LT1070/LT1071 5A and 2.5A High Efficiency Switching Regulators DESCRIPTION U FEATURES ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ Wide Input Voltage Range: 3V to 60V Low Quiescent Current: 6mA Internal 5A Switch (2.5A for LT1071) Very Few External Parts Required Self Protected Against Overloads Operates in Nearly All Switching Topologies Shutdown Mode Draws Only 50µA Supply Current Flyback Regulated Mode Has Fully Floating Outputs Comes in Standard 5-Pin Packages Can be Externally Synchronized (Consult Factory) U APPLICATIONS ■ ■ ■ ■ ■ ■ ■ Logic Supply 5V at 10A 5V Logic to ±15V Op Amp Supply Off-Line Converter Up to 200W Battery Upconverter Power Inverter (+ to –) or (– to +) Fully Floating Multiple Outputs For Lower Current Applications, See the LT1072 USER NOTE: This data sheet is only intended to provide specifications, graphs and a general functional description of the LT1070/LT1071. Application circuits are included to show the capability of the LT1070/LT1071. A complete design manual (AN19) should be obtained to assist in developing new designs. This manual contains a comprehensive discussion of both the LT1070 and the external components used with it, as well as complete formulas for calculating the values of these components. The manual can also be used for the LT1071 by factoring in the lower switch current rating. A second Application Note, AN25, which details off-line applications is available. The LT ®1070/LT1071 are monolithic high power switching regulators. They can be operated in all standard switching configurations including buck, boost, flyback, forward, inverting and “Cuk”. A high current, high efficiency switch is included on the die along with all oscillator, control and protection circuitry. Integration of all functions allows the LT1070/LT1071 to be built in a standard 5-pin TO-3 or T0-220 power package. This makes it extremely easy to use and provides “bust proof” operation similar to that obtained with 3-pin linear regulators. The LT1070/LT1071 operate with supply voltages from 3V to 60V, and draw only 6mA quiescent current. They can deliver load power up to 100W with no external power devices. By utilizing current mode switching techniques, they provide excellent AC and DC load and line regulation. The LT1070/LT1071 have many unique features not found even on the vastly more difficult to use low power control chips presently available. They use adaptive antisat switch drive to allow very wide ranging load currents with no loss in efficiency. An externally activated shutdown mode reduces total supply current to 50µA typical for standby operation. Totally isolated and regulated outputs can be generated by using the optional “flyback regulation mode” built into the LT1070/LT1071, without the need for optocouplers or extra transformer windings. , LTC and LT are registered trademarks of Linear Technology Corporation. U TYPICAL APPLICATION Maximum Output Power* Boost Converter (5V to 12V) 100 L2 10µH 80 L1** 150µH OUTPUT FILTER C3 100µF D1 VIN C3* 100µF + + LT1070 GND VC 12V 1A VSW C2 1000µF R1 10.7k 1% POWER (W)** BOOST 5V BUCK/BOOST VO = 30V 60 FLYBACK 40 ISOLATED 20 BUCK/BOOST VO = 5V FB R3 1k C1 1µF *REQUIRED IF INPUT LEADS ≥ 2" **PULSE ENGINEERING 92113 R2 1.24k 1% 0 0 10 30 20 INPUT VOLTAGE (V) 40 50 1070/71 TA02 1070/71 TA01 *ROUGH GUIDE ONLY. BUCK MODE POUT = 5A • VOUT. SPECIAL TOPOLOGIES DELIVER MORE POWER **DIVIDE VERTICAL POWER SCALE BY 2 FOR LT1071 1 LT1070/LT1071 W W U W ABSOLUTE MAXIMUM RATINGS (Note 1) Supply Voltage LT1070/LT1071 (Note 2) .................................... 40V LT1070HV/LT1071HV (Note 2)........................... 60V Switch Output Voltage LT1070/LT1071 .................................................. 65V LT1070HV/LT1071HV......................................... 75V Feedback Pin Voltage (Transient, 1ms) ................ ±15V Operating Junction Temperature Range Commercial (Operating) ....................... 0°C to 100°C Commercial (Short Circuit)................... 0°C to 125°C Industrial ......................................... – 40°C to 125°C Military ............................................ – 55°C to 150°C Storage Temperature Range ................ – 65°C to 150°C Lead Temperature (Soldering, 10 sec)................. 300°C W U U PACKAGE/ORDER INFORMATION VSW VC 1 4 2 CASE IS GND 3 VIN ORDER PART NUMBER ORDER PART NUMBER BOTTOM VIEW FB K PACKAGE 4-LEAD TO-3 METAL CAN TJMAX = 100°C, θJA = 35°C/ W, QJC = 2°C (LT1070C, I) TJMAX = 150°C, θJA = 35°C/ W, QJC = 2°C (LT1070M) TJMAX = 100°C, θJA = 35°C/ W, QJC = 4°C (LT1071C, I) TJMAX = 150°C, θJA = 35°C/ W, QJC = 4°C (LT1071M) LT1070CK LT1070HVCK LT1070HVMK LT1070IK LT1070MK LT1071CK LT1071HVCK LT1071HVMK LT1071MK ELECTRICAL CHARACTERISTICS FRONT VIEW 5 VIN 4 VSW 3 GND 2 FB 1 VC LT1070CT LT1070HVCT LT1070HVIT LT1070IT LT1071CT LT1071HVCT LT1071HVIT LT1071IT T PACKAGE 5-LEAD PLASTIC TO-220 TJMAX = 100°C, θJA = 75°C/ W, QJC = 2°C (LT1070C, I) TJMAX = 100°C, θJA = 75°C/ W, QJC = 4°C (LT1071C) VIN = 15V, VC = 0.5V, VFB = VREF, output pin open unless otherwise specified. SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS VREF Reference Voltage Measured at Feedback Pin, VC = 0.8V 1.224 1.214 1.244 1.244 1.264 1.274 V V 350 750 1100 nA nA ● IB Feedback Input Current VFB = VREF ● gm Error Amplifier Transconductance Error Amplifier Source or Sink Current Error Amplifier Clamp Voltage AV ∆IC = ±25µA 6000 7000 µmho µmho 150 120 200 ● 350 400 µA µA 2.30 0.52 V V 0.03 %/V VC = 1.5V Hi Clamp, VFB = 1V Lo Clamp, VFB = 1.5V Reference Voltage Line Regulation 3V ≤ VIN ≤ VMAX, VC = 0.8V Error Amplifier Voltage Gain 0.9V ≤ VC ≤ 1.4V Minimum Input Voltage IQ 3000 2400 4400 ● 1.80 0.25 ● 500 3V ≤ VIN ≤ VMAX, VC = 0.6V Control Pin Threshold Duty Cycle = 0 ● Normal/Flyback Threshold on Feedback Pin 2 800 V/V 2.6 3.0 6 9 0.8 0.6 0.9 1.08 1.25 V V 0.4 0.45 0.54 V ● Supply Current 0.38 V mA LT1070/LT1071 ELECTRICAL CHARACTERISTICS VIN = 15V, VC = 0.5V, VFB = VREF, output pin open unless otherwise specified. SYMBOL PARAMETER CONDITIONS VFB Flyback Reference Voltage IFB = 50µA ● Change in Flyback Reference Voltage BV VSAT ILIM 0.05 ≤ IFB ≤ 1mA Flyback Reference Voltage Line Regulation IFB = 50µA, 3V ≤ VIN ≤ VMAX (Note 3) Flyback Amplifier Transconductance (gm) ∆IC = ±10µA Flyback Amplifier Source and Sink Current VC = 0.6V, IFB = 50µA (Source) VC = 0.6V, IFB = 50µA (Sink) Output Switch Breakdown Voltage TYP MAX UNITS 15 14 16.3 17.6 18.0 V V 4.5 6.8 8.5 V 0.01 0.03 %/V 150 300 650 µmho ● ● 15 25 32 40 70 70 µA µA 3V ≤ VIN ≤ VMAX, ISW = 1.5mA (LT1070/LT1071) (LT1070HV/LT1071HV) ● ● 65 75 90 90 Output Switch “On” Resistance (Note 4) LT1070 LT1071 ● ● Control Voltage to Switch Current Transconductance LT1070 LT1071 Switch Current Limit (LT1070) Duty Cycle ≤ 50%, TJ ≥ 25°C Duty Cycle ≤ 50%, TJ < 25°C Duty Cycle = 80% (Note 5) ● ● ● 5 5 4 10 11 10 A A A Switch Current Limit (LT1071) Duty Cycle ≤ 50%, TJ ≥ 25°C Duty Cycle ≤ 50%, TJ < 25°C Duty Cycle = 80% (Note 5) ● ● ● 2.5 2.5 2.0 5.0 5.5 5.0 A A A 25 35 mA/A 40 45 47 kHz kHz 92 97 ∆IIN ∆ISW Supply Current Increase During Switch “On” Time f Switching Frequency 0.15 0.30 Maximum Switch Duty Cycle 35 33 90 Flyback Sense Delay Time Ω Ω 0.24 0.50 A/V A/V % µs 1.5 Shutdown Mode Supply Current 3V ≤ VIN ≤ VMAX, VC = 0.05V Shutdown Mode Threshold Voltage 3V ≤ VIN ≤ VMAX ● The ● denotes the specifications which apply over the full operating temperature range. Note 1: Absolute Maximum Ratings are those values beyond which the life of a device may be impaired. Note 2: Minimum switch “on” time for the LT1070/LT1071 in current limit is ≈1µs. This limits the maximum input voltage during short-circuit conditions, in the buck and inverting modes only, to ≈ 35V. Normal (unshorted) conditions are not affected. Mask changes are being implemented which will reduce minimum “on” time to ≤ 1µs, increasing maximum short-circuit input voltage above 40V. If the present LT1070/LT1071 (contact factory for package date code) is being operated in the buck or inverting mode at high input voltages and short-circuit conditions are expected, a resistor must be placed in series with the inductor, as follows: The value of the resistor is given by: R= V V 8 4 ● DC (Max) MIN 100 50 100 250 µA 150 250 300 mV mV t = Minimum “on” time of LT1070/LT1071 in current limit, ≈1µs f = Operating frequency (40kHz) VF = Forward voltage of external catch diode at ILIMIT ILIMIT = Current limit of LT1070 (≈ 8A), LT1071 (≈ 4A) RL = Internal series resistance of inductor Note 3: VMAX = 55V for LT1070HV and LT1071HV to avoid switch breakdown. Note 4: Measured with VC in hi clamp, VFB = 0.8V. ISW = 4A for LT1070 and 2A for LT1071. Note 5: For duty cycles (DC) between 50% and 80%, minimum guaranteed switch current is given by ILIM = 3.33 (2 – DC) for the LT1070 and ILIM = 1.67 (2 – DC) for the LT1071. t • f • VIN – VF – RL ILIMIT 3 LT1070/LT1071 U W TYPICAL PERFORMANCE CHARACTERISTICS Switch Current Limit vs Duty Cycle Maximum Duty Cycle 16 FOR LT1071, DIVIDE VERTICAL SCALE BY 2 96 2.2 95 2.0 94 1.8 10 – 55°C 25°C 8 125°C 6 TIME (µs) 12 DUTY CYCLE (%) 93 2 0 92 1.4 91 1.2 10 20 30 40 50 60 70 80 90 100 DUTY CYCLE (%) 90 –75 – 50 – 25 0 25 50 75 100 125 150 JUNCTION TEMPERATURE (°C) 1.0 –75 – 50 – 25 0 25 50 75 100 125 150 JUNCTION TEMPERATURE (°C) 1070/71 G01 1070/71 G02 1.6 2.9 SWITCH SATURATION VOLTAGE (V) SWITCH CURRENT = 5A MINIMUM INPUT VOLTAGE (V) Isolated Mode Flyback Reference Voltage Switch Saturation Voltage Minimum Input Voltage 2.8 2.7 2.6 SWITCH CURRENT = 0A 2.5 2.4 2.3 –75 – 50 – 25 1.4 22 150°C 1.2 100°C 1.0 25°C 0.8 – 55°C 0.6 0.4 0.2 0 0 25 50 75 100 125 150 TEMPERATURE (°C) 23 FOR LT1071, DIVIDE CURRENT BY 2 0 1 4 5 2 3 6 SWITCH CURRENT (A) 7 1.248 REFERENCE VOLTAGE (V) TJ = – 55°C –1 –2 –4 –5 10 30 40 20 INPUT VOLTAGE (V) 50 60 1070/71 G07 4 RFEEDBACK = 10k 0 25 50 75 100 125 150 TEMPERATURE (°C) 1070/71 G06 1.246 SWITCHING FREQUENCY 800 41 700 40 1.244 1.242 42 39 REFERENCE V0LTAGE 38 1.240 37 1.238 36 1.236 35 –3 0 17 15 – 75 – 50 – 25 8 1.234 – 75 – 50 – 25 34 0 25 50 75 100 125 150 TEMPERATURE (°C) 1070/71 G08 SWITCHING FREQUENCY (kHz) 1 0 18 Feedback Bias Current vs Temperature 1.250 4 TJ = 25°C RFEEDBACK = 1k 19 Reference Voltage vs Temperature 5 2 20 1070/71 G05 Line Regulation TJ = 150°C RFEEDBACK = 500Ω 21 16 1070/71 G04 3 1070/71 G03 FLYBACK VOLTAGE (V) 0 REFERENCE VOLTAGE CHANGE (mV) 1.6 4 FEEDBACK BIAS CURRENT (nA) SWITCH CURRENT (A) 14 Flyback Blanking Time 600 500 400 300 200 100 0 – 75 – 50 – 25 0 25 50 75 100 125 150 TEMPERATURE (°C) 1070/71 G09 LT1070/LT1071 U W TYPICAL PERFORMANCE CHARACTERISTICS 160 16 INPUT CURRENT (mA) 80 TJ = – 55°C TJ ≥ 25°C 40 12 11 50% DUTY CYCLE 10 9 10% DUTY CYCLE 8 20 0 1 0 4 2 3 SWITCH CURRENT (A) 0 10 1070/71 G10 Normal/Flyback Mode Threshold on Feedback Pin 60 40 30 40 20 INPUT VOLTAGE (V) 50 60 Shutdown Mode Supply Current 490 –22 180 4500 480 –20 470 –18 –14 440 –12 430 –10 FEEDBACK PIN CURRENT (AT THRESHOLD) 420 140 120 TJ = 150°C 100 80 60 – 55°C ≤ TJ ≤ 125°C 40 –6 20 –4 25 50 75 100 125 150 0 TEMPERATURE (°C) 0 410 400 –50 –25 –8 160 SUPPLY CURRENT (µA) 450 0 –250 200 –200 VOLTAGE 150 –150 100 –100 VC VOLTAGE IS REDUCED UNTIL REGULATOR CURRENT DROPS BELOW 300µA – 50 0 0 25 50 75 100 125 150 TEMPERATURE (°C) 1070/71 G16 IDLE SUPPLY CURRENT (mA) 250 VC PIN CURRENT (µA) –300 0 – 75 – 50 – 25 10 –350 300 50 11 – 400 60 gm = ∆I (VC PIN) ∆V (FB PIN) 3500 3000 2500 2000 1500 1000 0 –75 – 50 –25 10 20 30 40 50 60 70 80 90 100 VC PIN VOLTAGE (mV) 0 25 50 75 100 125 150 TEMPERATURE (°C) 1070/71 G14 1070/71 G14 Shutdown Thresholds CURRENT (OUT OF VC PIN) 50 4000 Idle Supply Current vs Temperature 400 20 40 30 SUPPLY VOLTAGE (V) 500 1070/71 G13 350 TRANSCONDUCTANCE (µmho) 5000 –16 10 Error Amplifier Transconductance 200 FEEDBACK PIN VOLTAGE (AT THRESHOLD) 0 1070/71 G12 –24 460 VC = 0V 1070/71 G11 500 FEEDBACK PIN CURRENT (µA) FEEDBACK PIN VOLTAGE (mV) VC = 50mV 80 *UNDER VERY LOW OUTPUT CURRENT CONDITIONS, DUTY CYCLE FOR MOST CIRCUITS WILL APPROACH 10% OR LESS *AVERAGE LT1070 POWER SUPPLY CURRENT IS FOUND BY MULTIPLYING DRIVER CURRENT BY DUTY CYCLE, THEN ADDING QUIESCENT CURRENT VC PIN VOLTAGE (mV) 100 0 6 5 120 20 0% DUTY CYCLE 7 Feedback Pin Clamp Voltage 500 VC = 0.6V 450 9 FEEDBACK VOLTAGE (mV) DRIVER CURRENT (mA) 100 ISWITCH ≤ 10mA 13 TJ = 25°C 140 90% DUTY CYCLE 14 120 160 TJ = 25°C 15 140 60 Supply Current vs Supply Voltage (Shutdown Mode) Supply Current vs Input Voltage* SUPPLY CURRENT (µA) Driver Current* vs Switch Current 8 7 6 5 VSUPPLY = 60V VSUPPLY = 3V 4 400 250 150 2 50 0 1070/71 G14 150°C 200 100 0 25 50 75 100 125 150 TEMPERATURE (°C) 25°C 300 3 1 –75 – 50 –25 – 55°C 350 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 FEEDBACK CURRENT (mA) 1070/71 G18 5 LT1070/LT1071 U W TYPICAL PERFORMANCE CHARACTERISTICS Switch “Off” Characteristics Transconductance of Error Amplifier VC Pin Characteristics 300 1000 900 6000 VC PIN CURRENT (µA) SWITCH CURRENT (µA) 600 500 VSUPPLY = 400 3V 300 15V 40V 55V VFB = 1.5V (CURRENT INTO VC PIN) 100 0 –100 VFB = 0.8V (CURRENT OUT OF VC PIN) – 200 200 – 300 100 0 10 20 30 40 50 60 70 80 90 100 SWITCH VOLTAGE (V) 30 5000 gm 4000 0 0.5 2.0 1.5 1.0 VC PIN VOLTAGE (V) 1070/71 G19 2.5 60 3000 90 2000 120 1000 150 0 180 –1000 – 400 0 0 θ 1k 10k 100k 1M FREQUENCY (Hz) PHASE (°) TRANSCONDUCTANCE (µmho) 200 800 700 – 30 7000 TJ = 25°C 210 10M 1070/71 G21 1070/71 G20 W BLOCK DIAGRAM 16V SWITCH OUT VIN 2.3V REG FLYBACK ERROR AMP 40kHz OSC LOGIC MODE SELECT DRIVER 5A, 75V SWITCH ANTISAT COMP – FB ERROR VC + AMP + CURRENT AMP SHUTDOWN CIRCUIT 1.24V REF 0.15V GAIN ≈ 6 0.02Ω (0.04Ω LT1071) – 1070/71 BD U OPERATION The LT1070/LT1071 is a current mode switcher. This means that switch duty cycle is directly controlled by switch current rather than by output voltage. Referring to the Block Diagram, the switch is turned “on” at the start of each oscillator cycle. It is turned “off” when switch current reaches a predetermined level. Control of output 6 voltage is obtained by using the output of a voltage sensing error amplifier to set current trip level. This technique has several advantages. First, it has immediate response to input voltage variations, unlike ordinary switchers which have notoriously poor line transient response. Second, it reduces the 90° phase shift at LT1070/LT1071 U OPERATION midfrequencies in the energy storage inductor. This greatly simplifies closed-loop frequency compensation under widely varying input voltage or output load conditions. Finally, it allows simple pulse-by-pulse current limiting to provide maximum switch protection under output overload or short-circuit conditions. A low dropout internal regulator provides a 2.3V supply for all internal circuitry of the LT1070/LT1071. This low dropout design allows input voltage to vary from 3V to 60V with virtually no change in device performance. A 40kHz oscillator is the basic clock for all internal timing. It turns “on” the output switch via the logic and driver circuitry. Special adaptive antisat circuitry detects onset of saturation in the power switch and adjusts driver current instantaneously to limit switch saturation. This minimizes driver dissipation and provides very rapid turn-off of the switch. A 1.2V bandgap reference biases the positive input of the error amplifier. The negative input is brought out for output voltage sensing. This feedback pin has a second function; when pulled low with an external resistor, it programs the LT1070/LT1071 to disconnect the main error amplifier output and connects the output of the flyback amplifier to the comparator input. The LT1070/ LT1071 will then regulate the value of the flyback pulse with respect to the supply voltage. This flyback pulse is directly proportional to output voltage in the traditional U TYPICAL APPLICATIONS transformer coupled flyback topology regulator. By regulating the amplitude of the flyback pulse, the output voltage can be regulated with no direct connection between input and output. The output is fully floating up to the breakdown voltage of the transformer windings. Multiple floating outputs are easily obtained with additional windings. A special delay network inside the LT1070/ LT1071 ignores the leakage inductance spike at the leading edge of the flyback pulse to improve output regulation. The error signal developed at the comparator input is brought out externally. This pin (VC) has four different functions. It is used for frequency compensation, current limit adjustment, soft starting and total regulator shutdown. During normal regulator operation this pin sits at a voltage between 0.9V (low output current) and 2.0V (high output current). The error amplifiers are current output (gm) types, so this voltage can be externally clamped for adjusting current limit. Likewise, a capacitor coupled external clamp will provide soft start. Switch duty cycle goes to zero if the VC pin is pulled to ground through a diode, placing the LT1070/LT1071 in an idle mode. Pulling the VC pin below 0.15V causes total regulator shutdown, with only 50µA supply current for shutdown circuitry biasing. See AN19 for full application details. (Note that maximum output currents are divided by 2 for the LT1071) Driving High Voltage NPN C1 Driving High Voltage FET (for Off-Line Applications, See AN25) VIN 10V TO 20V + VSW LT1070/LT1071 GND 1070/71 TA03 G D D1 S D2 R2** R1* Q1 Q1 D1 VIN VSW LT1070/LT1071 *SETS IB(ON) **SETS IB(OFF) GND 1070/71 TA16 7 LT1070/LT1071 U TYPICAL APPLICATIONS (Note that maximum output currents are divided by 2 for the LT1071) Negative Buck Converter D1 VIN C3 100µF + L1** 200µH C2 1000µF – 5.2V 4.5A Q1 2N3906 LT1070 FB VC GND LOAD VSW + OPTIONAL INPUT FILTER R1 4.64k L3 OPTIONAL OUTPUT FILTER C1 R2 1.24k R3 VIN – 20V + C4 200µF L2 4µH *REQUIRED IF INPUT LEADS ≥ 2" **PULSE ENGINEERING 92113 1070/71 TA12 Positive Buck Converter VIN D3 L2 4µH VIN + C5* C3 2.2µF OPTIONAL OUTPUT FILTER VSW + LT1070 D2 1N914 R1 3.74k 100µF VC GND C5 200µF FB R2 1.24k R3 470Ω C1 1µF + C2 1µF R4 10Ω L1** 100µH r + D1 C4 1000µF *REQUIRED IF INPUT LEADS ≥2" **PULSE ENGINEERING 92112 5V 4.5A 100mA MINIMUM 1070/71 TA14 Negative Current Boosted Buck Converter + C1 R1 R5 C3 • VIN + VSW T1 1:N D1 • Q1 2N3906 R4 12k R1 = LT1070 GND VC FB R3 R2 1.24k C2 – VIN 8 MINIMUM LOAD = 10mA 1070/71 TA13 VOUT – 0.6V 1mA – VOUT 5V 10A LT1070/LT1071 U TYPICAL APPLICATIONS (Note that maximum output currents are divided by 2 for the LT1071) Positive Current Boosted Buck Converter VIN 28V 470Ω 2W R6 470Ω C3 0.47µF C6 0.002µF D2 VIN • 1:N VSW N ≈ 0.25 LT1070 R2 1k GND R7 1.24k D1 FB VC VIN 7 6 C5* 100µF – R3 680Ω + • + 2 V V – LM308 COMP 3 4 R5 5k + C1 0.33µF 8 R4 1.24k 200pF R1 5k *REQUIRED IF INPUT LEADS ≥ 2" VOUT 5V 10A + C2 5000µF 1070/71 TA19 Positive to Negative Buck/Boost Converter Negative to Positive Buck/Boost Converter L1** 150µH OPTIONAL OUTPUT FILTER C3 VIN D1 VIN C4* 100µF VSW C2 1000µF + LT1070 + R1 11.3k Q1 L3 GND OPTIONAL INPUT FILTER VIN – 12V VC FB R3 2.2k C1 0.22µF R2 1.24k R5† 470Ω 1W D3† 1N4001 L2 VOUT 12V 2A C4 5µF VSW + LT1070 GND VC † TO AVOID START-UP PROBLEMS FOR INPUT VOLTAGES BELOW 10V, VIN 10V TO 30V CONNECT ANODE OF D3 TO VIN AND REMOVE R5. C5* C1 MAY BE REDUCED FOR 100µF LOWER OUTPUT CURRENTS. C1 ≈ (500µF)(IOUT) FOR 5V OUTPUTS, REDUCE R3 TO 1.5k, INCREASE C2 TO 0.3µF D2 R1 R4 1N914 47Ω AND REDUCE R6 TO 100Ω. 10.7k FB R3 5k C1 0.1µF R2 1.24k + C3 C1† 2µF 1000µF + R6 470Ω D1 1070/71 TA09 1070/71 TA05 L1** 200µH *REQUIRED IF INPUT LEADS ≥ 2" **PULSE ENGINEERING 92113 VOUT – 12V 2A *REQUIRED IF INPUT LEADS ≥ 2" **PULSE ENGINEERING 92113 9 LT1070/LT1071 U TYPICAL APPLICATIONS (Note that maximum output currents are divided by 2 for the LT1071) Current Boosted Boost Converter Voltage Boosted Boost Converter R4 680Ω 1W C3 0.68µF R4 D2 VIN + VIN 15V VSW LT1070 VC R3 10k C2 0.047µF VIN VIN 16V TO 24V + R2 1.24k D1 VOUT 28V 4A N VSW + R1 27k LT1070 + C1 VOUT 100V 300mA FB I D2 D1 R1 98k GND TOTAL INDUCTANCE = 4mH INTERLEAVE PRIMARY AND SECONDARY FOR LOW LEAKAGE INDUCTANCE 1 L1 N=5 C3 VC GND C1 200µF FB R2 1.24k R3 C2 1070/71 TA10 1070/71 TA11 Negative Input/Negative Output Flyback Converter Negative Boost Regulator D2 VSW C4* 470µF VIN –15V VIN + R1 27k + GND L1 200µH R6 • VIN LT1070 + C3 R3 3.3k C2 0.22µF RO (MINIMUM LOAD) + VC FB *R1 = R4 1.24k R5 *REQUIRED IF INPUT LEADS ≥ 2" VOUT –28V 1A C2 1070/71 TA17 – VIN 1070/71 TA15 External Current Limit External Current Limit VSW VX LT1070/LT1071 LT1070/LT1071 R2 + = 2V VIN FB GND R1 1k Q1 C1 1000pF RS 10 D1 VC GND VC R1 500Ω R2 1070/71 TA04 C2 C1 – VOUT GND D1 + Q1 2N3906 LT1070/LT1071 R2 1.24k VIN • R1* C3 10µF FB VC C1 1000µF T1 1:N VSW R2 5k R3 1k NOTE THAT THE LT1070/LT1071 GND PIN IS NO LONGER COMMON TO VIN– 1070/71 TA06 VOUT – 1.6V 200µA LT1070/LT1071 U TYPICAL APPLICATIONS (Note that maximum output currents are divided by 2 for the LT1071) Flyback Converter CLAMP TURN-ON SPIKE VSNUB L2 10µH C4 200µF OPTIONAL FILTER D1 VIN 20V TO 30V C3 0.47µF R4 + (N)(VIN) SECONDARY VOLTAGE AREA “c” = AREA “d” TO MAINTAIN ZERO DC VOLTS ACROSS SECONDARY c 0V d C1 2000µF ∆I IPRI R1 3.74k PRIMARY CURRENT 0 IPRI N SECONDARY CURRENT 0 FB IPRI VC R2 1.24k R3 1.5k C2 0.15µF LT1070 SWITCH CURRENT 0 IPRI SNUBBER DIODE CURRENT *REQUIRED IF INPUT LEADS ≥ 2" 1070/71 TA08 (I )(L ) t = PRI L VSNUB U PACKAGE DESCRIPTION 0.320 – 0.350 (8.13 – 8.89) VOUT + VF VSW LT1070 GND b 0V • N = 1/3 C4* 100µF VOUT 5V 6A 1 N D2 VIN + • + VF V PRIMARY FLYBACK VOLTAGE = OUT N LT1070/LT1071 SWITCH VOLTAGE AREA “a” = AREA “b” TO MAINTAIN ZERO DC VOLTS ACROSS PRIMARY a VIN Dimensions in inches (millimeters) unless otherwise noted. K Package 4-Lead TO-3 Metal Can T Package 5-Lead Plastic TO-220 (Standard) (LTC DWG # 05-08-1311) (LTC DWG # 05-08-1421) 0.760 – 0.775 (19.30 – 19.69) 0.390 – 0.415 (9.906 – 10.541) 0.060 – 0.135 (1.524 – 3.429) 0.165 – 0.180 (4.191 – 4.572) 0.147 – 0.155 (3.734 – 3.937) DIA 0.045 – 0.055 (1.143 – 1.397) 0.230 – 0.270 (5.842 – 6.858) 0.420 – 0.480 (10.67 – 12.19) 0.460 – 0.500 (11.684 – 12.700) 0.038 – 0.043 (0.965 – 1.09) 0.570 – 0.620 (14.478 – 15.748) 0.330 – 0.370 (8.382 – 9.398) 0.620 (15.75) TYP 0.700 – 0.728 (17.78 – 18.491) 1.177 – 1.197 (29.90 – 30.40) 0.470 TP P.C.D. 0.655 – 0.675 (16.64 – 19.05) 0.151 – 0.161 (3.84 – 4.09) DIA 2 PLC 0.167 – 0.177 (4.24 – 4.49) R 72° 18° 0.152 – 0.202 0.260 – 0.320 (3.861 – 5.131) (6.60 – 8.13) 0.095 – 0.115 (2.413 – 2.921) 0.013 – 0.023 (0.330 – 0.584) 0.057 – 0.077 (1.448 – 1.956) 0.028 – 0.038 (0.711 – 0.965) 0.135 – 0.165 (3.429 – 4.191) 0.155 – 0.195 (3.937 – 4.953) T5 (TO-220) 0398 0.495 – 0.525 (12.57 – 13.34) R K4(TO-3) 0695 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. 11 LT1070/LT1071 U TYPICAL APPLICATIONS (Note that maximum output currents are divided by 2 for the LT1071) Totally Isolated Converter OPTIONAL OUTPUT FILTER D1 15V 1:N C3 0.47µF R4 1.5k + • + N VIN +V + IN 5V C5* 100µF LT1070/LT1071 COM C4 500µF • VSW + C1 500µF N L1 10µF –15V C6 200µF N = 0.875 = 7:8 FOR VOUT = 15V ≈16V SWITCH VOLTAGE FB VC GND + L2 10µF C5 200µF VIN 500Ω tOFF 0V tON R2 C2 5k 0.01µF VF (DIODE FORWARD VOLTAGE) VOUT SECONDARY VOLTAGE 0V *REQUIRED IF INPUT LEADS ≥ 2" 1070/71 TA07 (N)(VIN) Forward Converter R4 C2 • I L1 70µH D1 T1 M N • + D2 VIN VIN 20V TO 30V D3 VC C1 2000µF • VSW LT1070 GND VOUT 5V 6A D4 R1 3.74k FB Q1 R3 C3 R6 C4 330Ω R5 1Ω R2 1.24k 1070/71 TA18 RELATED PARTS PART NUMBER DESCRIPTION COMMENTS LT1074/LT1076 High Voltage Switching Regulators 40V Input (60V for HV Versions), 100kHz, 5A and 2A LT1170/LT1171/ LT1172 100kHz High Efficiency Switching Regulators 40V Input (65V for HV Versions), 5A/2.5A/1.25A Internal Switch LT1370/LT1371 500kHz High Efficiency Switching Regulators 35V, 6A/3A Internal Switch LT1374/LT1376 100kHz High Efficiency Switching Regulators 25V Input, 4.5A/1.5A Internal Switch 12 Linear Technology Corporation 10701fd LT/TP 1098 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 1989