Order this document by MC33466/D The MC33466 series are micropower switching voltage regulators, specifically designed for handheld and laptop applications, to provide regulated output voltages using a minimum of external parts. A wide choice of output voltages are available. These devices feature a very low quiescent bias current of 15 µA typical. The MC33466H–XXJT1 series features a highly accurate voltage reference, an oscillator, a pulse width modulation (PWM) controller, a driver transistor (Lx), an error amplifier and feedback resistive divider. FIXED FREQUENCY PWM MICROPOWER DC–to–DC CONVERTER SEMICONDUCTOR TECHNICAL DATA The MC33466H–XXLT1 is identical to the MC33466H–XXJT1, except that a drive pin (EXT) for an external transistor is provided. Due to the low bias current specifications, these devices are ideally suited for battery powered computer, consumer, and industrial equipment where an extension of useful battery life is desirable. TAB 1 MC33466 Series Features: • Low Quiescent Bias Current of 15 µA • High Output Voltage Accuracy of ±2.5% • Low Startup Voltage of 0.9 V at 1.0 mA • Soft–Start = 500 µs • Surface Mount Package H SUFFIX PLASTIC PACKAGE CASE 1213 (SOT–89) PIN CONNECTIONS MC33466H–XXJT1 Ground 1 Output 2 Lx 3 ORDERING INFORMATION Device Output Voltage MC33466H–30JT1 MC33466H–33JT1 MC33466H–50JT1 3.0 3.3 5.0 Int. Switch S it h MC33466H–30LT1 MC33466H–33LT1 MC33466H–50LT1 3.0 3.3 5.0 Ext. S it h Switch Di Drive Type Operating Temperature Range (Top View) SOT–89 (T (Tape) ) MC33466H–XXLT1 Ground 1 Output 2 EXT 3 Other voltages from 2.5 V to 7.5 V, in 0.1 V increments are available. Consult factory for information. Tab (Tab is connected to Pin 2) (Top View) Motorola, Inc. 1999 MOTOROLA ANALOG IC DEVICE DATA (Tab is connected to Pin 2) Package (Tape/Reel) SOT–89 (T (Tape) ) 30° to +80°C 80°C TA = –30° Tab Rev 4, 08/1999 1 MC33466 Representative Block Diagrams MC33466H–XXJT1 D VO L 3 Vin 2 VLx Limiter Lx Cin Output (Voltage Feedback) Drive CO PWM Controller Phase Comp 50 kHz Oscillator Vref Soft–Start 1 Gnd MC33466H–XXLT1 L Vin D VO Cin 2 Rb Q 3 Output (Voltage Feedback) Drive EXT Cb CO PWM Controller 100 kHz Oscillator Phase Comp Soft–Start Vref 1 Gnd XX Denotes Output Voltage This device contains 100 active transistors. MAXIMUM RATINGS (TC = 25°C, unless otherwise noted.) ÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁ ÁÁÁÁÁ ÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁ ÁÁÁÁÁ ÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁ ÁÁÁÁÁ ÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁ ÁÁÁÁÁ ÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁ ÁÁÁÁÁ ÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁ ÁÁÁÁÁ ÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁ ÁÁÁÁÁ ÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁ ÁÁÁÁÁ ÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁ ÁÁÁÁÁ ÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁ ÁÁÁÁÁ ÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁ ÁÁÁÁÁ ÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁ ÁÁÁÁÁ ÁÁÁ Rating Symbol Value Unit Power Supply Voltage (Transient) VO 12 V Power Supply Voltage (Operating) VO 8.0 V External Pin Voltage VEXT –0.3 to VO V Lx Pin Voltage VLx 12 V EXT Pin Source/Sink Current IEXT 50/50 mA ILx 250 mA 500 200 mW °C/W Operating Junction Temperature PD RθJA TJ 125 °C Operating Ambient Temperature TA –30 to +80 °C Tstg –40 to +125 °C Lx Pin Sink Current Power Dissipation and Thermal Characteristics H Suffix, Plastic Package Case 1213 (SOT–89) Maximum Power Dissipation @ TA = 25°C Thermal Resistance, Junction–to–Air Storage Temperature Range NOTE: 2 ESD data available upon request. MOTOROLA ANALOG IC DEVICE DATA MC33466 ELECTRICAL CHARACTERISTICS (VCC = 2.0 V, IO = 10 mA and TA = 25°C, unless otherwise noted.) Characteristic Symbol Min Typ Max 40 80 50 100 60 120 Unit ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁ ÁÁÁÁ ÁÁÁÁ ÁÁÁÁ ÁÁÁ ÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁ ÁÁÁÁ ÁÁÁÁ ÁÁÁÁ ÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁ ÁÁÁÁ ÁÁÁÁ ÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁ ÁÁÁÁ ÁÁÁÁ ÁÁÁÁ ÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁ ÁÁÁÁ ÁÁÁÁ ÁÁÁÁ ÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁ ÁÁÁÁ ÁÁÁÁ ÁÁÁÁ ÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁ ÁÁÁÁ ÁÁÁÁ ÁÁÁÁ ÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁ ÁÁÁÁ ÁÁÁÁ ÁÁÁÁ ÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁ ÁÁÁÁ ÁÁÁÁ ÁÁÁÁ ÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁ ÁÁÁÁ ÁÁÁÁ ÁÁÁÁ ÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁ ÁÁÁÁ ÁÁÁÁ ÁÁÁÁ ÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁ ÁÁÁÁ ÁÁÁÁ ÁÁÁÁ ÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁ ÁÁÁÁ ÁÁÁÁ ÁÁÁÁ ÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁ ÁÁÁÁ ÁÁÁÁ ÁÁÁÁ ÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁ ÁÁÁÁ ÁÁÁÁ ÁÁÁÁ ÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁ ÁÁÁÁ ÁÁÁÁ ÁÁÁÁ ÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁ ÁÁÁÁ ÁÁÁÁ ÁÁÁÁ ÁÁÁ OSCILLATOR Frequency LX output EXT output fosc kHz Oscillator Minimum Startup Voltage (IO = 0 mA) Vstart – 0.8 0.9 V Oscillator Minimum Supply Voltage (IO = 0 mA) VCC 0.7 – – V 60 63 80 – – – – – – VLxLim 0.65 0.8 1.0 V ILKG – – 0.5 µA 1.5 1.575 2.0 – – – – – – 1.5 1.575 2.0 – – – – – – 70 80 90 2.925 3.218 4.875 3.0 3.3 5.0 3.075 3.383 5.125 0.5 2.0 – – – – 15 17 30 25 27 45 – – – 1.2 1.2 2.0 5.0 5.0 5.0 – – – 30 34.5 60 50 56 90 – – – 1.2 1.2 2.0 5.0 5.0 5.0 LX OUTPUT (JT1 SUFFIX) ON State Sink Current (VLx = 0.4 V) 30KT1 Suffix 33KT1 Suffix 50KT1 Suffix VLx Voltage Limit (Note 1) OFF State Leakage Current (VLx = 6.0 V) ILx mA EXT OUTPUT (LT1 SUFFIX) ON State Source Current (VEXT = VO – 0.4 V) 30LT1 Suffix 33LT1 Suffix 50LT1 Suffix OFF State Sink Current (VEXT = 0.4 V) 30LT1 Suffix 33LT1 Suffix 50LT1 Suffix Isource mA Isink mA TOTAL DEVICE Maximum Duty Ratio Each Cycle D Output Voltage 30KT1 or 30LT1 Suffix 33KT1 or 33LT1 Suffix 50KT1 or 50LT1 Suffix VO Soft–Start Time (Note 2) Tss Quiescent Bias Current (Vin = 2.0 V, IO = 0 mA) 30JT1 Suffix 33JT1 Suffix 50JT1 Suffix Quiescent Bias Current (Vin = VO + 0.5 V, IO = 0 mA) 30JT1 Suffix 33JT1 Suffix 50JT1 Suffix IQ Quiescent Bias Current (Vin = 2.0 V, IO = 0 mA) 30LT1 Suffix 33LT1 Suffix 50LT1 Suffix Quiescent Bias Current (Vin = VO + 0.5 V, IO = 0 mA) 30LT1 Suffix 33LT1 Suffix 50LT1 Suffix IQ % V ms µA ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁ ÁÁÁÁ ÁÁÁÁ ÁÁÁÁ ÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁ ÁÁÁÁ ÁÁÁÁ ÁÁÁÁ ÁÁÁ µA NOTES: 1. When the Lx switch is turned on, ILx current carried through the RDS(on) of the Lx switch results in VLx. When VLx reaches VLxLim, the Lx switch is turned off by the Lx switch protection circuit. 2. The soft–start circuit turn–on sequence is as follows: a) Vin is applied. b) The internal IC Vref is held at zero for 200 µs. During this time, the error amplifier output voltage ramps up to the positive voltage rail. c) The internal reference steps up to 0.7 V after 200 µs delay has timed out. d) The error amplifier output voltage integrates down to its steady state value. As the error amplifier output integrates down, the output Lx pin of EXT pin pulse width gradually widens to its steady operating value. MOTOROLA ANALOG IC DEVICE DATA 3 MC33466 Figure 1. Quiescent Current versus Temperature Figure 2. Quiescent Current versus Temperature 40 2.0 MC33466H–33JT1 IO = 0 mA Vin = 2.0 V I Q , QUIESCENT BIAS CURRENT (µ A) I Q , QUIESCENT BIAS CURRENT (µ A) 50 30 20 10 –40 0 –20 20 40 60 1.2 0.8 20 40 TA, AMBIENT TEMPERATURE (°C) Figure 3. Oscillator Frequency versus Temperature Figure 4. Maximum Duty Ratio versus Temperature 80 40 –20 0 20 40 60 60 80 80 70 60 –40 80 –20 0 20 40 TA, AMBIENT TEMPERATURE (°C) Figure 5. Lx Switching Current versus Temperature Figure 6. VLx Voltage Limit versus Temperature 1.0 VLxLim, V Lx VOLTAGE LIMIT (V) 200 160 120 80 0 –40 80 MC33466H–50JT1 L = 120 µH IO = 10 mA Vin = 3.0 V 90 TA, AMBIENT TEMPERATURE (°C) 40 60 100 MC33466H–50JT1 L = 120 µH IO = 10 mA Vin = 3.0 V 60 20 –40 I Lx , Lx SWITCHING CURRENT (mA) 0 –20 TA, AMBIENT TEMPERATURE (°C) Dmax , MAXIMUM DUTY RATIO (%) fosc , OSCILLATOR FREQUENCY (kHz) 1.6 0.4 –40 80 100 MC33466H–50JT1 IO = 10 mA Vin = 2.0 V –20 0 20 40 TA, AMBIENT TEMPERATURE (°C) 4 MC33466H–33JT1 IO = 0 mA Vin = 5.5 V 60 80 0.9 0.8 0.7 0.6 MC33466H–50JT1 IO = 10 mA Vin = 2.0 V 0.5 –40 –20 0 20 40 60 80 TA, AMBIENT TEMPERATURE (°C) MOTOROLA ANALOG IC DEVICE DATA MC33466 Figure 7. Output Voltage versus Output Current Figure 8. Output Voltage versus Output Current 6.0 6.0 5.0 4.0 Vin = 4.0 V Vin = 3.0 V Vin = 2.0 V VO , OUTPUT VOLTAGE (V) VO , OUTPUT VOLTAGE (V) Vin = 2.0 V 3.0 Vin = 1.0 V 2.0 1.0 MC33466H–50JT1 L = 120 µH TA = 25°C 0 20 40 60 80 100 120 Vin = 4.0 V 4.0 Vin = 1.5 V 3.0 2.0 MC33466H–50LT1 L = 28 µH TA = 25°C 1.0 0 100 200 Figure 9. Efficiency versus Output Current Vin = 2.0 V 600 80 Vin = 1.5 V 60 EFFICIENCY (%) EFFICIENCY (%) 500 100 80 Vin = 1.0 V 40 MC33466H–30JT1 L = 120 µH TA = 25°C Figure 17 20 0 5.0 10 Vin = 1.5 V 60 15 20 25 Vin = 0.9 V 0 30 Vin = 2.0 V 40 MC33466H–30LT1 L = 28 µH TA = 25°C Figure 18 20 0 100 200 300 400 500 IO, OUTPUT CURRENT (mA) IO, OUTPUT CURRENT (mA) Figure 11. Startup/Hold Voltage versus Output Current Figure 12. Startup/Hold Voltage versus Output Current 600 1.6 VLxLim, V Lx VOLTAGE LIMIT (V) 2.0 Vstart /V hold , VOLTAGE LIMIT (V) 400 Figure 10. Efficiency versus Output Current 100 1.6 1.2 Vstart 0.8 0.4 0 300 IO, OUTPUT CURRENT (mA) IO, OUTPUT CURRENT (mA) 0 Vin = 3.0 V 5.0 MC33466H–50JT1 L = 120 µH TA = 25°C Figure 17 Vhold 0 2.0 4.0 6.0 8.0 IO, OUTPUT CURRENT (mA) MOTOROLA ANALOG IC DEVICE DATA 10 12 1.4 1.2 Vstart 1.0 MC33466H–50LT1 L = 28 µH TA = 25°C Figure 18 0.8 Vhold 0.6 0 20 40 60 80 100 120 IO, OUTPUT CURRENT (mA) 5 MC33466 Figure 14. Startup/Hold Voltage versus Temperature MC33466H–50JT1 L = 120 µH IO = 10 mA Vin = 3.0 V Figure 17 5.2 5.1 5.0 4.9 4.8 –40 –20 0 20 40 60 80 1.0 0.8 Vstart 0.6 Vhold MC33466H–50JT1 L = 120 µH IO = 3.0 mA Figure 17 0.4 0.2 –40 –20 0 20 40 60 Figure 15. Supply Current versus Input Voltage Figure 16. Load Transient Response 250 250 MC33466H–50JT1 L = 120 µH IO = 10 mA Figure 17 200 MC33466H–50JT1 L = 120 µH IO = 1.0 to 30 mA Vin = 3.0 V Figure 17 5.4 VO , OUTPUT VOLTAGE (V) I CC , SUPPLY CURRENT (µ A) 80 TA, AMBIENT TEMPERATURE (°C) TA, AMBIENT TEMPERATURE (°C) 150 100 50 5.2 I O , OUTPUT CURRENT (µ A) VO , OUTPUT VOLTAGE (V) Vstart/V hold, STARTUP/HOLD VOLTAGE (V) Figure 13. Output Voltage versus Temperature 200 150 5.0 100 4.8 50 4.6 0 0 1.0 2.0 3.0 4.0 Vin, INPUT VOLTAGE (V) 6 5.0 6.0 0 10 20 30 40 50 0 60 t, TIME (ms) MOTOROLA ANALOG IC DEVICE DATA MC33466 DEFINITIONS Quiescent Bias Current – Current which is used to operate the switching regulator chip and is not delivered to the load. Leakage Current – Current drawn through a transistor junction, under a specified collector voltage, when the transistor is off. FUNCTIONAL DESCRIPTION Introduction The MC33466 series are monolithic power switching regulators optimized for dc–to–dc converter applications where power drain must be minimized. The combination of features in this series allows the system designer to directly implement step–up, step–down or flyback converters with a small number of external components. Potential applications include low power consumer products and battery powered portable products. Typical application circuits are shown in Figures 17 through 21. Operating Description The MC33466 series converters operate as a fixed frequency voltage mode regulator. Operation is intended to be in the discontinuous mode, where the inductor current ramps up to a peak value which is greater than or equal to twice the value of the dc input current during the on–time of the transistor switch. During the off–time of the transistor switch, the inductor current ramps down to zero and remains at zero until another switching cycle begins. Because the output voltage pin is also used as the supply voltage for powering internal circuitry, an external startup circuit is needed in step–down converter and flyback designs to provide initial power to the integrated circuit to begin switching. The startup circuit needed can be three discrete components, as shown in Figure 19, or a micropower undervoltage sensor, as shown in Figure 20. Oscillator The oscillator frequency, is internally programmed to 50 kHz. The timing capacitor (CT) discharge to charge ratio of the oscillator is designed for a maximum duty cycle of 80% at the Lx or EXT output. During the charge of CT, the oscillator generates an internal blanking pulse that holds the PWM control off, disabling the output transistor drive. The oscillator peak and valley thresholds are 0.5 V and ground, respectively. Pulse Width Modulator The Pulse Width Modulator consists of a comparator with the oscillator ramp voltage applied to the inverting input, while the error amplifier output is applied to the noninverting input. Output switch conduction is initiated when the timing capacitor is charged to its peak voltage value. When the timing capacitor ramp discharges to a voltage below the error amplifier output, the comparator resets a latch terminating output transistor drive for the duration of the oscillator ramp period. Error Amplifier and Reference An Error Amplifier is provided which has a nominal 80 dB of voltage gain at dc. Internal compensation components provide poles at 0.25 Hz, 30 kHz and 33 kHz. Two zeros are provided at 1.0 kHz and at 2.5 kHz. The output voltage value is set by the internal voltage divider and a 0.7 V reference which is trimmed to an accuracy of ±2.5%. Because the loop compensation components are located within the IC, discontinuous mode operation is recommended for most applications. Driver and Output Switch To aid in system design flexibility and conversion efficiency, two output driver options are provided. The MC33466H–XXJT1 converters have an internal drive transistor which is capable of sinking currents greater than 60 mA into the Lx pin. An internal VLx limiter circuit senses if the Lx pin voltage exceeds 1.0 V during ton and turns off the drive transistor. The MC33466H–XXJT1 provides output drive for an external transistor. Applications The following converter applications show the simplicity and flexibility of the converter architecture. Three main converter topologies are demonstrated in Figures 17 through 21. Figure 17. MC33466H–50KT1 Typical Step–Up Application Figure 18. MC33466H–50LT1 Typical Step–Up Application MBRD520LT1 MBRD520LT1 28 µH 120 µH Vin Vin MC33466H–50KT1 2 3 Lx VO VO 22 µF 22 µF 22 µF 300 MMBT2222ALT1 Gnd 1 MOTOROLA ANALOG IC DEVICE DATA 0.01 µF MC33466H–50LT1 2 VO VO 5.0 V 3 100 µF EXT Gnd 1 7 MC33466 Figure 19. MC33466H–33JT1 Step–Down Application Startup Circuit MMBT2222ALT1 1.5 k BZX84C3V3LT1 3.3 V 47 µH MMBT2907ALT1 Vin MBRD0520LT1 1.0 k 330 µF VO 3.3 V 320 mA MC33466H–33JT1 100 3 Lx 2 VLx Limiter Output Drive PWM Controller 330 µF 330 µF Phase Comp 50 kHz Oscillator Soft–Start Vref 1 Test 8 Gnd Condition Results Line Regulation Vin = 5.0 V to 10 V, IO = 320 mA 7 mV = ±0.1% Load Regulation Vin = 7.0 V, IO = 3.3 mA to 320 mA 3 mV = ±0.04% Output Ripple Vin = 7.0 V, IO = 320 mA 70 mVpp Efficiency Vin = 7.0 V, IO = 320 mA 63.8% MOTOROLA ANALOG IC DEVICE DATA MC33466 Figure 20. Micropower Step–Down Application Startup Circuit MC33464N–30ATR MMBT2222ALT1 2 In Out Gnd 3 1 10 k 10 k 47 µH MMBT2907ALT1 Vin 5.0 V 100 µF VO 3.3 V 300 mA MBRD0520LT1 1.0 k MC33466H–33JT1 100 3 Lx 2 VLx Limiter Output 100 µF Drive PWM Controller Phase Comp 50 kHz Oscillator Soft–Start Vref 1 NOTE: Gnd Using the MC33464N–30ATR reduces current drawn in the startup circuit to 1 mA during normal operation. MOTOROLA ANALOG IC DEVICE DATA 9 MC33466 Figure 21. Flyback Application Startup Circuit 1.5 k MMBT2222ALT1 3.3 V MMBT2907ALT1 Vin 100 µF VO 3.3 V 1.0 k MC33466H–33KT1 100 3 Lx 2 VLx Limiter Output 100 µF Drive PWM Controller Phase Comp 50 kHz Oscillator Soft–Start Vref 1 10 Gnd MOTOROLA ANALOG IC DEVICE DATA MC33466 Figure 22. Design Equations Calculation Step–Down Step–Up Flyback L t (Vin –2IVO)(ton) t (Vin2I)(ton) t (Vin2I)(ton) O ton in D fs D t IL(avg) D fs t (V ) O (V ) in IO IL(pk) (V in in (V D fs * t V ) in O (V ) O ƪǒ Ǔ ƫ V Ns (V ) in Np Iin * VO)(ton) (V L Vripple(pp) I L(pk) in ȱȧǒ Ȳ 1 8fsC Ǔ O 2 ) VO Iin * Vsat)(ton) L O (V ȳȧ ȴ ) (ESR)2 in * Vsat)(ton) L 1 2 The following converter design characteristics must be chosen: Vin – Nominal Operating dc input voltage VO – Desired dc output voltage IO – Desired dc output current Vripple(pp) – Desired peak–to–peak output ripple voltage. For best performance the ripple voltage should be kept to a low value since it will directly affect line and load regulation. Capacitor CO should be a low equivalent series resistance (ESR) electrolytic designed for switching regulator applications. D – Operating duty cycle = ton(fs). This parameter must be chosen to be <0.5 for step–up and flyback applications. NOTES: 1. Vsat – Saturation voltage of the switching transistor. 2. Iin – DC input switch. 3. fs – Switching frequency, nominally 50 kHz. 4. RO – Load resistance. RO = VO/IO. 5. Ns, Np – In flyback applications Ns is the number of turns of the secondary transformer winding; Np is the number of the primary winding turns. Design Example – Step–down Application Required: Vin = 8.0 V, an output voltage of 3.3 V at 300 mA is desired with an output ripple of less than 300 mVpp. + I O + 11 W V R O O t VO + 3.38 + 0.41. Choose D = 0.33. V 1. Because this is a discontinuous mode design, D in 2. t on 3. L + 6.6 µs. [ fsD + (500.33 kHz) 3.3)(6.6 µs) + 51.7 µH. t (Vin –2IVO)(ton) + (8 – [2(0.3)] O Choose L = 47 µH. Coilcraft part number DO3316P–473. 4. I L(pk) 5. ESR 3.3)(6.6 µs) + (Vin – VLO)(ton) + (8 – (47 + 660 mA. µH) t V ripple(pp) I L(pk) mV) + (300 + 0.455 W. (660 mA) Choose CO = two parallel AVX 330 µF tantalum chip capacitors. Part Number TAJE337M006. Specified maximum ESR for each is 0.9 Ω. The complete design schematic is shown in Figure 19. MOTOROLA ANALOG IC DEVICE DATA 11 MC33466 OUTLINE DIMENSIONS H SUFFIX PLASTIC PACKAGE CASE 1213–01 (SOT–89) ISSUE O A D A2 C B D1 E1 E L1 B 0.10 B1 e M C B S A S 2X 0.10 M C B S A S C NOTES: 1. DIMENSIONS ARE IN MILLIMETERS. 2. INTERPRET DIMENSIONS AND TOLERANCING PER ASME Y14.5M, 1994. 3. DATUM C IS A SEATING PLANE. DIM A2 B B1 C D D1 E E1 e e1 L1 MILLIMETERS MIN MAX 1.40 1.60 0.37 0.57 0.32 0.52 0.30 0.50 4.40 4.60 1.50 1.70 ––– 4.25 2.40 2.60 1.50 BSC 3.00 BSC 0.80 ––– e1 Motorola reserves the right to make changes without further notice to any products herein. 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Mfax is a trademark of Motorola, Inc. How to reach us: USA / EUROPE / Locations Not Listed: Motorola Literature Distribution; P.O. Box 5405, Denver, Colorado 80217. 1–303–675–2140 or 1–800–441–2447 JAPAN: Motorola Japan Ltd.; SPD, Strategic Planning Office, 141, 4–32–1 Nishi–Gotanda, Shinagawa–ku, Tokyo, Japan. 81–3–5487–8488 Customer Focus Center: 1–800–521–6274 Mfax: [email protected] – TOUCHTONE 1–602–244–6609 ASIA/PACIFIC: Motorola Semiconductors H.K. Ltd.; Silicon Harbour Centre, Motorola Fax Back System – US & Canada ONLY 1–800–774–1848 2, Dai King Street, Tai Po Industrial Estate, Tai Po, N.T., Hong Kong. – http://sps.motorola.com/mfax/ 852–26668334 HOME PAGE: http://motorola.com/sps/ 12 ◊ MC33466/D MOTOROLA ANALOG IC DEVICE DATA