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74HCT423PW Arkusz danych(PDF) 2 Page - NXP Semiconductors |
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74HCT423PW Arkusz danych(HTML) 2 Page - NXP Semiconductors |
2 / 14 page 1998 Jul 08 2 Philips Semiconductors Product specification Dual retriggerable monostable multivibrator with reset 74HC/HCT423 FEATURES • DC triggered from active HIGH or active LOW inputs • Retriggerable for very long pulses up to 100% duty factor • Direct reset terminates output pulse • Schmitt-trigger action on all inputs except for the reset input • Output capability: standard (except for nREXT/CEXT) • ICC category: MSI GENERAL DESCRIPTION The 74HC/HCT423 are high-speed Si-gate CMOS devices and are pin compatible with low power Schottky TTL (LSTTL). They are specified in compliance with JEDEC standard no. 7A. The 74HC/HCT423 are dual retriggerable monostable multivibrators with output pulse width control by two methods. The basic pulse time is programmed by selection of an external resistor (REXT) and capacitor (CEXT). The external resistor and capacitor are normally connected as shown in Fig.6. Once triggered, the basic output pulse width may be extended by retriggering the gated active LOW-going edge input (nA) or the active HIGH-going edge input (nB). By repeating this process, the output pulse period (nQ = HIGH, nQ = LOW) can be made as long as desired. When nRD is LOW, it forces the nQ output LOW, the nQ output HIGH and also inhibits the triggering. Figures 7 and 8 illustrate pulse control by reset. The basic output pulse width is essentially determined by the values of the external timing components REXT and CEXT. For pulse widths, when CEXT < 10 000 pF, see Fig.9. When CEXT > 10 000 pF, the typical output pulse width is defined as: tW = 0.45 × REXT × CEXT (typ.), where, tW = pulse width in ns; REXT = external resistor in kΩ; CEXT = external capacitor in pF. Schmitt-trigger action in the nA and nB inputs, makes the circuit highly tolerant to slower input rise and fall times. The “423” is identical to the “123” but cannot be triggered via the reset input. QUICK REFERENCE DATA GND = 0 V; Tamb = 25 °C; tr = tf = 6 ns Notes 1. CPD is used to determine the dynamic power dissipation (PD in µW): PD = CPD × VCC2 × fi +∑ (CL × VCC2 × fo) + 0.75 × CEXT × VCC2 × fo + D × 16 × VCC where: fi = input frequency in MHz fo = output frequency in MHz D = duty factor in % ∑ (CL × VCC2 × fo) = sum of outputs CL = output load capacitance in pF VCC = supply voltage in V CEXT = timing capacitance in pF 2. For HC the condition is VI = GND to VCC For HCT the condition is VI = GND to VCC − 1.5 V SYMBOL PARAMETER CONDITIONS TYPICAL UNIT HC HCT tPHL/ tPLH propagation delay CL = 15 pF; VCC = 5 V; REXT =5 kΩ; CEXT = 0 pF nA, nB to nQ, nQ25 26 ns nRD to nQ, nQ20 22 ns CI input capacitance 3.5 3.5 pF tW minimum output pulse width nQ, nQ notes 1 and 2 75 75 ns |
Podobny numer części - 74HCT423PW |
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Podobny opis - 74HCT423PW |
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