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DM74LS221M データシート(PDF) 4 Page - National Semiconductor (TI) |
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DM74LS221M データシート(HTML) 4 Page - National Semiconductor (TI) |
4 / 6 page Operating Rules 1 An external resistor (RX) and an external capacitor (CX) are required for proper operation The value of CX may vary from 0 to approximately 1000 mF For small time constants high-grade mica glass polypropylene polycar- bonate or polystyrene material capacitor may be used For large time constants use tantalum or special alumi- num capacitors If timing capacitor has leakages ap- proaching 100 nA or if stray capacitance from either ter- minal to ground is greater than 50 pF the timing equations may not represent the pulse width the device generates 2 When an electrolytic capacitor is used for CX a switching diode is often required for standard TTL one-shots to pre- vent high inverse leakage current This switching diode is not needed for the ’LS221 one-shot and should not be used Furthermore if a polarized timing capacitor is used on the ’LS221 the positive side of the capacitor should be con- nected to the ‘‘CEXT’’ pin (Figure 1 ) TLF6409 – 8 FIGURE 1 3 For CX ll 1000 pF the output pulse width (TW)isde- fined as follows TW e KRX CX where RX is in kX CX is in pF TW is in ns K Ln2 e 070 4 The multiplicative factor K is plotted as a function of CX below for design considerations TLF6409 – 3 FIGURE 2 5 For CX k 1000 pF see Figure 3 for TW vs CX family curves with RX as a parameter TLF6409 – 4 FIGURE 3 6 To obtain variable pulse widths by remote trimming the following circuit is recommended TLF6409 – 5 Note ‘‘Rremote’’ should be as close to the one-shot as possible FIGURE 4 7 Output pulse width versus VCC and temperatures Figure 5 depicts the relationship between pulse width variation versus VCC Figure 6 depicts pulse width variation versus temperatures TLF6409 – 6 FIGURE 5 TLF6409 – 7 FIGURE 6 4 |
同様の部品番号 - DM74LS221M |
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同様の説明 - DM74LS221M |
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