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 Á Á ÁÁÁÁÁÁÁÁÁÁÁÁÁÁ Á Á ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ Á Á ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ Á Á ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ Á Á ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ Á Á ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ Á Á 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 ÁÁÁ Á Á Á Á Á Á Á Á Á Á Á ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ Á Á Á Á Á Á Á Á ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁ Á Á Á Á Á ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ Á Á Á Á Á Á ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ Á Á Á Á Á Á ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ Á Á Á Á Á Á ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ Á Á Á Á Á Á ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ Á Á Á Á Á Á ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ Á Á Á Á Á Á Á ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ Á Á Á Á Á Á ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ Á Á Á Á Á Á ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ Á ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁ Á Á Á Á Á Á Á Á Á Á Á ÁÁÁ Á Á Á Á ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ Á ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ Á Á Á Á Á Á ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁ Á Á Á Á ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁ Á Á Á Á Á Á ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ Á Á Á Á Á Á Á Á Á Á Á ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ Á Á Á Á Á 1. Indicates test circuits shown on next page. ÁÁÁ Á Á Á ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ Á Á Á ÁÁÁ Á Á Á ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ Á Á ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ Á Á Á ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ Á Á ÁÁÁ Á Á Á ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ Á Á Á ÁÁÁ Á Á Á ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ Á Á Á ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ Á Á Á ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ Á Á Á ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ Á Á Á ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ Á Á ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ Á Á Á ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ Á Á MAXIMUM RATINGS (TC = 25°C, unless otherwise noted.) ELECTRICAL CHARACTERISTICS (VDD = 1.9 V, TA = 25°C, unless otherwise noted.) Storage Temperature Range Operating Ambient Temperature Operating Junction Temperature 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 EXT Pin Source/Sink Current External Pin Voltage Power Supply Voltage (Operating) Power Supply Voltage (Transient) Rating Symbol VEXT PD RθJA TJ IEXT VDD VDD Tstg TA TOTAL DEVICE EXT OUTPUT OSCILLATOR 2 Output Voltage Temperature Coefficient IOUT = 10 mA, –40°C ≤ TA ≤ 85°C Internal Resistor (VOUT to GND) Quiescent Bias Current (VOUT = 2.1 V, IO = 0 mA) Quiescent Bias Current (VOUT = 1.9 V, IO = 0 mA) Output Voltage OFF State Sink Current (VEXT = 1.9 V) ON State Source Current (VEXT = GND) Oscillator Duty Cycle Oscillator Minimum Supply Voltage (IO = 0 mA) Frequency 20 VOUT , OUTPUT VOLTAGE (V) 25 EFFICIENCY 30 35 40 0 Figure 1. Output Voltage versus Output Current IOUT, OUTPUT CURRENT (mA) Characteristic 20 40 Vin = 3.6 V MC33468 60 Symbol D VOUT D TA Isource Isink VOUT IQ IQ RVout VDD fosc D –0.3 to VDD + 0.3 –55 to +125 –40 to +85 Value 20 30 40 50 60 70 80 50/50 125 150 667 10 12 0 1.950 Figure 2. Efficiency versus Output Current Min 2.0 1.5 1.5 65 © Motorola, Inc. 1999 – – – – – MOTOROLA ANALOG IC DEVICE DATA mW °C/W Unit mA °C °C °C IOUT, OUTPUT CURRENT (mA) V V V 2.000 Typ ±50 180 3.0 0.7 15 75 – – – 20 2.050 Max 5.0 0.8 25 – – – – – – 40 ppm/oc Unit kHz MW mA mA µA µA % V V Vin = 3.6 V Rev 1, 09/1999 Note1 D C E A A B B B 60 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 – Estimate