TLF6137 – 7

The minimum recommended value for R for the oscillator input is 9 kX An RC time constant of approximately

FIGURE 6 Parallel Backplane Outputs

TLF6137 – 8

FIGURE 7 External Backplane Clock

Figure 8 shows a four wire remote display that takes advan-

tage of the device’s serial input to move many bits of display

information on a few wires

USING AN EXTERNAL CLOCK

The MM5452MM5453 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 7 a flip-flop is used to assure

a 50% duty cycle The oscillator input is grounded to pre-

vent 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 9 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 stair-

case 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

With a buffer amplifier the same staircase waveform can be

used for many displays The digital-to-analog converter

need not be linear logarithmic or other non-linear functions

can be displayed by using weighted resistors or special

DACs This system can be used for status indicators spec-

trum analyzers audio level and power meters tuning indica-

tors and other applications

6