X28HC64 查看數據表（PDF） - Renesas Electronics
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X28HC64 Datasheet PDF : 18 Pages
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X28HC64
System Considerations
Because the X28HC64 is frequently used in large memory arrays,
it is provided with a two-line control architecture for both read
and write operations. Proper usage can provide the lowest
possible power dissipation, and eliminate the possibility of
contention where multiple I/O pins share the same bus.
To gain the most benefit, it is recommended that CE be decoded
from the address bus, and be used as the primary device
selection input. Both OE and WE would then be common among
all devices in the array. For a read operation, this assures that all
deselected devices are in their standby mode, and that only the
selected device(s) is/are outputting data on the bus.
Because the X28HC64 has two power modes, standby and
active, proper decoupling of the memory array is of prime
concern. Enabling CE will cause transient current spikes. The
magnitude of these spikes is dependent on the output capacitive
loading of the I/Os. Therefore, the larger the array sharing a
common bus, the larger the transient spikes. The voltage peaks
associated with the current transients can be suppressed by the
proper selection and placement of decoupling capacitors. As a
minimum, it is recommended that a 0.1µF high frequency
ceramic capacitor be used between VCC and VSS at each device.
Depending on the size of the array, the value of the capacitor
may have to be larger.
In addition, it is recommended that a 4.7µF electrolytic bulk
capacitor be placed between VCC and VSS for each eight devices
employed in the array. This bulk capacitor is employed to
overcome the voltage droop caused by the inductive effects of
the PC board traces.
1.4
5.5VCC
1.2
1.0
0.8
0.6
- 55°C
+ 25°C
+ 125°C
1.4
1.2
5.5VCC
1.0
5.0VCC
0.8
4.5VCC
0.6
0.4
0.4
0.2
0M
10M
20M
FREQUENCY (Hz)
FIGURE 11. NORMALIZED ICC(RD) BY TEMPERATURE
OVER FREQUENCY DATA PROTECTION
0.2
0M
10M
20M
FREQUENCY (Hz)
FIGURE 12. NORMALIZED ICC(RD) AT 25% OVER THE VCC RANGE
AND FREQUENCY
FN8109 Rev 4.00
June 27, 2016
Page 8 of 18
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