Datasheet

MM5452, MM5453
SNLS367C –FEBRUARY 1995–REVISED MARCH 2013 www.ti.com
*The minimum recommended value for R for the oscillator input is 9 kΩ. An RC time constant of approximately 4.91 ×
10
−4
should produce a backplane frequency between 30 Hz and 150 Hz.
Figure 9. Parallel Backplane Outputs
Figure 10. External Backplane Clock
Figure 11 shows a four wire remote display that takes advantage of the device’s serial input to move many bits of
display information on a few wires.
USING AN EXTERNAL CLOCK
The MM5452/MM5453 LCD Drivers can be used with an externally supplied clock, provided it has a duty cycle of
50%. Deviations from a 50% duty cycle result in an offset voltage on the LCD. In Figure 10, a flip-flop is used to
assure a 50% duty cycle. The oscillator input is grounded to prevent oscillation and reduce current consumptions
in the chips. The oscillator is not used.
Using an external clock allows synchronizing the display drive with AC power, internal clocks, or DVM integration
time to reduce interference from the display.
Figure 12 is a general block diagram that shows how the device’s serial input can be used to advantage in an
analog display. The analog voltage input is compared with a staircase voltage generated by a counter and a
digital-to-analog converter or resistor array. The result of this comparison is clocked into the MM5452, MM5453.
The next clock pulse increments the staircase and clocks the new data in.
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