HCC4538B Datasheet, PDF (8/14 Pages) STMicroelectronics – DUAL MONOSTABLE MULTIVIBRATOR

HCC/HCF4538B
Power Down Mode
During a rapid power-down conditiona, as would
occur with a power supply short circuit or with a
poorly filtered power supply, the energy stored in CX
could discharge into Pin 2 or 14. To Avoid possible
device damage in this mode, when C_X is ≤0.5 micro-
farad, a aprotection diode with a 1 Ampere or higher
rating (1N5395 or equivalent) and a separate
ground return for C_X should be provided as shown
in Fig. 1
An alternate protection method is shown in Fig. 2,
where a 51 Ω current limit resistor is inserted in
series with CX. Note that a small pulse width de-
crease will occour however, and RX must be appro-
priately increased to obtain the originally desired
pulse width.
Figure 1: rapid Power Down Protection Circuit
Figure 2: Alternate rapid Power Down Protection
Circuit
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