CD4055B and CD4056B types are single-digit BCD-to-7-segment decoder/driver circuits that provide level-shifting functions on the chip. This feature permits the BCD input-signal swings (VDDto VSS) to be the same as or different from the 7-segment output-signal swings (VDDto VEE). For example, the BCD input-signal (VDDto VSS) may be as small as 0 to -3 V, whereas the output-display drive-signal swing (VDDto VEE) may be as large as from 0 to -15 V. If VDDto VEEexceeds 15 V, VDDto VSSshould be at least 4V (0 to -4V). The 7-segment outputs are controlled by the DISPLAY-FREQUENCY (DF) input which causes the selected segment outputs to be low, high, or a square-wave output (for liquid-crystal displays). When the DF input is low the output segments will be high when selected by the BCD inputs. When the DF input is high, the output segments will be low when selected by the BCD inputs. When a square-wave is present at the DF input, the selected segments will have a square-wave output that is 180° out of phase with the DF input. Those segments which are not selected will have a square-wave output that is in phase with the input. DF square-wave repetition rates for liquid-crystal displays usually range form 30 Hz (well above flicker rate) to 200 Hz (well below the upper limit of the liquid-crystal frequency response). The CD4055B provides a level-shifted high-amplitude DF output which is required for driving the common electrode in liquid-crystal displays. The CD4056B provides a strobed-latch function at the BCD inputs. Decoding of all input combinations on the CD4055B and CD4056B provides displays of 0 to 9 as well as L, P, H, A, -, and a blank position.

The CD4054B provides level shifting similar to the CD4055B and CD4056B independently strobed latches, and common DF control on 4 signal lines. The CD4054B is intended to provide drive-signal compatibility with the CD4055B and CD4056B 7-segment decoder types for the decimal point, colon, polarity, and similar display lines. A level-shifted high-amplitude DF output can be obtained from any CD4054B output line by connecting the corresponding input and strobe lines to a low and high level, respectively and applying a square wave to DFIN. The CD4054B may also be utilized for logic-level "up conversion" or "down conversion". For example, input-signal swings (VDDto VSS) for +5 to 0 V can be converted to output-signal swings (VDDto VEE) of +5 to -5 V. The level-shifted function on all three types permits the use of different input- and output-signal swings. The input swings from a low level of VSSto a high level of VDDwhile the output swings from a low level of VEEto the same high level of VDD. Thus, the input and output swings can be selected independently of each other over a 3-to 18 V range. VSSmay be connected to VEEwhen no level-shift function is required.

For the CD4054B and CD4056B, data are transferred from input to output by placing a high voltage level at the strobe input. A low voltage at the strobe input latches the data input and the corresponding output segments remain selected (or non-selected) while the strobe is low.Read more