CD74HC4538-Q1 Datasheet, PDF (9/16 Pages) Texas Instruments – HIGH-SPEED CMOS LOGIC DUAL RETRIGGERABLE PRECISION MONOSTABLE MULTIVIBRATOR

CD74HC4538-Q1
HIGH-SPEED CMOS LOGIC DUAL RETRIGGERABLE
PRECISION MONOSTABLE MULTIVIBRATOR
SCLS595A − NOVEMBER 2004 − REVISED APRIL 2008
power-down mode
TYPICAL APPLICATION DATA
During a rapid power-down condition (as would occur with a power-supply short circuit with a poorly filtered
power supply), the energy stored in C_X could discharge into pin 2 or pin 14. To avoid possible device damage
in this mode when C_X is w 0.5 µF, a protection diode with a 1-A rating or higher (1N5395 or equivalent) and a
separate ground return for C_X should be provided (see Figure 5).
An alternate protection method is shown in Figure 6, where a 51-Ω current-limiting resistor is inserted in series
with C_X . Note that a small pulse-duration decrease occurs, however, and R_X must be increased appropriately
to obtain the originally desired pulse duration.
R_X
2 (14)
V_CC
16
R_X
2 (14)
V_CC
16
C_X
≥0.5 µF
1 (15)
8
51 Ω
C_X
≥0.5 µF
1 (15)
8
Figure 5. Rapid-Power-Down
Protection Circuit
Figure 6. Alternative Rapid-Power-Down
Protection Circuit
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