MC100E016 데이터 시트보기 (PDF) - ON Semiconductor
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MC100E016 Datasheet PDF : 12 Pages
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OUT
EL01
MC10E016, MC100E016
APPLICATIONS INFORMATION (continued)
LO
CLOCK
Q0 −> Q7
CE
PE
E016
LSB
CLK TC
PO −> P7
Q0 −> Q7
Q0 −> Q7
Q0 −> Q7
CE
PE
E016
CE
PE
E016
CE
PE
E016
MSB
CLK TC
EL01
PO −> P7
CLK TC
EL01
PO −> P7
CLK TC
PO −> P7
Figure 6. 32−Bit Cascaded E016 Programmable Divider
Figure 6 shows a typical block diagram of a 32−bit divider
chain. Once again to maximize the frequency of operation
EL01 OR gates were used. For lower frequency applications
a slower OR gate could replace the EL01. Note that for a
16−bit divider the OR function feeding the PE (program
enable) input CANNOT be replaced by a wire OR tie as the
TC output of the least significant E016 must also feed the CE
input of the most significant E016. If the two TC outputs
were OR tied the cascaded count operation would not
operate properly. Because in the cascaded form the PE
feedback is external and requires external gating, the
maximum frequency of operation will be significantly less
than the same operation in a single device.
Maximizing E016 Count Frequency
The E016 device produces 9 fast transitioning
single−ended outputs, thus VCC noise can become
significant in situations where all of the outputs switch
simultaneously in the same direction. This VCC noise can
negatively impact the maximum frequency of operation of
the device. Since the device does not need to have the Q
outputs terminated to count properly, it is recommended that
if the outputs are not going to be used in the rest of the system
they should be left unterminated. In addition, if only a subset
of the Q outputs are used in the system only those outputs
should be terminated. Not terminating the unused outputs
will not only cut down the VCC noise generated but will also
save in total system power dissipation. Following these
guidelines will allow designers to either be more aggressive
in their designs or provide them with an extra margin to the
published data book specifications.
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