On Tue, 1 Dec 1998, Troy P. wrote:

> I recently purchased a 6 digit LCD from Digikey (part no. 153-1021) and
> it said that I needed to use 6 driver chips (part no. CD 4543BE). First
> of all these chips do not have any provisions for driving the decimal
> points so how do I control them. Also they call this LCD a STATIC type
> does that mean that I do NOT need a square wave for the backplane.

Static means that the segments are not multiplexed, you still need to
drive the LCD with A.C. but it is enough to have one square wave with 505
duty cycle.

The dots need extra drivers when using 4543Bs. These are usually XOR gates
from a 4077B (?). Each dot needs an XOR gate to drive it. The gate
receives the dot state (ON: HIGH usually) from your logic on an input and
the backplane signal on the other. The 4543B's also need to be driven out
of phase with the backplane signal (backplane signal XORed with '1' will
do fine).

The backplane proper needs to be driven too but it is good to investigate
its capacitance, it may need higher drive than the segments (a HC gate or
two should be enough).

hope this helps,

Peter