M27C800 View Datasheet(PDF) - STMicroelectronics
Part Name
Description
Manufacturer
M27C800 Datasheet PDF : 17 Pages
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Figure 5. Word-Wide Read Mode AC Waveforms
M27C800
A0-A18
E
G
Q0-Q15
VALID
tAVQV
tGLQV
tELQV
tAXQX
VALID
tEHQZ
tGHQZ
Hi-Z
AI01596B
Note: BYTEVPP = VIH.
Two Line Output Control
Because EPROMs are usually used in larger
memory arrays, this product features a 2-line con-
trol function which accommodates the use of mul-
tiple memory connection. The two-line control
function
allows:
a. the lowest possible memory power dissipation
b. complete assurance that output bus contention
will not occur.
For the most efficient use of these two control
lines, E should be decoded and used as the prima-
ry device selecting function, while G should be
made a common connection to all devices in the
array and connected to the READ line from the
system control bus. This ensures that all deselect-
ed memory devices are in their low power standby
mode and that the output pins are only active
when data is required from a particular memory
device.
System Considerations
The power switching characteristics of Advanced
CMOS EPROMs require careful decoupling of the
supplies to the devices. The supply current ICC
has three segments of importance to the system
designer: the standby current, the active current
and the transient peaks that are produced by the
falling and rising edges of E.
The magnitude of the transient current peaks is
dependent on the capacitive and inductive loading
of the device outputs. The associated transient
voltage peaks can be suppressed by complying
with the two line output control and by properly se-
lected decoupling capacitors. It is recommended
that a 0.1µF ceramic capacitor is used on every
device between VCC and VSS.
This should be a high frequency type of low inher-
ent inductance and should be placed as close as
possible to the device. In addition, a 4.7µF electro-
lytic capacitor should be used between VCC and
VSS for every eight devices. This capacitor should
be mounted near the power supply connection
point. The purpose of this capacitor is to overcome
the voltage drop caused by the inductive effects of
PCB traces.
7/17
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