82C82 Datasheet, PDF (3/7 Pages) Intersil Corporation – CMOS Octal Latching Bus Driver

82C82
Application Information
Decoupling Capacitors
The transient current required to charge and discharge the
300pF load capacitance specified in the 82C82 data sheet is
determined by:
I = C_L(dv/dt)
(EQ. 1)
Assuming that all outputs change state at the same time and
that dv/dt is constant;
I = C_L
(EQ. 2)
(_---V_{----C----C-t--R---}x_-/--t-F-8_---0_----%_------)
(EQ. 3)
where tR = 20ns, V_CC = 5.0V, C_L = 300pF on each of eight
outputs.
I = (8 x 300 x 10^-12)x (5.0V x 0.8)/(20 x 10^–9) = 480mA ^{(EQ. 4)}
This current spike may cause a large negative voltage spike
on V_CC, which could cause improper operation of the device.
To filter out this noise, it is recommended that a 0.1µF
ceramic disc decoupling capacitor be placed between V_CC
and GND at each device, with placement being as near to
the device as possible.
ALE
MULTIPLEXED
BUS
ICC
ADDRESS
ADDRESS
STB
DATA IN
V_CC
P
N
V_CC
P
P
INTERNAL
DATA
N
N
FIGURE 18. SYSTEM EFFECTS OF GATED INPUTS
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