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HCF4047BM1 数据表(PDF) 9 Page - STMicroelectronics |
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HCF4047BM1 数据表(HTML) 9 Page - STMicroelectronics |
9 / 12 page HCF4047B 9/12 6 - POWER CONSUMPTION In the standby mode (Monostable or Astable), power dissipation will be a function of leakage current in the circuit, as shown in the static electrical characteristics. For dynamic operation, the power needed to charge the external timing capacitor C is given by the following formula : Astable Mode : P = 2CV2f. (Output at Pin 13) P = 4CV2f. (Output at Pin 10 and 11) (2.9CV2) (Duty Cycle) Monostable Mode : P = —————————— T (Output at Pin 10 and 11) The circuit is designed so that most of the total power is consumed in the external components. In practice, the lower the values of frequency and voltage used, the closer the actual power dissipation will be to the calculated value. Because the power dissipation does not depend on R, a design for minimum power dissipation would be a small value of C. The value of R would depend on the desired period (within the limitations discussed above). 7 - TIMING-COMPONENT LIMITATIONS The capacitor used in the circuit should be non-polarized and have low leakage (i.e. the parallel resistance of the capacitor should be an order of magnitude greater than the external resistor used). Three is no upper or lower limit for either R or C value to maintain oscillation. However, in consideration of accuracy, C must be much larger than the inherent stray capacitance in the system (unless this capacitance can be measured and taken into account). R must be much larger than the COS/MOS "ON" resistance in series with it, which typically is hundreds of ohms. In addition, with very large values of R, some short-term instability with respect to time may be noted. The recommended values for these components to maintain agreement with previously calculated formulas without trimming should be : C > 100pF, up to any practical value, for astable modes ; C > 1000pF, up to any practical value, for monostable modes. 10K Ω< R < 1MΩ. TEST CIRCUIT CL = 50pF or equivalent (includes jig and probe capacitance) RL = 200KΩ RT = ZOUT of pulse generator (typically 50Ω) |
类似零件编号 - HCF4047BM1 |
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类似说明 - HCF4047BM1 |
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