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HCF4047M013TR 数据表(PDF) 8 Page - STMicroelectronics |
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HCF4047M013TR 数据表(HTML) 8 Page - STMicroelectronics |
8 / 12 page HCF4047B 8/12 Where tM = monostable mode pulse width. Values for tM are as follows : Typ : VTR = 0.5 VDD tM = 2.48 RC Min : VTR = 0.33 VDD tM = 2.71 RC Max : VTR = 0.67 VDD tM = 2.48 RC Thus if tM = 2.48 RC is used, the maximum variation will be (+ 9.3%, - 0.0%). Note : In the astable mode, the first positive half cycle has a duration of TM ; succeeding durations are tA/2. In addition to variations from unit to unit, the monostable pulse width may vary as a function of frequency with respect to VDD and temperature. 4 - RETRIGGER MODE The HCF4047B can be used in the retrigger mode to extend the output-pulse duration, or to compare the frequency of an input signal with that of the internal oscillator. In the retrigger mode the input pulse is applied to terminals 8 and 12, and the output is taken from terminal 10 or 11. As shown in fig.A normal monostable action is obtained when one retrigger pulse is applied. Extended pulse duration is obtained when more than one pulse is applied. For two input pulses, tRE = t1’ + t1 + 2t2. For more than two pulses, tRE (Q OUTPUT) terminates at some variable time tD after the termination of the last retrigger pulse. tD is variable because tRE (Q OUTPUT) terminates after the second positive edge of the oscillator output appears at flip-flop 4 (see logic diagram). FIGURE A : Retrigger-mode waveforms 5 - EXTERNAL COUNTER OPTION Time tM can be extended by any amount with the use of external counting circuitry. Advantages include digitally controlled pulse duration, small timing capacitors for long time periods, and extremely fast recovery time. A typical implementation is shown in fig. B. The pulse duration at the output is text = (N - 1) (tA) + (tM + tA/2) Where text = pulse duration of the circuitry, and N is the number of counts used. FIGURE B : Implementation of external counter option |
类似零件编号 - HCF4047M013TR |
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类似说明 - HCF4047M013TR |
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