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Design of a Digital Choral Folder
Parameter (Symbol)
Min
Max
Low Input Voltage (VIL)
0
0.8 V
High Input Voltage (VIH)
2V
-
Low Output Voltage (VOL)
0
0.4 V
High Output Voltage (VOH)
2.8 V
VCC V
Output Current (IIO)
-
24 mA
Leakage Current (IL)
-
5 µA
Voltage Supply (VCC)
2.7 V
3.6 V
Current Supply (ICC)
100 mA
Table 4: 74LVC125A Characteristics (-40 to +85 °C)
The 74LVC125A is a cheap part, readily available, and it can do the job required. All of
the voltage, current, and frequency requirements of the design can be met with this chip.
There is no obvious reason not to use it as the switching element in the two screen PCB,
and unless a reason presents itself this will be the switching element used to go forward
with the design.
Figure 32: SN74LVC125A Quad Line Driver Logic Diagram
In summary, the signal switching approach for this design is to switch only the SDOE and
nnnn signals. When these signals are blocked, the screen will not be able to output data
to the active matrix of TFTs on the panel and no change should be observed in the
persistent image. The most straightforward mechanism for signal switching the output
enable signals is to use a line driver IC. The 74LVC125A quad line driver meets all of
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