dissipation is determined 0.2 120 µA µA 5 µA 1 % 0.5 0.3 UNITS dB dB dB dB dB dB 55 ● Adjust Pin Current Change MAX % 0.003 % 15/20 1.7/4.0 1.5/4.0 1.5/4.0 °C/W °C/W °C/W °C/W by the input/output differential and the output current. Guaranteed maximum power dissipation will not be available over the full input/output range. See Short-Circuit Current curve for available output current. Note 4: Dropout voltage is specified over the full output current range of the device. Test points and limits are shown on the Dropout Voltage curve. Note 5: Minimum load current is defined as the minimum output current required to maintain regulation. At 25V input/output differential the device is guaranteed to regulate if the output current is greater than 10mA. sn1086 1086ffs 4 LT1086 Series U W TYPICAL PERFORMANCE CHARACTERISTICS LT1086 Short-Circuit Current Minimum Operating Current (Adjustable Device) LT1086 Load Regulation 2.5 10 0.10 TJ = 150°C 2.0 TJ = 25°C TJ = –55°C 1.5 1.0 0.5 0 GUARANTEED OUTPUT CURRENT 0 25 10 15 20 5 INPUT/OUTPUT DIFFERENTIAL (V) 30 MINIMUM OPERATING CURRENT (mA) OUTPUT VOLTAGE DEVIATION (%) SHORT-CIRCUIT CURRENT (A) ∆I = 1.5A 0.05 0 –0.05 –0.10 –0.15 –0.20 –50 –25 0 8 7 6 TJ = 150°C TJ = 25°C TJ = –55°C 5 4 3 2 1 0 25 50 75 100 125 150 TEMPERATURE (°C) LT1086 • TPC01 9 0 20 15 10 25 30 5 INPUT/OUTPUT DIFFERENTIAL (V) LT1086 • TPC02 Temperature Stability LT1086 • TPC03 LT1086 Maximum Power Dissipation* Adjust Pin Current 100 2 35 20 1 0 –1 80 LT1086MK 15 70 60 POWER (W) ADJUST PIN CURRENT (µA) OUTPUT VOLTAGE CHANGE (%) 90 50 40 LT1086CT 10 LT1086CK 30 5 20 10 –2 –50 –25 0 0 –50 –25 25 50 75 100 125 150 TEMPERATURE (°C) 0 50 60 70 80 90 100 110 120 130 140 150 CASE TEMPERATURE (°C) *AS LIMITED BY MAXIMUM JUNCTION TEMPERATURE LT1086 • TPC05 LT1086 • TPC04 LT1086 • TPC06 LT1086 Ripple Rejection vs Current LT1086 Ripple Rejection 100 LT1086-5 Ripple Rejection 80 100 VRIPPLE ≤ 3VP-P VRIPPLE ≤ 0.5VP-P 80 RIPPLE REJECTION (dB) 60 (VIN – VOUT) ≥ VDROPOUT 50 40 30 CADJ = 200µF AT FREQUENCIES < 60Hz CADJ = 25µF AT FREQUENCIES > 60Hz IOUT = 1.5A 20 10 fR = 20kHz VRIPPLE ≤ 0.5VP-P 70 60 50 40 30 VOUT = 5V CADJ = 25µF COUT = 25µF 20 10 0 100 1k 10k FREQUENCY (Hz) 100k LT1086 • TPC07 (VIN – VOUT) ≥ 3V 60 50 (VIN – VOUT) ≥ VDROPOUT 40 30 20 10 IOUT = 1.5A 0 0 10 VRIPPLE ≤ 3VP-P VRIPPLE ≤ 0.5VP-P 70 80 (VIN – VOUT) ≥ 3V 70 fR = 120Hz VRIPPLE ≤ 3VP-P 90 RIPPLE REJECTION (dB) 90 RIPPLE REJECTION (dB) 0 25 50 75 100 125 150 TEMPERATURE (°C) 0 0.25 0.75 1.0 1.25 0.5 OUTPUT CURRENT (A) 1.5 LT1086 • TPC08 10 100 1k 10k FREQUENCY (Hz) 100k LT1086 • TPC09 sn1086 1086ffs 5 LT1086 Series U W TYPICAL PERFORMANCE CHARACTERISTICS LT1086-5 Ripple Rejection vs Current 100 80 90 fR = 20kHz VRIPPLE ≤ 0.5VP-P 50 40 30 VOUT = 5V CADJ = 25µF COUT = 25µF 20 10 90 80 60 (VIN – VOUT) ≥ 3V 50 40 (VIN – VOUT) ≥ VDROPOUT 30 20 1.25 0.75 1.0 0.5 OUTPUT CURRENT (A) 1.5 100 10 1k 10k FREQUENCY (Hz) LT1086 Line Transient Response 0 –20 CADJ = 0 VOUT = 10V IOUT = 0.2A CIN = 1µF TANTALUM COUT = 10µF TANTALUM 12 100 TIME (µs) 0 200 0.2 CADJ = 0 0.1 0 –0.1 CADJ = 1µF –0.2 CIN = 1µF TANTALUM COUT = 10µF TANTALUM VOUT = 10V VIN = 13V PRELOAD = 100mA 1.5 1.0 0 0.8 0.6 0.4 0.2 0 100 100 90 0.05 fR = 120Hz VRIPPLE ≤ 3VP-P RIPPLE REJECTION (dB) 80 0 –0.05 –0.10 70 60 fR = 20kHz VRIPPLE ≤ 0.5VP-P 50 40 30 VOUT = 5V CADJ = 25µF COUT = 25µF 20 –0.15 0 0.1 0.3 0.4 0.2 OUTPUT CURRENT (A) 0.5 LT1086 • TPC16 –0.20 –50 –25 0 25 LT1086H Ripple Rejection vs Current 10 0 5 10 15 20 INPUT/OUTPUT DIFFERENTIAL (V) LT1086 • TPC15 ∆I = 0.5A TJ = – 55°C TJ = 25°C TJ = 150°C GUARANTEED OUTPUT CURRENT 0 50 TIME (µs) 0 0.10 INDICATES GUARANTEED TEST POINT OUTPUT VOLTAGE DEVIATION (%) MINIMUM INPUT/OUTPUT DIFFERENTIAL (V) 1.0 LT1086H Load Regulation 2 1.5 LT1086H Short-Circuit Current LT1086 • TPC14 LT1086H Dropout Voltage 1 0.75 1.0 1.25 0.5 OUTPUT CURRENT (A) LT1086 • TPC12 0.5 LT1086 • TPC13 – 55°C ≤ TJ ≤ 150°C 0°C ≤ TJ ≤ 125°C 0.25 1.2 –0.3 13 11 VOUT = 5V CADJ = 25µF COUT = 25µF 0 SHORT-CIRCUIT CURRENT (A) INPUT VOLTAGE DEVIATION (V) OUTPUT VOLTAGE DEVIATION (V) CADJ = 1µF LOAD CURRENT (A) OUTPUT VOLTAGE DEVIATION (mV) 60 14 30 LT1086 Load Transient Response 40 –40 40 0 100k 0.3 –60 fR = 20kHz VRIPPLE ≤ 0.5VP-P 50 LT1086 • TPC11 LT1086 • TPC10 20 60 10 IOUT = 1.5A 0 0.25 fR = 120Hz VRIPPLE ≤ 3VP-P 70 20 10 0 0 RIPPLE REJECTION (dB) RIPPLE REJECTION (dB) RIPPLE REJECTION (dB) 70 60 100 VRIPPLE ≤ 3VP-P VRIPPLE ≤ 0.5VP-P 70 fR = 120Hz VRIPPLE ≤ 3VP-P 80 LT1086-12 Ripple Rejection vs Current LT1086-12 Ripple Rejection 25 50 75 100 125 150 TEMPERATURE (°C) LT1086 • TPC17 0 0 0.1 0.3 0.4 0.2 OUTPUT CURRENT (A) 0.5 LT1086 • TPC18 sn1086 1086ffs 6 LT1086 Series U W TYPICAL PERFORMANCE CHARACTERISTICS LT1086H Maximum Power Dissipation* LT1086H Ripple Rejection 5 100 VRIPPLE ≤ 3VP-P VRIPPLE ≤ 0.5VP-P 90 (VIN – VOUT) ≥ 3V 70 4 (VIN – VOUT) ≥ VDROPOUT 60 POWER (W) RIPPLE REJECTION (dB) 80 50 40 3 LT1086MH 2 30 CADJ = 200µF AT FREQUENCIES < 60Hz CADJ = 25µF AT FREQUENCIES > 60Hz IOUT = 0.5A 20 10 1 0 10 100 1k 10k FREQUENCY (Hz) 0 100k 50 60 70 80 90 100 110 120 130 140 150 CASE TEMPERATURE (°C) *AS LIMITED BY MAXIMUM JUNCTION TEMPERATURE LT1086 • TPC19 LT1086 • TPC20 W BLOCK DIAGRAM VIN + – THERMAL LIMIT 1086 • BD VADJ VOUT sn1086 1086ffs 7 LT1086 Series U W U U APPLICATIONS INFORMATION The LT1086 family of 3-terminal regulators is easy to use and has all the protection features that are expected in high performance voltage regulators. They are short-circuit protected and have safe area protection as well as thermal shutdown to turn off the regulator should the temperature exceed about 165°C at the sense point. These regulators are pin compatible with older 3-terminal adjustable devices, offer lower dropout voltage and more precise reference tolerance. Further, the reference stability with temperature is improved over older types of regulators. The only circuit difference between using the LT1086 family and older regulators is that they require an output capacitor for stability. Stability The circuit design used in the LT1086 family requires the use of an output capacitor as part of the device frequency compensation. For all operating conditions, the addition of 150µF aluminum electrolytic or a 22µF solid tantalum on the output will ensure stability. Normally capacitors much smaller than this can be used with the LT1086. Many different types of capacitors with widely varying characteristics are available. These capacitors differ in capacitor tolerance (sometimes ranging up to ±100%), equivalent series resistance, and capacitance temperature coefficient. The 150µF or 22µF values given will ensure stability. When using the LT1086 the adjustment terminal can be bypassed to improve ripple rejection. When the adjustment terminal is bypassed the requirement for an output capacitor increases. The values of 22µF tantalum or 150µF aluminum cover all cases of bypassing the adjustment terminal. For fixed voltage devices or adjustable devices without an adjust pin bypass capacitor, smaller output capacitors can be used with equally good results. The table below shows approximately what size capacitors are needed to ensure stability. Recommended Capacitor Values INPUT OUTPUT ADJUSTMENT 10µF 10µF Tantalum, 50µF Aluminum None 10µF 22µF Tantalum, 150µF Aluminum 20µF 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 LT1086 regulators. Another possible stability problem that can occur in monolithic IC regulators is current limit oscillations. These can occur because in current limit, the safe area protection exhibits a negative impedance. The safe area protection decreases the current limit as the input-to-output voltage increases.That is the equivalent of having a negitive resistance since increasing voltage causes current to decrease. Negative resistance during current limit is not unique to the LT1086 series and has been present on all power IC regulators. The value of negative resistance is a function of how fast the current limit is folded back as input-to-output voltage increases. This negative resistance can react with capacitors or inductors on the input to cause oscillation during current limiting. Depending on the value of series resistance, the overall circuitry may end up unstable. Since this is a system problem, it is not necessarily easy to solve; however, it does not cause any problems with the IC regulator and can usually be ignored. Protection Diodes In normal operation the LT1086 family does not need any protection diodes. Older adjustable regulators required protection diodes between the adjustment pin and the output and from the output to the input to prevent overstressing the die. The internal current paths on the LT1086 adjustment pin are limited by internal resistors. Therefore, even with capacitors on the adjustment pin, no protection diode is needed to ensure device safety under short-circuit conditions. Diodes between input and output are usually not needed. The internal diode between the input and the output pins of the LT1086 family can handle microsecond surge currents of 10A to 20A. Even with large output capacitances, it is very difficult to get those values of surge currents in normal operation. Only with high value output capacitors such as 1000µF to 5000µF, and with the input pin instantaneously shorted to ground, can damage occur. A crowbar circuit at the input of the LT1086 can generate those kinds of currents and a diode from output to input is then recommended. Normal power supply cycling or even sn1086 1086ffs 8 LT1086 Series U W U U APPLICATIONS INFORMATION plugging and unplugging in the system will not generate current large enough to do any damage. the power supply may need to be cycled down to zero and brought up again to make the output recover. 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. Ripple Rejection D1 1N4002 (OPTIONAL) VIN IN LT1086 OUT ADJ + R1 CADJ 10µF + VOUT COUT 150µF R2 LT1086 • AI01 Overload Recovery Like any of the IC power regulators, the LT1086 has safe area protection. The safe area protection decreases the current limit as input-to-output voltage increases and keeps the power transistor inside a safe operating region for all values of input-to-output voltage. The LT1086 protection is designed to provide some output current at all values of input-to-output voltage up to the device breakdown. When power is first turned on, as the input voltage rises, the output follows the input, allowing the regulator to start up into very heavy loads. During the start-up, as the input voltage is rising, the input-to-output voltage differential remains small, allowing the regulator to supply large output currents. With high input voltage, a problem can occur wherein removal of an output short will not allow the output voltage to recover. Older regulators such as the 7800 series also exhibited this phenomenon, so it is not unique to the LT1086. The problem occurs with a heavy output load when the input voltage is high and the output voltage is low, such as immediately after a removal of a short. The load line for such a load may intersect the output current curve at two points. If this happens there are two stable output operating points for the regulator. With this double intersection For the LT1086 the typical curves for ripple rejection reflect values for a bypassed adjust pin. This curve will be true for all values of output voltage. For proper bypassing and ripple rejection approaching the values shown, the impedance of the adjust pin capacitor at the ripple frequency should equal the value of R1, (normally 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 13µF if R1 = 100Ω; at 10kHz only 0.16µF is needed. For circuits without an adjust pin bypass capacitor the ripple rejection will be a function of output voltage. The output ripple will increase directly as a ratio of the output voltage to the reference voltage (VOUT/VREF). For example, with the output voltage equal to 5V and no adjust pin capacitor, the output ripple will be higher by the ratio of 5V/1.25V or four times larger. Ripple rejection will be degraded by 12dB from the value shown on the LT1086 curve. Typical curves are provided for the 5V and 12V devices since the adjust pin is not available. Output Voltage The LT1086 develops a 1.25V reference voltage between the output and the adjust terminal (see Figure 1). By placing resistor R1 between these two terminals, a constant current is caused to flow through R1 and down through R2 to set the overall output voltage. Normally this current is chosen to be the specified minimum load current of 10mA. Because IADJ is very small and constant when compared with the current through R1, it represents a small error and can usually be ignored. For fixed voltage devices R1 and R2 are included in the device. VIN IN LT1086 OUT ADJ IADJ 50µA ( VOUT = VREF 1 + R2 R1 + VREF ) R1 VOUT 10µF TANTALUM R2 + IADJ R2 1086 • F01 Figure 1. Basic Adjustable Regulator sn1086 1086ffs 9 LT1086 Series U U W U APPLICATIONS INFORMATION Load Regulation Thermal Considerations Because the LT1086 is a 3-terminal device, it is not possible to provide true remote load sensing. Load regulation will be limited by the resistance of the wire connecting the regulator to the load. The data sheet specification for load regulation is measured at the bottom of the package. Negative side sensing is a true Kelvin connection, with the bottom of the output divider returned to the negative side of the load. Although it may not be immediately obvious, best load regulation is obtained when the top of the resistor divider R1 is connected directly to the case not to the load, as illustrated in Figure 2. If R1 were connected to the load, the effective resistance between the regulator and the load would be: The LT1086 series of regulators have internal power and thermal limiting circuitry designed to protect the device under overload conditions. For continuous normal load conditions however, maximum junction temperature ratings must not be exceeded. It is important to give careful consideration to all sources of thermal resistance from junction to ambient. This includes junction-to-case, caseto-heat sink interface and heat sink resistance itself. New thermal resistance specifications have been developed to more accurately reflect device temperature and ensure safe operating temperatures. The data section for these new regulators provides a separate thermal resistance and maximum junction temperature for both the Control Section and the Power Transistor. Previous regulators, with a single junction-to-case thermal resistance specification, used an average of the two values provided here and therefore could allow excessive junction temperatures under certain conditions of ambient temperature and heat sink resistance. To avoid this possibility, calculations should be made for both sections to ensure that both thermal limits are met. ( ) RP R2 + R1 , RP = Parasitic Line Resistance R1 RP PARASITIC LINE RESISTANCE VIN IN LT1086 OUT ADJ R1* RL R2* *CONNECT R1 TO CASE CONNECT R2 TO LOAD 1086 • F02 Figure 2. Connections for Best Load Regulation Connected as shown, RP is not multiplied by the divider ratio. RP is about 0.004Ω 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. Note that the resistance of the package leads for the H package ≈ 0.06Ω/inch. While it is usually not possible to connect the load directly to the package, it is possible to connect larger wire or PC traces close to the case to avoid voltage drops that will degrade load regulation. For fixed voltage devices the top of R1 is internally Kelvin connected and the ground pin can be used for negative side sensing. 10 For example, using a LT1086CK (TO-3, Commercial) and assuming: VIN(max continuous) = 9V, VOUT = 5V, IOUT = 1A, TA = 75°C, θHEAT SINK = 3°C/W, θCASE-TO-HEAT SINK = 0.2°C/ W for T package with thermal compound. Power dissipation under these conditions is equal to: PD = (VIN – VOUT)(IOUT) = 4W Junction temperature will be equal to: TJ = TA + PD (θHEAT SINK + θ CASE-TO-HEAT SINK + θJC) For the Control Section: TJ = 75°C + 4W(3°C/W + 0.2°C/ W + 1.5°C/ W) = 94.6°C 95°C < 125°C = TJMAX (Control Section Commercial Range) For the Power Transistor: TJ = 75°C + 4W(3°C/ W + 0.2°C/ W + 4°C/ W) = 103.8°C 103.8°C < 150°C = TJMAX (Power Transistor Commercial Range) sn1086 1086ffs LT1086 Series U W U U APPLICATIONS INFORMATION In both cases the junction temperature is below the maximum rating for the respective sections, ensuring reliable operation. Junction-to-case thermal resistance for the K and T packages is specified from the IC junction to the bottom of the case directly below the die. This is the lowest resistance path for heat flow. While this is also the lowest resistance path for the H package, most available heat sinks for this package are of the clip-on type that attach to the cap of the package. The data sheet specification for thermal resistance for the H package is therefore written to reflect this. In all cases proper mounting is required to ensure the best possible heat flow from the die to the heat sink. Thermal compound at the case-to-heat sink interface is strongly recommended. In the case of the H package, mounting the device so that heat can flow out the bottom of the case will significantly lower thermal resistance (≈ a factor of 2). If the case of the device must be electrically isolated, a thermally conductive spacer can be used as long as its added contribution to thermal resistance is considered. Note that the case of all devices in this series is electrically connected to the output. U TYPICAL APPLICATIONS 5V, 1.5A Regulator VIN ≥ 6.5V IN LT1086 5V AT 1.5A OUT 121Ω 1% ADJ + + 10µF 10µF* TANTALUM 365Ω 1% LT1086 • AI02 *REQUIRED FOR STABILITY SCSI-2 Active Termination TERMPWR 1N5817 110Ω 2% 110Ω 110Ω 2% 110Ω 110Ω 2% 110Ω IN LT1086-2.85 OUT GND 4.25V TO 5.25V + 10µF TANTALUM + 10µF TANTALUM 0.1µF CERAMIC 18 TOTAL LT1086 • TA03 sn1086 1086ffs 11 LT1086 Series U TYPICAL APPLICATIONS 5V Regulator with Shutdown 1.2V to 15V Adjustable Regulator VIN IN LT1086 VOUT† OUT R1 121Ω ADJ + C1* 10µF + R2 5k IN VIN LT1086 + 5V OUT 121Ω 1% ADJ + 10µF C2 100µF 100µF 1k 365Ω 1% 2N3904 TTL 1k *NEEDED IF DEVICE IS FAR FROM FILTER CAPACITORS R2 †V OUT = 1.25V 1 + R1 ( ) LT1086 • TA05 LT1086 • TA04 Battery Charger LT1086 ( ( VOUT – 1.25 1 + R2 R1 ( – RS 1 + R2 R1 ) dIF = dVOUT ) VOUT VIN > 12V ) R1 5V TO 10V + GND 100µF + 1k 10µF* LT1086 • TA06 R2 LT1086-5 OUT 10µF LT1086 • TA07 *OPTIONAL IMPROVES RIPPLE REJECTION 1 ( – RS 1 + R2 R1 ) Regulator with Reference VIN > 11.5V IN + 1.25V ADJ IF = OUT IN VIN Adjusting Output Voltage of Fixed Regulators IF RS IN + LT1086-5 OUT GND 10µF Protected High Current Lamp Driver + 10V OUT LT1086 TTL OR CMOS 100µF ADJ 5V LT1029 15V IN 12V 1A 10k LT1086 • TA08 LT1086 • TA10 Remote Sensing RP (MAX DROP 300mV) VIN IN LT1086 ADJ + 10µF VIN 7 100µF 25Ω + VOUT 5V OUT 121Ω 6 – LM301A 1 + 8 4 365Ω 2 100pF 1k 3 RL 5µF + 25Ω RETURN RETURN LT1086 • TA09 sn1086 1086ffs 12 LT1086 Series U TYPICAL APPLICATIONS High Efficiency Dual Linear Supply L1 285µH IN MBR360 10k 1k + HEAT SINK 2N6667 Q1 DARLINGTON 1000µF ADJ 30k + MDA201 8 4700µF + 7 – 12V 1.5A OUT 124Ω* 2.4k 510k + LT1086 LT1004-2.5 + 20k* 2 100µF 30.1k* D1 1N4002 1.07k* LT1011 – 3 4 L1 285µH STANCOR P-8685 IN HEAT SINK 2N6667 Q2 DARLINGTON 1000µF MBR360 10k 1k + 130VAC TO 90VAC 30k 8 4700µF + 7 – 124Ω* 2.4k + MDA201 OUT ADJ 510k + LT1086 LT1004-2.5 + 20k* 2 100µF 30.1k* 1.07k* D2 1N4002 LT1011 – 3 4 *1% FILM RESISTORS MDA = MOTOROLA L1 = PULSE ENGINEERING, INC. #PE-92106 LT1086 • TA11 –12V 1.5A High Efficiency Dual Supply FEEDBACK PATH MUR410 5V OUTPUT (TYPICAL) + 470µF MUR410 IN LT1086 ADJ + 470µF VIN 12V 1.5A OUT 124Ω* + + 10µF 10µF 1N4002 10µF 1N4002 1.07k* MUR410 IN SWITCHING REGULATOR LT1086 OUT ADJ + 470µF 124Ω* + + 10µF 1.07k* *1% FILM RESISTORS LT1086 • TA12 –12V 1.5A sn1086 1086ffs 13 LT1086 Series U TYPICAL APPLICATIONS Improving Ripple Rejection Battery Backed Up Regulated Supply VIN IN + 5.2V LINE 5V BATTERY LT1086-5 OUT VIN ≥ 6.5V GND 10µF LT1086 IN OUT ADJ + 10µF 50Ω 150µF R2 365Ω 1% SELECT FOR CHARGE RATE IN + 6.5V LT1086-5 OUT + C1 10µF* LT1086 • TA14 + GND 10µF VOUT = 5V R1 121Ω 1% *C1 IMPROVES RIPPLE REJECTION. XC SHOULD BE ≈ R1 AT RIPPLE FREQUENCY 100µF LT1086 • TA13 Automatic Light Control IN VIN LT1086 ADJ + Low Dropout Negative Supply OUT VIN 1.2k IN 100µF 10µF LT1086-12 OUT GND + + 100µF 10,000µF LT1086 • TA15 VOUT = –12V LT1086 • TA16 FLOATING INPUT U PACKAGE DESCRIPTION H Package 3-Lead TO-39 Metal Can (Reference LTC DWG # 05-08-1330) 0.350 – 0.370 (8.890 – 9.398) 0.200 (5.080) TYP 0.305 – 0.335 (7.747 – 8.509) 0.050 (1.270) MAX REFERENCE PLANE 0.165 – 0.185 (4.191 – 4.699) PIN 1 0.029 – 0.045 (0.737 – 1.143) * 0.100 (2.540) 0.028 – 0.034 (0.711 – 0.864) 0.016 – 0.021** (0.406 – 0.533) DIA 0.100 (2.540) 0.500 (12.700) MIN 45° H3(TO-39) 1098 *LEAD DIAMETER IS UNCONTROLLED BETWEEN THE REFERENCE PLANE AND 0.045" BELOW THE REFERENCE PLANE 0.016 – 0.024 **FOR SOLDER DIP LEAD FINISH, LEAD DIAMETER IS (0.406 – 0.610) OBSOLETE PACKAGE sn1086 1086ffs 14 LT1086 Series U PACKAGE DESCRIPTION K Package 2-Lead TO-3 Metal Can (Reference 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 OBSOLETE PACKAGE M Package 3-Lead Plastic DD Pak (Reference LTC DWG # 05-08-1460) 0.256 (6.502) 0.060 (1.524) TYP 0.060 (1.524) 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 ( +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 sn1086 1086ffs 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. 15 LT1086 Series U PACKAGE DESCRIPTION T Package 3-Lead Plastic TO-220 (Reference 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) 0.570 – 0.620 (14.478 – 15.748) 0.460 – 0.500 (11.684 – 12.700) 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) 0.095 – 0.115 (2.413 – 2.921) 0.050 (1.270) TYP T3 (TO-220) 1098 RELATED PARTS PART NUMBER DESCRIPTION COMMENTS LT1129 700mA, Micropower, LDO VIN = 4.2V to 30V, VOUT(MIN) = 3.75V, IQ = 50µA, ISD = 16µA, DD, SOT-223, S8, TO-220, TSSOP-20 Packages LT1528 3A LDO for Microprocessor Applications VIN = 4V to 15V, VOUT(MIN) = 3.30V, IQ = 400µA, ISD = 125µA, Fast Transient Response, DD, TO-220 Packages LT1585 4.6A LDO , with Fast Transient Response VIN = 2.5V to 7V, VOUT(MIN) = 1.25V, IQ = 8mA, Fast Transient Response, DD, TO-220 Packages LT1761 100mA, Low Noise Micropower, LDO VIN = 1.8V to 20V, VOUT(MIN) = 1.22V, IQ = 20µA, ISD = <1µA, Low Noise < 20µVRMS P-P, Stable with 1µF Ceramic Capacitors, ThinSOTTM Package LT1762 150mA, Low Noise Micropower, LDO VIN = 1.8V to 20V, VOUT(MIN) = 1.22V, IQ = 25µA, ISD = <1µA, Low Noise < 20µVRMS P-P, MSOP Package LT1763 500mA, Low Noise Micropower, LDO VIN = 1.8V to 20V, VOUT(MIN) = 1.22V, IQ = 30µA, ISD = <1µA, Low Noise < 20µVRMS P-P, S8 Package LT1764/LT1764A 3A, Low Noise, Fast Transient Response, LDOs VIN = 2.7V to 20V, VOUT(MIN) = 1.21V, IQ = 1mA, ISD = <1µA, Low Noise < 40µVRMS P-P, “A” Version Stable with Ceramic Capacitor, DD, TO-220 Packages LT1962 VIN = 1.8V to 20V, VOUT(MIN) = 1.22V, IQ = 30µA, ISD = <1µA, Low Noise < 20µVRMS P-P, MS8 Package 300mA, Low Noise Micropower, LDO LT1963/LT1963A 1.5A, Low Noise, Fast Transient Response, LDOs VIN = 2.1V to 20V, VOUT(MIN) = 1.21V, IQ = 1mA, ISD = <1µA, Low Noise < 40µVRMS P-P,“A” Version Stable with Ceramic Capacitor, DD, TO-220, SOT-223, S8 Packages LT1964 VIN = –0.9V to –20V, VOUT(MIN) = –1.21V, IQ = 30µA, ISD = 3µA, Low Noise < 30µVRMS P-P, Stable with Ceramic Capacitors, ThinSOT Package 200mA, Low Noise Micropower, Negative LDO ThinSOT is a trademark of Linear Technology Corporation. sn1086 1086ffs 16 Linear Technology Corporation LT/TP 0703 1K REV F • PRINTED IN USA 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com © LINEAR TECHNOLOGY CORPORATION 1988