VARIABLE FREQUENCY MICROPOWER DC-to-DC CONVERTER

www.DataSheet4U.com Order this document by MC33468/D MC33468 Variable Frequency Micropower Step-up DC-DC Converter The MC33468 is a micropower step–up switching voltage regulator, specifically designed for handheld and pager applications, to provide a regulated output voltage using a minimum of external parts. This device features a quiescent bias current of 3.0 µA typical. The MC33468 features a highly accurate voltage reference, an error amplifier, an oscillator, a variable frequency modulation (VFM) controller, a drive pin (EXT) for an external transistor, and feedback resistors. The Vout pin is fixed at 2V in the IC. The output of the converter with an inductor, a diode, a capacitor, a drive transistor, and feed–back resistors can have an output of 30V. VARIABLE FREQUENCY MICROPOWER DC–to–DC CONVERTER SEMICONDUCTOR TECHNICAL DATA MC33468 Features: • Low Quiescent Bias Current of 3.0 µA • • • • • High Output Voltage Accuracy of ±2.5% Low Startup Voltage of 0.8 V at No Load Output Voltage Set With External Resistors Operating Temperature Range: –40°C to +85°C Surface Mount Package N SUFFIX PLASTIC PACKAGE CASE 1212 (SOT–23–5) Quantity 3000 1 5 ORDERING INFORMATION Device MC33468SN–20ATR * “XX” denotes the lot number. Output Voltage 2.0 Marking 0KXX* Reel Size 7” Tape Width 8 mm PIN DESCRIPTION PIN CONNECTIONS Description Ground Input Ground Vdd EXT 1 2 3 (Top View) 4 N/C 5 VOUT ÁÁÁÁÁÁÁÁÁÁÁÁÁÁ Á Á ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁ Á Á ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁ Á ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁÁÁÁ Á 1 2 3 4 5 GND VDD EXT NC External Transistor Drive No Connection VOUT Voltage Output Pin (Fixed at 2V) Pin No. Symbol Representative Block Diagram 2 VDD 3 EXT Oscillator Drive 5 VOUT Vref 1 Gnd MOTOROLA ANALOG IC DEVICE DATA 1 MC33468 MAXIMUM RATINGS (TC = 25°C, unless otherwise noted.) VOUT , OUTPUT VOLTAGE (V) 30 EFFICIENCY ÁÁÁ Á Á Á Á Á ÁÁÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁ Á Á Á Á Á Á ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁ Á Á Á Á Á ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁÁ Á ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ Á ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁ Á Á Á Á Á ÁÁÁÁÁÁ ÁÁÁ Á Á Á Á ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ Á ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁ Á ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁ Á Á Á Á ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁ Á Á Á Á Á Á ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁÁ ÁÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁ ÁÁÁ Á ÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ Á ÁÁ ÁÁÁ Á ÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ Á ÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁ ÁÁÁ Á ÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ Á ÁÁ ÁÁÁ Á ÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ Á ÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ Á ÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ Á ÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ Á ÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ Á ÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁ Power Supply Voltage (Transient) VDD VDD 12 10 V V V Power Supply Voltage (Operating) External Pin Voltage VEXT IEXT –0.3 to VDD + 0.3 50/50 EXT Pin Source/Sink Current mA Power Dissipation and Thermal Characteristics N Suffix, Plastic Package Case 1212 (SOT–23–5) Maximum Power Dissipation @ TA = 250°C Thermal Resistance, Junction–to–Air Operating Junction Temperature Operating Ambient Temperature Storage Temperature Range PD RθJA TJ TA 150 667 125 mW °C/W °C °C °C –40 to +85 Tstg –55 to +125 Rating Symbol Value Unit ELECTRICAL CHARACTERISTICS (VDD = 1.9 V, TA = 25°C, unless otherwise noted.) Characteristic Symbol Min OSCILLATOR Frequency fosc – – Typ Max Unit Note1 180 0.7 75 – kHz V B B B Oscillator Minimum Supply Voltage (IO = 0 mA) Oscillator Duty Cycle VDD D 0.8 – 65 % EXT OUTPUT ON State Source Current (VEXT = GND) OFF State Sink Current (VEXT = 1.9 V) Output Voltage Isource Isink VOUT IQ IQ RVout 1.5 1.5 – – – – mA mA C D TOTAL DEVICE 1.950 – – – 2.000 15 – 3.0 2.050 25 – – 5.0 V Quiescent Bias Current (VOUT = 1.9 V, IO = 0 mA) Quiescent Bias Current (VOUT = 2.1 V, IO = 0 mA) Internal Resistor (VOUT to GND) Output Voltage Temperature Coefficient IOUT = 10 mA, –40°C ≤ TA ≤ 85°C µA µA A A E 2.0 MW D VOUT D TA ±50 ppm/oc 1. Indicates test circuits shown on next page. Figure 1. Output Voltage versus Output Current 40 Vin = 3.6 V 35 60 50 40 25 30 20 20 80 70 Figure 2. Efficiency versus Output Current Vin = 3.6 V 0 20 40 60 0 20 40 60 IOUT, OUTPUT CURRENT (mA) IOUT, OUTPUT CURRENT (mA) © Motorola, Inc. 1999 Rev 1, 09/1999 2 MOTOROLA ANALOG IC DEVICE DATA MC33468 A VDD A EXT GND Oscilloscope VOUT A EXT GND B VDD VOUT C VDD VOUT EXT GND D VDD VOUT EXT GND E VDD VOUT EXT GND A Figure 3. Test Circuit Schematics MOTOROLA ANALOG IC DEVICE DATA 3 MC33468 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. 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. Since the VDD pin is connected to the input no external startup circuit is needed. Oscillator The oscillator frequency, is internally programmed to 180 kHz. The duty ratio of the oscillator is designed for a constant value of 0.75 nominal. Hence the nominal on–time of the power switch is: 0.75 D ton 4.16 µs f osc (180 kHz) FUNCTIONAL DESCRIPTION Introduction The MC33468 is a monolithic power switching regulator optimized for dc–to–dc converter applications where power drain must be minimized. The MC33468 uses Variable Frequency Modulation to step up the input DC voltage to a higher accurate output voltage. Potential applications include low power consumer products and battery powered portable products. Typical application circuits are shown in Figure 4. Operating Description The MC33468 converter operates as a fixed on–time, variable off–time voltage mode ripple 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 + + + Feedback Comparator The output voltage is sensed and fed to a high speed comparator noninverting input through an internal resistive divider. The comparator inverting input is connected to an internally trimmed reference. With a voltage mode ripple converter operating under normal conditions, output switch conduction is initiated and terminated by the oscillator, off–time is controlled by the high speed voltage feedback comparator. Figure 4. Typical 2.0 V Application with BJT VOUT VDD VIN EXT Gnd VOUT Figure 5. Design Equations for Step–Up Calculation ton L Equation D f osc t (V IL(avg) IL(pk) Vripple(pp) (n)(V )2(t on) in P O Iin in * V sat)(t on) L [ (ton)(I ) O (C ) O 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 directly affects regulation. Capacitor CO should have a low equivalent series resistance (ESR). NOTE: 1. Vsat – Saturation voltage of the switching transistor. n – Estimated circuit efficiency. 4 MOTOROLA ANALOG IC DEVICE DATA MC33468 Figure 6. Typical 2.0 V Appl