74HC4538-Q100 View Datasheet(PDF) - NXP Semiconductors.
Part Name
Description
MFG CO.
74HC4538-Q100 Datasheet PDF : 23 Pages
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NXP Semiconductors
74HC4538-Q100; 74HCT4538-Q100
Dual retriggerable precision monostable multivibrator
12. Application information
12.1 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
001aak193
Fig 10. Power-down protection circuit
12.2 Graphs
1.6
normalized
K factor
(K)
1.2
1.0
0.8
0.6
10−10
10−9
1 kΩ
2 kΩ
5.6 kΩ
51 kΩ
1 MΩ
10−8
10−7
10−6
VCC = 4.5 V; Tamb = 25 C.
Fig 11. Typical pulse width accuracy versus external capacitance
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1.12
REXT ×
CEXT
(tW)
0.84
0.70
0.56
10−5
0.42
10−4
CEXT (F)
74HC_HCT4538_Q100
Product data sheet
All information provided in this document is subject to legal disclaimers.
Rev. 1 — 2 August 2012
© NXP B.V. 2012. All rights reserved.
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