LT1170MK

LT1 170/LT1 171/LT1172 100kHz, 5A, 2.5A and 1.25A High Efficiency Switching Regulators FEATURES s s s DESCRIPTIO s s s s s s s s 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 50µA 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 The LT®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 50µA typically for standby operation. , LTC and LT are registered trademarks of Linear Technology Corporation. SwitcherCAD is a trademark of Linear Technology Corporation. APPLICATIO S s s s s 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. TYPICAL APPLICATIO 5V L1** 50µH Boost Converter (5V to 12V) Maximum Output Power* L2 10µH C3 100µF POWER (W) ** OUTPUT FILTER 100 LT1170 VIN VSW D1 MBR330 80 + + LT1170 C3* 100µF GND VC R3 1k C1 1µF *REQUIRED IF INPUT LEADS ≥ 2" FB C2 1000µF R1 10.7k 1% 12V 1A 60 BOOST 40 R2 1.24k 1% 20 BUCK-BOOST VO = 5V 0 0 10 30 20 INPUT VOLTAGE (V) 40 50 ** COILTRONICS 50-2-52 PULSE ENGINEERING 92114 1170/1/2 TA01 U BUCK-BOOST VO = 30V FLYBACK * 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. LT1170/1/2 TA02 U U 1 LT1 170/LT1 171/LT1172 ABSOLUTE AXI U RATI GS 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 ............... – 65°C to 150°C Lead Temperature (Soldering, 10 sec)................. 300°C PACKAGE/ORDER I FOR ATIO TOP VIEW GND 1 VC 2 FB 3 NC* 4 J8 PACKAGE 8-LEAD CERDIP 8 7 6 5 E2 VSW E1 VIN ORDER PART NUMBER LT1172MJ8 LT1172CJ8 LT1172CN8 LT1172IN8 LT1172CS8 LT1172IS8 S8 PART MARKING 1172 1172I ORDER PART NUMBER LT1170MK LT1170CK LT1171MK LT1171CK LT1172MK LT1172CK 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 = 150°C, θJA = 100°C/W (J) TJMAX = 100°C, θJA = 100°C/W (N) TJMAX = 100°C, θJA = 120°C/W to 150°C/W depending on board layout (S) BOTTOM VIEW VSW 1 4 VIN K PACKAGE 4-LEAD TO-3 METAL CAN 2 3 VC CASE IS GND FB TJMAX θJC LT1170MK 150°C 2°C/W LT1170CK 100°C 2°C/W LT1171MK 150°C 4°C/W LT1171CK 100°C 4°C/W LT1172MK 150°C 8°C/W LT1172CK 150°C 8°C/W Based on continuous operation. TJMAX = 125°C for intermittent fault conditions. *θ will vary from approximately 25°C/W with 2.8 VIN 5 sq. in. of 1oz. VSW 4 copper to 45°C/W GND 3 with 0.20 sq. in. of FB 2 1oz. copper. VC 1 Somewhat lower Q PACKAGE values can be 5-LEAD DD obtained with TJMAX = 100°C, θJA = *°C/W additional copper layers in multilayer boards. FRONT VIEW θJA 35°C/W 35°C/W 35°C/W 35°C/W 35°C/W 35°C/W ORDER PART NUMBER LT1170CQ LT1171HVCQ LT1170IQ LT1172CQ LT1171CQ LT1172HVIQ LT1171IQ 2 U U W WW U W (Note 1) Operating Junction Temperature Range LT1170/71/72M ......................... – 55°C to 150°C LT1170/71/72HVC, LT1170/71/72C (Oper.) .............. 0°C to 100°C LT1170/71/72HVC C LT1170/71/72C (Sh. Ckt.) .......... 0°C to 125°C LT1170/71/72HVI, LT1170/71/72I (Oper.) .......... – 40°C to 100°C LT1170/71/72HVI, I LT1170/71/72I (Sh. Ckt.) ...... – 40°C to 125°C TOP VIEW NC 1 NC 2 GND 3 VC 4 FB 5 NC 6 NC 7 NC 8 16 NC 15 NC 14 E2 13 VSW 12 E1 11 VIN 10 NC 9 NC ORDER PART NUMBER LT1172CSW SW PACKAGE 16-LEAD PLASTIC SO WIDE TJMAX = 100°C, θJA = 150°C/W Based on continuous operation. TJMAX = 125°C for intermittent fault conditions. FRONT VIEW 5 4 3 2 1 T PACKAGE 5-LEAD PLASTIC TO-220 VIN VSW GND FB VC ORDER PART NUMBER LT1170CT LT1170IT LT1170HVCT LT1170HVIT LT1171CT LT1171IT LT1171HVCT LT1172CT LT1172HVCT TJMAX θJC θJA LT1170CT/LT1170HVCT 100°C 2°C/W 75°C/W LT1171CT/LT1171HVCT 100°C 4°C/W 75°C/W LT1172CT/LT1172HVCT 100°C 8°C/W 75°C/W Based on continuous operation. TJMAX = 125°C for intermittent fault conditions. LT1 170/LT1 171/LT1172 The q denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VIN = 15V, VC = 0.5V, VFB = VREF, output pin open, unless otherwise noted. SYMBOL PARAMETER VREF IB gm Reference Voltage Feedback Input Current Error Amplifier Transconductance Error Amplifier Source or Sink Current Error Amplifier Clamp Voltage Reference Voltage Line Regulation AV IQ Error Amplifier Voltage Gain Minimum Input Voltage (Note 5) Supply Current Control Pin Threshold Normal/Flyback Threshold on Feedback Pin VFB Flyback Reference Voltage (Note 5) Change in Flyback Reference Voltage Flyback Reference Voltage Line Regulation (Note 5) Flyback Amplifier Transconductance (gm) Flyback Amplifier Source and Sink Current BV Output Switch Breakdown Voltage Output Switch “On” Resistance (Note 3) Control Voltage to Switch Current Transconductance ILIM Switch Current Limit (LT1170) IFB = 50µA q ELECTRICAL CHARACTERISTICS CONDITIONS MIN q q TYP 1.244 1.244 350 MAX 1.264 1.274 750 1100 6000 7000 350 400 2.30 0.52 0.03 UNITS V V nA nA µmho µmho µA µA V V %/V V/V Measured at Feedback Pin VC = 0.8V VFB = VREF ∆IC = ±25µA 1.224 1.214 q 3000 2400 150 120 1.80 0.25 4400 200 VC = 1.5V q Hi Clamp, VFB = 1V Lo Clamp, VFB = 1.5V 3V ≤ VIN ≤ VMAX VC = 0.8V 0.9V ≤ VC ≤ 1.4V q q 0.38 500 800 2.6 6 3.0 9 1.08 1.25 0.54 17.6 18.0 9 0.03 650 70 70 V mA V V V V V V %/V µmho µA µA V V V 3V ≤ VIN ≤ VMAX, VC = 0.6V Duty Cycle = 0 q 0.8 0.6 0.4 15.0 14.0 4.5 0.9 0.45 16.3 6.8 0.01 0.05 ≤ IFB ≤ 1mA IFB = 50µA 7V ≤ VIN ≤ VMAX ∆IC = ± 10µA VC = 0.6V IFB = 50µA 3V ≤ VIN ≤ VMAX, ISW = 1.5mA LT1170 LT1171 LT1172 LT1170 LT1171 LT1172 Duty Cycle = 50% Duty Cycle = 50% Duty Cycle = 80% (Note 4) Duty Cycle = 50% Duty Cycle = 50% Duty Cycle = 80% (Note 4) Duty Cycle = 50% Duty Cycle = 50% Duty Cycle = 80% (Note 4) TJ ≥ 25°C TJ < 25°C TJ ≥ 25°C TJ < 25°C TJ ≥ 25°C TJ < 25°C q q q q q q q q q 150 Source Sink LT1170/LT1171/LT1172 LT1170HV/LT1171HV/LT1172HV LT1172S8 q q q q q q q q 300 32 40 90 90 80 0.15 0.30 0.60 8 4 2 15 25 65 75 60 VSAT 0.24 0.50 1.00 Ω Ω Ω A/V A/V A/V 5 5 4 2.5 2.5 2.0 1.25 1.25 1.00 10 11 10 5.0 5.5 5.0 3.0 3.5 2.5 A A A A A A A A A (LT1171) (LT1172) 3 LT1 170/LT1 171/LT1172 The q denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VIN = 15V, VC = 0.5V, VFB = VREF, output pin open, unless otherwise noted. SYMBOL PARAMETER ∆IIN Supply Current Increase During Switch On-Time ∆ISW f DCMAX Switching Frequency q ELECTRICAL CHARACTERISTICS CONDITIONS MIN TYP 25 MAX 35 112 115 97 250 250 300 UNITS mA/A kHz kHz % µA mV mV µs 88 85 85 100 92 100 Maximum Switch Duty Cycle Shutdown Mode Supply Current Shutdown Mode Threshold Voltage Flyback Sense Delay Time (Note 5) 3V ≤ VIN ≤ VMAX VC = 0.05V 3V ≤ VIN ≤ VMAX q q 100 50 150 1.5 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 ≈ 0.6µs. 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 = 0.6µs, 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. 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. TYPICAL PERFOR A CE CHARACTERISTICS Switch Current Limit vs Duty Cycle* 16 2.9 SWITCH SATURATION VOLTAGE (V) SWITCH CURRENT (A) 12 25°C MINIMUM INPUT VOLTAGE (V) 8 –55°C 125°C 4 * DIVIDE VERTICAL SCALE BY TWO FOR LT1171, BY FOUR FOR LT1172. 0 0 10 20 30 40 50 60 70 80 90 100 DUTY CYCLE (%) 1170/1/2 G01 4 UW Minimum Input Voltage 1.6 SWITCH CURRENT = IMAX 2.8 2.7 2.6 SWITCH CURRENT = 0A 2.5 2.4 2.3 –75 –50 –25 Switch Saturation Voltage 1.4 150°C 1.2 1.0 0.8 0.6 0.4 0.2 0 0 1 * DIVIDE CURRENT BY TWO FOR LT1171, BY FOUR FOR LT1172. 2 4 5 6 3 SWITCH CURRENT (A)* 7 8 25°C –55°C 100°C 0 25 50 75 100 125 150 TEMPERATURE (°C) 1170/1/2 G02 1170/1/2 G03 LT1 170/LT1 171/LT1172 TYPICAL PERFOR A CE CHARACTERISTICS Line Regulation 5 1.250 REFERENCE VOLTAGE CHANGE (mV) 4 REFERENCE VOLTAGE (V) 3 2 1 0 –1 –2 –3 –4 –5 0 10 TJ = – 55°C TJ = 150°C FEEDBACK BIAS CURRENT (nA) TJ = 25°C 30 40 20 INPUT VOLTAGE (V) Supply Current vs Supply Voltage (Shutdown Mode) 160 140 TJ = 25°C SUPPLY CURRENT (mA) SUPPLY CURRENT (µA) DRIVER CURRENT (mA) 120 100 80 60 40 20 0 0 10 30 20 40 SUPPLY VOLTAGE (V) 50 60 VC = 0V VC = 50mV Shutdown Mode Supply Current 200 180 160 TRANSCONDUCTANCE (µmho) SUPPLY CURRENT (µA) VC PIN CURRENT (µA) 140 120 100 80 60 40 20 0 0 10 20 30 40 50 60 70 80 90 100 VC PIN VOLTAGE (mV) 1170/1/2 G10 TJ = 150°C –55°C ≤ TJ ≤ 125°C UW 50 1170/1/2 G04 1170/1/2 G07 Reference Voltage vs Temperature 800 700 600 500 400 300 200 100 1.248 1.246 1.244 1.242 1.240 1.238 1.236 1.234 –75 –50 –25 Feedback Bias Current vs Temperature 60 25 50 75 100 125 150 TEMPERATURE (°C) 0 1170/1/2 G05 0 –75 –50 –25 0 25 50 75 100 125 150 TEMPERATURE (°C) 1170/1/2 G06 Driver Current* vs Switch Current 160 140 120 100 80 60 40 20 0 0 1 2 3 SWITCH CURRENT (A) 4 5 1170/1/2 G08 Supply Current vs Input Voltage* 15 14 13 12 11 10 9 8 7 6 5 0 10 30 40 20 INPUT VOLTAGE (V) 50 60 1170/1/2 G09 TJ = 25°C NOTE THAT THIS CURRENT DOES NOT INCLUDE DRIVER CURRENT, WHICH IS A FUNCTION OF LOAD CURRENT AND DUTY CYCLE. 90% DUTY CYCLE 50% DUTY CYCLE 10% DUTY CYCLE 0% DUTY CYCLE TJ = – 55°C TJ = ≥ 25°C * AVERAGE LT1170 POWER SUPPLY CURRENT IS FOUND BY MULTIPLYING DRIVER CURRENT BY DUTY CYCLE, THEN ADDING QUIESCENT CURRENT. * UNDER VERY LOW OUTPUT CURRENT CONDITIONS, DUTY CYCLE FOR MOST CIRCUITS WILL APPROACH 10% OR LESS. Error Amplifier Transconductance 5000 4500 4000 3500 3000 2500 2000 1500 1000 500 0 –75 –50 –25 0 25 50 75 100 125 150 TEMPERATURE (°C) 1170/1/2 G11 VC Pin Characteristics 300 200 100 0 TJ = 25°C –100 –200 VFB = 0.8V (CURRENT OUT OF VC PIN) –300 –400 0 0.5 1.5 2.0 1.0 VC PIN VOLTAGE (V) 2.5 VFB = 1.5V (CURRENT INTO VC PIN) gm = ∆I (VC PIN) ∆V (FB PIN) 1170/1/2 G12 5 LT1 170/LT1 171/LT1172 TYPICAL PERFOR A CE CHARACTERISTICS Idle Supply Current vs Temperature 11 10 IDLE SUPPLY CURRENT (mA) VC = 0.6V FEEDBACK VOLTAGE (mV) 9 8 7 6 5 4 3 2 1 –75 –50 –25 0 25 50 75 100 125 150 TEMPERATURE (°C) 1170/1/2 G13 SWITCH CURRENT (µA) VSUPPLY = 60V VSUPPLY = 3V Shutdown Thresholds 400 350 CURRENT (OUT OF VC PIN) – 400 – 350 – 300 – 250 – 200 VOLTAGE 150 100 50 VC VOLTAGE IS REDUCED UNTIL REGULATOR CURRENT DROPS BELOW 300µA 0 – 150 –100 – 50 TIME (µs) 250 200 1.8 1.6 1.4 1.2 1.0 –75 –50 –25 0 25 50 75 100 125 150 JUNCTION TEMPERATURE (°C) 1170/1/2 G17 FLYBACK VOLTAGE (V) VC PIN VOLTAGE (mV) 300 0 –75 –50 –25 0 25 50 75 100 125 150 TEMPERATURE (°C) 1170/1/2 G16 Transconductance of Error Amplifier 7000 6000 θ –30 0 30 gm 60 90 120 150 180 1k 10k 1M 100k FREQUENCY (Hz) 210 10M 1170/1/2 G19 TRANSCONDUCTANCE (µmho) 5000 4000 3000 2000 1000 0 FEEDBACK PIN VOLTAGE (mV) –1000 6 UW Feedback Pin Clamp Voltage 500 450 400 350 300 250 200 150 100 50 0 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 FEEDBACK CURRENT (mA) 1170/1/2 G14 Switch “Off” Characteristics 1000 900 –55°C 25°C 150°C 800 700 600 500 VSUPPLY = 3V 400 300 200 100 0 0 10 20 30 40 50 60 70 80 90 100 SWITCH VOLTAGE (V) 1170/1/2 G15 VSUPPLY = 15V VSUPPLY = 40V VSUPPLY = 55V Flyback Blanking Time 2.2 2.0 VC PIN CURRENT (µA) Isolated Mode Flyback Reference Voltage 23 22 21 20 19 18 17 16 15 –75 –50 –25 RFB = 10k RFB = 1k RFB = 500Ω 0 25 50 75 100 125 150 TEMPERATURE (°C) 1170/1/2 G18 Normal/Flyback Mode Threshold on Feedback Pin 500 490 480 470 460 450 440 430 420 410 400 –50 –25 0 FEEDBACK PIN CURRENT (AT THRESHOLD) FEEDBACK PIN VOLTAGE (AT THRESHOLD) –24 –22 FEEDBACK PIN CURRENT (µA) –20 –18 –16 –14 –12 –10 –8 –6 –4 25 50 75 100 125 150 TEMPERATURE (°C) 1170/1/2 G20 PHASE (DEG) LT1 170/LT1 171/LT1172 BLOCK DIAGRA FB † 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. 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 W VIN 16V SWITCH OUT 2.3V REG FLYBACK ERROR AMP 5A, 75V SWITCH 100kHz OSC LOGIC DRIVER LT1172 MODE SELECT COMP ANTISAT – + ERROR AMP VC + SHUTDOWN CIRCUIT 1.24V REF CURRENT AMP GAIN ≈ 6 0.15V (LT1170 AND LT1171 ONLY) – 0.02 Ω (0.04 Ω LT1171) (0.16 Ω LT1172) 0.16 Ω E1† E2 1170/1/2 BD U 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 7 LT1 170/LT1 171/LT1172 OPERATIO 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 50µA 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 *See note under block diagram. 8 U 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 50°C/W and 35°C/W respectively. The miniDIPs, however, are rated at 100°C/W in ceramic (J) and 130°C/W in plastic (N). 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 (1Ω 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 • (1Ω)(0.6) = 0.25W PD(TOT) = (5V)(0.018A) + 0.25 = 0.34W LT1 170/LT1 171/LT1172 OPERATIO Temperature rise in a plastic miniDIP would be 130°C/W times 0.34W, or approximately 44°C. The maximum ambient temperature would be limited to 100°C (commercial temperature limit) minus 44°C, or 56°C. 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. Synchronizing with Bipolar Transistor VIN LT1170 GND U 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 0.3µs. C2 sets the pulse width at ≅ 0.2µs. The effect of a synchronizing pulse on the LT1170/LT1171/LT1172 amplifier offset can be calculated from:  KT   V tS fS IC + C   q R3    ∆VOS = IC KT = 26mV at 25°C q tS = pulse width fS = pulse frequency IC = VC source current (≈ 200µA) VC = operating VC voltage (1V to 2V) R3 = resistor used to set mid-frequency “zero” in frequency compensation network. ( )( ) With tS = 0.2µs, 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 MOS Transistor VIN LT1170 VC C2 39pF R3 C1 2N2369 R2 2.2k FROM 5V LOGIC 1170/1/2 OP01 GND VC D1 1N4158 VN2222* R2 2.2k * SILICONIX OR EQUIVALENT D2 1N4158 FROM 5V LOGIC 1170/1/2 OP02 R1 3k C2 100pF R3 C1 9 LT1 170/LT1 171/LT1172 TYPICAL APPLICATIO S Flyback Converter VIN 20V TO 30V VIN C4* 100µF D2 MUR110 VSW + LT1170 FB GND VC R3 1.5k C2 0.15µF *REQUIRED IF INPUT LEADS ≥ 2" R2 1.24k 0 IPRI 0 IPRI E2 LT1172 E1 GND VC OPTIONAL SHUTDOWN VN2222 C4 0.047µF 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 = 0.7Ω. INDUCTOR SERIES RESISTANCE SHOULD BE LESS THAN 0.4Ω FOR HIGH EFFICIENCY. *** OUTPUT RIPPLE IS ABOUT 200mVP-P TO 400mVP-P WITH C2 = 2µF TANTALUM. IF LOWER RIPPLE IS DESIRED, INCREASE C2, OR ADD A 10Ω , 1µF TANTALUM OUTPUT FILTER. 1170/1/2 TA04 10 + U L2 OPTIONAL FILTER 5µH C4 100µF VIN N* = 1/3 D3 25V 1W 1 N* D1 VOUT 5V 6A VSNUB CLAMP TURN-ON SPIKE a b 0V c VOUT + Vf N • VIN d R1 3.74k 0 IPRI/N ∆I IPRI + Vf V PRIMARY FLYBACK VOLTAGE = OUT N LT1170 SWITCH VOLTAGE AREA “a” = AREA “b” TO MAINTAIN ZERO DC VOLTS ACROSS PRIMARY SECONDARY VOLTAGE AREA “c” = AREA “d” TO MAINTAIN ZERO DC VOLTS ACROSS SECONDARY + C1 2000µF 0V PRIMARY CURRENT SECONDARY CURRENT LT1170 SWITCH CURRENT SNUBBER DIODE CURRENT 0 (I )(L ) t = PRI L VSNUB 1170/1/2 TA03 LCD Contrast Supply 5V* VIN VSW L1** 50µH VBAT* 3V TO 20V + R2 100k R1 200k D1 1N914 C1 1µF TANTALUM VOUT –10V TO –26V D2 FB R3 15k C3 0.0047µF D3 C2*** 2µF TANTALUM LT1 170/LT1 171/LT1172 TYPICAL APPLICATIO S Driving High Voltage FET (for Off-Line Applications, See AN25) G VIN D1 VSW D Q1 10V TO 20V + LT1170 GND 1170/1/2 TA05 Negative-to-Positive Buck-Boost Converter† L1** 50µH VIN C4* 100µF + LT1170 FB R3 2.2k C1 0.22µF R2 1.24k OPTIONAL INPUT FILTER L3 GND VIN –20V * 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. * REQUIRED IF INPUT LEADS ≥ 2" ** PULSE ENGINEERING 92114 COILTRONICS 50-2-52 C3* 100µF + LT1170 FB GND VC C1 R3 R2 1.24k Q1 2N3906 OPTIONAL INPUT FILTER L3 VIN –20V U VC (Note that maximum output currents are divided by 2 for LT1171, by 4 for LT1172.) External Current Limit VX LT1170 R2 ≈ 2V R1 500Ω D1 GND VC 1170/1/2 TA06 External Current Limit L2 OPTIONAL OUTPUT FILTER D1 VIN VSW C3 + VSW LT1170 VIN GND R1 1k Q1 C1 1000pF RS C2 VC FB + C2 1000µF Q1 R1 11.3k VOUT 12V 2A – R2 NOTE THAT THE LT1170 GND PIN IS NO LONGER COMMON TO VIN–. 1170/1/2 TA08 1170/1/2 TA07 Negative Buck Converter + D1 VIN VSW L1** 50µH C2 1000µF R1 4.64k R4 12k LOAD –5.2V 4.5A OPTIONAL OUTPUT FILTER L2 4µH + C4 200µF 1170/1/2 TA09 11 LT1 170/LT1 171/LT1172 TYPICAL APPLICATIO S Positive-to-Negative Buck-Boost Converter D3† 1N4001 R5† 470Ω, 1W VIN 10V TO 30V VIN C4 1µF + LT1170 R1 10.7k GND VC FB R3 5k C2 0.1µF R2 1.24k D2 1N914 R4 47Ω INPUT VOLTAGE > VBAT + 2V < 35V D1 1N5819 200µF 35V C1 + C2 2.2µF 35V TANTALUM + RUN = 0V SHUTDOWN = 5V INPUT VOLTAGE† 4.5V TO 20V 1k 1N5818 L1** 300µH Q1* E2 10µF TANT V IN VSW + LT1172 E1 GND 2µF 12 U R6 78k + VSW C5 100µF* * 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 ≈ (500µF)(IOUT). FOR 5V OUTPUTS, REDUCE R3 TO 1.5k, INCREASE C2 TO 0.3µF, AND REDUCE R6 TO 100Ω. + C3 2µF + D1 C1† 1000µF R6 470Ω VOUT –12V 2A L1** 50µH 1170/1/2 TA10 High Efficiency Constant Current Charger R3 25k ICHRG = 1.244V • R4 = 1A AS SHOWN R3 • R5 VSW LT1171 VIN GND FB VC C4 0.01µF V + R2 1k – + R4 1k * L2 REDUCES RIPPLE CURRENT INTO THE BATTERY BY ABOUT 20 :1. IT MAY BE OMITTED IF DESIRED. LT1006 V– + C3 0.47µF L1 100µH, 1A R5 0.05Ω L2* 10µH, 1A 2N3904 R7 22k R8 1k D2 MBR340 + C4 200µF 25V 1A + BATTERY 2V TO 25V 1170/1/2 TA11 Backlight CCFL Supply (see AN45 for details) L2*** 33pF 3kV A LAMP 0.02µF Q2* B D1 1N914 D2 1N914 50k INTENSITY ADJUST R3 10k R1 560Ω VC FB C6 1µ F * 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. + LT1 170/LT1 171/LT1172 TYPICAL APPLICATIO S Positive Buck Converter VIN D3 C3 2.2µF + + C5* 100µF GND C4* 470µF + GND VC VIN –15V * REQUIRED IF INPUT LEADS ≥ 2" U * REQUIRED IF INPUT LEADS ≥ 2" ** PULSE ENGINEERING 92114 COILTRONICS 50-2-52 VIN L2 4µH VSW LT1170 R1 3.74k VC FB R3 470Ω C1 1µF D1 R2 1.24k r D2 1N914 OPTIONAL OUTPUT FILTER C5 200µF + C2 1µF L1** 50µH C4 1000µF R4 10Ω 5V, 4.5A 100mA MINIMUM 1170/1/2 TA13 + Negative Boost Regulator D2 VIN VSW LT1170 FB R2 1.24k D1 VOUT – 28V, 1A 1170/1/2 TA14 R1 27k + C3 10µF + C1 1000µF RO (MINIMUM LOAD) L1 50µH R3 3.3k C2 0.22µF Driving High Voltage NPN C1 D2 R2** R1* Q1 D1 VIN VSW LT1170 * SETS IB (ON) ** SETS IB (OFF) GND 1170/1/2 TA15 13 LT1 170/LT1 171/LT1172 TYPICAL APPLICATIO S Forward Converter D1 T1 R4 C2 1 M N D2 VIN VSW VIN 20V TO 30V LT1170 FB GND VC Q1 R3 C3 R6 330Ω R5 1Ω R2 1.24k D4 D3 C1 2000µF VIN + C1 330µF 35V C6 0.02µF D1 MBR330p MODE LOGIC 220pF 2.5V = SHUTDOWN OPEN = BURST MODE 14 U L1 25µH VOUT 5V, 6A + R1 3.74k C4 1170/1/2 TA16 High Efficiency 5V Buck Converter 10µH 3A 100µF 16V VSW LT1170 FB VC VIN + GND D2 1N4148 OPTIONAL OUTPUT FILTER R1 680Ω C4 0.1µF C5 0.03µF C3 4.7µF TANT + L1 50µH R2* 0.013Ω + VC VIN LT1432 MODE GND DIODE V+ VLIM VOUT × C2 390µF 16V VOUT 5V 3A** * 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 LT1 170/LT1 171/LT1172 PACKAGE DESCRIPTIO CORNER LEADS OPTION (4 PLCS) 0.045 – 0.068 (1.143 – 1.727) FULL LEAD OPTION 0.300 BSC (0.762 BSC) 0.008 – 0.018 (0.203 – 0.457) NOTE: LEAD DIMENSIONS APPLY TO SOLDER DIP/PLATE OR TIN PLATE LEADS U Dimensions in inches (millimeters) unless otherwise noted. J8 Package 8-Lead CERDIP (Narrow 0.300, Hermetic) (LTC DWG # 05-08-1110) 0.005 (0.127) MIN 0.405 (10.287) MAX 8 7 6 5 0.023 – 0.045 (0.584 – 1.143) HALF LEAD OPTION 0.025 (0.635) RAD TYP 1 2 3 0.220 – 0.310 (5.588 – 7.874) 4 0.200 (5.080) MAX 0.015 – 0.060 (0.381 – 1.524) 0° – 15° 0.045 – 0.065 (1.143 – 1.651) 0.014 – 0.026 (0.360 – 0.660) 0.100 (2.54) BSC 0.125 3.175 MIN J8 1298 15 LT1 170/LT1 171/LT1172 PACKAGE DESCRIPTIO 0.320 – 0.350 (8.13 – 8.89) 0.760 – 0.775 (19.30 – 19.69) 0.060 – 0.135 (1.524 – 3.429) 0.420 – 0.480 (10.67 – 12.19) 0.300 – 0.325 (7.620 – 8.255) 0.009 – 0.015 (0.229 – 0.381) ( +0.035 0.325 –0.015 8.255 +0.889 –0.381 ) *THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS. MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.010 INCH (0.254mm) 16 U Dimensions in inches (millimeters) unless otherwise noted. K Package 4-Lead TO-3 Metal Can (LTC DWG # 05-08-1311) 1.177 – 1.197 (29.90 – 30.40) 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 0.470 TP P.C.D. 0.038 – 0.043 (0.965 – 1.09) 18° 72° 0.490 – 0.510 (12.45 – 12.95) R K4(TO-3) 1098 N8 Package 8-Lead PDIP (Narrow 0.300) (LTC DWG # 05-08-1510) 0.400* (10.160) MAX 8 7 6 5 0.255 ± 0.015* (6.477 ± 0.381) 1 2 3 4 0.130 ± 0.005 (3.302 ± 0.127) 0.045 – 0.065 (1.143 – 1.651) 0.065 (1.651) TYP 0.125 (3.175) 0.020 MIN (0.508) MIN 0.018 ± 0.003 (0.457 ± 0.076) N8 1098 0.100 (2.54) BSC LT1 170/LT1 171/LT1172 PACKAGE DESCRIPTIO 0.256 (6.502) 0.060 (1.524) 0.060 (1.524) 0.183 (4.648) 0.075 (1.905) 0.300 (7.620) BOTTOM VIEW OF DD PAK HATCHED AREA IS SOLDER PLATED COPPER HEAT SINK +0.012 0.143 –0.020 0.067 (1.70) 0.028 – 0.038 BSC (0.711 – 0.965) 0.013 – 0.023 (0.330 – 0.584) 0.010 – 0.020 × 45° (0.254 – 0.508) 0.008 – 0.010 (0.203 – 0.254) 0°– 8° TYP 0.014 – 0.019 (0.355 – 0.483) TYP *DIMENSION DOES NOT INCLUDE MOLD FLASH. MOLD FLASH SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE **DIMENSION DOES NOT INCLUDE INTERLEAD FLASH. INTERLEAD FLASH SHALL NOT EXCEED 0.010" (0.254mm) PER SIDE 0.016 – 0.050 (0.406 – 1.270) U Dimensions in inches (millimeters) unless otherwise noted. Q Package 5-Lead Plastic DD Pak (LTC DWG # 05-08-1461) 0.060 (1.524) TYP 0.390 – 0.415 (9.906 – 10.541) 15° TYP 0.165 – 0.180 (4.191 – 4.572) 0.045 – 0.055 (1.143 – 1.397) +0.008 0.004 –0.004 0.330 – 0.370 (8.382 – 9.398) 0.059 (1.499) TYP ( +0.203 0.102 –0.102 ) 0.095 – 0.115 (2.413 – 2.921) 0.050 ± 0.012 (1.270 ± 0.305) Q(DD5) 1098 ( +0.305 3.632 –0.508 ) S8 Package 8-Lead Plastic Small Outline (Narrow 0.150) (LTC DWG # 05-08-1610) 0.189 – 0.197* (4.801 – 5.004) 8 7 6 5 0.228 – 0.244 (5.791 – 6.197) 0.150 – 0.157** (3.810 – 3.988) 1 2 3 4 0.053 – 0.069 (1.346 – 1.752) 0.004 – 0.010 (0.101 – 0.254) 0.050 (1.270) BSC SO8 1298 17 LT1 170/LT1 171/LT1172 PACKAGE DESCRIPTIO 0.291 – 0.299** (7.391 – 7.595) 0.010 – 0.029 × 45° (0.254 – 0.737) 0° – 8° TYP 0.009 – 0.013 (0.229 – 0.330) NOTE 1 0.016 – 0.050 (0.406 – 1.270) NOTE: 1. 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 *DIMENSION DOES NOT INCLUDE MOLD FLASH. MOLD FLASH SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE **DIMENSION DOES NOT INCLUDE INTERLEAD FLASH. INTERLEAD FLASH SHALL NOT EXCEED 0.010" (0.254mm) PER SIDE 18 U Dimensions in inches (millimeters) unless otherwise noted. SW Package 16-Lead Plastic Small Outline (Wide 0.300) (LTC DWG # 05-08-1620) 0.398 – 0.413* (10.109 – 10.490) 16 15 14 13 12 11 10 9 NOTE 1 0.394 – 0.419 (10.007 – 10.643) 1 2 3 4 5 6 7 8 0.093 – 0.104 (2.362 – 2.642) 0.037 – 0.045 (0.940 – 1.143) 0.050 (1.270) BSC 0.004 – 0.012 (0.102 – 0.305) 0.014 – 0.019 (0.356 – 0.482) TYP S16 (WIDE) 1098 LT1 170/LT1 171/LT1172 PACKAGE DESCRIPTIO 0.390 – 0.415 (9.906 – 10.541) 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) 0.700 – 0.728 (17.78 – 18.491) 0.620 (15.75) TYP BSC 0.067 (1.70) 0.028 – 0.038 (0.711 – 0.965) Information furnished by Linear Technology Corporation is believed to be accurate and reliable. However, no responsibility is assumed for its use. Linear Technology Corporation makes no representation that the interconnection of its circuits as described herein will not infringe on existing patent rights. U Dimensions in inches (millimeters) unless otherwise noted. T Package 5-Lead Plastic TO-220 (Standard) (LTC DWG # 05-08-1421) 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) 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) 0.135 – 0.165 (3.429 – 4.191) * MEASURED AT THE SEATING PLANE T5 (TO-220) 0399 19 LT1 170/LT1 171/LT1172 TYPICAL APPLICATIO VIN 28V GND C5* 100µF + * REQUIRED IF INPUT LEADS ≥ 2" RELATED PARTS PART NUMBER LT1070/LT1071/LT1072 LT1074/LT1076 LT1082 LT1268/LT1268B LT1269/LT1271 LT1270/LT1270A LT1370 LT1371 LT1372/LT1377 LT1373 LT1374 LT1375/LT1376 LT1425 LT1507 LT1533 DESCRIPTION 5A/2.5A/1.25A High Efficiency Switching Regulators 5.5A/2A Step-Down Switching Regulators 1A, High Voltage, High Efficiency Switching Regulator 7.5A, 150kHz Switching Regulators 4A High Efficiency Switching Regulators 8A and 10A High Efficiency Switching Regulators 500kHz High Efficiency 6A Switching Regulator 500kHz High Efficiency 3A Switching Regulator 500kHz and 1MHz High Efficiency 1.5A Switching Regulators 250kHz Low Supply Current High Efficiency 1.5A Switching Regulator 4A, 500kHz Step-Down Switching Regulator 1.5A, 500kHz Step-Down Switching Regulators Isolated Flyback Switching Regulator 500kHz Monolithic Buck Mode Switching Regulator Ultralow Noise 1A Switching Regulator COMMENTS 40kHz, VIN to 60V, VSW to 75V 100kHz, Also for Positive-to-Negative Conversion VIN to 75V, VSW to 100V, Telecom VIN to 30V, VSW to 60V 100kHz/60kHz, VIN to 30V, VSW to 60V 60kHz, VIN to 30V, VSW to 60V High Power Boost, Flyback, SEPIC Good for Boost, Flyback, Inverting, SEPIC Directly Regulates ± VOUT Low 1mA Quiescent Current Synchronizable, VIN to 25V Up to 1.25A Out from an SO-8 6W Output, ± 5% Regulation, No Optocoupler Needed 1.5A Switch, Good for 5V to 3.3V Push-Pull,