CD40109B contains four low-to-high-voltage level-shifting circuits. Each circuit will shift a low-voltage digital-logic input signal (A, B, C, D) with logical 1 = VCC and logical 0 = VSS to a high-voltage output signal (E, F, G, H) with logical 1 = VDD and logical 0 = VSS.
The RCA-CD40109, unlike other low-to-high level-shifting circuits, does not require the presence of the high-voltage supply (VDD) before the application of either the low-voltage supply (VCC) or the input signals. There are no restrictions on the sequence of application of VDD, VCC, or the input signals. In addition, with one exception there are no restrictions on the relative magnitudes of the supply voltages or input signals within the device maximum ratings, provided that the input signal swings between VSS and at least 0.7 VCC; VCC may exceed VDD, and input signals may exceed VCC and VDD. When operated in the mode VCC > VDD, the CD40109 will operate as a high-to-low level-shifter.
The CD40109 also features individual three-state output capability. A low level on any of the separately enabled three-state output controls produces a high-impedance state in the corresponding output.