LT1170/LT1171/LT1172 100kHz, 5A, 2.5A and 1.25A High Efficiency Switching Regulators U FEATURES DESCRIPTIO Wide Input Voltage Range: 3V to 60V Low Quiescent Current: 6mA Internal 5A Switch (2.5A for LT1171, 1.25A for LT1172) Shutdown Mode Draws Only 50A Supply Current Very Few External Parts Required Self-Protected Against Overloads Operates in Nearly All Switching Topologies Flyback-Regulated Mode Has Fully Floating Outputs Comes in Standard 5-Pin Packages LT1172 Available in 8-Pin MiniDIP and Surface Mount Packages Can Be Externally Synchronized U APPLICATIO S Logic Supply 5V at 10A 5V Logic to 15V Op Amp Supply Battery Upconverter Power Inverter (+ to -) or (- to +) Fully Floating Multiple Outputs USER NOTE: This data sheet is only intended to provide specifications, graphs, and a general functional description of the LT1170/LT1171/LT1172. Application circuits are included to show the capability of the LT1170/LT1171/LT1172. 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 LT1170/LT1171/LT1172 by factoring in the higher frequency. A CAD design program called SwitcherCADTM is also available. The LT(R)1170/LT1171/LT1172 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 LT1170/LT1171/LT1172 to be built in a standard 5-pin TO-3 or TO-220 power package as well as the 8-pin packages (LT1172). This makes them extremely easy to use and provides "bust proof" operation similar to that obtained with 3-pin linear regulators. The LT1170/LT1171/LT1172 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 LT1170/LT1171/LT1172 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 50A typically for standby operation. , LTC and LT are registered trademarks of Linear Technology Corporation. SwitcherCAD is a trademark of Linear Technology Corporation. U TYPICAL APPLICATIO Boost Converter (5V to 12V) 5V Maximum Output Power* L1** 50H L2 10H OUTPUT FILTER 100 * ROUGH GUIDE ONLY. BUCK MODE POUT = (5A)(VOUT) SPECIAL TOPOLOGIES DELIVER MORE POWER. ** DIVIDE VERTICAL POWER SCALE BY TWO FOR LT1171, BY FOUR FOR LT1172. LT1170 VSW + LT1170 C3* 100F + C2 1000F 80 R1 10.7k 1% 12V 1A FB GND VC R3 1k C1 1F *REQUIRED IF INPUT LEADS 2" ** COILTRONICS 50-2-52 PULSE ENGINEERING 92114 R2 1.24k 1% POWER (W) ** D1 MBR330 VIN C3 100F BOOST LT1170/1/2 TA02 FLYBACK 40 20 BUCK-BOOST VO = 5V 0 1170/1/2 TA01 BUCK-BOOST VO = 30V 60 0 10 30 20 INPUT VOLTAGE (V) 40 50 117012ff 1 LT1170/LT1171/LT1172 W W W AXI U U ABSOLUTE RATI GS (Note 1) Supply Voltage LT1170/71/72HV (Note 2) .................................. 60V LT1170/71/72 (Note 2) ....................................... 40V Switch Output Voltage LT1170/71/72HV ................................................ 75V LT1170/71/72 ..................................................... 65V LT1172S8 ........................................................... 60V Feedback Pin Voltage (Transient, 1ms) ................ 15V Storage Temperature Range ............... - 65C to 150C Lead Temperature (Soldering, 10 sec)................. 300C Operating Junction Temperature Range LT1170/71/72M (OBSOLETE) .. - 55C to 150C LT1170/71/72HVC, LT1170/71/72C (Oper.) .............. 0C to 100C LT1170/71/72HVC C LT1170/71/72C (Sh. Ckt.) .......... 0C to 125C LT1170/71/72HVI, LT1170/71/72I (Oper.) .......... - 40C to 100C LT1170/71/72HVI, I LT1170/71/72I (Sh. Ckt.) ...... - 40C to 125C U U W PACKAGE/ORDER I FOR ATIO ORDER PART NUMBER TOP VIEW GND 1 8 E2 VC 2 7 VSW FB 3 6 E1 NC* 4 5 VIN N8 PACKAGE 8-LEAD PDIP S8 PACKAGE 8-LEAD PLASTIC SO * Do not connect Pin 4 of the LT1172 DIP or SO to external circuitry. This pin may be active in future revisions. TJMAX = 100C, JA = 100C/W (N) TJMAX = 100C, JA = 120C/W to 150C/W depending on board layout (S) LT1172CN8 LT1172IN8 LT1172CS8 LT1172IS8 S8 PART MARKING 1172 1172I ORDER PART NUMBER FRONT VIEW 5 4 3 2 1 VIN VSW GND FB VC Q PACKAGE 5-LEAD DD TJMAX = 100C, JA = *C/W * will vary from approximately 25C/W with 2.8 sq. in. of 1oz. copper to 45C/W with 0.20 sq. in. of 1oz. copper. Somewhat lower values can be obtained with additional copper layers in multilayer boards. LT1170CQ LT1170IQ LT1170HVCQ LT1171CQ LT1171IQ LT1171HVCQ LT1171HVIQ LT1172CQ LT1172HVCQ LT1172HVIQ ORDER PART NUMBER TOP VIEW NC 1 16 NC NC 2 15 NC GND 3 14 E2 VC 4 13 VSW FB 5 12 E1 NC 6 11 VIN NC 7 10 NC NC 8 9 LT1172CSW NC SW PACKAGE 16-LEAD PLASTIC SO WIDE TJMAX = 100C, JA = 150C/W Based on continuous operation. TJMAX = 125C for intermittent fault conditions. ORDER PART NUMBER FRONT VIEW 5 VIN 4 VSW 3 GND 2 FB 1 VC T PACKAGE 5-LEAD PLASTIC TO-220 TJMAX JC JA LT1170CT/LT1170HVCT 100C 2C/W 75C/W LT1171CT/LT1171HVCT 100C 4C/W 75C/W LT1172CT/LT1172HVCT 100C 8C/W 75C/W Based on continuous operation. TJMAX = 125C for intermittent fault conditions. LT1170CT LT1170IT LT1170HVCT LT1170HVIT LT1171CT LT1171IT LT1171HVCT LT1171HVIT LT1172CT LT1172HVCT 117012ff 2 LT1170/LT1171/LT1172 U U W PACKAGE/ORDER I FOR ATIO ORDER PART NUMBER VC 1 TOP VIEW GND 1 8 E2 VC 2 7 VSW FB 3 6 E1 NC* 4 5 VIN LT1172MJ8 LT1172CJ8 ORDER PART NUMBER BOTTOM VIEW VSW 4 2 3 VIN CASE IS GND LT1170MK LT1170CK LT1171MK LT1171CK LT1172MK LT1172CK FB K PACKAGE 4-LEAD TO-3 METAL CAN TJMAX JC LT1170MK 150C 2C/W LT1170CK 100C 2C/W LT1171MK 150C 4C/W LT1171CK 100C 4C/W LT1172MK 150C 8C/W LT1172CK 150C 8C/W Based on continuous operation. TJMAX = 125C for intermittent fault conditions. J8 PACKAGE 8-LEAD CERDIP * Do not connect Pin 4 of the LT1172 DIP or SO to external circuitry. This pin may be active in future revisions. TJMAX = 150C, JA = 100C/W JA 35C/W 35C/W 35C/W 35C/W 35C/W 35C/W OBSOLETE PACKAGES ELECTRICAL CHARACTERISTICS The denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25C. VIN = 15V, VC = 0.5V, VFB = VREF, output pin open, unless otherwise noted. SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS VREF 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 Reference Voltage Feedback Input Current VFB = VREF gm AV Error Amplifier Transconductance IC = 25A Error Amplifier Source or Sink Current VC = 1.5V Error Amplifier Clamp Voltage 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 (Note 5) IQ 3000 2400 4400 6000 7000 mho mho 150 120 200 350 400 A A 2.30 0.52 V V 0.03 %/V 1.80 0.25 500 3V VIN VMAX, VC = 0.6V Control Pin Threshold Duty Cycle = 0 Normal/Flyback Threshold on Feedback Pin VFB Flyback Reference Voltage (Note 5) IFB = 50A Change in Flyback Reference Voltage 0.05 IFB 1mA Flyback Reference Voltage Line Regulation (Note 5) IFB = 50A 7V VIN VMAX Flyback Amplifier Transconductance (gm) IC = 10A 800 2.6 Supply Current 0.38 V/V 3.0 V 6 9 0.8 0.6 0.9 1.08 1.25 V V 0.4 0.45 0.54 V 15.0 14.0 16.3 17.6 18.0 V V 4.5 6.8 9 V 0.01 0.03 %/V 300 650 mho 150 mA 117012ff 3 LT1170/LT1171/LT1172 ELECTRICAL CHARACTERISTICS The denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25C. VIN = 15V, VC = 0.5V, VFB = VREF, output pin open, unless otherwise noted. SYMBOL PARAMETER MIN TYP MAX Flyback Amplifier Source and Sink Current VC = 0.6V IFB = 50A Source Sink 15 25 32 40 70 70 BV Output Switch Breakdown Voltage 3V VIN VMAX, ISW = 1.5mA LT1170/LT1171/LT1172 LT1170HV/LT1171HV/LT1172HV LT1172S8 65 75 60 90 90 80 VSAT Output Switch "On" Resistance (Note 3) LT1170 LT1171 LT1172 Control Voltage to Switch Current Transconductance LT1170 LT1171 LT1172 Switch Current Limit (LT1170) Duty Cycle = 50% Duty Cycle = 50% Duty Cycle = 80% (Note 4) TJ 25C TJ < 25C 5 5 4 10 11 10 A A A (LT1171) Duty Cycle = 50% Duty Cycle = 50% Duty Cycle = 80% (Note 4) TJ 25C TJ < 25C 2.5 2.5 2.0 5.0 5.5 5.0 A A A (LT1172) Duty Cycle = 50% Duty Cycle = 50% Duty Cycle = 80% (Note 4) TJ 25C TJ < 25C 1.25 1.25 1.00 3.0 3.5 2.5 A A A 25 35 mA/A 100 112 115 kHz kHz ILIM CONDITIONS IIN ISW Supply Current Increase During Switch On-Time f Switching Frequency DCMAX Maximum Switch Duty Cycle Shutdown Mode Supply Current 3V VIN VMAX VC = 0.05V Shutdown Mode Threshold Voltage 3V VIN VMAX Flyback Sense Delay Time (Note 5) Note 1: Absolute Maximum Ratings are those values beyond which the life of the device may be impaired. Note 2: Minimum effective switch "on" time for the LT1170/71/72 (in current limit only) is 0.6s. This limits the maximum safe input voltage during an output shorted condition. Buck mode and inverting mode input voltage during an output shorted condition is limited to: (R)(IL) + Vf VIN (max, output shorted) = 15V + (t)(f) buck and inverting mode R = Inductor DC resistance IL = 10A for LT1170, 5A for LT1171, and 2.5A for LT1172 Vf = Output catch diode forward voltage at IL t = 0.6s, f = 100kHz switching frequency Maximum input voltage can be increased by increasing R or Vf. External current limiting such as that shown in AN19, Figure 39, will provide protection up to the full supply voltage rating. C1 in Figure 39 should be reduced to 200pF. 0.15 0.30 0.60 88 85 85 100 50 A A V V V 0.24 0.50 1.00 8 4 2 UNITS A/V A/V A/V 92 97 % 100 250 A 150 250 300 mV mV 1.5 s Transformer designs will tolerate much higher input voltages because leakage inductance limits rate of rise of current in the switch. These designs must be evaluated individually to assure that current limit is well controlled up to maximum input voltage. Boost mode designs are never protected against output shorts because the external catch diode and inductor connect input to output. Note 3: Measured with VC in hi clamp, VFB = 0.8V. ISW = 4A for LT1170, 2A for LT1171, and 1A for LT1172. Note 4: For duty cycles (DC) between 50% and 80%, minimum guaranteed switch current is given by ILIM = 3.33 (2 - DC) for the LT1170, ILIM = 1.67 (2 - DC) for the LT1171, and ILIM = 0.833 (2 - DC) for the LT1172. Note 5: Minimum input voltage for isolated flyback mode is 7V. VMAX = 55V for HV grade in fully isolated mode to avoid switch breakdown. 117012ff 4 LT1170/LT1171/LT1172 U W TYPICAL PERFOR A CE CHARACTERISTICS Switch Current Limit vs Duty Cycle* Minimum Input Voltage 16 Switch Saturation Voltage 2.9 1.6 12 25C -55C 8 125C 4 * DIVIDE VERTICAL SCALE BY TWO FOR LT1171, BY FOUR FOR LT1172. 0 0 2.7 2.6 SWITCH CURRENT = 0A 2.5 2.4 2.3 -75 -50 -25 10 20 30 40 50 60 70 80 90 100 DUTY CYCLE (%) 2 1 TJ = 25C -1 -2 -5 10 0.6 0.4 30 40 20 INPUT VOLTAGE (V) 50 60 * DIVIDE CURRENT BY TWO FOR LT1171, BY FOUR FOR LT1172. 0.2 0 1.248 700 1.246 1.244 1.242 1.240 1.238 400 300 200 0 -75 -50 -25 25 50 75 100 125 150 TEMPERATURE (C) 0 Supply Current vs Input Voltage* 15 160 140 120 120 TJ = 25C 14 NOTE THAT THIS CURRENT DOES NOT INCLUDE DRIVER CURRENT, WHICH IS A FUNCTION OF LOAD CURRENT AND DUTY CYCLE. SUPPLY CURRENT (mA) DRIVER CURRENT (mA) SUPPLY CURRENT (A) 13 40 100 TJ = - 55C 80 60 TJ = 25C 40 12 11 10 90% DUTY CYCLE 9 50% DUTY CYCLE 8 10% DUTY CYCLE 7 20 20 VC = 0V 6 0 0 0 10 30 20 40 SUPPLY VOLTAGE (V) 50 60 1170/1/2 G07 0 25 50 75 100 125 150 TEMPERATURE (C) 1170/1/2 G06 TJ = 25C 140 8 500 1170/1/2 G05 160 60 7 600 Driver Current* vs Switch Current VC = 50mV 4 5 6 3 SWITCH CURRENT (A)* 100 1.234 -75 -50 -25 Supply Current vs Supply Voltage (Shutdown Mode) 80 2 Feedback Bias Current vs Temperature 800 1170/1/2 G04 100 1 1170/1/2 G03 1.236 0 -55C 1.250 -3 -4 25C 0.8 0 FEEDBACK BIAS CURRENT (nA) REFERENCE VOLTAGE (V) REFERENCE VOLTAGE CHANGE (mV) 4 TJ = 150C 100C 1.0 Reference Voltage vs Temperature 5 TJ = -55C 150C 1.2 1170/1/2 G02 Line Regulation 0 1.4 0 25 50 75 100 125 150 TEMPERATURE (C) 1170/1/2 G01 3 SWITCH SATURATION VOLTAGE (V) MINIMUM INPUT VOLTAGE (V) SWITCH CURRENT (A) SWITCH CURRENT = IMAX 2.8 0% DUTY CYCLE 5 0 1 2 3 SWITCH CURRENT (A) 4 5 1170/1/2 G08 * AVERAGE LT1170 POWER SUPPLY CURRENT IS FOUND BY MULTIPLYING DRIVER CURRENT BY DUTY CYCLE, THEN ADDING QUIESCENT CURRENT. 0 10 30 40 20 INPUT VOLTAGE (V) 50 60 1170/1/2 G09 * UNDER VERY LOW OUTPUT CURRENT CONDITIONS, DUTY CYCLE FOR MOST CIRCUITS WILL APPROACH 10% OR LESS. 117012ff 5 LT1170/LT1171/LT1172 U W TYPICAL PERFOR A CE CHARACTERISTICS Shutdown Mode Supply Current Error Amplifier Transconductance 5000 180 4500 140 TJ = 150C 120 100 80 60 -55C TJ 125C 40 20 gm = I (VC PIN) V (FB PIN) 3500 3000 2500 2000 1500 0 -400 0 25 50 75 100 125 150 TEMPERATURE (C) FEEDBACK VOLTAGE (mV) 9 8 VSUPPLY = 60V VSUPPLY = 3V 5 4 3 2 500 1000 450 900 400 300 25C 250 150C 200 150 100 0 - 250 200 - 200 VOLTAGE 150 - 150 100 -100 VC VOLTAGE IS REDUCED UNTIL REGULATOR CURRENT DROPS BELOW 300A - 50 0 25 50 75 100 125 150 TEMPERATURE (C) 0 1170/1/2 G16 10 20 30 40 50 60 70 80 90 100 SWITCH VOLTAGE (V) 1170/1/2 G15 Isolated Mode Flyback Reference Voltage 2.2 23 22 2.0 1.8 TIME (s) - 300 250 VSUPPLY = 55V 1170/1/2 G14 - 350 300 VSUPPLY = 40V 0 Flyback Blanking Time CURRENT (OUT OF VC PIN) VSUPPLY = 15V 300 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 FEEDBACK CURRENT (mA) VC PIN CURRENT (A) VC PIN VOLTAGE (mV) 500 VSUPPLY = 3V 400 200 - 400 0 -75 -50 -25 600 50 Shutdown Thresholds 50 700 100 0 25 50 75 100 125 150 TEMPERATURE (C) 2.5 800 -55C 350 1170/1/2 G13 350 1.5 2.0 1.0 VC PIN VOLTAGE (V) Switch "Off" Characteristics 0 400 0.5 1170/1/2 G12 SWITCH CURRENT (A) IDLE SUPPLY CURRENT (mA) VC = 0.6V 1 -75 -50 -25 0 Feedback Pin Clamp Voltage 11 6 -200 1170/1/2 G11 Idle Supply Current vs Temperature 7 TJ = 25C -100 VFB = 0.8V (CURRENT OUT OF VC PIN) 1170/1/2 G10 10 0 -300 0 -75 -50 -25 10 20 30 40 50 60 70 80 90 100 VC PIN VOLTAGE (mV) 100 1000 500 0 VFB = 1.5V (CURRENT INTO VC PIN) 200 4000 FLYBACK VOLTAGE (V) SUPPLY CURRENT (A) 160 VC Pin Characteristics 300 VC PIN CURRENT (A) TRANSCONDUCTANCE (mho) 200 1.6 1.4 1.2 21 RFB = 500 20 19 RFB = 1k 18 17 RFB = 10k 16 1.0 -75 -50 -25 0 25 50 75 100 125 150 JUNCTION TEMPERATURE (C) 1170/1/2 G17 15 -75 -50 -25 0 25 50 75 100 125 150 TEMPERATURE (C) 1170/1/2 G18 117012ff 6 LT1170/LT1171/LT1172 U W TYPICAL PERFOR A CE CHARACTERISTICS Transconductance of Error Amplifier Normal/Flyback Mode Threshold on Feedback Pin -24 0 490 -22 480 -20 30 5000 4000 60 gm 90 3000 120 2000 1000 150 0 180 -1000 210 10M 1k 10k 1M 100k FREQUENCY (Hz) -18 470 FEEDBACK PIN VOLTAGE (AT THRESHOLD) 460 -16 -14 450 -12 440 FEEDBACK PIN CURRENT (AT THRESHOLD) 430 -10 420 -8 410 -6 400 -50 -25 0 FEEDBACK PIN CURRENT (A) 500 PHASE (DEG) TRANSCONDUCTANCE (mho) 6000 -30 FEEDBACK PIN VOLTAGE (mV) 7000 -4 25 50 75 100 125 150 TEMPERATURE (C) 1170/1/2 G19 1170/1/2 G20 W BLOCK DIAGRA VIN 16V 2.3V REG SWITCH OUT FLYBACK ERROR AMP LT1172 5A, 75V SWITCH 100kHz OSC LOGIC DRIVER ANTISAT MODE SELECT COMP - FB ERROR AMP VC + + SHUTDOWN CIRCUIT 1.24V REF CURRENT AMP GAIN 6 - 0.02 (0.04 LT1171) (0.16 LT1172) 0.16 0.15V (LT1170 AND LT1171 ONLY) E1 E2 ALWAYS CONNECT E1 TO THE GROUND PIN ON MINIDIP, 8- AND 16-PIN SURFACE MOUNT PACKAGES. E1 AND E2 INTERNALLY TIED TO GROUND ON TO-3 AND TO-220 PACKAGES. 1170/1/2 BD 117012ff 7 LT1170/LT1171/LT1172 U OPERATIO The LT1170/LT1171/LT1172 are current mode switchers. 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 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 midfrequencies in the energy storage inductor. This greatly simplifies closedloop 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 conditions. A low dropout internal regulator provides a 2.3V supply for all internal circuitry on the LT1170/LT1171/LT1172. This low dropout design allows input voltage to vary from 3V to 60V with virtually no change in device performance. A 100kHz oscillator is the basic clock for all internal timing. It turns "on" the output switch via the logic and driver circuitry. Special adaptive anti-sat 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 turnoff 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 LT1170/LT1171/LT1172 to disconnect the main error amplifier output and connects the output of the flyback amplifier to the comparator input. The LT1170/ LT1171/LT1172 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 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 LT1170/ LT1171/LT1172 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 LT1170/LT1171/LT1172 in an idle mode. Pulling the VC pin below 0.15V causes total regulator shutdown, with only 50A supply current for shutdown circuitry biasing. See AN19 for full application details. Extra Pins on the MiniDIP and Surface Mount Packages The 8- and 16-pin versions of the LT1172 have the emitters of the power transistor brought out separately from the ground pin. This eliminates errors due to ground pin voltage drops and allows the user to reduce switch current limit 2:1 by leaving the second emitter (E2) disconnected. The first emitter (E1) should always be connected to the ground pin. Note that switch "on" resistance doubles when E2 is left open, so efficiency will suffer somewhat when switch currents exceed 300mA. Also, note that chip dissipation will actually increase with E2 open during normal load operation, even though dissipation in current limit mode will decrease. See "Thermal Considerations" next. Thermal Considerations When Using the MiniDIP and SW Packages The low supply current and high switch efficiency of the LT1172 allow it to be used without a heat sink in most applications when the TO-220 or TO-3 package is selected. These packages are rated at 50C/W and 35C/W respectively. The miniDIPs, however, are rated at 100C/W in ceramic (J) and 130C/W in plastic (N). *See note under block diagram. 117012ff 8 LT1170/LT1171/LT1172 U OPERATIO Care should be taken for miniDIP applications to ensure that the worst case input voltage and load current conditions do not cause excessive die temperatures. The following formulas can be used as a rough guide to calculate LT1172 power dissipation. For more details, the reader is referred to Application Note 19 (AN19), "Efficiency Calculations" section. Average supply current (including driver current) is: IIN 6mA + ISW (0.004 + DC/40) ISW = switch current DC = switch duty cycle Switch power dissipation is given by: PSW = (ISW)2 * (RSW)(DC) RSW = LT1172 switch "on" resistance (1 maximum) Total power dissipation is the sum of supply current times input voltage plus switch power: PD(TOT) = (IIN)(VIN) + PSW In a typical example, using a boost converter to generate 12V at 0.12A from a 5V input, duty cycle is approximately 60%, and switch current is about 0.65A, yielding: IIN = 6mA + 0.65(0.004 + DC/40) = 18mA PSW = (0.65)2 * (1)(0.6) = 0.25W PD(TOT) = (5V)(0.018A) + 0.25 = 0.34W Temperature rise in a plastic miniDIP would be 130C/W times 0.34W, or approximately 44C. The maximum ambient temperature would be limited to 100C (commercial temperature limit) minus 44C, or 56C. In most applications, full load current is used to calculate die temperature. However, if overload conditions must also be accounted for, four approaches are possible. First, if loss of regulated output is acceptable under overload conditions, the internal thermal limit of the LT1172 will protect the die in most applications by shutting off switch current. Thermal limit is not a tested parameter, however, and should be considered only for noncritical applications with temporary overloads. A second approach is to use the larger TO-220 (T) or TO-3 (K) package which, even without a heat sink, may limit die temperatures to safe levels under overload conditions. In critical situations, heat sinking of these packages is required; especially if overload conditions must be tolerated for extended periods of time. The third approach for lower current applications is to leave the second switch emitter (miniDIP only) open. This increases switch "on" resistance by 2:1, but reduces switch current limit by 2:1 also, resulting in a net 2:1 reduction in I2R switch dissipation under current limit conditions. The fourth approach is to clamp the VC pin to a voltage less than its internal clamp level of 2V. The LT1172 switch current limit is zero at approximately 1V on the VC pin and 2A at 2V on the VC pin. Peak switch current can be externally clamped between these two levels with a diode. See AN19 for details. LT1170/LT1171/LT1172 Synchronizing The LT1170/LT1171/LT1172 can be externally synchronized in the frequency range of 120kHz to 160kHz. This is accomplished as shown in the accompanying figures. Synchronizing occurs when the VC pin is pulled to ground with an external transistor. To avoid disturbing the DC characteristics of the internal error amplifier, the width of the synchronizing pulse should be under 0.3s. C2 sets the pulse width at 0.2s. The effect of a synchronizing pulse on the LT1170/LT1171/LT1172 amplifier offset can be calculated from: KT VC + t f I S S C q R3 VOS = IC KT = 26mV at 25C q tS = pulse width fS = pulse frequency IC = VC source current ( 200A) VC = operating VC voltage (1V to 2V) R3 = resistor used to set mid-frequency "zero" in frequency compensation network. ( )( ) 117012ff 9 LT1170/LT1171/LT1172 U OPERATIO With tS = 0.2s, fS = 150kHz, VC = 1.5V, and R3 = 2k, offset voltage shift is 3.8mV. This is not particularly bothersome, but note that high offsets could result if R3 were reduced to a much lower value. Also, the synchronizing transistor must sink higher currents with low values of R3, so larger drives may have to be used. The transistor must be capable of pulling the VC pin to within 200mV of ground to ensure synchronizing. Synchronizing with Bipolar Transistor Synchronizing with MOS Transistor VIN VIN LT1170 LT1170 VC GND VC GND C2 39pF R3 R1 3k R3 2N2369 C1 R2 2.2k D1 1N4158 VN2222* C1 FROM 5V LOGIC C2 100pF R2 2.2k D2 1N4158 * SILICONIX OR EQUIVALENT 1170/1/2 OP01 FROM 5V LOGIC 1170/1/2 OP02 U TYPICAL APPLICATIO S Flyback Converter L2 OPTIONAL FILTER 5H CLAMP TURN-ON SPIKE VSNUB C4 100F a VIN N* = 1/3 VIN 20V TO 30V D3 25V 1W D2 MUR110 VIN C4* 100F D1 VOUT 5V 6A 1 N* + b 0V VOUT + Vf c C1 2000F N * VIN 0V d R1 3.74k I PRIMARY CURRENT 0 LT1170 IPRI/N FB GND SECONDARY VOLTAGE AREA "c" = AREA "d" TO MAINTAIN ZERO DC VOLTS ACROSS SECONDARY IPRI VSW + V + Vf PRIMARY FLYBACK VOLTAGE = OUT N LT1170 SWITCH VOLTAGE AREA "a" = AREA "b" TO MAINTAIN ZERO DC VOLTS ACROSS PRIMARY SECONDARY CURRENT VC 0 IPRI R3 1.5k C2 0.15F *REQUIRED IF INPUT LEADS 2" R2 1.24k LT1170 SWITCH CURRENT 0 IPRI SNUBBER DIODE CURRENT 0 (I )(L ) t = PRI L VSNUB 1170/1/2 TA03 117012ff 10 LT1170/LT1171/LT1172 U TYPICAL APPLICATIO S (Note that maximum output currents are divided by 2 for LT1171, by 4 for LT1172.) LCD Contrast Supply 5V* L1** 50H VIN VSW E2 LT1172 + R2 100k R1 200k D1 1N914 C1 1F TANTALUM VOUT -10V TO -26V FB E1 VC D2 C4 0.047F VN2222 R3 15k C3 0.0047F D3 + GND OPTIONAL SHUTDOWN VBAT* 3V TO 20V C2*** 2F TANTALUM D2, D3 = ER82.004 600mA SCHOTTKY. OTHER FAST SWITCHING TYPES MAY BE USED. * VIN AND BATTERY MAY BE TIED TOGETHER. MAXIMUM VALUE FOR VBAT IS EQUAL TO THE NEGATIVE OUTPUT + 1V. WITH HIGHER BATTERY VOLTAGES, HIGHEST EFFICIENCY IS OBTAINED BY RUNNING THE LT1172 VIN PIN FROM 5V. SHUTTING OFF THE 5V SUPPLY WILL AUTOMATICALLY TURN OFF THE LT1172. EFFICIENCY IS ABOUT 80% AT IOUT = 25mA. R1, R2, R3 ARE MADE LARGE TO MINIMIZE BATTERY DRAIN IN SHUTDOWN, WHICH IS APPROXIMATELY VBAT /(R1 + R2 + R3). ** FOR HIGH EFFICIENCY, L1 SHOULD BE MADE ON A FERRITE OR MOLYPERMALLOY CORE. PEAK INDUCTOR CURRENTS ARE ABOUT 600mA AT POUT = 0.7. INDUCTOR SERIES RESISTANCE SHOULD BE LESS THAN 0.4 FOR HIGH EFFICIENCY. *** OUTPUT RIPPLE IS ABOUT 200mVP-P TO 400mVP-P WITH C2 = 2F TANTALUM. IF LOWER RIPPLE IS DESIRED, INCREASE C2, OR ADD A 10 , 1F TANTALUM OUTPUT FILTER. 1170/1/2 TA04 Driving High Voltage FET (for Off-Line Applications, See AN25) G VIN 10V TO 20V External Current Limit D Q1 VX D1 LT1170 VSW R2 + 2V LT1170 R1 500 D1 GND VC GND 1170/1/2 TA05 1170/1/2 TA06 117012ff 11 LT1170/LT1171/LT1172 U TYPICAL APPLICATIO S (Note that maximum output currents are divided by 2 for LT1171, by 4 for LT1172.) Negative-to-Positive Buck-Boost Converter L1** 50H External Current Limit L2 VIN OPTIONAL OUTPUT FILTER LT1170 + D1 VIN C4* 100F VSW + + LT1170 R1 11.3k C2 1000F VOUT 12V 2A - VIN VC GND L3 R1 1k FB R2 Q1 FB C1 1000pF R3 2.2k C1 0.22F VIN -20V VC GND Q1 OPTIONAL INPUT FILTER VSW C3 R2 1.24k C2 RS NOTE THAT THE LT1170 GND PIN IS NO LONGER COMMON TO VIN-. * REQUIRED IF INPUT LEADS 2" ** PULSE ENGINEERING 92114, COILTRONICS 50-2-52 THIS CIRCUIT IS OFTEN USED TO CONVERT -48V TO 5V. TO GUARANTEE FULL SHORT-CIRCUIT PROTECTION, THE CURRENT LIMIT CIRCUIT SHOWN IN AN19, FIGURE 39, SHOULD BE ADDED WITH C1 REDUCED TO 200pF. 1170/1/2 TA08 1170/1/2 TA07 Negative Buck Converter + D1 * REQUIRED IF INPUT LEADS 2" ** PULSE ENGINEERING 92114 COILTRONICS 50-2-52 VIN VSW C3* 100F OPTIONAL INPUT FILTER L3 L1** 50H + Q1 2N3906 LT1170 LOAD R1 4.64k -5.2V 4.5A R4 12k FB GND VC OPTIONAL OUTPUT FILTER C1 R3 VIN -20V C2 1000F R2 1.24k + C4 200F L2 4H 1170/1/2 TA09 117012ff 12 LT1170/LT1171/LT1172 U TYPICAL APPLICATIO S Positive-to-Negative Buck-Boost Converter D3 1N4001 R5 470, 1W + VIN C4 1F VSW VIN 10V TO 30V * REQUIRED IF INPUT LEADS 2" ** PULSE ENGINEERING 92114, COILTRONICS 50-2-52 TO AVOID STARTUP PROBLEMS FOR INPUT VOLTAGES BELOW 10V, CONNECT ANODE OF D3 TO VIN, AND REMOVE R5. C1 MAY BE REDUCED FOR LOWER OUTPUT CURRENTS. C1 (500F)(IOUT). FOR 5V OUTPUTS, REDUCE R3 TO 1.5k, INCREASE C2 TO 0.3F, AND REDUCE R6 TO 100. C5 100F* + LT1170 D2 1N914 R1 10.7k FB VC GND R4 47 R3 5k C2 0.1F + R2 1.24k + C3 2F C1 1000F R6 470 D1 VOUT -12V 2A L1** 50H 1170/1/2 TA10 High Efficiency Constant Current Charger INPUT VOLTAGE > VBAT + 2V < 35V R3 25k VSW D1 1N5819 LT1171 VIN C2 2.2F 35V TANTALUM C1 + 200F 35V + RUN = 0V SHUTDOWN = 5V C3 0.47F C4 0.01F R7 22k R8 1k - V- R4 1k + L2* 10H, 1A L1 100H, 1A R5 0.05 2N3904 R6 78k * L2 REDUCES RIPPLE CURRENT INTO THE BATTERY BY ABOUT 20 :1. IT MAY BE OMITTED IF DESIRED. LT1006 FB VC GND + V R2 1k + 1.244V * R4 = 1A AS SHOWN R3 * R5 ICHRG = + D2 MBR340 C4 200F 25V 1A + BATTERY 2V TO 25V 1170/1/2 TA11 Backlight CCFL Supply (see AN45 for details) INPUT VOLTAGE 4.5V TO 20V L2*** 1k L1** 300H 1N5818 A 33pF 3kV LAMP Q1* V IN E2 10F TANT VSW 0.02F + LT1172 VC + 2F D2 1N914 Q2* B E1 GND D1 1N914 FB C6 1 F R3 10k 50k INTENSITY ADJUST R1 560 * Q1,Q2 = BCP56 OR MPS650/561 1170/1/2 TA12 ** COILTRONICS CTX300-4 *** SUMIDA 6345-020 OR COILTRONICS 110092-1 A MODIFICATION WILL ALLOW OPERATION DOWN TO 4.5V. CONSULT FACTORY. 117012ff 13 LT1170/LT1171/LT1172 U TYPICAL APPLICATIO S Positive Buck Converter VIN * REQUIRED IF INPUT LEADS 2" ** PULSE ENGINEERING 92114 COILTRONICS 50-2-52 D3 C3 2.2F L2 4H VIN + VSW LT1170 + D2 1N914 R1 3.74k C5* 100F VC GND OPTIONAL OUTPUT FILTER C5 200F FB + R2 1.24k R3 470 C1 1F C2 1F R4 10 L1** 50H r C4 1000F D1 5V, 4.5A + 100mA MINIMUM 1170/1/2 TA13 Negative Boost Regulator D2 VIN VSW R1 27k LT1170 C4* 470F VIN -15V + + C3 10F + C1 1000F RO (MINIMUM LOAD) FB GND L1 50H VC R3 3.3k C2 0.22F R2 1.24k D1 VOUT -28V, 1A 1170/1/2 TA14 * REQUIRED IF INPUT LEADS 2" Driving High Voltage NPN C1 D2 R2** R1* Q1 D1 VIN VSW LT1170 * SETS IB (ON) ** SETS IB (OFF) GND 1170/1/2 TA15 117012ff 14 LT1170/LT1171/LT1172 U TYPICAL APPLICATIO S Forward Converter D1 L1 25H VOUT 5V, 6A T1 C2 R4 1 M N D2 C1 2000F + R1 3.74k D3 VIN VSW VIN 20V TO 30V D4 LT1170 FB R6 330 VC GND Q1 R3 R2 1.24k R5 1 C4 C3 1170/1/2 TA16 High Efficiency 5V Buck Converter VIN + C1 330F 35V 10H 3A VIN VSW LT1170 FB VC GND C6 0.02F R1 680 C5 0.03F C4 0.1F D1 MBR330p C3 4.7F TANT DIODE LT1432 <0.3V = NORMAL MODE >2.5V = SHUTDOWN OPEN = BURST MODE + OPTIONAL OUTPUT FILTER + L1 50H R2* 0.013 + VC VIN MODE LOGIC 220pF 100F 16V D2 1N4148 V+ x C2 390F 16V VOUT 5V 3A** VLIM VOUT MODE GND * R2 IS MADE FROM PC BOARD COPPER TRACES. ** MAXIMUM CURRENT IS DETERMINED BY THE CHOICE OF LT1070 FAMILY. SEE APPLICATION SECTION. 1170/1/2 TA17 117012ff 15 LT1170/LT1171/LT1172 U PACKAGE DESCRIPTIO J8 Package 8-Lead CERDIP (Narrow .300 Inch, Hermetic) (Reference LTC DWG # 05-08-1110) CORNER LEADS OPTION (4 PLCS) .005 (0.127) MIN .023 - .045 (0.584 - 1.143) HALF LEAD OPTION .045 - .068 (1.143 - 1.650) FULL LEAD OPTION .405 (10.287) MAX 8 7 6 5 .025 (0.635) RAD TYP .220 - .310 (5.588 - 7.874) 1 2 3 4 .300 BSC (7.62 BSC) .200 (5.080) MAX .015 - .060 (0.381 - 1.524) .008 - .018 (0.203 - 0.457) 0 - 15 NOTE: LEAD DIMENSIONS APPLY TO SOLDER DIP/PLATE OR TIN PLATE LEADS .045 - .065 (1.143 - 1.651) .014 - .026 (0.360 - 0.660) .100 (2.54) BSC .125 3.175 MIN J8 0801 K Package 4-Lead TO-3 Metal Can (Reference LTC DWG # 05-08-1311) 1.177 - 1.197 (29.90 - 30.40) .320 - .350 (8.13 - 8.89) .760 - .775 (19.30 - 19.69) .470 TP P.C.D. .060 - .135 (1.524 - 3.429) .655 - .675 (16.64 - 19.05) .151 - .161 (3.84 - 4.09) DIA 2 PLC .420 - .480 (10.67 - 12.19) .167 - .177 (4.24 - 4.49) R .038 - .043 (0.965 - 1.09) 72 18 .490 - .510 (12.45 - 12.95) R K4(TO-3) 0801 OBSOLETE PACKAGES 117012ff 16 LT1170/LT1171/LT1172 U PACKAGE DESCRIPTIO N8 Package 8-Lead PDIP (Narrow .300 Inch) (Reference LTC DWG # 05-08-1510) .300 - .325 (7.620 - 8.255) ( +.035 .325 -.015 +0.889 8.255 -0.381 .130 .005 (3.302 0.127) .045 - .065 (1.143 - 1.651) .065 (1.651) TYP .009 - .015 (0.229 - 0.381) .400* (10.160) MAX 8 7 6 1 2 3 5 .255 .015* (6.477 0.381) ) .125 (3.175) .020 MIN (0.508) MIN .018 .003 (0.457 0.076) .100 (2.54) BSC 4 N8 0502 NOTE: 1. DIMENSIONS ARE INCHES MILLIMETERS *THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS. MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED .010 INCH (0.254mm) Q Package 5-Lead Plastic DD Pak (Reference LTC DWG # 05-08-1461) .256 (6.502) .060 (1.524) TYP .060 (1.524) .390 - .415 (9.906 - 10.541) .165 - .180 (4.191 - 4.572) .045 - .055 (1.143 - 1.397) 15 TYP .060 (1.524) .183 (4.648) +.008 .004 -.004 +0.203 0.102 -0.102 .059 (1.499) TYP .330 - .370 (8.382 - 9.398) ( ) .095 - .115 (2.413 - 2.921) .075 (1.905) .300 (7.620) +.012 .143 -.020 +0.305 3.632 -0.508 ( BOTTOM VIEW OF DD PAK HATCHED AREA IS SOLDER PLATED COPPER HEAT SINK .067 (1.702) .028 - .038 BSC (0.711 - 0.965) TYP ) Q(DD5) 0502 .420 .276 .080 .420 .050 .012 (1.270 0.305) .013 - .023 (0.330 - 0.584) .325 .350 .205 .565 .565 .320 .090 .090 .067 .042 RECOMMENDED SOLDER PAD LAYOUT NOTE: 1. DIMENSIONS IN INCH/(MILLIMETER) 2. DRAWING NOT TO SCALE .067 .042 RECOMMENDED SOLDER PAD LAYOUT FOR THICKER SOLDER PASTE APPLICATIONS 117012ff 17 LT1170/LT1171/LT1172 U PACKAGE DESCRIPTIO S8 Package 8-Lead Plastic Small Outline (Narrow .150 Inch) (Reference LTC DWG # 05-08-1610) .045 .005 .050 BSC N .245 MIN .160 .005 1 .030 .005 TYP .010 - .020 x 45 (0.254 - 0.508) 2 3 N/2 RECOMMENDED SOLDER PAD LAYOUT 7 8 .053 - .069 (1.346 - 1.752) .008 - .010 (0.203 - 0.254) .189 - .197 (4.801 - 5.004) NOTE 3 .004 - .010 (0.101 - 0.254) 0- 8 TYP .016 - .050 (0.406 - 1.270) .014 - .019 (0.355 - 0.483) TYP INCHES (MILLIMETERS) 2. DRAWING NOT TO SCALE 3. THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS. MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED .006" (0.15mm) NOTE: 1. DIMENSIONS IN 5 6 N .150 - .157 (3.810 - 3.988) NOTE 3 .228 - .244 (5.791 - 6.197) .050 (1.270) BSC N/2 SO8 0502 1 2 3 4 SW Package 16-Lead Plastic Small Outline (Wide .300 Inch) (Reference LTC DWG # 05-08-1620) .050 BSC .045 .005 .030 .005 TYP .398 - .413 (10.109 - 10.490) NOTE 4 16 N 15 14 13 12 11 10 9 N .325 .005 .420 MIN .394 - .419 (10.007 - 10.643) NOTE 3 1 2 3 N/2 N/2 RECOMMENDED SOLDER PAD LAYOUT 1 .005 (0.127) RAD MIN .009 - .013 (0.229 - 0.330) .291 - .299 (7.391 - 7.595) NOTE 4 .010 - .029 x 45 (0.254 - 0.737) 3 4 5 6 .093 - .104 (2.362 - 2.642) 7 8 .037 - .045 (0.940 - 1.143) 0 - 8 TYP NOTE 3 .016 - .050 (0.406 - 1.270) NOTE: 1. DIMENSIONS IN 2 .050 (1.270) BSC .004 - .012 (0.102 - 0.305) .014 - .019 (0.356 - 0.482) TYP INCHES (MILLIMETERS) 2. DRAWING NOT TO SCALE 3. PIN 1 IDENT, NOTCH ON TOP AND CAVITIES ON THE BOTTOM OF PACKAGES ARE THE MANUFACTURING OPTIONS. THE PART MAY BE SUPPLIED WITH OR WITHOUT ANY OF THE OPTIONS 4. THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS. MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED .006" (0.15mm) S16 (WIDE) 0502 117012ff 18 LT1170/LT1171/LT1172 U PACKAGE DESCRIPTIO T Package 5-Lead Plastic TO-220 (Standard) (Reference LTC DWG # 05-08-1421) 0.390 - 0.415 (9.906 - 10.541) 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) 0.460 - 0.500 (11.684 - 12.700) 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) SEATING PLANE 0.152 - 0.202 0.260 - 0.320 (3.861 - 5.131) (6.60 - 8.13) 0.095 - 0.115 (2.413 - 2.921) 0.155 - 0.195* (3.937 - 4.953) 0.013 - 0.023 (0.330 - 0.584) BSC 0.067 (1.70) 0.028 - 0.038 (0.711 - 0.965) 0.135 - 0.165 (3.429 - 4.191) * MEASURED AT THE SEATING PLANE T5 (TO-220) 0399 117012ff 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. 19 LT1170/LT1171/LT1172 U TYPICAL APPLICATIO Positive Current Boosted Buck Converter VIN 28V 470 2W C3 0.47F C6 0.002F D2 VIN R6 470 1: N VSW LT1170 R2 1.24k R7 1k N 0.25 D1 FB VIN VC GND 7 C5* 100F + R3 680 C4 0.01F 6 - 2 + 3 LM308 C1 0.33F 4 R5 5k 8 200pF R4 1.24k R1 5k + * REQUIRED IF INPUT LEADS 2" VOUT 5V, 10A C2 5000F 1170/1/2 TA18 RELATED PARTS PART NUMBER DESCRIPTION COMMENTS LT1070/LT1071/LT1072 5A/2.5A/1.25A High Efficiency Switching Regulators 40kHz, VIN to 60V, VSW to 75V LT1074/LT1076 5.5A/2A Step-Down Switching Regulators 100kHz, Also for Positive-to-Negative Conversion LT1082 1A, High Voltage, High Efficiency Switching Regulator VIN to 75V, VSW to 100V, Telecom LT1268/LT1268B 7.5A, 150kHz Switching Regulators VIN to 30V, VSW to 60V LT1269/LT1271 4A High Efficiency Switching Regulators 100kHz/60kHz, VIN to 30V, VSW to 60V LT1270/LT1270A 8A and 10A High Efficiency Switching Regulators 60kHz, VIN to 30V, VSW to 60V LT1370 500kHz High Efficiency 6A Switching Regulator High Power Boost, Flyback, SEPIC LT1371 500kHz High Efficiency 3A Switching Regulator Good for Boost, Flyback, Inverting, SEPIC LT1372/LT1377 500kHz and 1MHz High Efficiency 1.5A Switching Regulators Directly Regulates VOUT LT1373 250kHz Low Supply Current High Efficiency 1.5A Switching Regulator Low 1mA Quiescent Current LT1374 4A, 500kHz Step-Down Switching Regulator Synchronizable, VIN to 25V LT1375/LT1376 1.5A, 500kHz Step-Down Switching Regulators Up to 1.25A Out from an SO-8 LT1425 Isolated Flyback Switching Regulator 6W Output, 5% Regulation, No Optocoupler Needed LT1507 500kHz Monolithic Buck Mode Switching Regulator 1.5A Switch, Good for 5V to 3.3V LT1533 Ultralow Noise 1A Switching Regulator Push-Pull, <100VP-P Output Noise 117012ff 20 Linear Technology Corporation LT/TP 1002 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 1991