74HC4538PW-Q100 データシートの表示（PDF） - Nexperia B.V. All rights reserved

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74HC4538PW-Q100

Dual retriggerable precision monostable multivibrator

Nexperia B.V. All rights reserved 

Nexperia

11 Application information

74HC4538-Q100

Dual retriggerable precision monostable multivibrator

11.1 Power-down considerations

A large capacitor (CEXT) may cause problems when powering-down the monostable due

to energy stored in this capacitor. When a system containing this device is powered-

down or rapid decrease of VCC to zero occurs, the monostable may sustain damage, due

to the capacitor discharging through the input protection diodes. To avoid this possibility,

use a damping diode (DEXT) preferably a germanium or Schottky type diode able to

withstand large current surges and connect as shown in Figure 10

DEXT

GND

CEXT

REXT

VCC

nCEXT

nREXT/CEXT

Figure 10. Power-down protection circuit

001aak193

11.2 Graphs

1.6

normalized

K factor

(K)

1.2

1 kΩ

2 kΩ

5.6 kΩ

51 kΩ

1 MΩ

1.0

0.8

0.6

10- 10

10- 9

10- 8

10- 7

10- 6

VCC = 4.5 V; Tamb = 25 °C.

Figure 11. Typical pulse width accuracy versus external capacitance

001aak196 1.12

REXT ×

CEXT

(tW)

0.84

0.70

0.56

10- 5

0.42

10- 4

CEXT (F)

74HC4538_Q100

Product data sheet

All information provided in this document is subject to legal disclaimers.

Rev. 3 — 17 March 2017

© Nexperia B.V. 2017. All rights reserved.

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