This example circuit shows a typical application of direct drive decoder/driver ICs for numeric displays. The CD4056 is a BCD to 7 segment latch/decoder/driver and the CD4054 is a 4 segment driver. Alpha characters decoded by the CD4056 are limited to L, H, P, A and -. The CD4054 drives display specific annunciators such as a single digit, colons, decimal points or polarity signs.

Required signals are 4 bits of BCD data, digit strobe, annunciator bits and square-wave display drive - the 32 HZ input shown on the drawing. The circuit is expandable for displays with more digits or annunciators.

Both devices are CMOS and can operate from 4 to 20 volts. See the "List of LCD Driver Chips" for information on obtaining this or many other IC's for direct driving LCD's. Our Applications Note "Direct Driving an LCD" has additional basic direct drive information.