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Moteur de recherche de fiches techniques de composants électroniques |
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Moteur de recherche de fiches techniques de composants électroniques |
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TC7660EOA Fiches technique(PDF) 8 Page - Microchip Technology |
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TC7660EOA Fiches technique(HTML) 8 Page - Microchip Technology |
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8 / 12 page  8 TC7660 CHARGE PUMP DC-TO-DC VOLTAGE CONVERTER © 2001 Microchip Technology Inc. DS21465A TC7660-7 9/30/96 Figure 6. External Clocking Figure 7. Lowering Oscillator Frequency Positive Voltage Multiplication The TC7660 may be employed to achieve positive voltage multiplication using the circuit shown in Figure 8. In this application, the pump inverter switches of the TC7660 are used to charge C1 to a voltage level of V+– VF (where V+ is the supply voltage and VF is the forward voltage drop of diode D1). On the transfer cycle, the voltage on C1 plus the supply voltage (V+) is applied through diode D2 to capacitor C2. The voltage thus created on C2 becomes (2 V+) – (2 VF), or twice the supply voltage minus the combined forward voltage drops of diodes D1 and D2. The source impedance of the output (VOUT) will depend on the output current, but for V+ = 5V and an output current of 10 mA, it will be approximately 60 Ω. Figure 8. Positive Voltage Multiplier Combined Negative Voltage Conversion and Positive Supply Multiplication Figure 9 combines the functions shown in Figures 3 and 8 to provide negative voltage conversion and positive volt- age multiplication simultaneously. This approach would be, for example, suitable for generating +9V and – 5V from an existing +5V supply. In this instance, capacitors C1 and C3 perform the pump and reservoir functions, respectively, for the generation of the negative voltage, while capacitors C2 and C4 are pump and reservoir, respectively, for the multi- plied positive voltage. There is a penalty in this configuration which combines both functions, however, in that the source impedances of the generated supplies will be somewhat higher due to the finite impedance of the common charge pump driver at pin 2 of the device. Figure 9. Combined Negative Converter and Positive Multiplier Efficient Positive Voltage Multiplication/Conversion Since the switches that allow the charge pumping op- eration are bidirectional, the charge transfer can be per- formed backwards as easily as forwards. Figure 10 shows a TC7660 transforming – 5V to +5V (or +5V to +10V, etc.). The only problem here is that the internal clock and switch- drive section will not operate until some positive voltage has been generated. An initial inefficient pump, as shown in Figure 9, could be used to start this circuit up, after which it will bypass the other (D1 and D2 in Figure 9 would never turn on), or else the diode and resistor shown dotted in Figure 10 can be used to "force" the internal regulator on. 1 2 3 4 8 7 6 5 TC7660 + V + + CMOS GATE 10 µF VOUT 10 µF 1 k Ω V + 1 2 3 4 8 7 6 5 + V + VOUT C1 COSC + C2 TC7660 1 2 3 4 8 7 6 5 + V + VOUT = (2 V +) – (2 VF) C1 D1 + + C3 C4 VOUT = – (V+– VF) C2 TC7660 D2 + 1 2 3 4 8 7 6 5 V+ VOUT = (2 V+) – (2 VF) + C2 D1 D2 + C1 TC7660 |
Numéro de pièce similaire - TC7660EOA |
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Description similaire - TC7660EOA |
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